α-Sulfenylation of acylsilanes and aldehydes with N- (phenylthio)succinimide

Article abstract of DOI:10.1016/S0040-4039(00)00515-3

The reactions of acylsilanes with N-(phenylthio)succinimide in the presence of p-toluenesulfonic acid in acetonitrile give α-sulfenylated acylsilanes in good yields. Aldehydes with α-alkyl substituent afford moderate yields of α-sulfenylated products unde

Full text of DOI:10.1016/S0040-4039(00)00515-3

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 3911–3914
α-Sulfenylation of acylsilanes and aldehydes with
N-(phenylthio)succinimide
Chih-Hao Huang, Kang-Shyang Liao, Surya Kanta De and Yeun-Min Tsai ∗
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, Republic of China
Received 14 February 2000; revised 22 March 2000; accepted 24 March 2000
Abstract
The reactions of acylsilanes with N-(phenylthio)succinimide in the presence of p-toluenesulfonic acid in
acetonitrile give α-sulfenylated acylsilanes in good yields. Aldehydes with α-alkyl substituent afford moderate
yields of α-sulfenylated products under the same conditions. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: imides; silicon and compounds; sulfides.
α-Sulfenylated carbonyl compounds are useful intermediates in organic synthesis.1 Preparation of
these compounds often involves SN2 displacement of α-halogenated carbonyl compounds.1a Direct
sulfenylation methods are also available;1a,c however, these methods usually require basic conditions.
Recently, we needed to prepare α-sulfenylated acylsilane 2 from bromoacylsilane 1.2,3 Due to the
presence of a bromo functional group, we tried to avoid using basic conditions.4 We found that N-
(phenylthio)succinimide 35 could be used to convert acylsilanes to α-sulfenylated acylsilanes under
acidic conditions.6,7
Our results are shown in Table 1. The reaction of acylsilane 1 (entry 1) with 1 equivalent of imide 3 and
0.1 equivalent of p-toluenesulfonic acid in dichloromethane at room temperature overnight gave sulfide 2
in excellent yield (92%). Surprisingly, under the same reaction conditions (entry 2), acylsilane 42 afforded
10% of sulfide 5. The difference between acylsilanes 4 and 1 is a single methylene unit. We found that
this type of reaction is faster in a more polar solvent such as acetonitrile. When acylsilane 4 was treated
with imide 3 (1 equiv.) in the presence of a catalytic amount of p-toluenesulfonic acid (0.1 equiv.) in
acetonitrile for 8 h (entry 3), we obtained an 80% yield of sulfide 5. The reaction conditions used in entry
∗
Corresponding author. E-mail: ymtsai@mail.ch.ntu.edu.tw (Y.-M. Tsai)
0040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)00515-3
tetl 16794

3912
Table 1
α-Sulfenylation of acylsilanes with N-phenylthiosuccinimide 3a

3913
Table 2
α-Sulfenylation of aldehydes and ketones with N-phenylthiosuccinimide 3a
3 turned out to be quite useful for analogous acylsilanes 6 and 8 (entries 4 and 5). However, for shorter
acylsilanes such as 10 (entry 6), no reaction occurred when using 0.1 equivalent of p-toluenesulfonic
acid. In the presence of 1 equivalent of p-toluenesulfonic acid, propanoylsilane 10 reacted with imide 3
in acetonitrile for 5 h to afford a 90% yield of sulfide 11.
Ethanoylsilane 12 (entry 8) was the least reactive one that we have studied. Under the conditions
described above for the preparation of sulfide 11 (entry 7), we observed no reaction for ethanoylsilane
12. Reaction occurred when we used borontrifluoride etherate; however, bis-sulfenylation became
competitive. As shown in entry 8, the reaction of ethanoylsilane 12 with imide 3 in the presence of
borontrifluoride etherate (0.5 equiv.) in acetonitrile for 6 h proceeded in about a 60% conversion. The
monosulfide 13 and bis-sulfide 14 were present in a 3:2 ratio, respectively.
The α-sulfenylation reactions are not limited to acylmethyldiphenylsilanes. As shown in entry 9 (Table
1), bromoacylsilane 152 with a bulky t-butyldimethylsilyl group (TBDMS) underwent α-sulfenylation
with imide 3 (2.2 equiv.) in the presence of p-toluenesulfonic acid (0.1 equiv.) in acetonitrile (6 h) to give
sulfide 16 in an 83% yield. Under similar reaction conditions, acyltrimethylsilane 178 (entry 10) afforded
sulfide 184a in good yield (86%).
When we applied this method to aldehydes and ketones, only α-substituted aldehydes were sulfenyla-
ted in mild yields. As shown in Table 2, a dismal 19% yield of sulfide 209 (entry 1) was obtained by the
reaction of straight chain hexanal 19 with imide 3 in the presence of borontrifluoride etherate (1 equiv.)

3914
at room temperature in acetonitrile for 21 h. With the presence of an α-methyl substituent, aldehyde 21
(entry 2) led to 68% of sulfide 22 in 3 h under similar conditions. All the ketones that we have studied
reacted poorly as shown in entries 3 and 4. Sulfenylation occurred preferentially at the more substituted
side of the unsymmetric ketones with low yields.
The reactivity pattern observed in these sulfenylation reactions correlates well with the enol content
of the carbonyl compounds.10 It was reported recently that the enol content of acylsilanes is higher than
aldehydes and ketones.11 In this study, the acylsilanes show the highest reactivity towards imide 3 under
acidic conditions. Among the acylsilanes, ethanoylsilane 12 is the least reactive. Presumably, acylsilane
12 is the least enolizable acylsilane that we have studied. Ketones are known to have lower enol content
than aldehyde.10 Here, we found that the ketones are poor substrates in this reaction.
Acknowledgements
Financial support by the National Science Council of the Republic of China is gratefully acknowled-
ged.
References
1. (a) Trost, B. M. Chem. Rev. 1978, 78, 363–382. (b) Trost, B. M. Acc. Chem. Res. 1978, 11, 453–461. (c) Foray, G.;
Peñéñory, A. B.; Rossi, R. A. Tetrahedron Lett. 1997, 38, 2035–2038.
2. Chang, S.-Y.; Jiaang, W.-T.; Cherng, C.-D.; Tang, K.-H.; Huang, C.-H.; Tsai, Y.-M. J. Org. Chem. 1997, 62, 9089–9098.
3. For recent reviews about acylsilanes, see: (a) Ricci, A.; Degl’Innocenti, A. Synthesis 1989, 647–660. (b) Page, P. C. B.;
Klair, S. S.; Rosenthal, S. Chem. Soc. Rev. 1990, 19, 147–195. (c) Cirillo, P. F.; Panek, J. S. Org. Prep. Proc. Int. 1992, 24,
553–582. (d) Page, P. C. B.; McKenzie, M. J.; Klair, S. S.; Rosenthal, S. In Acyl Silanes; Rappoport, Z.; Apeloig, Y., Eds.
The chemistry of organic silicon compounds. John Wiley & Sons: New York, 1998; Vol. 2, Chap. 27, pp. 1599–1665.
4. For the preparation of α-sulfenylated acylsilanes through enol silyl ethers, see: (a) Minami, N.; Abe, T.; Kuwajima, I. J.
Organometal. Chem. 1978, 145, C1–C3. (b) Reich, H. J.; Holtan, R. C.; Bolm, C. J. Am. Chem. Soc. 1990, 112, 5609–5617.
(c) Thomas, S. E.; Tustin, G. J. Tetrahedron 1992, 48, 7629–7640.
5. Groebel, W. Chem. Ber. 1960, 93, 284–285.
6. For α-selenylation of ketones and aldehydes with N-(phenylseleno)phthalimide under acidic conditions, see: Cossy, J.;
Furet, N. Tetrahedron Lett. 1993, 34, 7755–7756.
7. For the use of sulfenamide derivatives to convert ketones to their β-ketosulfides, see: (a) Mukaiyama, T.; Kobayashi, S.;
Kumamoto, T. Tetrahedron Lett. 1970, 5115–5118. (b) Kumamoto, T.; Kobayashi, S.; Mukaiyama, T. Bull. Chem. Soc.
Jpn. 1972, 45, 866–870.
8. Miller, J. A.; Zweifel, G. Synthesis 1981, 288–289.
9. Seebach, D.; Teschner, M. Chem. Ber. 1976, 109, 1601–1616.
10. Guthrie, J. P.; Cullimore, P. A. Can. J. Chem. 1979, 57, 240–248.
11. