phosphorylated, silylated, and stannylated derivatives of α-mercaptocarbonyl compounds

1070-3632/01/7103-0403$25.00C2001 MAIK [Nauka/Interperiodica]

Russian Journal of General Chemistry,Vol. 71, No. 3,2001, pp. 4033419. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 3,2001,pp. 4403456.Original Russian Text CopyrightC 2001 by Pudovik,Burilov.

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Phosphorylated, Silylated, and Stannylated Derivativesof a-Mercaptocarbonyl Compounds

M. A. Pudovik and A. P. Burilov

Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center,Russian Academy of Sciences, Kazan, Tatarstan, Russia

Received August 11, 2000

Abstract-The authors are summing up their research in the field of phosphorylation, silylation, and stannyla-tion of a-mercaptocarbonyl compounds. Synthetic methods were developed for a series of new saturated andunsaturated organosilicon(tin) reagents that were applied to organophosphorus syntheses. Representatives ofnew classes of heterocyclic compounds were prepared: 1,3,2-oxathiaphospholenes with four- and five-coordinate phosphorus. A new thiophosphite3thiophosphate rearrangement initiated by molecular oxygenwas discovered.

INTRODUCTION

In the last decades the efforts of chemists are to agreat extent directed to the synthesis of new typesfunctionally substituted organophosphorus compoundscontaining unusual sequence of bonds and variouscombinations of substituents. The attention to thisfield of chemistry is largely due to the possibility ofappearance in this type compounds of interestingintramolecular transformations. In particular, combina-tion in one molecule of a phosphorus atom and acarbonyl group (phosphorylateda-heterocarbonylcompounds) provides a possibility to perform un-common intramolecular transformations affording newlinear and cyclic unsaturated organophosphorus com-pounds with variously coordinated central atom, andto extend significantly the theoretical understandingof the reactivity of P(III) acids derivatives. Into thestudy of phosphorylation of hydroxy anda-amino-carbonyl compounds with derivatives of P(III) acidslargely contributed Yu.G. Gololobov [1] andF.S. Mu-khametov [2] with collaborators. To the beginning ofour investigations on elementoylation ofa-mercapto-carbonyl compounds appeared only some publicationson reactions ofa-mercaptoacetic acid and its anilideswith P(III) acid halides and amides [3, 4]. Yet theperformance of reactions betweena-mercaptocarbonylcompounds and derivatives of P(III) acids with thehelp of silylating and stannylating agents permitsrevealing of the specific features of the reactivityinherent ina-mercaptocarbonyl compounds due to thepresence of the mercapto group, preparation of newtypes of linear and cyclic compounds containing P, S,Si, Sn, and investigation of their characteristics. A

very promising synthesis is that of silylateda-mer-captocarbonyl compounds. Since the energy of O3Siand S3Si bonds are considerably different, in theseries of the above compounds may be expected intra-molecular transformations including a migration oftrimethylsilyl groups. On the other hand, Si,Sn-containing a-mercaptocarbonyl compounds are un-doubtedly interesting as starting objects for phos-phorylation with P(III) acid chlorides and acyl halides.

1. Silylation and Stannylationof a-Mercaptoketones

The principal approach to the synthesis of organo-phosphorus compounds with a carbonyl group in theb-position is based on reacting the correspondinga-hydroxy(amino, mercapto)-substituted carbonylcompounds with chlorides and amides of P(III) acids.An alternative to this preparation technique forb-ketophosphites (amidophosphites, thiophosphites)consists in reactions of Si, Sn-organic derivatives ofthe a-functionally substituted carbonyl compoundswith halides of P(III) and P(IV) acids.

The silylated a-mercaptoketones and derivativesthereof are convenient reagents for introducing variousstructural fragments into organic and organoelementalmolecules.

The silylation of the simplest member of thea-mercaptocarbonyl compounds series, mercapto-acetoneIa, with trimethylchlorosilane in the presenceof an equimolar amount of triethylamine affordsketone IIa , thermally unstable compound tarring atfractional distillation [5].

RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 3 2001

404 PUDOVIK, BURILOV

MeC(O)CHRSH + Me3SiClIa, Ib

7776 MeC(O)CHRSSiMe3,3Et3N .HCl

Et3N

IIa, IIb

IIa 76 MeC=CHRSH,gOSiMe3

III

R = H (a), Me (b).

In order to confirm the structure of the compoundand to elucidate the factors leading to polymerizationwe studied the unpurified reaction product by meansof IR spectroscopy. In the IR spectrum of the reactionmixture was observed an absorption band at1710 cm31 belonging to the stretching vibrations ofC=O bond. On storing compoundIIa at 20oC for 2 hor after short heating the intensity of the 1710 cm31

(C=O) band in its IR spectrum considerably decreased,and appeared an absorption band in 1610 cm31 regioncorresponding to the stretching vibrations of C=Cbond, and a band at 2520 cm31 from S3H bond vibra-tions. The comparison of the IR absorption bands ledto conclusion that compoundIIa transformed into thecorresponding vinylmercaptanIII that easily poly-merized at fractionation. Thus we observed for thefirst time in such systems an example of S6O1,4-migration of a trimethylsilyl group from sulfur tooxygen atom. The process apparently can occur eitherintraor intermolecularly, and its driving force is theformation of an energetically feasible Si3O bond.Since we failed to isolate individual 1-(trimethylsilyl-thio)-2-propanoneIIa or vinylmercaptanIII we at-tempted to protect the mercapto group of the formedvinylmercaptan with a trimethylsilyl group. The silyla-tion of mercaptoacetoneIa with trimethylchlorosilanein the presence of triethylamine at the reagents ratio1 :2 :2 afforded in 34% yield compoundIVa . The useas silylating agent ofN,O-bis(trimethylsilyl)acetamideraised the yield of the final product to 76%. Asshowed the1H NMR spectrum, substituted alkeneIVawas a mixture ofE and Z isomers [5].

Ia, Ib + 2Me3SiCl7776 MeC=CH(R)SSiMe3,32Et3N .HCl

2Et3N

gOSiMe3

IVa, IVb

R = H (a), Me (b).

The stability of the S-silylation product is consi-derably higher if to thea-carbon is introduced a

methyl group. In the reaction between 3-mercapto-2-butanoneIb and trimethylchlorosilane in the presenceof triethylamine was obtained and isolated in anindividual state compoundIIb that was stored un-changed at least for 10 days. The silylation of 3-(tri-methylsilylthio)-2-butanone IIb with the secondmolecule of trimethylchlorosilane (in the presence oftriethylamine at prolonged heating) afforded com-pound IVb [5].

The presence ina-mercaptoketones of two reactivecenters (mercapto and keto groups) suggests a possi-bility to synthesize silicon-containing heterocycles.The silylation of mercaptobutanoneIb with dimethyl-dichlorosilane in the presence of 2 mol of triethyl-amine resulted in 2,2,4,5-tetramethyl-1,3,2-oxathia-silolene V in 65% yield [6].

Ib + Me2SiCl2 7762B

32B.HCl $??cc

Me

Me

O

SSiMe2

V

As already mentioned above the synthesis of com-pound IIa failed due to S6O 1,4-migration of thetrimethylsilyl group followed by oligomerization ofthe arising alkene. We presumed that stable sulfur-containing organoelemental compounds would beobtained with organotin reagents (taking into accountthe higher strength of Sn3S bond as compared to thatof Sn3O bond) [7]. To this end we studied thereac-tions of mercaptoketonesIa andIb with triethylchloro-stannane in the presence of sodium isopropylate; as aresult we obtained in high yield compoundsVIa andVIb [8].

Ia, Ib + Et3SnCl776 MeC(O)CH(R)SSnEt3,i-PrONa

3NaClVIa, VIb

R = H (a), Me (b).

