Tetrahedron Letters, Vol.32, No.50, pp 7411-7414, 1991 0040~4039/91 $3.00 + .00 Printed in Great Britain Pergamon Press plc

The First S y n t h e s i s o f Al iphat ic S . 1 ~ n e s from Thiono-e s t er s

Margareth Lemari6 , Th i -Nh~n P h a m , and Patr i ck Metzner*

Laboratoire de Chimie des Composds Thio-organiques (Associ~ au C N R S ) ,

ISMRA, 6 Boulevard du Mardchal Juin, 14050 Caen, France.

(E Mail: METZNEROFRCAEN51)

Abstract . React ion of var ious th iono-esters wi th one equivalent of rneta-chloroperoxybenzoic acid at 0°C in d i ch lo rome thane furnishes the co r r e spond ing sulfines, ev idenced for the first time. These th iocarbonyl oxides are ra ther uns table at room t empera tu r e and give carboxylic esters, with loss of sulfur. The overal l sequence prov ides an easy and quant i ta t ive C=S ~ C=O t r ans fo rma t ion .

Sulf ines ( th ioca rbony l oxides) are cu r ren t ly the subject of in tense inves t iga t ion . ]-4

Despi te the initial a s sumpt ion that al iphat ic members cannot be p repa red by direct oxidat ion of

th iocarbonyl compounds1,3,5, 6, it is possible to achieve this for thioketones 7 and dithioesters.8, 9

O

s s

A DARC-Chemical Abstracts subs t ruc tura l re t r ieval showed that only three examples of

th iones ter sulf ines were known, 10,11 in the heterocycl ic series. We dec ided to invest igate the

ox ida t ion of a va r ie ty of th ionesters , 12 to a t t empt the p r epa ra t i on of their sulf ines and, if

possible, evaluate their stabilities.

Reaction of th ionesters 1-9 wi th one equiva len t of meta-chloroperoxybenzoic acid, in

d ich lo romethane , was carr ied out at 0°C for a shor t t ime (30 sec - I0 rain). After w ork -up 13

c h r o m a t o g r a p h i c pu r i f i ca t i on was a v o i d e d wi th i m m e d i a t e N M R ana lys i s o f the c rude

material . It was found to consist of a mixture of the sulfines 10-17 and the carboxylic esters 18-26

(table). IH N M R spec t roscopy revea led the presence of both E and Z isomers of the sulfines.

Methoxy signals were observed a round 3.8 and 4.6 p p m respect ively. For the cases of methyl

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th iop iva la te 4 and th iobenzoate 8 only the Z isomers were seen. The presence of sulfines was

confirmed by 1:~C NMR shifts of ca 210 and 215 p p m for the E and Z sulfinyl carbons respectively (entries 4-7, 9).

0 0

S MCPBA, CH2C12 ~ S S / / - S O ).. +

R ~ ' N 0°C, 0-5-10 min R O M e R / ~ ' N " ~ O M e O M e R O M e

E Z 1-9 10-17 18-26

The s tab i l i t i e s of su l f ines were e x a m i n e d at r o o m t e m p e r a t u r e by NMR. Their

convers ion into carboxylic esters 18-26, with precipi ta t ion of sulfur, was observed. The reaction

half t ime ranges from less than one to several hours. Sulfines, where R is a s t ra ight alkyl chain,

dr-'compose the most quickly, wherea.~ h indered R groups (entries 4, 6 and 7) s tabil ize the sulfine

moie ty .

So, the synthet is of a var ie ty of sulfines by direct oxidat ion of thionesters has been carried

out for the first time. This was achieved even when the subst ra tes are enethio l izable (entries 1,

3, 5, 6), in contrast to the expectat ion that divinyl disulf ides w o u l d be formed.

It should be noted that the th iocarbonyl group is a t tacked select ively in the presence of a

carbonocarbon double bond (entries 5-7).

Moni tor ing the crude mix ture suppor t s the view that sulf ines are the p r ima ry oxidat ion

products . Loss of sul fur is observed , fo l lowed by format ion of the co r r e spond ing carboxyl ic

esters. By ana logy wi th p rev ious speculat ion, we be l ieve that the p roduc t ion of esters results

f rom a t h e r m a l l y a l l owed e lec t rocy l iza t ion reac t ion of sulf ines , i n t e r m e d i a t e fo rma t ion of

o x a t h i i r a n e 27, f o l l owed by loss of sulfur . We d i d not o b s e r v e any rearrangement of

in te rmedia te 27, in contrast to our recent resultsS, 9 with di thioesters (SR group instead of OMe).

R O X ~ O M e

27

Due to quant i ta t ive format ion of esters this sequence m a y be cons idered as an efficient

C - S into C=O group t ransformat ion (for a rev iew see ref. 14). It involves use of an equivalent of

MCPBA and s t a n d i n g the p r o d u c t at room t e m p e r a t u r e overn igh t . An a d v a n t a g e is the

avoidance of the use of heavy metals such as mercury or silver.

We have thus ob ta ined var ious sulfines: al iphatic, aounsatura ted and aromat ic ones. The

rather shor t life of these sulf ines however makes their use in synthes is difficult , unless they

could be t r apped by a reagent present in situ and compat ib le wi th the oxidat ion condit ions.

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T a b l e . O x i d a t i o n of T h i o n e s t e r s w i t h M C P B A .

