sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds
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Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds
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2001 Russ. Chem. Rev. 70 655
(http://iopscience.iop.org/0036-021X/70/8/R03)
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Abstract. Data on the use of sulfonium ylides in the synthesis ofData on the use of sulfonium ylides in the synthesis ofcarbocyclic and heterocyclic compounds published over the lastcarbocyclic and heterocyclic compounds published over the last15 years are analysed, systematised and generalised. The bibliog-15 years are analysed, systematised and generalised. The bibliog-raphy includes 139 referencesraphy includes 139 references..
I. Introduction
The chemistry of ylides attracted considerable interest in the early1950s after Wittig has discovered the reaction of phosphoniumylides with carbonyl compounds giving rise to alkenes.1 Inves-tigations carried out by Corey 2 and Franzen 3, 4 extended theWittig reaction to sulfur ylides and initiated extensive studies ofsulfonium ylides. The further development of the chemistry ofthese compounds demonstrated that they could be widely used inorganic synthesis.
Sulfur ylides contain a negatively charged carbon atomdirectly bound to a positively charged sulfur atom. In the generalform, these compounds can be represented by two resonancestructures, viz., ylide 1 and ylene 2.5
Sulfonium (1) and sulfoxonium (3) ylides containing twoorganic substituents at the sulfur atoms are most often used inorganic synthesis.6 ± 9 Sulfinyl ylides (4), sulfonyl ylides (5),thiocarbonyl ylides (6) and iminosulfuranes (7) are also known.8
Sulfur ylides act as nucleophilic reagents, their reactivitiesbeing inversely proportional to their stability. Ylides are stabilisedthrough the electron density delocalisation under the action ofelectron-withdrawing substituents at the carbanionic centre. Theproperties of stabilised sulfur ylides are summarised and com-paredwith the properties of non-stabilised ylides in reviews.6, 10, 11
The reactions of sulfur ylides with compounds containingC=X bonds (X=O, C or N) gained wide acceptance in organicsynthesis. These reactions proceed as the nucleophilic additionfollowed by 1,3-elimination of a sulfur-containing group to formepoxide, cyclopropane or aziridine, respectively.6
The data on these reactions were surveyed in detail in themonograph 6 and in a series of studies.7, 12 ± 16 Due to theirzwitterionic character, sulfonium ylides are also widely used inrearrangements generating new C7C bonds (often with highstereo- and regioselectivity).16 ± 20 In the last decade, interest insulfur ylides was quickened owing to their successful use inasymmetric synthesis.16 A one-stage procedure, which has beendeveloped recently for the synthesis of optically active epoxidesand aziridines,21, 22 represents a considerable achievement in thisfield. Optically pure sulfur ylides, which are generated in situ inreactions of catalytic amounts of chiral sulfides with diazocompounds in the presence of dirhodium tetraacetate or copperacetylacetonate, react with aldehydes or imines to give epoxides oraziridines, respectively, and the sulfide is recovered and recycled tothe catalytic cycle. This procedure was used for the syntheses ofvarious substituted epoxides and aziridines in good yields andwith high enantioselectivity.16, 23 ± 25
+ 7S C S C
1 2
+ 7+ 7++ 7
S
O
S C
O
S C NS
3 4 5 6 7
7+S C
O
O
7C
X= O, C, N.
CX
R4 R3
C
H R2
7R12S
+ 7R1
2S CHR2CX
R4
R3
C
HR2R1
2S+
7CX
R4
R3
S N Lakeev, I OMaydanova Institute of Biology, Ufa Scientific Centre of
the Russian Academy of Sciences, prosp. Oktyabrya 69, 450054 Ufa,
Russian Federation. Fax (7-347) 235 26 41. Tel. (7-347) 235 53 41.
E-mail: [email protected] (S N Lakeev)
F Z Galin Institute of Organic Chemistry, Ufa Scientific Centre of the
Russian Academy of Sciences, prosp. Oktyabrya 71, 450054 Ufa,
Russian Federation. Fax (7-347) 235 60 66. Tel. (7-347) 235 52 88.
E-mail: [email protected]
G A Tolstikov N N Vorozhtsov Novosibirsk Institute of Organic
Chemistry, Siberian Branch of the Russian Academy of Sciences,
prosp. Akad. Lavrent'eva 9, 630090 Novosibirsk, Russian Federation.
Fax (7-383) 234 47 52. Tel. (7-383) 234 38 50. E-mail: [email protected]
Received 21 December 2000
Uspekhi Khimii 70 (8) 744 ± 762 (2001); translated by T N Safonova
DOI 10.1070/RC2001v070n08ABEH000645
Sulfur ylides in the synthesis of heterocyclic and carbocycliccompounds
S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
Contents
I. Introduction 655
II. Rearrangements of cyclic sulfur ylides 656
III. Intramolecular cyclisation of sulfur ylides 665
IV. Reactions of thiocarbonyl ylides 667
V. Cycloaddition of ylides to alkenes 669
Russian Chemical Reviews 70 (8) 655 ± 672 (2001) # 2001 Russian Academy of Sciences and Turpion Ltd
Sulfur ylides also find wide application in the synthesis ofother cyclic compounds as well as of hetero-, macro- andpolycyclic structures, including natural compounds and theiranalogues. Special-purpose reviews devoted to this aspect arelacking. The only study dealing with this problem 13 has coveredthe results published up to 1986 inclusive. The present reviewsurveys the data on the use of sulfur ylides in syntheses of complexcyclic, heterocyclic and natural compounds published over the last15 years. Systematisation and analysis of the available data willhelp in evaluating the possibilities of the use of sulfur ylides in thesynthesis of complex structures and give a deeper insight intoprospects of the further development of this line of investigation.Reactions of ylides giving rise to three-membered carbo- andheterocycles are beyond the scope of the present review.
II. Rearrangements of cyclic sulfur ylides
Sigmatropic rearrangements of cyclic sulfur ylides were inves-tigated in most detail. In these studies, sulfur ylides were used inthe synthesis of various carbo- and heterocyclic compounds. Thereactions are carried out with the use of either ylides generated insitu or individual compounds prepared in advance. The 1,2-Stevens rearrangements 18, 20 and 2,3-sigmatropic rearrangementsof sulfur ylides find most extensive synthetic applications.16 ± 20, 26
1. 1,2-Stevens rearrangementsThe 1,2-Stevens rearrangements of sulfur and nitrogen ylides werediscovered in 1928.27 According to orbital symmetry rules, theconcerted mechanism of this thermal rearrangement is forbid-den.28 Hence, the most probable mechanism involves the dissoci-ation ± recombination process. It was demonstrated 29, 30 that therearrangements proceed through the formation of a radical pair,the rate of radical recombination being higher than the rate oftheir diffusion into a solvent.
The employment of rearrangements of sulfur ylides in thesynthesis of cyclic compounds appeared to be particularly prom-ising in connection with the development of the carbene methodfor the generation of cyclic sulfur ylides.20, 31 ± 34 Ylides are formedthrough the electrophilic addition of a carbenoid species, which isgenerated from the diazo group under the action of transitionmetal (predominantly, Rh or Cu) compounds, to the sulfuratom.34 These reactions are most often performed with stablediazoesters or diazoketones. Recently,35, 36 it was demonstratedthat trimethylsilyldiazomethane can also be successfully used forthe generation of sulfur ylides.
Sometimes the process is complicated by a side reaction ofinsertion of the carbene formed into the C7H bond. Thusintramolecular cyclisation of diazosulfide 8 afforded not only themajor reaction product 9, generated through the 1,2-rearrange-ment of intermediate unstable tricyclic thiophenium ylide 10, butalso a product of insertion into the C7H bond (11).37
New stable four-to-seven-membered cyclic ylides were syn-thesised by intramolecular cyclisation of diazosulfides and theirthermal rearrangements giving rise to heterocyclic compoundswere carried out virtually simultaneously by two independentresearch groups.38 ± 40 It was demonstrated 38, 39 that six- andseven-membered cyclic ylides 12a,b underwent the 1,2-Stevensrearrangement on heating to give the corresponding substitutedcyclic thioesters 13a,b in 40%± 60% yields.