2. Silylation of Mercaptoacetic acid Esters

In the literature a reaction is described of trimethyl-chlorosilane with mercaptoacetic acid and its esters[9] resulting in the corresponding silicon and sulfurcontaining compounds with a carboxy group. Weperformed an exhaustive silylation of mercaptoaceticacid VII and its esters in order to prepare therefromsilicon-containing alkenes. It turned out however thatthe reaction of acidVII with trimethylchlorosilane inthe presence of triethylamine (at reagents ratio 1 :3 :3)at boiling in benzene stopped at the stage of trimethyl-silyl (trimethylsilylthio)acetateVIII formation.


PHOSPHORYLATED, SILYLATED, AND STANNYLATED DERIVATIVES 405

HSCH2COOH + 3Me3SiCl

VII

7776 Me3SiSCH2COOSiMe3.32B.HCl

3B

VIII

Taking into consideration the weak enolizationability of the carbonyl group in carboxylic acidsderivatives we used strong bases, sodium or lithiumbis(trimethylsilyl)amides, for cleavage of a protonfrom thea-carbon. Reaction of compoundVIII withhexamethyldisilazane salts followed by treating thereaction mixture with trimethylchlorosilane furnished1-trimethylsilylthio-2,2-bis(trimethylsilyloxy)etheneX in over 70% yield [10, 11].

Me3SiSCH-_COSiMe3gO...3

M+ 9999

3

3

9999

3

3

9 9VIII + MN(SiMe3)2 7776

3HN(SiMe3)2IX

776 Me3SiSCH=COSiMe3,gOSiMe3

Me3SiCl

3MClX

M = Li, Na.

The fractionation of the reaction mixture affordedalongside compoundX a high-boiling reactionproduct that was according to1H and 13C NMR andIR spectra 2,4-bis(trimethylsilylthio)-1,3-bis(trimethyl-silyloxy)-2-buten-1-one (XIII ). The latter compoundwas obtained as a mixture ofZ and E isomers.

Replacing a hydrogen atom in compoundVIIIby a metal atom forms anionIX with delocalizedcharge.

VIII + IX 76Me3SiS3CH3COSiMe3g

MO3C3CH2SSiMe3gOSiMe3

oO99999999

3

3

99999999

3

3XI

Me3SiS3CH3COSiMe3gg

OSiMe3

oO 99999999

3

3XII

Me3SiSO3C3CH2SSiMe37776Me3SiCl

3MCl

99999999

3

3

77763HOSiMe3

Me3SiS3C3COSiMe

Me3SiSO3C3CH2SSiMe3

oOo

XIII

A nucleophilic attack of a carbon atom of thisambident system on a carbon atom of the carbonylgroup of acetateVIII results in intermediateXI . Thesilylation of the latter with trimethylchlorosilane givescompoundXII that under conditions of the reactioneliminates a silanol molecule to afford the final reac-tion productXII . The presence in compoundXIII ofreadily leaving trimethylsilyl groups makes it apromising reagent for preparation of unsaturatedorganic and organoelement structures.

Taking into consideration the data obtained wewere interested how would affect the silylation patternthe replacement of trimethylsilyl group in compoundVIII by alkoxy group. The study was carried out onreaction of methyl trimethylsilylthioacetateXIVa andethyl trimethylsilylthioacetateXIVb with trimethyl-chlorosilane in the presence of sodium and lithiumbis(trimethylsilyl)amides. It was established that withmethyl acetateXIVa the reaction resulted completelyin condensation productXVa.

Me3SiS3C3COOR,oRO3C3CH2SSiMe3

XVa, XVb

7699999976 Me3SiS3CH=C ,ieOR

OSiMe3

XVI

777ClSiMe3

3MCl

Me3SiSCH2COR + MN(SiMe3)2oO

XIVa, XIVb

M = Li, Na; R = Me (XIVa, XVa ), Et (XIVb, XVb, XVI ).

At the same time at the use of ethyl acetateXIVbthe main product formed 1-trimethylsilyl-2-trimethyl-siloxy-2-ethoxyethene (XVI ), and compoundXVbforms in negligible amount. CompoundXVI onstorage or at heating isomerizes into ethyl (1-trimethyl-silyl-1-trimethylsilylthio)acetateXVII due to O6C1,3-migration of trimethylsilyl group [12].

XVI 76 Me3SiSCHCOOEt.gSiMe3

XVII

Abnormal behavior of compoundXVI as comparedto that of compoundX consisting in unusual O6C1,3-migration of trimethylsilyl group is due apparentlyto a combination of electronic and steric effects ofsubstituents at the oxygen atom of the double bond.



3. S-Silylated (Stannylated) a-Mercaptoketonesin the Synthesis of Organophosphorus Compounds.

In section 1 we described the preparation ofa-mercaptoketones containing S3Si IIa and IIb andS3Sn VIa and VIb bonds that should be easilycleaved by phosphorus acids chlorides. We usedlinear and cyclic chlorides of phosphorus(III) acids as

ÄÄÄÄÄÄÄÄÄÄÄÄ

phosphorylating agents.

The reaction of silylatedIIb and stannylatedVIbderivatives ofa-mercaptobutanone with diethyl anddiisopropyl chlorophosphites proceeds at room tem-perature resulting in each case in a single product ofthiophosphite structureXIXa and XIXb (dP 1883189 ppm).

(RO)2PCl + MeCOCH(Me)SEMe3 7776 (RO)2PSCH(Me)SOMe76 (RO)2PCH(Me)COMe,3Me3SiCl

O2

XVIIIa, XVIIIb IIb, VIb XIXa, XIXb XXa, XXb

98 1/8S8

(RO)2PSCH(Me)COMeoSXXIa, XXIb

R = Et (XVIIIa, XIXa 3XXIa ), i-Pr (XVIIIb, XIXb 3XXIb ); E = Si (IIb ), Sn (VIb ).ÄÄÄÄÄÄÄÄÄÄÄÄ

The compounds are stable to heating to 150oC;however at contact with the air oxygen they isomerizewith strong heat evolution into the correspondingdialkyl thiophosphonatesXXa and XXb (dP 88391 ppm). CompoundsXIXa and XIXb readily takeup sulfur to afford dithiophosphatesXXIa andXXIb .

The reaction of silylthiobutanoneIIb with 2-chloro-1,3,2-dioxaphospholaneXXII in the first stage givesthiophosphiteXXIII (dP 182 ppm) that even at shortexposure to air oxygen immediately isomerizes intothiophosphonateXXIV [13]. Unlike that under inertatmosphere in 24 h in the31P NMR spectrum of thereaction mixture the signal of thiophosphiteXXIII


disappears, and two signals arise with the chemicalshifts of 154 and 136 ppm in 5 :1 ratio. The signal atdP 136 ppm completely disappears within 2 days.Basing on 31P NMR data we supposed that in themixture are present 1,3,2-oxathiaphospholeneXXVand 1,3,2-dioxaphospholaneXXVI . We failed toisolate these compounds in the individual state due totarring of the reaction mixture at heating. Thereforewe treated the crude reaction products with acetylchloride in the presence of triethylamine and thensucceeded in isolation of a compound (dP 154 ppm)that with the use of1H NMR and IR spectra andelemental analysis was identified as 1,3,2-oxathia-phospholeneXXVII .

IIb +$O

OPCl 7776

3Me3SiCl$O

OPSH(Me)COMe76$

O

O"EEPO

O

9H cc

Me

Me

99999

3

3

99999

3

3

76 $??cc

Me

MePO(CH2)2OH

O

O+$

O

OPOC=CSHgg

Me

Me98O2

$O

OP(S)CH(Me)COMe

XXIV

XXII XXIII XXV XXVI


CompoundXXVII was also prepared by indepen-dent synthesis by reaction of 2-chloro-1,3,2-oxathia-phospholeneXXVIII with ethylene gl-cole acetateXXIX .

Thus the intramolecular interaction of trivalentphosphorus and the oxygen of the carbonyl group inthe appropriate thiophosphites provides a possibilityof new processes affording via an intermediate spiro-



XXV + MeCOCl

$??cc

Me

Me

O

OPCl + HO(CH2)2OCOMe

7777777799997

77763B .HCl

B

$??cc

Me

Me

O

OPO(CH2)2OCOMe

XXVIII XXIX

XXVII

phosphorane the corresponding compoundsXXV andXXVI . Taking into account the published and ourproper data we assumed that the stabilization of theintermediate spirophosphorane may be attained byintroducing a pyrocatechol fragment to the phosphorusatom. To this end we studied the reaction betweensilylthiobutanoneIIb and 2-chloro-1,3,2-benzodioxa-phospholeXXX . The reaction progress was monitoredby 31P NMR spectroscopy.

IIb +5KO

OPCl 7776

3Me3SiCl5KO

OPSCHCOMegMe

XXX XXXI

5KO

O"EEcc

Me

MeP9H

O

S+5K

O

OPOC=CSHgMe

76

XXXII XXXIII

We established that the reaction proceeded forseveral hours at room temperature to afford thiophos-phite XXXI (dP 227 ppm). The latter within 233 daysis converted into a mixture of two phosphorus-con-taining compounds: the main one is spirophosphoraneXXXII (dP 37 ppm, 1JPH 790 Hz), and the minorproduct is phosphiteXXXIII (~5%) (dP 130 ppm).On dissolving crystalline spirophosphoraneXXXII inthe 31P NMR spectrum again appear two signals atdP130 and37 ppm in 1 :19 ratio. We believe that thesignal at dP 130 ppm may be ascribed to vinylphosphite XXXIII that in solution occurs in anequilibrium with spirophosphoraneXXX . The cycleclosure in thiophosphiteXXXI is effected by electro-philic attack of phosphorus atom on the oxygen of thecarbonyl group. The existence of spirophosphoraneXXXII can be regarded as evidence for the schemesuggested earlier for the reaction between silylthio-butanoneIIb and chlorophospholaneXXII .

In the course of investigation of silylthiobutanoneIIb phosphorylation with phosphorus trichloride (at1 :1 ratio) by31P NMR method we fixed a formationof dichlorothiophosphiteXXXVa (dP 203 ppm) [13]which under the reaction conditions underwent cycliza-tion with liberation of hydrogen chloride to furnishoxathiaphospholeneXXVIIIa (dP 210 ppm).

IIb + RPCl2 776 ClPSCHCOMe3Me3SiCl

gRgMe

XXXIVa,XXXIVb

XXXVa,XXXVb

$??cc

Me

Me

O

OPR76

3HCl

XXVIII, XXXVI

XXXIV , R = Cl (a), Ph (b); XXXVI , R = Ph.

Similar reaction pattern is observed on treatingsilylthiobutanoneIIb with phenyl dichlorophosphineXXXIVb [13]. The reaction occurs at room tempera-ture and results in 2-phenyl-4,5-dimethyl-1,3,2-oxa-thiaphospholeneXXXVI (dP 164 ppm).

Summing up the properties of P(III) acids thio-esters containing a carbonyl group in theb-positionwe can state the following. The heterocyclization isfavored by enhanced electrophilicity of phosphorusatom, and further transformations are determined bythe character of substituent at P(III) atom. A newfeature of P(III) acids thioesters with a carbonyl groupin b-position is an easily occurring thiophosphite3thiophosphate rearrangement under effect of molecularoxygen.

4. Synthesis of Organophosphorus CompoundsStarting with 1-Trimethylsilylthio-2-trimethylsilyl-oxypropene and 2,2,4,5-Tetramethyl-1,3,2-oxathia-

silolene

A special place among organophosphorus com-pounds belongs to substances with a vinyl fragmentattached to phosphorus via heteroatom. The prepara-tion methods are sufficiently well developed and theproperties are studied for vinyl phosphites [14] andvinyl amidophosphites [15]. Vinyl thiophosphites arepoorly investigated due to the difficulty of theirsynthesis. The first vinyl thiophosphites were preparedby Yu.G. Gololobovet al. [16, 17]; they showed thaton heating the compounds can isomerize into thio-phosphonates [18].



In silylthiopropaneIVa synthesized by us two re-action centers are present: sulfur and oxygen atomslinked to a double C=C bond. Also there are readilyleaving trimethylsilyl groups. This structure is proneto form new unsaturated linear and cyclic compoundsin reaction with P(III) acids halides. As phosphorylat-ing agents was used a series of mono- and dichloro-phosphites, and phosphorus trichloride. Reaction ofcompoundIVa with diethyl chlorophosphiteXVIIIa ,diisopropyl chlorophosphiteXVIIIb , acid chlorideXXX , tetraethyldiamidochlorophosphiteXXXVIIoccurred only at sulfur atom and afforded substitutionproducts O,O-dialkyl-S-(2-trimethylsiloxy-1-propen-1-yl)thiophosphitesXXXVIII 3XLI [19]. The reactionscheme apparently includes an electrophilic attack ofP(III) atom on sulfur followed by elimination of tri-methylchlorosilane.

IVa + R2PCl 7776 R2PSCH=C3OSiMe3,gMe

3Me3SiClXVIIIa,XVIIIb,XXX,

XXXVII

XXXVIII 3XLI

R = OEt (XVIIIa, XXXVIII ), OPr-i (XVIIIb, XXXIX ),NEt2 (XXXVII, XL ), o-O2C6H4 (XXX, XLI ).

It should be noted that compoundsXXXIX andXLcontaining isopropyl and diethylamide substituentsattached to phosphorus exist as a single stereoisomer.Yet alkeneXLI is a mixture ofE andZ isomers. Theobserved distinctions are due apparently to a pheno-menon described in the literature: a decrease in theenergy barrier to rotation around C=C bond if donorand acceptor groups are bonded at different terminalcarbons of the alkene fragment [20]. On introductionto the phosphorus atom of an acceptor pyrocatecholsubstituent the energy barrier to rotation is reducedand consequently appears a mixture ofE and Zisomers.

The observed decrease in the yield of thiophosphiteXLI is caused by partial thermal degradation of theZ isomer resulting in 2-trimethylsilyl-1,3,2-benzodi-oxaphospholeXLII and thiirene that polymerizesunder the experimental conditions [21].

XLI 762KO

OPOSiMe3 + Me3C=C3Hei

S

9999

3

3

9999

3

3XLII

The easiest reaction is that between propeneIVaand chlorophospholaneXXX (at 310oC); reactionswith the other P(III) acids chlorides occur only at

heating to 1003120oC. The data obtained are con-sistent with the suggested reaction pattern includingan electrophilic attack of phosphorus on the sulfuratom. The second trimethylsilyl group linked tooxygen interestingly is not replaced by P(III) fragmenteven at long heating (at reagents ratio 1 :2).

The possibility of cyclization was demonstrated bythe example of reaction between compoundIVa withP(III) acids dichlorides. The reaction of propeneIVawith ethyl- XLIVa and isopropyl dichlorophosphitesXLIVb , and also with PCl3 XXXIVa afforded in highyield 1,3,2-oxathiaphospholenesXLIVa , XLIVb , andXLV .

IVa + RPCl2 777632Me3SiCl

XXXIVa,XXXIVb

K?ei

O

OPR

Me

H

XLIVa, XLV

R = OEt (XLIIIa, XLIVa ), OPr-i (XLIIIb, XLIVb ), Cl(XXXIVa, XLV ).

Oxathiaphospholenes were also obtained startingwith 2,24,5-tetramethyl-1,3,2-oxathiasiloleneV. Itsreaction with PCl3 (XXXIVa ) or Bu2NPCl2 (XLVI )is carried out at heating to 1303150oC for 1 h andgave rise to 1,3,2-oxathiaphospholenesXXXVIII andXLVII [6].

V + RPCl2 77763Me3SiCl2 $??cc

Me

Me

O

OPR

XXVIII, XLVII

XXXIVa,XLVI

R = Cl (XXVIII, XXXIVa ), NBu2 (XLVI, XLVII ).

The vinyl thiophosphites obtained unlike the earlierprepared alkyl(alkenyl)thiophosphites are not prone toisomerization either on heating or in the presence ofthe air oxygen [13, 18].

5. Reactions of Silylated Derivativesof a-Mercaptoacetic Acid and its Esters with P(III)

Acids Chlorides

Note that 1-trimethylsilylthio-2,2-bis(trimethyl-silyloxy)etheneX prepared by us is very sensitiveto various proton-donor reagents. For instance, thepresence in the reaction mixture of hydrogen chloridein even catalytic amounts results in immediate reac-tion of the latter with etheneX, and thus acid catalysisis impossible in reactions of compoundX with P(III)acids chlorides. This property may be used in moredetailed study of reaction mechanism and provides



wide possibilities for application of compoundX tothe synthesis of various organic and organophos-phorus unsaturated systems. We used as phosphorylat-ing agents diphenylchlorophosphineXLVIII , tetra-ethyldiamidochlorophosphiteXXXVII , diethyl chloro-phosphite XVIIIa , dioxaphospholeXXX , ethyl di-chlorophosphiteXLIIIa .

Reaction of etheneX and chlorophosphineXLVIIIproceeds at room temperature and yields thiophos-phinite XLIXa that decomposes at fractionation toafford O-trimethylsilyldiphenylthiophosphinate L(pathway a).

X + R2PCl 77763Me3SiCl

R2PSCH=C(OSiMe3)2

XLIXa 3XLIXc

Ph2P(S)OSiMe3 + [Me3SiOC=CH],

R2PSCHCOOSiMe3,gSiMe3

L

LIa, LIb

76a99999976b

7

R = Ph (XLIXa ), NEt2 (XLIXb, LIa ), OEt (XLIXc, LIb ).

The reaction of etheneX with chlorophosphiteXXXVII is similar to that with diphenylchlorophos-phine and affords thiophosphateXLIXb that at frac-tional distillation in a vacuum converts into com-poundLIa (pathwayb) due to O6C 1,3-migration ofa trimethylsilyl group [22]. Dissimilar paths of trans-formation occurring with intermediate compoundsXLIXa and XLIXb are due, on the one hand, tostabilization of vinyl thiophosphinate structureXLIXaby the presence of the phenyl groups at the centralatom, and on the other hand, to the possibility ofintramolecular processes resulting in the thermo-dynamically feasible thiophosphinateL .

The reaction of etheneX with diethyl chlorophos-phite gives rise to a mixture of two isomers,XLIXband LIb . As show31P NMR and IR spectra, at pro-longed standing thiophosphiteXLIXb is completelytransformed into isomerLIb [23]. Thus the reactionsof compound X with chlorides XVIIIa , XXXVII ,XLVIII proceed exclusively at sulfur atom to affordthe corresponding thioesters of P(III) acids that under-go rearrangement with O6C 1,3-migration of a tri-methylsilyl group. The driving force of the latterprocess is apparently the thermodynamical stabilityof the rearrangement product due to carboxy groupformation.

The second group of phosphorylating reagentscontains dioxaphospholeXXX , ethyl XLIVa , and

butyl dichlorophosphitesLII . The main characteristicof these compounds is a significantly increased elec-trophilicity of P(III) atom. The reaction of compoundX with acid chlorideXXX occurs at room temperatureand takes several days. As a result arises a thermallyunstable vinyl phosphiteLIII that in the process ofisolation transforms into phosphitesLIV (dP132 ppm) (pathwaya) andXLII (dP 122 ppm); cyclo-phosphiteLIV polymerizes within 4 days. The struc-ture of compoundLIV is confirmed by the presenceof a molecular ion (M+ 284) in the electron impactspectrum, and also by the appearance in the IR spec-trum of a band at 2150 cm31 corresponding to theC=C bond vibrations.

X + XXX 7776 KO

OPOC=CHSSiMe33Me3SiCl 5gOSiMe3

LIII

KO

OPOC=CSiMe35LIV

XLII + [Me33SiCH=C=O]

3Me3SiOH999997776

7776a

b

7

The first act of the transformations considered isthe replacement of trimethylsilyl group at the oxygenin etheneX by benzodioxaphospholene moiety withtrimethylchlorosilane elimination. As a result formscompound LIII (dP 134 ppm). The latter duringfractional distillation suffers two type transformations:It loses a trimethylsilanol molecule to afford unsatura-ted phosphiteLIV (pathwaya), and decomposes intosilyl phosphiteXLII and ketene that undergoes poly-merization (pathwayb).

The phosphorylation of etheneX with ethylXLIVa and butyl LII dichlorophosphites occurs atroom temperature within 24 h and affords 2-alkoxy-4-trimethylsilyl-1,3,2-oxathiaphospholan-5-ones (LVIIaand LVIIb ) [23]. Apparently the process includes anucleophilic attack of the oxygen from the trimethyl-silyloxy group on the trivalent phosphorus atom withliberation of trimethylchlorosilane and intermediateformation of vinyl phosphitesLVa andLVb (dP 1673169 ppm) that cyclize into unstable phospholenesLVIb which through O6C 1,3-migration of a tri-methylsilyl group afford the final phospholanonesLVIIa and LVIIb (dP 1443148 ppm).

The studies were further extended to phosphoryla-tion of an analog of alkeneX, compoundXVI , withacid chloridesXXXVII and XLVIII . The reaction ofcompound XVI with diamidochlorophosphiteXXXVII was found to furnish thiophosphiteLVIIIa(dP 121 ppm) that under the reaction conditions re-



X + ROPCl2 7763Me3SiCl

Me3SiS3CH=Cie

OSiMe3

OP(Cl)ORXLIIIa,

LIILVa, LVb

77763Me3SiCl K?ei

S

OP3OR

LVIIa, LVIIb

H

Me3SiO

KeS

OP3OR

HjMe3SiOqO

76

LVIIa, LVIIb

XLV 3XLVIII , R = Et (a), Bu (b).

arranged into isomeric compoundLIX (dP 124 ppm)(pathwaya) [12]. The addition of sulfur to the latterprovided dithiophosphateLX (dP 94 ppm).

76

a

b

9999976

XVI + R2PCl 7776 R2PSCH=COEt3Me3SiCl

XXXVII,XLVIII

LVIIIa, LVIIIb

gOSiMe3

7

R =ENEt2

R =Ph

(Et2N)2PSCHCOOEt76 (Et2N)2PSCHCOOEt,gSiMe3 gSiMe3oS1/8S8

LXLIX

L + [Me3SiO3C=C3H],

R = Et2N (a), Ph (b).

The reaction between etheneXVI and diphenylchlorophosphineXLVIII gives thermally unstablethiophosphinateLIXb (dP 32 ppm) that at fractiona-tion transforms into trimethylsilylthiophosphinateL(dP 68 ppm) [12]. Thus by an example of reactionsbetween silicon-containing alkenes X, XVI and P(III)acid chlorides was demonstrated that depending onthe structure of the latter was affected either sulfur oroxygen atom. These reactions are convenient prepara-tion methods for various cyclic and open-chain P,S,Si-containing compounds.

6. Phosphorylation of a-Mercaptoketoneswith P(III) Acids Halides and Amides

We described above silylation and stannylation ofa-mercaptocarbonyl compounds and the possibility touse the products obtained in the synthesis of functio-nalized organophosphorus compounds. We presumed

that unusual organophosphorus compounds might beobtained by direct phosphorylation ofa-mercapto-ketones whose molecules contained three reactivesites (mercapto and keto groups, and a labile protonof CH group) dictating the principal pathways of theprocess. No publications on these reactions existed,and to fill in this gap we studied the reactions of thea-mercaptoketones with some P(III) acids halides andamides.

MercaptoacetoneIa at room temperature does notreact with P(III) acids chlorides, the reaction occursonly at heating in benzene, and the synthetic result isnot affected by the reagents ratio. The main reactionproduct always is 2,5-dimethyl-2,5-endoxy-1,4-di-thione LXIa [22].

2Ia, Ib 776RPCl2 8==OdijdS

S

Me

R`H

HR`Me

LXIa, LXIb

R = Cl, OEt, NEt2; R` = H (a), Me (b).

In the similar way proceeds the reaction betweenmercaptobutanoneIb with P(III) acids chloridesaffording 2,3,5,6-tetramethyl-2,5-endoxy-1,4-dithioneLXIb [22]. Taking into account some published datawe can rationalize this uncommon direction of thereaction. Thea-mercaptoketones are known to under-go cyclization easily into sulfur-containing hetero-cycles in the presence of traces of mineral acids [24].In the case in question the reaction starts with forma-tion of a phosphorylated derivativeLXII accompaniedwith hydrogen chloride liberation. The latter effectsthe a-mercaptoketone condensation into the corres-ponding substituted dithioneLXI . The water liberatedin the process of condensation is consumed in reactionswith the P(III) acid chloride and with the phosphoryla-teda-mercaptoketoneLXII . In both cases arises meta-phosphorous acid chloride that eliminating the hyd-rogen chloride transforms into metaphosphite thatfurther polymerizes [25].

Ia, Ib + RPCl2 7647 RPSCHCOMe + HCl.ggCl

R`

LXII

The polymeric derivatives of the metaphosphorousacid are nondistillable viscous fluids of alternatingcomposition that prevents isolation thereof in anindividual state. Thus the research we carried out onthe reactions ofa-mercaptoketones and P(III) acidschlorides revealed the significant dissimilarity of their



chemical behavior from that of the oxygen and nitro-gen analogs.

To exclude the effect of hydrogen chloride the re-action of a-mercaptoketonesIa and Ib with phos-phorus trichlorideXXXIVa , ethyl dichlorophosphiteXLIIIa , and N,N-diethylamidodichlorophosphiteLXIIIb was performed in the presence of 2 equiv ofbase [22, 26, 27].

3Et3N .HClRPSCHCOMe7647 RPSC=CMegg

Cl

R` gR`g

Cl

gOH9999993

9999993

A B

7776

Ia, Ib + RPCl2XXXIVa,LXIIIa,LXIIIb

77763Et3N .HCl

Et3N

$??cc

R`

Me

O

OPR

LXIVa 3LXIVb

3 3

LXIV , R = NEt2, R` = H (a); R = OEt, R̀ = Me (b); R =NEt2, R` = Me (c).

The reactions occur at31035oC yielding unsatu-rated P,O,S-containing 5-membered heterocycles,1,3,2-oxathiaphospholenesLXVa 3LXVc [26, 27].Note that variation of the initial reagents ratio, reac-tion temperature, and solvent nature did not helps todetect the intermediate monochlorothiophosphitesA.This means that the heterocyclization rate in thepresence of a base is higher or equal to the rate offormation of the primary phosphorylation productA.The results obtained suggest the following pattern ofthe process [22]. At the first stage occurs phosphoryla-tion of thea-mercaptoketone to yield the intermediatecompoundA. It is known [28] that the CH-acidity oforganic compounds containing a thioalkyl group isconsiderably enhanced due to stabilization of theconjugate carbanion by the sulfur atom. Therefore theenolization of the intermediate compoundA should befavored and consequently the heterocyclization shouldoccur considerably easier than with the correspondingnitrogen and oxygen analogs. The heterocyclizationmay be described as a succession of equilibrium trans-formations including the attack of the oxygen fromthe carbonyl group on the phosphorus atom in theintermediateA, and the intramolecular phosphoryla-tion in the enol formB with simultaneous eliminationof hydrogen chloride.

Unlike the reaction of phosphorus trichloride with

the tertiarya-hydroxyketones that results in 1,3,2-di-oxaphospholenes with an exocyclic C=C bond [29],the similar reaction of 3-mercapto-3-methyl-2-buta-none LXV in the presence of triethylamine affordstris(1,1-dimethyl-2-oxopropyl)trithiophosphite (dP92 ppm).

PCl3 + 3HSCCOMegg

Me

Me $kcgMeMe

CH2 O

SPCl

P(SCCOMe)3gMe

gMe

777633Et3N .HCl

3Et3N999997776

3Et3N

LXVI

7

LXV

The phosphorylation of mercaptobutanoneLXVwith ethyl(butyl) dichlorophosphite in the presence of2 moles of triethylamine affords dithiophosphitesLXVIIa and LXVIIb [22].

LXV + ROPCl2 77762Et3N

3Et3N .HClROP(SCCOMe)2,gg

Me

MeLXVIIa, LXVIIb

R = Et (a), Bu (b).

The specific behavior of tertiarya-mercaptoketonesin the phosphorylation reveals in the lack of hetero-cycles among the reaction products. It is known thatP(III) acids thioesters more readily disproportionateinto thermodynamically stable trithiophosphites thantheir oxygen analogs [30]. Therefore probably thedisproportionation of the corresponding P(III) acidthioesters occurs faster than heterocyclization.

The above described data show that the phosphory-lation of variousa-mercaptoketones with P(III) acidsdi- and trihalides depending on the structure ofa-mercaptoketones results either in heterocyclization ordisproportionation products. There is no publisheddata on reactions between3mercaptoketones andmonohalides of P(III) acids. Yet the development ofmethods for the synthesis ofb-ketothiophosphiteswould have permitted application thereof as startingcompounds for creation of new types phosphorus-sulfur-containing structures. In this connection weundertook the study of phosphorylation ofa-mer-captoketones with monochlorides of P(III) acids.

The reaction of mercaptoacetoneIa and mercapto-butanone Ib with diethyl(diisopropyl) chlorophos-phites XVIIIa and XVIIIb and with chlorophos-



pholaneXX in the presence of triethylamine gave riseinstead of expected thioesters of P(III) acids to dialkylthiophosphonatesLXVIIIa 3LXVIIIc [13].

Ia, Ib + (RO)2PCl7776 (RO)2PSCH2COMe3Et3N .HCl

Et3N

XVIIIa,XVIIIb,

XX

76 (RO)2P(S)CH2COMe,LXVIIIa 3LXVIIIc

O2

LXX 3LXXII , R = OMe (a), OBu (b).

In the reactions of tri- and diamides of P(III) acids


we succeeded to fix the formation of intermediatephosphorylation productsLXIX whose chemicalshifts in the31P NMR spectra were in the range 1243175 ppm depending on the substituents at the phos-phorus atom. The process takes the second pathbwhen the mixture of an appropriate P(III) amide anda-mercaptoketone is heated to 130oC. Thus in contrastto the behavior ofa-hydroxyketones thea-mercapto-ketones in reactions with P(III) amides can take a newroute resulting ina-mercaptoketones desulfurizationand in diamidothiophosphates formation. This pro-perty of thea-mercaptoketones is consistent with thepublished data on P(III) amides sulfurization effectedby mercaptans [33].

Ia + RP(NEt2)2

RPSCH2COMe76$??cO

SPR

Me+ RPSCH2COMe,ogS

NEt2g

NEt2LXIX LXXa, LXXb LXXIa, LXXIb

7763Et2NH477

776 RP(S)(NEt2)2 + MeCH2COMe,

999999 b

a

LXIIa, LXIIb LXIII

7

LXX 3LXXII, R = OMe (a), OBu (b).ÄÄÄÄÄÄÄÄÄÄÄÄ

It is necessary to note that the pathwayb resultingin thioamodophosphates formation is irreversiblewhereas the phosphorylation ofa-mercaptoketones(route a) is a reversible process. The equilibrium canbe shifted to the initial compounds by diethylaminethat liberates in the first stage of the process (if thereaction is carried out under rigid conditions withoutelimination of diethylamine from the reaction sphere),or by the action of diethylamine evolving in thecourse of heterocyclization (the latter process resultsin decreased yield of 1,3,2-oxathiaphospholenes).Among the significant results of the investigation onreactions betweena-mercaptoketones and P(III) acidsamides and chlorides should be mentioned the de-velopment of preparation methods for new unsaturatedP,S-containing heterocycles, 1,3,2-oxathiaphospho-lenes, possessing interesting chemical properties.

7. Chemical Propertiesof 1,3,2-Oxathiaphospholenes

Chemical behavior of 1,3,2-oxathiaphospholenes isdetermined by the presence in the molecule of severalreactive sites (trivalent phosphorus atom, thiol sulfur,C=C bond), and also by mutual influence of the un-saturated cyclic fragment and the phosphorus atom.

To establish more complete understanding of thespatial arrangement and electron density distributionin the 1,3,2-oxathiaphospholenes we investigated themolecular structure of 2-chloro-5-methyl-1,3,2-oxa-thiaphospholene by means of gas phase electrono-graphy [34], and measured photoelectronic spectra ofsome 1,3,2-oxathiaphospholenes [35]. The data of gasphase electronography [34] indicated that the mole-cular structure of 2-chloro-5-methyl-1,3,2-oxathia-phospholene corresponded to P-envelope with an axialP3Cl bond. From the photoelectronic spectra (ioniza-tion potentials, eV) of some oxathiaphosphacyclanes-(cyclenes) [35] was established that the unsaturatedoxathiaphospholene ring was more electron-withdraw-ing (9.36 eV for 2-chloro-5-methyl-1,3,2-oxathia-phospholene) than the saturated oxathiaphospholaneone (9.16 eV for 2-chloro-5-methyl-1,3,2-oxathia-phospholane). Note that the ionization potential of2-chloro-1,3,2-dioxaphospholane (10.2 eV) is con-siderably higher than that of the sulfur analog. There-fore the ionization potential of 1,3,2-dioxaphospho-lenes should be significantly higher than that of 1,3,2-oxathiaphospholenes. The ionization potential valuescharacterize the nucleophilic nature of the phosphorusatom in these systems: The increase in the ionizationpotential evidences the reduced nucleophilicity of the



phosphorus atom. Therefore 1,3,2-oxathiaphospho-lenes should easier react with electrophilic reagentsthan 1,3,2-dioxaphospholenes. This fact provides apossibility to synthesize 1,3,2-oxathiaphospholeneswith tetra- and pentacoordinate phosphorus. On theother hand, the strength of the oxathiaphospholenering can be evaluated by reactions with proton-donorreagents.

7.1. Reaction of 2-Substituted1,3,2-Oxathiaphospholenes with Proton3Donor

Reagents and P(III) Acids Dichlorides

The high stability of 1,3,2-oxazaphospholines and1,3,2-dioxaphospholenes against the proton-donorreagents is well known: The hydrolysis thereof re-quires fairly rigid conditions [36]. In order to comparethe chemical properties in the series of 1,3,2-dihetero-phosphacyclenes we studied reactions of 2-substituted


1,3,2-oxathiaphospholenes with alcohols, phenols, andcarboxylic acids under previously applied conditions[36, 37].

2-Diethylamino-5-methyl-1,3,2-oxathiaphospho-lene (LXIVa ) reacts with ethanol at 70380oC withcleavage of the endocyclic P3O and P3S bonds, withconservation of the P3N fragment yielding diethyl-amidophosphiteLXXIV and mercaptoacetone. Thehighest yield of these products is attained at the use of2 equiv of ethanol.

Yet in reaction of oxathiaphospholeneLXIVa withphenol as show by31P NMR spectra the first bond torupture is P3N to afford phospholeneLXXV (dP166 ppm) that in the course of further phenolysis firstgives phosphiteLXXVI (dP 132 ppm), and then tri-phenylphosphite (dP 128 ppm).

(EtO)2PNEt2 + MeCCH2SH,oO

LXXIV

$??cO

SPOPh

Me776PhOH (PhO)2POC=CHSH776 (PhO)3P.gMe

PhOH

776

776

999999

7

2EtOH

PhOH

3Et2NH

LXIVa

LXXV LXXXVI


The different way of reacting showed by oxathia-phospholeneLXIVa with alcohols and phenols isapparently due to decrease in nucleophilicity and in-crease in acidity in going from ethanol to phenol. Inthe first case occurs the nucleophilic attack of theethanol molecule on the electrophilic phosphorusatom of compoundLXIVa with the rupture of an en-docyclic P3O or P3S bond, whereas in the secondcase the exocyclic nitrogen atom is initially proto-nated, and the diethylamino group is then replaced byphenoxy group. Similarly occurs the reaction betweenoxathiaphospholeneLXIVa with the acetic and tri-fluoroacetic acids resulting in the correspondingphosphacyclanesLXXVIIa and LXXVIIb [37].

LXIVa + 2HX 77763Et2NH .HX $??cO

SPX

Me

LXXVIIa, LXXVIIb

LXXVII, X = OCOMe (a), OCOCF3 (b).

The replacement of the exocyclic diethylamino orethoxy group was observed in reactions of oxathia-

phospholenesXLIVa and XLIVb with ethyl di-chlorophosphite and diethylaminodichlorophosphite[37].

7.2. Reaction of 2-Chloro-1,3,2-oxathiaphospholeneswith N,O-Bis(trimethylsilyl)acetamide

and Hexamethyldisilazane

The phosphorylation ofN,O-bis(trimethylsilyl)-acetamide with 2-chloro-1,3,2-oxathiaphospholenes atheating provides 2-trimethylsiloxy-1,3,2-oxathiaphos-pholenesLXXIXa 3LXXIXc in 75380% yield [38].

77763Me3SiCl $??cO

SPNCOMe

R

cR`gSiMe3

7763MeCN $??cO

SPOSiMe3

R

cR`

$??cO

SPCl

R

cR` + MeCON(SiMe3)2

LXXVIIIa 3LXXVIIIc LXXIXa 3LXXIXc

LXXVIII, LXXIX, R = Me, R̀ = H (a); R = R̀ = Me (b);R = R̀ = (CH2)4 (c).



Note that at performing these reactions under mildconditions we succeeded in observing the formation ofintermediate compoundsLXXVIII with chemicalshiftsdP 1393142 ppm. Aiming at functionalization of2-chloro-1,3,2-oxathiaphospholenes we appliedanother well-known silylating reagent, hexamethyldi-silazane. The reaction of 2-chloro-1,3,2-oxathiaphos-pholenes with the hexamethyldisilazane was carriedout at 150oC with distilling off the liberated trimethyl-chlorosilane, and it gave rise to 2-trimethylsilylamino-1,3,2-oxathiaphospholenesLXXXa and LXXXab .

$??cO

SPCl

Me

cR + HN(SiMe3)2

77763Me3SiCl $??cO

SPNHSiMe3

Me

cRLXXXa, LXXXb

R = H (a), Me (b).

7.3. Reactions of 2-Substituted1,3,2-Oxathiaphospholenes with Sulfur,Thiophosphoryl Chloride, Alkyl Iodides,

and Diketones

2-Dialkylamino(alkoxy)-1,3,2-oxathiaphospholenesadd sulfur only at heating (120oC, 0.5 h) to afford inhigh yield 2-substituted 2-thioxo-1,3,2-oxathiaphos-pholenes LXXXIa3LXXXIac [39].

$??cO

SPR

Me

c + 1/8S8 76Me $??

cO

SPR

Me

cMe

D oS

LXXXa 3LXXXc

R = NEt2 (a), NBu2 (b), OEt (c).

Oxidation of 2-substituted 1,3,2-oxathiaphospho-lenes with dimethyl sulfoxide (4 h, 100oC) furnishedthe corresponding phospholenesLXXXIIa andLXXXIIb [39].

$??c

PRMe

+ Me2SO 776S

O3Me2S $??c

P(O)RMe S

O

LXXXIIa, LXXXIIb

R = NEt2 (a), OEt (b).

The reaction of 2-ethoxy-5-methyl-1,3,2-oxathia-phospholeneXLIVa with methyl iodide occurs atheating (2 h, 1003120oC) and provides 2,5-dimethyl-

2-oxo-1,3,2-oxathiaphospholenesLXXXIIIa andLXXXIIIb [39]. Under more rigid conditions pro-ceeds the reaction between 2-ethoxy-5-methyl-1,3,2-oxathiaphospholene and benzyl iodide [40].

XLIVa + RI 76 $??cO

SP

Me hfOEt

RI3

999999

3

3

+999999

3

3

763EtI $??cO

SP(O)R

Me

LXXXIIIa, LXXXIIIb

LXXXIII , R = Me (a), CH2Ph (b).

2-Thioxo-2-chloro-1,3,2-oxathiaphospholenesLXXXIVa and LXXXIVb were prepared by heating(0.5 h, 150oC) of a mixture of 2-chloro-1,3,2-oxathia-phospholenes with thiophosphoryl chloride [39].

$??cO

SPCl

Me

cR + P(S)Cl3 7763PCl3 $??cO

SP(S)Cl

Me

cRLXXXIVa, LXXXIVb

R = H (a), Me (b).

The heating of oxathiaphospholeneLXXXIVbwith phosphorus pentasulfide in the presence ofcatalytic amount of AlCl3 (2 h, 1703180oC) provided2-thioxo-2-chloro-4,5-dimethyl-1,3,2-dithiaphospho-lene LXXXV (dP 99 ppm) [39].

5LXXXIVb + P2S5 7763P2O5

AlCl3

$??cS

SP(S)Cl

Me

cMe

LXXXV

CompoundLXXXV apparently arises in keepingwith the scheme suggested for the reaction of 2-thioxo-2-chloro-D4-1,3,2-oxaazaphospholene with the phos-phorus pentasulfide in the presence of AlCl3, and thereaction includes several stages with the initial oneconsisting in cleavage of the cyclic fragment underthe action of AlCl3 [41].

Compounds containing pentacoordinate phosphorusand P3S bond are virtually unknown. The reactions of2-diethylamino-5-methyl-1,3,2-oxathiaphospholeneLXIVa with diacetyl and dibenzoyl afford new bi-cyclic spirophosphoranesLXXXVIa and LXXXVIb ,light yellow viscous fluids with specific odor [39].



LXIVa +O=C3RgO=C3R

76 $??cO

S

Me

"EEPO

O

cc

R

R

9NEt2

LXXXVIa, LXXXVIb

LXXXVI , R = Me (a), Ph (b).

7.4. Reactions of 2-substituted1,3,2-Oxathiaphospholenes with Acyl Halides

The reactions of trivalent phosphorus acids thio-esters with carboxylic acids halides are known toafford P(III) acids halides and thiol esters of thecarboxylic acids [42]. In this connection it was inte-resting to investigate the reactions of 2-substituted1,3,2-oxathiaphospholenes with various acyl halidesand to look for reactions with ring opening.

OxathiaphospholeneLXIVa reacts with acetyl andbenzoyl chlorides in benzene at 0oC affording chloro-thiophosphiteXLV [43].

LXIVa + RC(O)Cl 76 XLV + RC(O)NEt2.

The physical constants of oxathiaphospholeneXLV are in agreement with those of an analogouscompound obtained earlier [26].

OxathiaphospholeneLXIVa with acetyl bromideprovides cyclic bromothiophosphiteLXXXVII . Bymeans of dynamic31P NMR spectroscopy were ob-served the following variations with time after mixingthe reaction mixture of oxathiaphospholeneLXIVaand acetyl bromide at310oC: The signal of theoriginal phospholeneLXIVa at dP 147 ppm rapidlydecreased, and a peak appeared atdP 180 ppm cor-responding to the intermediateS-(1-acetylthio-1-propene-2-yl)-N,N-diethylamidobromophosphiteLXXXVIII that in 5310 min became the principal


signal, and then it decreased with simultaneous ap-pearance of a resonance atdP 237 ppm belonging tobromophospholeneLXXXVII .

LXIVa + MeCBr76oO

CoC

djdjH

Me OPjdBr

NEt2

SCMeoO

LXXXVIII

$??cO

S

MePBr+ CH3C(O)NEt2

LXXXVII

76

Thus at lower reaction temperature we were ableto observe the formation of intermediate compoundLXXXVIII and to describe the reaction of phos-pholene LXIVa with acetyl bromide includingprimary rupture of the endocyclic P3S bond.

The reaction of ethoxyphospholeneXLIVa withacetyl bromide occurs at room temperature to yieldbromophospholeneLXXXVII (dP 237 ppm) andO-ethyl-O-(1-acetylthio-1-propen-2-yl)acetylphos-phonateLXXXIX (dP 38 ppm) as a mixture ofZ andE isomers [43]. In keeping with the data obtained inthe study of the reaction between phospholeneLXIVaand acetyl bromide by31P NMR spectroscopy thefollowing reaction scheme may be assumed for thereaction of phospholeneXLIVa with acetyl bromide[43]. At the first stage of the reaction occurs cleavageof the P3S bond of the oxathiaphospholene ring underthe action of acetyl bromide affording an intermediateC that undergoes disproportionation into vinyl phos-phitesD andE. The heterocyclization of intermediateD provides reaction productLXXXVII , and reactionof the liberated acetyl bromide with phosphiteEfinally results in ketophosphonateLXXXIX .

CoC

djdjH

Me OPjdBr

OEt

SCMeoO

99999999

3

3

99999999

3

3

22LXIVa + 2MeCBr76oO

7647

C D E

CoC

djdjH

Me OPjdBr

Br

SCMeoO

99999999

3

3

CoC

djdjH

Me OPjdOEt

OEt

SCMeoO

99999999

3

3

76 LXXXVII + CoC

djdjH

Me OPjdC(O)CH3

OEt

SCMeoO

+ MeCBr.oO

LXXXIX



Unlike acetyl bromide, benzoyl chloride reacts withoxathiaphospholeneXLIVa only at heating (3 h,1003110oC) yielding chlorophospholeneXLV andO,O-diethyl benzoylphosphonateXC (dP 32 ppm)[43]. The formation of the final reaction products maybe described by a series of successive transformation:opening of the heterocycle at P3S bond; disproporti-onation of compoundC, heterocyclization of dichloro-phosphiteD, and reaction of benzoyl chloride withvinyl phosphiteE. It is known that vinyl phosphitesreact with acetyl halides conserving the unsaturatedfragment of the molecule [44]. Abnormal behavior ofcompoundE in the reaction with benzoyl chloride isdue to the following reasons. According to the pub-lished data, in the aromatic sulfur-containing hetero-cycles (1,3-dithiolium salts) [45] the cation is sta-


bilized by a phenyl substituent and destabilized by analkyl one. In keeping with these findings we canpresume that at elevated temperature apparentlyoccurs an equilibrium between structuresF and G,and the positive charge in cationG is delocalized andstabilized by the phenyl group.

99djdjR

R`

O3P(OEt)2

S3C3PhoO

7647 $.......+O

S

cc

R

R`

cPh

O-_P(OEt)23

F G

Although the concentration of theG form is low itis the most reactive one and it reacts with the benzoylchloride to yield ketophosphonateXC and vinylchloride.

CoHC

djd

R OPjdCl

OEt

SCPhoO

99999999

3

3

7647

CoC

djdjR`

R OPjdCl

Cl

SCPhoO

99999999

3

3

CoC

djdjR`

R OPjdOEt

OEt

SCPhoO

99999999

3

3

oO

2XLIVa + 2PhCCl7647D

99999999

3

3

2

7776 XLVI + (EtO)2PCPh +3PhC(O)Cl

oOoO

CoC

djd

R Cl

SCMeoO

99999999

3

3

jR`

99999999

3

3XC


Thus during the study of reactions between 2-ethoxy-1,3,2-oxathiaphosphonates with acyl halideswas found a new reaction route including ring openingfollowed by transformation of the intermediatelyformed vinyl phosphates. The above reaction schemeswere supported by simulation of the intermediatestages.

By reaction of S-acetyl(benzoyl)mercaptoacetoneswith diethyl and pyrocatechol chlorophosphites in thepresence of triethylamine were obtained vinyl phos-phites XCIa3XCIc [46].

RCSCH2CMe + ClPR2̀ 77763Et3N.HCl

Et3N RCSCH=CCH3,oOoO

oOgOPR̀2

XCIa3XCIc

R = Me, R̀ = OEt (a); R = Ph, R̀ = OEt (b); R = Me,R` = o-OC6H4O (c).

The reactions of vinyl phosphitesXCIa3XCIc withacetyl bromide and benzoyl chloride were carried outat the same temperature as used in the simulatedprocesses.

It was established that although the reaction ofcompound XCIa with acetyl bromide occurred atroom temperature, yet the reaction with benzoylchloride required prolonged heating to 1003110oC. Inboth cases were isolated the corresponding ketophos-phonatesLXXXIX , XCII . Their structure was con-firmed by 1H, 31P, and IR spectra, and also by com-parison of the physical constants of compoundLXXXIX with those of a model compound.

The reaction of vinyl phosphiteXCb with benzoylchloride was carried out at 1003110oC for 233 h. Themain product was benzoylphosphonateLXXXIX .

Thus the simulation of separate stages of the reac-tion between oxathiaphospholeneXLIVa with acylhalides confirmed the validity of the assumed schemes,



CoC

djdjH

Me OPjdC(O)R̀

OEt

SCMeo

oOR`C(O)X

3EtX

O

LXXXIX, XCII

XC + PhCSCH=CMeoOg

Cl

99999

3

3

99999

3

3

999999999999

7777776

7777776R = Ph, PhC(O)Cl

XCIa, XCIb 7

R` = Me (LXXXIX ), Ph (XCII ).

and the b-functionally substituted vinyl phosphitesturned out to be interesting objects for heterocycliza-tion process study.

The capability to transformations of vinyl phos-phites with a functional group in theb-position was


also observed in the reactions of compoundsXCIaand XCIb with trimethylsilyldiethylamine XCIII .This reaction occurred at 1203130oC and yieldedO,O-diethyl-S-(2-trimethylsiloxy-1-propen-1-yl)-4,5-benzo-1,3,2-dioxaphospholaneXCVb . Alongside thiscompound were isolatedO,O-diethyl-N,N-diethyl-amidophosphite XCVIIa or 2-diethylamino-1,3,2-benzodioxaphospholeXCVIIb [46].

The monitoring of the reaction progress by31PNMR spectroscopy demonstrated that after heating ofthe reaction mixture for 30 min to 1203130oC in thespectrum was observed a signal atdP 1363138 ppmcorresponding to intermediate compoundsXCIVa andXCIVb ; as the heating was continued appeared thesignals of the reaction productsLXXXIVa andLXXXIVb (dP 184 and 187 ppm). Taking intoaccount the data in the literature on the reaction ofsilylated amines with thioacetic acid esters [47] thefollowing scheme of reaction may be presumed.

C=Ceiei

Me

R2PO

H

SSiMe376

1C=C ,eiei

Me H

SPR2Me3SiOXCIVa, XCIVb XCVa, XCVb

C=Ceiei

Me H

SCMeMe3SiO oO

+ R2PNEt2 76 XCVa, XCVb .02

3MeC(O)NEt2777776

a, D

777776

9999999 b

7XCIa, XCIb + Me3SiNEt2XCIII

XCVI

LXXIVa,LXXIVb,XCVIIa,XCVIIb

XCIV, XCV, XCVII , R = OEt (a), o-OC6H4O (b).ÄÄÄÄÄÄÄÄÄÄÄÄ

The presence in compoundsXCIa and XCIb oftwo reactive sites (a phosphorus atom and a carbonatom of carbonyl group) provides a possibility of tworeaction pathways. At greater electrophilicity of thephosphorus in compoundXCIb the prevailing route isb, and in vinyl phosphiteXCIa it is the pathwaya.The forming intermediateXCIV is unstable and underthe experimental conditions it provides thiophosphitesXCVa and XCVb via S6O 1,4-exchange migrationof trimethylsilyl and phosphorus-containing groups.The experimental data show that no compoundXCVaand XCVb arises in reactions of 1-acetylthio-2-tri-methylsiloxy-1-propeneXCVI with amidophosphitesXCVIIa and XCVIIb . This unusual synthetic out-come, the occurrence of the S6O 1,4-exchangemigration of trimethylsilyl and phosphorus-containinggroups, demonstrates the great synthetic potential of

vinyl phosphites with a sulfur atom linked to variousmoieties located inb-position.

Thus the investigations of the reactions betweenS-acetylated a-mercaptoketones with P(III) acidshalides revealed the curious transformations of vinylphosphites (intramolecular rearrangement including anS6O 1,4-exchange migration of trimethylsilyl andphosphorus-containing groups; heterocyclization into1,3,2-oxathiaphospholenes). Into the range of reac-tions under study are included the disproportionationprocesses leading to 1,3,2-oxathiaphospholenes, andalso to ketophosphonates and to the other compounds.These transformations on the one hand support theassumed schemes of reactions between 1,3,2-oxathia-phospholenes, and on the other hand possess indepen-



dent value permitting preparation of compounds withvinylthiol moiety.

As a whole the investigation of reactions betweena-mercaptoketones and P(III) acids chlorides andamides revealed the specific features of the chemicalbehavior of thea-mercaptoketones that was distinctfrom their heteroanalogs (a-amino-, a-hydroxy-ketones). Besides as a result of the investigationsperformed were developed synthetic procedures forpreparation of oxathiaphospholenes and P(III) acidsthioesters containing in thea-position a keto group.The compounds obtained are unquestionably interest-ing for the synthesis of new functionalized derivativesof organic, and in particular organoelement, com-pounds.

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phosphorylated, silylated, and stannylated derivatives of α-mercaptocarbonyl compounds

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