E n t r y T h i o n e s t e r S u l f i n e S u l f i n e N M R R a t i o E/Z 1H 13C s u l f i n e / r a t i o O M e C=S=O es t e r

E Z E Z

Ester

S I I

1 . - ~ 1 10 50 : 50 CTHI5 OMe

3.83 4.65 33 : 67 a 18

S H

2 ~ 2 0 : I00 b CloH21 OMe

3 ~ 3 11 38 : 62 OMe

S I I

4 ..JI... 4 12 0 : 100 tBu OMe

3.83 4.63 3 7 : 6 3 a

19

20

4.62 208.9 65 : 35 a 21

8

5 ~ 5 13 57 : 43 3.80 4.59 195.4 221.8 36 : 64b OMe

22

S V I I

6 " ~ ' ~ O M e 6 14 88 : 12 3.80 4.56 201.4 224.3 9 7 : 3 c 23

7 OMe 7 15 8 2 : 1 8 4.03 4.56 208.9 215.9 9 6 : 4 d 24

4.70 10 : 90 a

S

" ~ 8 1 6 0 : 100 8 Ph" OMe

S I I

9 p h , , G , ~ O M e _ _ 9 17 75 : 25 3,92 4,62 209.7 67 : 33 a

25

26

a) The NMR spectrum was recorded 35-40 rain after the end of the oxidation, b) The NMR spectrum was recorded 80 rain after the end of the oxidation, c) The NMR spectrum was recorded 105 rain after the end of the oxidation, d) The NMR spectrum was recorded 95 rain after the end of the oxidation.

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References

1. Zwanenburg, B. Recl. Tray. Chim. Pays-Bas 1982, 10I, 1-27.

2. Zwanenburg, B. Rev. Heteroatom Chem. 1988, 1, 218-234.

3. Zwanenburg, B. Phosphorus, Sulfur Silicon Relat. Elem. 1989, 43, 1-24.

4. Zwanenburg, B.; Lenz, B. G. In Houben-Weyl Methoden der Organischen Chemie; Klamann, D., Ed.; Thieme: Stuttgart, 1985; Band Ell , Tell 1, p. 911-949.

5. Porskamp, P. A. T. W.; van der Leij, M.; Lammerink, B. H. M.; Zwanenburg, B. Recl. Trav. Chim. Pays-Bas 1983, 102, 400-404.

6. van der Leij, M.; Zwanenburg, B. Tetrahedron Lett. 1978, 3383-3386.

7. Le Nocher, A.-M.; Metzner, P. Tetrahedron Lett. 1991, 32, 747-750.

8. Metzner, P.; Pham, T. N. J. Chem. Soc., Chem. Commun. 1988, 390-391.

9. Metzner, P. Phosphorus, Sulfur Silicon Relat. Elem. 1991, 59, 1-16.

10. Buggle, K.; Fallon, B. Monatsh. Chem. 1987, 118, 1197-1199.

11. Lenz, B. G.; Regeling, H.; Zwanenburg, B. Tetrahedron Lett. 1984, 25, 5947-5948.

12. Thionesters 1-9 were prepared according to the following methods. Reaction of carboxylic esters with Lawesson reagent in xylene at reflux for 24 hr furnishedlS, 16 thionesters 1, 3, 8 and 9 with respective yields of 49 %, 54 %, 66 %, 42 %. O-Methyl undecanethioate 2 was synthesized in a 41% yield by treatment of the trimethylsilyl- keteneacetal from methyl undecanoate with hydrogen sulfide. 17 Reaction of pivalonitrile with acidic methanol and basic sulfhydrolysis of the resulting imidoester18,19 led to O-methyl 2,2-dimethylbutanethioate 4 (yield: 26 %). 4-Unsaturated thionesters 5-7 were obtained with the aid of a Claisen rearrangement: O-methyl thioacetate, propanethioate and 2-methylpropanethioate were first prepared according to ref. 19 and then S-allylated by deprotonation with LDA and reaction with appropriate allylic halides; resulting ketenedithioacetals undergo thio-Claisen rearrangement 2° at room tecnperature over several hours or days to afford thionesters 5-7.

13. The reaction mixture was diluted with dichloromethane, washed three times with an aqueous solution of sodium hydrogenocarbonate and then with brine. The organic phase was dried over magnesium sulfate and then concentrated by evaporation of dichloromethane. NMR analysis of the crude material was effected as soon as possible.

14. Metzner, P. Synthesis, in the press.

15. Pedersen, B. S.; Scheibye, S.; Clausen, K.; Lawesson, S.-O. Bull. Soc. Chim. Belg. 1978, 87, 293-297.

16. Bunnelle, W. H.; McKinnis, B. R.; Narayanan, B. A. J. Org. Chem. 1990, 55, 768-770.

I7. Corey, E. J.; Wright, S. W. Tetrahedron Lett. 1986, 25, 2639-2640.

18. McElvain, S. M.; Venerable, J. T. J. Am. Chem. Soc. 1950, 72, 1661-1669.

19. Coates, R. M.; Firsan, S. J. J. Org. Chem. 1986, 51, 5198-5209.

20. Schuijl, P. J. W.; Brandsma, L. Recl. Tray. Chim. Pays-Bas 1968, 87, 929-939.

(Received in France 26 September 1991)