Decomposition of the diazoallyl sulfide 12b catalysed byRh2(OAc)4 afforded directly the rearranged thiepane 13b (theyield was 59%); intermediate cyclic sulfonium ylide was notdetected. The fact that the thiepane 13b was formed through the2,3-rearrangement rather than through the [1,2]-shift was exem-plified by the reactions of diazosulfides 12c ± e containing theprenyl, cinnamyl or crotyl substituent at the sulfur atom, whichwere accompanied by the allylic inversion.
On heating, four- (14) and six-membered S-phenyl-substi-tuted (15) sulfur ylides underwent the 1,4-rearrangement to formderivatives of dihydro- (16) and tetrahydrofuran (17), respec-
X =Me3Si(CH2)2SO2N, O; ML= Rh2(OAc)4 , Cu(acac)2 .
+ 7
R22S
R22S CHR3
X
R1
X
R1 R2
ML
LM
R3
HN2
N2R3
7
S
R3
R2R1+
SR3R1
R2 *1,2R2
R1 SR3
+ 7C N2
ML
7N2
S
C ML S C
MeO2CCC O
N2 8
S
7
Rh2(OAc)4
S+
O
CO2Me
*1,2
S
O
CO2Me
S
OHMeO2C
10 9
11
R= Bn, n=1 (a); R=H2C=CHCH2 , n= 2 (b).
+ 7
(H2C)n
N2RS
O
CO2Et
Rh2(OAc)4
PhH, D(H2C)n
O
CO2EtSR
D
12a,b
(H2C)n
O
CO2EtS
R13a,b
+ 7
(H2C)n
N2S
O
CO2Et
Rh2(OAc)4 (H2C)n
O
CO2EtS
D
12c ± eR1 R2 R1 R2
R1
R2
(H2C)n
O
CO2EtS
13c ± e
R1=R2=Me, n=1 (c); R1=Ph, R2=H, n=2 (d);
R1=Me, R2=H, n=2 (e).
656 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
tively.40 Seven-membered and some six-membered cyclic ylidesdecompose giving rise to unsaturated sulfur-free compounds.40
The 1,2-rearrangement of cyclic ylide 18 stabilised by twoethoxycarbonyl groups, which was formed in the reaction of 2,3-dihydroisothiazol-3-one with diazomalonic ester, was accompa-nied by insertion of carbene into the S7N bond to form 3,4-dihydro-1,3-thiazin-4(2H )-one 19.41
Substituted 1,3-dithianes 20 were synthesised by the 1,2-rearrangement proceeding with the cleavage of the S7S bond ofintermediate 1,2-dithiolane ylides 21.42 The ylides 21 were gen-erated by the reactions of cyclic disulfides with carbenes, whichwere prepared from diazo compounds under conditions of cata-lytic or photochemical reactions. If cyclic disulfides contain morethan four substituents, the C7S bond in the ylides 21 can becleaved. Subsequent desulfation of intermediates 22 affordedthietanes 23.
The generation of cyclic ylides by intramolecular reactions ofsulfur-containing compounds with carbenes followed by theirthermal rearrangements was successfully used in the synthesis ofcarbocyclic natural compounds. Thus the 1,2-rearrangement ofylide 24 proceeded with ring contraction to give substitutedcyclopentane 25. The latter served as the key compound in thesynthesis of sesquiterpenes (�)-cuparene (26) and (�)-laurene(27).43, 44
An analogous strategy was applied to the synthesis of pyrro-lizidine alkaloids, viz., (�)-trachelanthamidine (28a), (�)-isore-tronecanol (28b) and (�)-supinidine (29).45, 46 Diazoketone 30wasconverted under the action of a rhodium catalyst into bicyclicsulfonium ylide 31 whose subsequent rearrangement afforded acompound of the pyrrolizidine series (32). The latter was used forthe synthesis of the alkaloids 28a,b and 29.
1,2-Rearrangements proceed with high stereoselectivity, par-ticularly, at low temperature and in viscous solvents. Thesereactions involving chiral sulfides can be employed in asymmetricsynthesis.18 In particular, the Stevens rearrangement allows one tosolve the key problem in the synthesis of natural nitrogen-containing compounds consisting in the stereoselective formationof new C7C bonds at the a position with respect to the nitrogenatom. Thus a new approach to 6-amidocarbopenicillan antibioticswas exemplified by the synthesis of bicyclic b-lactam 33.47
Photolysis of diazoketone 34 afforded ylide 35, which wasrearranged to give the compound 33, the new C7C bond beingformed stereoselectively.
+
7Rh2(OAc)4
SPh
O
CO2Et
15
1608C
O
CO2EtPhS
17
O
PhS(H2C)3
CO2Et
N2
+
7
S
O CO2Et
Ph
808CO
OEt
SPh
O14 16 (50%)
Rh2(OAc)4O
PhSH2C
CO2Et
N2
+
SNEt
O
N2C(CO2Me)2 *1,2
Rh2(OAc)4 SNEt
O
EtO2C CO2Et7
S
NEt
O
CO2EtEtO2C
18 19 (70%)
S S
R3
R1
R2
R4
R5
CR62
S S
R3
R1
R2
R4
R5
R62C
+
7
21
7R62C=S
20
R1
R2
R4
R5
S S
R3
R6 R6
7
S
R3
R4
R5
R1
R2
SR6
2C
+
7
S
R3
R4
R5
R1
R2
SR6
2C
+
22
S
R3
R4
R5
R1
R2
23
N2
CO2Et4-MeC6H4
SPhMe Rh2(OAc)4
+
7S
Ph
CO2EtMe
4-MeC6H4
24
Me
4-MeC6H4
PhS
EtO2C 25
...
...
Me
MeMe
4-MeC6H4
26
27MeMe
4-MeC6H4
7
N
SPh
O
(CH2)2CCO2Et
N2
30
Rh2(OAc)4
31
N
S
O
Ph
CO2Et+
...N
R1
R2H
28a,b
R1 = CH2OH, R2 = H (a);
R1 = H, R2 = CH2OH (b).
...
N
H CH2OH
29
N
O
PhSCO2Et
32
Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds 657
This synthetic approach was further developed in the stereo-selective synthesis of alkaloids (+)-heliotridine (36a) and (+)-ret-ronecine (36b).48
The catalytic reaction of optically active sulfide 37, which can bereadily derived from (S)-malic acid, with dibenzyl diazomalonateafforded ylide 38 whose 1,2-rearrangement proceeded with highstereoselectivity. It is believed that the first stage of this reactioninvolved the cleavage of the C7S bond to produce salt 39. Theattack of the carbanion on the C=N bond proceeded predom-inantly from the less shielded side to form 2,3-trans-pyrrolidonederivative 40, which was used as the starting compound in thesynthesis of the alkaloids 36a,b.
The application of the intramolecular rearrangement of cyclicsulfonium ylides allowed the development of a newmethod for thepreparation of lactones,49 which were used in the synthesis ofC-nucleosides. Diazoacetyl thioglycoside 41 was prepared fromprecursor 42 according to the modified Corey method.50 Whenrefluxed in benzene with a catalytic amount of rhodium acetate,the compound 41 was converted into lactone 45 through sulfurylide 43 and oxonium intermediate 44. The lactone 45 served asthe key compound in the synthesis of nucleoside antibiotic(+)-showdomycin.
2. 2,3-Sigmatropic rearrangementsIn the last two decades, the synthesis of cyclic compounds madewide use of 2,3-sigmatropic rearrangements of allylic and benzylsulfur ylides. Baldwin was the first to carry out these studies 51 ± 53
as early as 1968. Since then the 2,3-sigmatropic rearrangements ofylides have found many applications.
The rearrangement of allylic ylides into homoallylic sulfidescan be represented in general form as follows:
According to the orbital symmetry rules, 2,3-sigmatropicrearrangements are allowed 28 and they proceed either on heatingor photolysis of ylides with complete inversion of the allylicsubstituent.54, 55 Since these reactions proceed by a concertedmechanism, high regio-, diastereo- and enantioselectivity areachieved, which is of particular interest from the standpoint oftheir application in asymmetric synthesis.
A gentle and efficient procedure for the synthesis of 3-allyl-isothiochroman-4-one (46) 56 involves the 2,3-sigmatropic rear-rangement of cyclic sulfur ylide 47 formed by intramolecularcyclisation of diazosulfide 48 under the action of a rhodiumcatalyst.
The use of chiral allylic sulfides in 2,3-sigmatropic rearrange-ments offers considerable possibilities for enantioselective synthe-ses of cyclic compounds, including analogues of naturalcompounds.
Thus the synthesis of optically active thioxanones 49a ± d wasbased on the 2,3-sigmatropic rearrangement of optically purecyclic sulfur ylide 51, which proceeded with high asymmetricinduction.57, 58 Crotyl thiodiazoester 50 derived from L-valinewas converted into the corresponding cyclic allylic sulfur ylideby either rhodium-catalysed intramolecular cyclisation or depro-tonation of sulfonium salt 52 derived from the compound 50. Therearrangement of the ylide 51 afforded four isomeric thioxanones49a ± d. The best yield and diastereoselectivity were achieved ondeprotonation of the sulfonium salt 52.
+7N
OH
H
N
S
O
CO2C6H4NO2-4
Bn
Me35
N
OH
N
SMeH
O
N2
CO2C6H4NO2-4
Bn
hn
34
RMe
Me
RMe
Me
Bn
N
OH
H
N
O
SMeCO2C6H4NO2-4
33 (72%)RMe
Me
TBS is ButMe2Si;
36a: R1 = (CH2)2OC(O)But, R2 = H, R3 = OH;
36b: R1 = (CH2)2OC(O)But, R2 = OH, R3 = H.
...
N
R3
H CH2OHR2
36a,b
NR1
SPh
TBSO
O 37
N2C(CO2Bn)2
Rh2(OAc)4
7+
NR1
S
TBSO
O
CO2Bn
CO2Bn
Ph
38
O
+
NR1
TBSO
39
7
CO2Bn
CO2Bn
PhS CO2BnCO2Bn
SPh
NR1
TBSO
O
H
40 (82.6%)
77
++
OO
OSPhHO
OO
OSPhCOHC
N2 O
41 (91%)42
OO
O
O
SPh
O
43
OO
O
O
O
SPh
44
OO
O
O
O
SPh
45 (56%)
Rh2(OAc)4
PhH
HCCOCl
NNHTs
RS
H2C7 CH2
CH
CH2
RS
H2C CH2
CH2
CH2
RS
H2C CH2
CH
H2C+
46
S
O
CHN2
S
O
[Rh]
S
O
7
+
48 47
*2,3
658 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
Starting Reagent Total Isomer ratio
compound yield (%)49a 49b 49c 49d
(Z)-50 [Rh] 35 84 8 7 1
(E)-50 [Rh] 28 10 83 2 5
(Z)-52 DBU 66 94 4 2 traces
(E)-52 DBU 64 4 93 1 2
The reactions involving the Z-isomers of the compounds 50and 52 yielded the thioxanone 49a as the major product, whereasthe reactions with the participation of the E-isomers gave rise tothe thioxanone 49b. This stereoselectivity was attributed 59 to theendo conformation of the allyl-containing five-membered ring inthe prevailing transition states A or B.
Substituted five-to-eight-membered lactones 53a,b and 54a,bwere prepared by the 2,3-sigmatropic rearrangements of allylicsulfonium ylides 55a,b and 56a,b generated from the correspond-ing diazoesters under the action of dirhodium tetraacetate.60 ± 63
Lactone 57 was prepared according to an analogous proce-dure and was used in the stereoselective synthesis of perhy-dro[2,3-b]furanone derivative 58.62
The rearrangement of sulfur ylides, which were prepared bytreatment of sulfur-containing diazoketones 59 and 60 withdirhodium tetraacetate in boiling benzene, was used in a newapproach to the synthesis of bridging d-lactones 61 64 as well as ofspiro-fused five- and six-membered lactones 62a,b 65 and spiro-carbocyclic compounds 62c,d.66
S
O
O
N2
Pri
Me
50
HBF4.Et2O
S
O
O
Pri
+
BFÿ4
52
51
[Rh]
DBU
778 8C
Me
+S
O
O
Pri
7
Me
DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene.
S
O
O
Pri
H
Me
+ +S
O
O
Pri
H
Me
+S
O
O
Pri
H
Me
S
O
O
Pri
H
Me
49a 49b 49c 49d
+
7
O
S
OMe
Pri B
O
S
OMe
Pri
49b
O
S
O
Me
Pri
7
+
O
S
O
Me
Pri
49a
A
O
ON2
RO2C
(CH2)nPhS
Rh2(OAc)4+
7O
OPhS
RO2C
(CH2)n (H2C)nO
O
CO2RPhS
55a,b 53a,b
R=Me, Et; n= 1, 2.
(CH2)n
O
ORO2C
PhS
54a,b
7
O
O
N2
RO2C
(CH2)n
SPh
Rh2(OAc)4
S (CH2)n
O
O
Ph
RO2C
+
*2,3
56a,b
O Me
EtO2C
PhS
O
...
57
OO
H
H
H
Me
O
58
7
R=H, Me; n= 1, 2.
R1, R2 = Alk; X = O, n= 1 (a), 2 (b); X = CH2, n= 1 (c), 2 (d).
O
N2
O
CO2Et
SPh
R
59
Rh2(OAc)4
PhH, D
61
(H2C)n
O O
SPhCO2Et
R
(H2C)n
CH2SPh
R1
X
O
N2
CO2R2
60
PhH, D
Rh2(OAc)4
+
S
O
O
Ph
RCO2Et
(H2C)n
(H2C)n
R1=Pri,
R2=Et
X
(H2C)n
R1
SPh
O
62a ± d
CO2R2+
7X
S
(H2C)n R1
Ph
R1O2CO
A
62cO
Pri
...
63
Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds 659
Spiroannelation using the [2,3]-sigmatropic rearrangement viacyclic allylic sulfonium ylide was applied in the enantioselectivesynthesis of sesquiterpene (+)-acorenone B (63).66 High stereo-selectivity of the sigmatropic rearrangement is attributed to thefact that the less sterically hindered side opposite to the isopropylgroup is favourable for the attack of the carbanion on thesulfonium reaction centre (transition state A).
Rhodium-catalysed stereoselective cyclisation of diazosulfide64 followed by the 2,3-rearrangement of the resulting ylideafforded cis-2-oxa-9-vinyldecalin derivative 65, which served asthe starting compound in the synthesis of vernolepin (66).67
The rhodium-, copper- and palladium-catalysed stereoselec-tive reactions of diazosulfides 67a and 67b were studied.68
Depending on conditions, these reactions can afford eithersulfonium ylides, which undergo the 2,3-sigmatropic rearrange-ment to form bicyclic compounds 68a and 68b, or tricyclic cyclo-propane derivatives 69a and 69b. The latter are products ofintramolecular cyclopropanation. Decomposition of the diazo-amides 67a,b in the presence of the rhodium complex withcaprolactam gave rise predominantly to the azabicyclooctanes68a,b, whereas cyclopropane derivatives were selectively formedas the major products in the presence of catalysts containingelectron-withdrawing ligands [Rh2(OAc)4 , Cu(acac)2 , Cu(OTf)2or Pd(OAc)2].
The rearrangements of diaminosulfoxonium salts of type 70 toform dihydro-2,1-benzoisothiazole derivatives 71 weredescribed.69 Treatment of the salts 70, which were prepared byalkylation of sulfonimidoamides, with ButOK resulted in the 2,3-sigmatropic rearrangement of intermediate ylides 72 to producecyclohexadieneimine derivatives 73 in the first stage. The transferof the hydrogen atom in the latter compounds was accompaniedby rearomatisation. Cyclisation of intermediates 74 afforded thefinal products 71.
Yet another promising synthetic application of sulfur ylides isbased on the 2,3-sigmatropic rearrangements of cyclic allylicsulfonium ylides proceeding with ring expansion.17, 70
Ylides can be generated by reactions of cyclic a-vinyl sulfideswith diazo compounds in the presence of copper 17, 70 or rhodiumcatalysts 71 or by reactions of bases 17, 70 with sulfonium salts.These procedures were used for the preparation of various macro-cyclic compounds. For example, the synthesis of thiacycloundeca-4,7-diene derivative 75, which is a precursor of aglycon of macro-lide antibiotic methymycin, viz., methyneolide 76, was carried outstarting from tetrasubstituted thiolane 77.72 ± 74 The rearrange-ment of ylide 78 derived from salt 79 afforded thiacyclooctene 80from which ylide 81 was synthesised in several steps. The subse-quent stereoselective 2,3-sigmatropic rearrangement of the ylide81 gave rise to thiacycloundecadiene 75 (Scheme 1).
The 2,3-sigmatropic rearrangements of bicyclic allylic sulfo-nium ylides, which gave rise to compound 82 containing thethiabicyclo[6.3.1]undec-3-ene fragment, was used in the totalsynthesis of cytochalasines.75, 76 In this synthesis, vinyl iodide 83served as the starting compound. The key stage of this synthesisinvolved the rearrangement of ylide 84 generated from sulfoniumsalt 85 under the action of potassium carbonate.
Difficultly accessible bicyclic unsaturated disulfides 86 (the so-called betweenanene structures) and 87 were synthesised.77, 78
Heating of dithioketal 88 with diazoacetate in the presence ofCuSO4 afforded ylide 89, which underwent the 2,3-sigmatropic
64
O
MeO
N2
O
CO2Me
SPh
Rh2(OAc)4
O
MeOH
PhSCO2Me
O
65 (77%)
...O
OH
O
O
OH
66
N
H
O
SPh
N2
67a
N
H
SPh
O68a
+cat, PhH
67b
N
H
O
N2
PhS
cat, PhH+
68b
N
H
SPh
O
N
H
O69a
CH2SPh
69b
N
H
O
CH2SPh
+7
+
BFÿ4
70
ButOK
608C
NMe
S NCH2
O
O
X 72
NMe
S NMe
O
O
X
7
S N
O
O
NMe
X 73
S N
O
O
NHMe
X
ButOK
O
NMe
XO7 HN
74
N
S O
X
Me
71
S N O
X=Me, Cl.
Z is the carbon atom or a heteroatom.
7
S
(H2C)n
Z
S
(H2C)n
Z
R+
*2,3S
(H2C)n
Z
R
CH2TMS
I
NPh
Ac O
OAcS
O83
MeCN
70 8C S+
O
OAc
85
I7K2CO3
CH2TMS
NPh
Ac O
OAcS
O84
S+
O
OAc
7
82 (65%)
660 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
rearrangement to give two geometric isomers 86 and 87 in a ratioof 4 : 1.
The structures of the 2,3-sigmatropic rearrangement productsof acetylenic ylides 90a ± c derived from the corresponding sulfo-nium salts 91a ± c depend on the nature of the substituent at thetriple bond. Thus the ylides containing alkyl substituents wereconverted into allenic sulfides 92a,b, whereas the phenyl substitu-ent promoted isomerisation into 1,3-diene 93c.79
Aryl-substituted ylides 94 and 95, which were formed ondesilylation of salts 96 and 97, underwent the Sommelet ±Hauserrearrangement giving rise predominantly to substituted 2,5,8,9-tetrahydrodibenzo[c, f ]thionines 98 80 and 3,4,6,7-tetrahdydro-1H-5,2-benzooxathionines 99, respectively.81
Analogous thermal 2,3-sigmatropic rearrangements accom-panied by ring expansion proceeded in the case of a-vinyliminosulfurane ylides 100a ± c, which were prepared by treatmentof sulfides 101a ± c with chloramine T in methanol at *20 8C.82
The rearrangements of the ylides 100a ± c afforded azathiacy-clenes 102a ± c. It should be noted that treatment of 2-vinyl-thiepane 101c with chloramine T gave rise to the final product102c even at room temperature. Attempts to isolate the inter-mediate ylide 100c failed.
Compound n Yield Temperature of the Yield of
101 of 100 (%) rearrangement /8C 102 (%)
a 1 70 140 55
b 2 61 140 54
c 3 7 *20 61
+
7
(CH2)8
SS
88
N2C(R1)CO2R2, CuSO4, D
(CH2)8
SS
R2
CO2R1
89
*2,3
S
S (CH2)8
R1
CO2R2
86
+
S
(H2C)8
R1
CO2R2
87
S
S+
OEtOC
C
R
OTf7
91a ± c
DBU
90a ± c
S+
OEtOC
C
R
7
R=Me (a), Bu (b), Ph (c).
R =Me, Bu
R = Ph
C
S
CO2Et
R92a,b
S
CO2Et
Ph93c
R=H, Me, Cl, CF3 .
R1, R2 = H, Me, OMe, CF3.
S+ 7SiMe3
R
OTf7
CH2
R
S
R96 94 98
S+
7R1
R2
O
S
SiMe3
+
OTf7
DMSO, 20 8C
CsF, DBU+
R1
R2
O
S
CH2
97 95
R1
R2
S
O
99
CsF, DBU
DMSO, 20 8C
(CH2)n
S
101a ± c
chloramine T
MeOH, 20 8C
*2,3(CH2)n
S
NTs
+
7N S
(CH2)n
Ts
100a ± c 102a ± c
Tf = F3CSO2; (a) TfOCH2CO2Et; (b) K2CO3; (c) TfOCHMeCOEt, K2CO3.
+ +S
a b c
S
CO2Et
OTf7 S
RO
CO2Et7
77 7879
SEtO2C
OR
S
OR
80 (36%)
7 S
OR
Et O
+
81
S
OR
Et O 75 (89%)
...
O
OH
OEt
HO
O
76
RO RO Scheme 1
Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds 661
Under the same conditions, benzoiminosulfuranes 103 and104 produced 1,2- (105) and 3,4-benzothiazonines (106), respec-tively.82
The reactions of 3,4-disubstituted 2,5-dichlorothiophenes 107with diazoketones in the presence of rhodium catalysts affordedderivatives of a new heterocyclic system, viz., of 1,4-oxathiocine108.83, 84 The reaction scheme involves the formation of sulfurylides 109 and their subsequent thermal 2,3-sigmatropic rear-rangement proceeding through intermediates 110. Heating ofoxathiocine 111 at 110 8C gave rise to benzene derivative 112due to elimination of the sulfur atom and 1,2-shift of the chlorineatom. It should be noted that the reactions of diazoketones withthiophenes, which do not contain chlorine atoms at positions 3and 5, do not yield oxathiocine derivatives.
The 2,3-sigmatropic rearrangements of bi- and tricyclic sulfurylides derived from substituted thiaphenanthrenes and isothio-chromans, respectively, afforded both ring expansion productsand spirane compounds.85 ± 88 The direction of the reaction andthe structures of the final products depend essentially on thenature of the substituents at the sulfur atom and at position 1 ofthe initial ylide. For example, the reaction of stabilised ylide 113with succinimide gave rise to the ring expansion product, viz.,2-phenyl-4,5-dihydro-3,5-benzooxathionine 114, in high yield.The reaction mechanism involves deprotonation of intermediate115 with the imide anion to form exocyclic methylide 116 whose2,3-sigmatropic rearrangement yielded the target product 114.85
The reaction of the ylide 113 with phthalimide proceeded analo-gously.
The reaction of 1-cyanoisothiochroman ylide 117a proceededby the samemechanism; however, due to the presence of the cyanogroup, the 2,3-sigmatropic rearrangement of intermediate exome-thylide 118a proceeded differently to form spirocyclic compound119.86 On thermolysis, the compound 119 was isomerised totetrahydrothiepin 120, whereas its reactions with acetylenedicar-boxylic esters afforded cycloadducts 121a,b. The course of thereaction is substantially affected by the substituent at the sulfuratom. Thus the bulkier ethyl substituent in the ylide 117b hindersthe 2,3-rearrangement and the reaction gave rise to a mixture ofbenzothiopyran 122 and dimer 123.
Due to the presence of one more substituent (Cl, Br or Me) atposition 1 in ylides 124, their reactions proceeded through the2,3-sigmatropic rearrangement involving the S7N bond. Thereactions of the ylides 124 with succinimide afforded ketenimines125, which gave amides 126 or enol acetates 127 upon acidhydrolysis.86
+
S
140 8C
S
NTs7
S NTs
103 (70%) 105 (55%)
7+
SNTs
104 (83%)
SNTs
S140 8C
106 (57%)
chloramine T
chloramine T
+
S
R1 R1
ClCl
[Rh], R2CN2COR3
S
R1 R1
ClCl
R2
R3
O7
60 ± 100 8C
109107
S
R1 R1
ClO
Cl
R2 R3
110
S O
R1 R1
Cl
R3R2
Cl
108
111
S O
Cl
MeEtO2C
Cl110 8C
O
ClCl
MeEtO2C
S
OH
MeEtO2C
Cl
Cl
112
R1 =H, Cl; R2 = CO2Et, CO2But, Ts; R3 =Me;
R2 ±R3 = COCH2CMe2CH2.
NH, PhH, D
O
O
S+Me
COPh 115
NH
O O7
N
O
O
7
O
S
Ph114
7 S+Me
COPh113
7S+CH2
COPh116
SCH2
OPh
117a
a or b
CN
S
H
119 (85%)
7S+CH2
CN
118a
c
d
S
NC 120
EtO2C
CO2Et
HNC
S
121a
+
EtO2C
CO2Et
HNC
S
121b
7 S+Me
CN
7 S
CN
e
S+Et
CN117b 122
+
(CH2)2SEt
NC
CN
EtS(CH2)2
123
(d) EtO2CC:CCO2Et; (e) EtOH, D.
(a) EtOH or MeOH, D; (b) NH, PhH; (c) 205 8C;
O
O
662 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
The reactions of the 1-cyano ylides 117a,b with activatedacetylenes (dimethyl acetylenedicarboxylate ormethyl propiolate)afforded fused compounds 128 and 129a,b.86 The methyl deriva-tive 117a gave a mixture of the compounds 128 and 129a (*1 : 1)in 75% total yield. The reaction mechanism involves the inter-mediate formation of zwitterions 130a,b whose isomerisation cantake two different pathways (path a and path b). Intramoleculardeprotonation of the S-methyl group (path a) gave rise to ylide131whose 2,3-sigmatropic rearrangement afforded the compound128. The nucleophilic attack of the vinyl anion on the positivelycharged sulfur atom produced unstable s-sulfurane intermediate132a, which was converted into the ylide 129a. The ethyl deriva-tive 117b gave only the doubly stabilised ylide 129b in 31% yield.
The reactions of stabilised isothiochromene sulfonium ylides133a,b with acetylenic dienophiles proceeded differently.87 Thesecompounds reacted as heterodiene systems and the reactionsproceeded as [4+2]-cycloaddition to yield intermediates 134a,b.Depending on the solvent, subsequent conversions of theseintermediates afforded either dihydrocyclopropa[a]naphthalenederivatives 135a,b (in aprotic solvents) or naphthalene derivative136a (in protic solvents). It should be noted that only [2+1]-adduct 137 was formed in high yield in the reaction of thecompound 133a with methyl propiolate in sulfolane. This adductwas generated by the interaction of intermediate 138 with thestarting ylide 133a.
The reaction of 2-cyano-a-thiochromene ylide 139 withdimethyl acethylenedicarboxylate afforded the ring expansionproduct 140 in low yield.
The reactions of tricyclic sulfur ylide 141a stabilised by theadjacent cyano group (the thiaphenathrene derivative) with acti-vated acetylenes produced spirocyclic compounds 142 (the yieldswere up to 31%), which underwent the 1,5-rearrangement uponheating to give dibenzothionine derivatives 143 in yields of up to95%.88 It is assumed that the reaction mechanism involves theformation of zwitterionic intermediates 144, which are rearrangedto exocyclic sulfonium ylides 145. The ylides 145 can undergo the
7
a
S+CH2
CNR124 125
b
c
C N
S
R
NH
S
OR
126
NH
S
OAcR
127a) NH, PhH; b) HCl; c) AcOH.
O
O
R=Me, Cl, Br;
7
S+Me
NC
R2
117aR1C CR2
130a
R1
7
+
7
S
R1NCR2
path a
path b
131
7S+CH2
NC
R1 R2
128
129a
SMe
R1NC
R2
117b
130b
R1C CR2 S+Et
NC
R1 R2
path b
S
R2
Me
132a
NC
R1
7
R1 =H, R2 = CO2Me (129a); R1 = R2 = CO2Me (129b).
S
R2
Et
132b
NC
R1
+
SEt
R1NC
R2
129b
+7
7
+SMe
R1
R2C CR3
133a,bSMe
R2R3
R1
134a,b
+
R1 = CN
EtOH
SMe
SMe
R2R3
NC
7
CN
R3
R2
136a (19%)
135a,b
R1
R3
R2
PhH
R1 = CN (a), COPh (b); R2 = H, R3 = CO2Me;
R2 = R3 = CO2Me, CO2Et.
+
7133a
HC CCO2Me
SO2
SMe
NC
CO2Me
NC
CO2Me133a
NC
CO2Me
CNMeS
138 137
HMeS HMeS
+
S
Ph
CNMe
7
139
MeO2CC CCO2Me
SCO2Me
CO2Me
CNPh
140 (12%)
Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds 663
Sommelet ±Hauser rearrangement to produce the compounds142. In the case of the ethyl-substituted ylide 141b, spirocycliccompounds were not formed; instead, the reaction affordeddibenzothiepin derivatives 146 as the major products (the yieldswere up to 38%). Since the ethyl substituent at the sulfur atom inthe compound 141b causes steric hindrances to the Somme-let ±Hauser, this compound underwent the 1,2-Stevens rearrange-ment to form the ring expansion product 146. The rearrangementsof the zwitterions 144 afforded dibenzothiocine derivatives (in theyields of up to 22%) along with the compounds 146 (see thescheme for the formation of the compound 129a).86
The reactions of sulfur ylides 147a ± f, viz., 9-alkyl-9-thia-10-azaphenanthrenes, with dimethyl acetylenedicarboxylate gave riseto dibenzothiazonium derivatives (compounds 148 and 149),dibenzothiazocine derivatives (compounds 150), 2-alkylsulfinyl-20-vinylamionbiphenyls 151 and bis(biphenylylimino)ethanederivatives 152 (Scheme 2).89
The composition of the reaction products depends substan-tially on the substituent at the sulfur atom. Thus the compound147a produced predominantly dibenzothiazonine derivatives 149aand 148a, whereas the ylides 147b,c,d gave predominantly diben-zothiazocine derivatives 150 and biphenyls 151. The ylides 147e,f
7 S+CH2R1
CN
141a,b
R2C
PhH
CR2
7
S+CH2R1
NC
R2R2
144
7S CHR1
NC
+
145
R2
R2
R1=H (a), Me (b); R2=CO2Me, CO2Et.
R1=Me
R1=H
S
MeNC
R2R2
146
S
CN
R2
R2142
S
R2
R2NC
143
200 8C
R1 = CH2R2 (R2 = H (a), Me (b), Et (c), C5H11 (d)); R1 = Ph (e), CH=CPh2 (f).
N
2152a ± f
MeO2C
R1S
7+SR1
N
147a ± f
R1=CH2R2,
7
+
SR1
N
MeO2C
CO2Me
153a ± f149a ± d
SHN
CO2Me
R2
MeO2C
SN
CO2Me
R2
MeO2C
148a ± d
+ 7SCHR2
N
MeO2C
CO2Me
154a ± d
MeO2CC CCO2Me
147a ± fMeO2CC CCO2Me
+
7S
N
R1
MeO2C
CO2Me
155a ± f 150a ± f
SN
R1
MeO2C
CO2Me
H2O
SiOx
151a ± f
SNH O
R1
MeO2C
CO2Me
H2O
Scheme 2
664 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
containing the phenyl or vinyl substituent at the sulfur atomproduced only dibenzothiazocine derivatives 150e,f. The reactionmechanism involves the formation of zwitterions 153 and 154. Theexocyclic ylide 154was isomerised to form the compounds 148 and149. The zwitterion 153 can produce intermediate 155 from whichthe derivatives 150 and 151 are generated or can react with watergiving rise to the dimers 152. The reactions of 9-alkylthiaazaphe-nanthrenes 147a ± c with methyl propiolate afforded 1 : 2 adducts,which are dibenzothiazocine derivatives 156a ± c.89
The rearrangements of tricyclic sulfonium salts 157 under theaction of various bases have been studied thoroughly.90 Thustreatment with strong bases [lithium diisopropylamide(LDA),NaH or K2CO3] afforded ylides 158 and 159, which underwentthe 2,3- and 1,4-sigmatropic rearrangements to form spirovinyl-cyclopropane derivatives 160 or tricyclic compounds 161. Theratio of the reaction products depends on both the base used andthe nature of the substituents.
R1 R2 R3 Base Yield (%)
160 161
H Me Me LDA 35 52
Bz Me Me LDA 57 7
H Me Me NaH 28 70
Bz Me Me NaH 75 0
H H Me NaH 44 45
Me Me Me NaH 46 46
H Me Me K2CO3 21 22
Bz Me Me K2CO3 64 0
In the reactions with the salts 157, weak bases, such as Et3N,Et2NH, BuNH2 or AcOK, act as nucleophilic reagents and attackthe CH2 group adjacent to an electron-deficient centre to yieldring expansion products 162 in high yields.
Interesting results were obtained in studies of the rearrange-ments of dibenzothiocine salts 163a,b, which took place under theaction of a KOH solution in methanol.91 Thus the sulfoxide 163awas converted into a mixture of enantiomers of dibenzothiepinderivative 164a,b (in a ratio of*2 : 1). Under the same conditions,the sulfide 163b unexpectedly gave compound 165. The assumedreaction mechanism involves the tandem of the 2,3- and 1,3-sigmatropic rearrangements with the intermediate formation ofspirocyclic intermediates 166 and 167.
III. Intramolecular cyclisation of sulfur ylides
A promising approach to the synthesis of nitrogen-containingheterocycles, including analogues of alkaloids, is based on intra-molecular cyclisation of phthalimido-substituted sulfur ylidesstabilised by the carbonyl group.92 ± 98 Under the conditions ofthe Arndt ±Eistert reaction,99 N-phthaloyl-a- (168) and -b-aminoacids (169) generated bromo ketones, which were converted intothe corresponding sulfonium salts. Deprotonation of these saltsafforded stabilised ylides 170 and 171, respectively, which under-went intramolecular cyclisation on heating in toluene with anequimolar amount of benzoic acid 96 to give methylthio-substi-tuted pyrrolizidine- (172) and indolizidinediones 173 and 174. It issignificant that racemisation does not take place in the reactions
+
7
147a ± cHC CCO2Me
SR1
N
CO2Me
HC CCO2Me
+
7
SR1
N
CO2Me
CO2Me
+
7
SN
R1
CO2Me
CO2Me
156a ± c
BFÿ4
157
S
R3
R2
R1
+
S
R3
R2
R1
+
7
158
*2,3 S
R1
R3
R2
160
159
S
R3
R2
R1
+
7 *1,4
R1
S
R3
R2
161
X=NEt3BF4, NEt2, OAc, NHBu.
157
162
S
R3
R2
R1
X
+ +
7
S
S
(O)n
Me
Y7
S
S
(O)n
Me163a,b
*2,3
R1 = H, R2 = SMe (a);
R1 = SMe, R2 = H (b).
164a,b
S
O
R2R1
*1,3 S
MeS
167
S
(O)n
MeS
166
*1,3
S
SMe165
n=1, Y=SbCl6 (a); n=0, Y=BF4 (b).
Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds 665
involving optically active ylides. Longer-chain sulfur ylidesderived from g- and d-amino acids did not undergo cyclisation;instead, alkyl thioketones and oxobenzoates were formed as themajor products.96 The effect of the substituents in the phthalimidefragment on the regioselectivity of the reaction and the yields ofthe products was also studied.97
Ylides 175 and 176 containing the tetrahydrophthalimide orsuccinimide fragment, respectively, instead of the phthalimidefragment did not undergo cyclisation.97
Under the conditions of cyclisation, ylide 177, which wassynthesised from b-alanine and pyridine-2,3-dicarboxylic anhy-dride, selectively formed a tricyclic compound, viz., 5-methylthio-7,8-dihydro-4,8a-diazafluorene-6,9-dione (178).98
The assumed mechanism of a new type of intramolecularcyclisation, which is not quite typical of sulfoniumylides, involves,apparently, the attack of the anionic centre on one of the carbonylgroups of the phthalimide fragment followed by migration of themethyl group.100, 101 The reaction ends in elimination of themethanol fragments from intermediate 179 under the action ofbenzoic acid to form rearrangement product 180, methyl benzoateand water.
Intramolecular cyclisation of ylides 181 containing the sulfuratom in the ring gave rise to benzoates 182.
Diazosulfides (R )- or (S )-183 generated from D- or L-methio-nine, respectively, underwent cyclisation under the action of HBrto form optically active sulfonium salts (R )- or (S )-185 (the yieldswere 54 and 62%, respectively). Subsequent treatment of thesesalts with potassium carbonate afforded cyclic ylides (R )- or(S )-184 stabilised by the carbonyl group (the yields were 75%and 90%, respectively).102
A new approach to the stereoselective synthesis of amino acidsfrom chiral lactams through intermediate formation of b-ketosul-foxonium ylides was developed.103, 104 Previously,105, 106 it wasfound that these ylides were converted into intermediates of thecarbene type on photolysis or under the action of transitionmetals. The reactions of activated chiral lactams 186a,b withdimethylsulfoxonium methylide were demonstrated to produceylides 187a,b in high yields.103, 104 Under the action of rhodium
n= 1, 2.
+7+7N(CH2)nC(O)CHSMe2
O
O 175 176
N(CH2)nC(O)CHSMe2
O
O
+7
N
N(CH2)2C(O)CHSMe2
O
O 177
178 (58%)
N
N
O
OMeS
77
+N
O
O
O
HC
SMe2+
N
O
O OMe2S
+
N
O
MeO OMeS179
PhCO2H
7PhCO2Me,7H2ON
O
OMeS180
n=1, 2.
+7
O
O
N(CH2)nC(O)CHS
181
PhCO2H
O
N(CH2)n
OPhOCO(CH2)4S
182
+
Br7183
HBr
185O
O
N
CH2N2
O
SMe
O
O
N
O
SMeK2CO3
+
7O
SMe
O
O
N
184
+7
170a ± d
NCHC(O)CHSMe2
O
O
R
172a ± d
7PhCO2Me
N
O
SMe
O
R
NCHCO2H
O
O
R
168a ± d
a, b, c, d, e
(a) SOCl2; (b) CH2N2; (c) HBr; (d ) Me2S; (e) NaOH±K2CO3;
( f ) PhCO2H, 110 8C.
N(CH2)2CO2H
O
O
R1
R2
169a ± d
a, b, c, d, e
+7 f
171
N(CH2)2C(O)CHSMe2
O
O
R1
R2
173a ± d
N
OR1
R2
OMeS
+N
O
OSMeR1
R2
174a ± d
Compound 172 R Yield (%)
a H 86
b Me 85
c Pri 84
d Bn 83
Compound 169 R1 R2 Yield (%)
173 174
a H H 86
b NO2 H 52
c Cl H 75
d H NO2 38 35
666 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
catalysts, the reactions of the ylides 187a,b proceeded stereo-selectively giving rise to derivatives of 4-oxopyrrolidine 188a or 5-oxopiperidine 188b formed as a result of cyclisation of intermedi-ate carbenes 189a,b. The compounds 188a,b were used in thesynthesis of optically active a-amino acids.107
IV. Reactions of thiocarbonyl ylides
Considerable recent attention has been given to thiocarbonylylides, which are readily accessible and highly reactive intermedi-ates. Several procedures were developed for the preparation ofthiocarbonyl ylides among which are the 1,3-dipolar cycloaddi-tion of diazo compounds to thioketones to form 1,3,4-thiadiazo-lines followed by nitrogen elimination,108 the addition ofthioketones to oxiranes 109 or photoisomerisation of aryl vinylsulfides.110 Thiocarbonyl ylides readily undergo rearrangements.These compounds are involved in cycloaddition with dipolaro-philes and in 1,3- and 1,5-electrocyclisations, which often proceedwith high regio- and stereoselectivity. The reactions of thiocar-bonyl ylides with compounds of the RXH type (X=N, O or S)giving rise to 1 : 1 adducts were also studied.111 ± 113 Recently,cyclisation of carbenes generated by catalytic decomposition ofdiazothioamides has gained wide acceptance for the preparationof thiocarbonyl ylides.114 Thus diazothioamide 190 gave cyclicthiocarbonyl ylide 191 under the action of a rhodium catalyst. Theylide 191 was converted into enaminoketone 193 due to elimina-tion of sulfur from intermediate episulfide 192.115
Intramolecular cyclisation of diazothioamide 194 catalysed bydirhodium tetraacetate afforded thiocarbonyl ylide 195 stabilisedthrough the aromatic mesoionic structure. The ylide 195 reactedwith N-phenylmaleimide according to the scheme of the dienesynthesis to give adduct 196.115
Thiocarbonyl ylides were successfully used in the synthesis ofnatural alkaloids.116 ± 120 Thus non-stabilised ylide 198 was gen-erated from diazothioamide 197 under the action of rhodiumacetate followed by the rearrangement of the latter into episulfide199. Isomerisation of the compound 199 afforded thioketone 200,which underwent desulfurisation under the action of Raney nickelto yield dihydropyridone 201.116
This procedure was used for the synthesis of dihydropyridone202, which was the key intermediate in the total synthesis ofantibiotic indolisomycin 203.117, 118 Diazothioamide 204was usedas the starting compound.
Alkaloids helenine (205) 119 and cephalotaxine (206) 120 weresynthesised using compounds 207 and 208, respectively. The latterwere prepared by cyclisation of hydrazones 209 and 210, whichwere synthesised from substituted benzaldehydes and N-amino-1,2-diphenylaziridine, in the presence of dirhodium tetraacetate.The reactions proceeded through the corresponding carbenoidsand cyclic thiocarbonyl ylides (Scheme 3).
Thiocarbonyl ylide 211, whichwas generated in situ on heatingof a suspension of iodonium compound 212 in carbon disulfide inthe presence of copper acetylacetonate, underwent cyclisation toyield oxathiol heterocycle 213.121
The reaction of di-tert-butylthioketene (214) with diazomalo-nate afforded thioketene ylide 215, which underwent cyclisation togive 2-alkylidene-1,3-oxathiol 216.122
(H2C)n
N
CO2Bn
BocO
a
186a,b
(CH2)n NHBoc
CO2BnO (CH2)n
N
O
CO2Bn
Boc 188a,b189a,b
S
O7
MeMe
(CH2)n
O7
NHBoc
CO2Bn2+
187a,b
b
Boc = ButOCO; n= 1 (a), 2 (b);
(a) Me2S(O)CHÿ2 , DMSO, 20 8C; (b) [Rh2+].+
N2
O
S
CO2Et 190
N(Me)Ph
SO
CO2Et
N(Me)Ph
192
7
[Rh2+]
S+O
CO2Et
N(Me)Ph
191
O
CO2Et
N(Me)Ph
193 (90%)
7
NS
O
CO2Me
N2
Rh2(OAc)4 N S+
O CO2Me
194 195
NO O
Ph N
O
CO2Me
S NPh
O
O
196 (75%)
N
O
H
SH
202
...N
H
OH
203
204
N
S
N2
ORh2(OAc)4
H
7
N
S+O
H
Me
Me
O
S
O S213 (85%)
+7
Me
Me
O
O
IPhCS2
Cu(acac)2
Me
Me
O
O
S
212 211
C S
7
S
C
ButBut
N2C(CO2Me)2
Rh2(OAc)4
214
S
C
ButBut
C(CO2Me)2+
215
S
C
ButBut
CO2Me
OMe
O7
+
O
SMeO2C
MeO2C But
But
216
Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds 667
Various cumulenes and cumulene episulfides were preparedby the addition of alkenylidene dicarbenes to thioketenes.123
Episulfides 217 were isolated as stable crystal compounds, whichunderwent predominantly desulfurisation on heating or photol-ysis to give tetraenes 218 in yields from 50% to 69% and were alsopartially isomerised to episulfides 219. Substituted thietane-thiones 221 were obtained as by-products (9%± 20%) due to theintermolecular transfer of the sulfur atom through biradicalintermediate 220 (Scheme 4).
Vinylthiocarbonyl ylides generated from vinyldiazoalkanes222 and thiochromones 223 or 224 gave 1,3- (225) or 1,5-electro-cyclisation (226 or 227) products depending on the nature ofsubstituents in the ylide.124 Unstable thiirane 225 (R=H) wasimmediately converted into diene derivative 228 with eliminationof sulfur. The reactions of diazo compounds 222a,b with thio-chromone 224 proceeded through the formation of analogousdienes. Diazo compound 222c containing the bulkier phenylsubstituent was involved in 1,5-electrocyclisation with the thio-chromones 223 and 224 to give dihydrothiophene derivatives 226and 227, respectively.
N2
R C6H4Cl-4
CN
222
+
O
S
223
Rh2(OAc)4
R1 = CN, R2 = C6H4Cl-4 (55%); R1 =C6H4Cl-4, R2 = CN (28%).
O
S
Rh2(OAc)4
222
O
224 227
S R2
R1
Ph
O
S
R
C6H4Cl-4NC
R=H, Me
R = Ph
225 (74%)O
R=H
7S
C6H4Cl-4NC
R
228 (82%)
226 (66%)
O
S CN
C6H4Cl-4
R
R=H (a), Me (b), Ph (c).
Rh2(OAc)4N(CH2)2
Ph
PhNN
H
O
O
O
S
...O
N
O
O
208
N
O
O
H
HO
OMe206
210
N(CH2)2
Ph
PhNN
H
O
O
O
S
OMe
OMe
209
Rh2(OAc)4O
OMe
OMe
N
O
O
207
...
O
OMe
OMe
N
O
O
O HO
205
Scheme 3
+ 7C S+
R2
R1
C C
R4
R3 Cl
H
B
7HCl
D or hnR1
R2
SC C
R3
R4
C
S
C
R4
R3R1
R2
219
D or hn
C
R4
R3
S
R1
R2
CS
R1
R2 217
R3
R4
C
C C
R1
R2
R3
R4
C
S
S
R1
R2
+
221
218
C
R4
R3
S
R1
R2 S
R1
R2
C
R4
R3
220
R3
R4
C
Scheme 4
R1=R2=R3=R4=But; R1 ±R2=CMe2(CH2)3CMe2 , R3=R4=But; B is a base.
668 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
Amino-substituted thiocarbonyl ylide 229 underwent intra-molecular condensation of a new type providing an approach to1,6-dithia-3,9-diazaspiro[4.4]non-2-enes 230.125
The reactions of thiocarbonyl ylide 231 with thioamides 232were accompanied by unusual intramolecular cyclisation.108
Adduct 233 generated initially underwent cyclisation to give2-thia-4-azabicyclo[3.1.1]hept-2-ene derivative 234. This is thefirst example of the nucleophilic addition of a cyclobutanonederivative to the carbonyl group proceeding without opening ofthe four-membered ring.
V. Cycloaddition of ylides to alkenes
The reactions of stabilised sulfonium ylides with electron-deficientalkenes of the C=C7X=Y type generally afford cyclopropanes(the AdN ±E1,3 mechanism);6 however, five-membered hetero-cycles can also be formed due to the involvement of the activatingX=Y group, where X=Y=NO2 , N=O or N=NAr (theAdN ±E1,5 mechanism).10, 13
These reactions were considered in sufficient detail in thereview,13 which surveyed the data available up to 1986. Hence, wedwell only on the recent most interesting results published in theliterature.
The reactions of nitroalkenes with stabilised sulfonium ylideswere demonstrated 126, 127 to proceed stereoselectively to give bothtrans-4,5-dihydroisoxazole N-oxides 235 and substituted cyclo-propanes, the ratio of the reaction products being essentiallydependent on the a-alkyl substituent in nitroalkenes. In the case
of bulkier substituents R, heterocyclic adducts are formed insubstantially higher yields.
The reactions of arylmethylenecyanothioacetamides withstabilised sulfur ylides 236 proceeded stereoselectively to givemixtures of 2-amino-4,5-dihydrothiophenes 237 and cyclopro-panethiocarboxamides 238.128 In most cases, the dihydrothio-phenes 237 were obtained as the major reaction products. ForR=cyclo-C3H5, cyclopropane derivatives did not form at all.
A simple and efficient procedure for the preparation of 2,5-dihydrofurans 239 containing the N-tosylamino substituent isbased on the reaction of N-sulfonylimines with sulfur ylidesgenerated from cis-4-hydroxybut-2-enyldimethylsulfonium salts240.129 The assumed mechanism involves the formation of azir-idine derivative 241, ring opening through the attack of theinternal nucleophile and subsequent cyclisation to form 2,5-dihydrofuran. The reaction involving the trans-isomer of thesulfonium salt 240 afforded only the aziridine derivative.
As mentioned above, thiocarbonyl ylides are readily involvedin 1,3-dipolar cycloaddition to give the corresponding cyclo-adducts in high yields and with high regioselectively. Thus whenheated, dihydrothiadiazoles 242, which were formed in the reac-tions of diazomethane with derivatives of oxodithiocarboxylicacids 243, gave intermediate 244, which reacted with dienophilesto yield substituted thiolanes 246 ± 248.130 In the absence ofdienophile, the ylide 244 produced intramolecular cyclisationproduct 245.
N
S
MeMe
PhN
SCO2Me
CO2Me230
229
+
7
N
S
MeMe
SC
CO2MePhHN
CO2Me
PhMe, D
7
+
O S
CH2
231
+S
NH2R
232
OSMe
S
RHN
233
S
N
R
OH
MeS
234 (64%)
R=Me, Ph.
+
7
+
C
X
Y
R12SCHCOR2
HC
R2CY
X
CC
O
R12S R1
2S7
HC
R2CY
X
CC
O
7R12S 7R1
2S
X YH
R2CO
H
C(O)R2YX
C7+
+
ArCH C(R)NO2 +Me2SCH2COPh Br7Et3N, MeOH
Ar = 3-NO2C6H4, R = CO2Et (85%); Ar = Ph, R =Me (41%).
+
ON
O7
Ar R
O
Ph
235
C(S)NH2
Ar = 2-MeC6H4, 2-NO2C6H4, 4-MeOC6H4, 3-pyridyl, 2-thienyl;
R = Ph, 2-thienyl, cyclo-C3H5 .
+
ArCH C(CN)CSNH2 +Me2SCH2COR Br7Et3N, MeOH
236
SNH2RC(O)
Ar CN
+
Ar
RC(O)
CN
237 238
7
PhCH NTs +Me2SCH2 CH2OH
240
KOH, MeCN
20 8C, 7 min
NHO
Ph
Ts TsN
O
Ph
239 (52%,anti : syn= 2 : 1)241
+
BPhÿ4
OPh
TsHN
Sulfur ylides in the synthesis of heterocyclic and carbocyclic compounds 669
1,3-Dipolar cycloaddition of thiocarbonyl ylide 249 to sulfurdioxide gave rise to 1,2,4-oxadithiolane 2-oxide 250.131
The reaction of thiocarbonyl ylide 251, whichwas generated insitu from oxospiro[cyclobutanedihydrothiadiazole] 252, withtrans-1,2-bis(trifluoromethyl)-1,2-dicyanoethylene afforded thio-lane 253 and stable strained cyclic ketenimine 254 in a ratio of*1 : 4.132
Adamantanethione-S-methylide (255) reacted with methylacrylate to form substituted thiolane 257, whereas its reactionswith thioketones 256 gave rise to 1,3-dithiolanes 258a ± c and259a ± e. The reactions involving thiobenzophenone (256a), thio-fluorenone (256b) or thioxanthione (256c) produced tworegioisomers.133
1,3-Dipolar cycloaddition of thiocarbonyl ylides 260 to thia-zole-5(4H )-thiones 261 134 or azodimethyl carboxylate 262 135
proceeded with high regioselectivity to give the correspondingspirocyclic adducts 263 ± 266 in high yields.
Cycloaddition of the thiocarbonyl ylides 251 and 260a toN-sulfinylaniline and N-sulfinyltosylamide gave rise to bothsubstituted 1,3,4-dithiazolidine 3-oxides (adducts at the N=Sbond) and 1,2,4-oxadithiolane-2-tosylimides (adducts at theS=O bond).136 The reactions of thioketones with diazoacetatesperformed on heating in THF 137, 138 afforded acyl-substitutedthiocarbonyl ylides as the initial reaction products, which eitherunderwent 1,3- or 1,5-dipolar electrocyclisation or reacted withthe second thioketonemolecule to give a 1,3-dipolar cycloadditionproduct. The first example of 1,3-dipolar cycloaddition of thio-carbonyl ylide CH2=S7CH2 to fullerene C60 giving rise to atetrahydrothiophene derivative was reported.139 This product is aconvenient starting compound for subsequent functionalisation.
O
R
S
SMeCH2N2
770 8CNN
S
SMe
COR
243 242
7
O
R
S
SMe
+
244
D
7N2
CO2Et
EtO2C
NC
CN
247
S
SMe
COR
CO2Et
CNNC
EtO2C
248
MeS COR O
S
O
O
OO O
S
SMe
COR
CO2Me
CO2Me
246
S
O R
SMe245
+ 7
N N
SPri
PriD
7N2
S
Pri
Pri
CH2
SO2
O S
SPri
Pri
O249
250 (95%)
CF3
CF3
+ 7
N N
S
O
MeMe
MeMe
40 8C
252
O
MeMe
MeMe
S CH2
251
CN
CF3NC
F3C
O
MeMe
MeMe
S
CN
CN+ O
MeMe
MeMeN
C
S
CF3
CN
CF3
253254
7
S
CH2
+
255
S
MeO2C
257
SS
RR
+
CO2Me
R2C S256a ± e
258a ± c
R2C= Ph2C (a), (b), (c),
S
C C
(d), (e).O
S
S
R
R
259a ± e
CC
N
S
R2
R3
SR1
+ 7R4
2C S CH2
260a ± c
N
S
R2
R3
R1
S
S
PhPh
263
N
S
R2
R3
R1
S
S
O
264
N
S
R2
R3
R1
S
S
265
261
N N
MeO2C
CO2Me
260a ± d
N N
SR4
R4
CO2MeMeO2C266262
R42C = Ph2C (a), (b), (c), (d).O C
CC
670 S N Lakeev, I O Maydanova, F Z Galin, G A Tolstikov
* * *
As evident form the published data, the recent investigations dealtwith more and more complex conversions involving sulfur ylides.We believe that the synthesis of heterocyclic compounds withunique structures and the total synthesis of natural products andbiologically active synthetic analogues will be the major field ofapplication of ylides in the coming years. The reactions of ylidesproducing alkaloids and alkaloid-like compounds are worthy ofparticular attention because they have an increasingly importantplace among drugs used in oncology and cardiology. There is nodoubt that new biologically active compounds will be discoveredamong organosulfur heterocyclic compounds prepared by ylideprocedures.
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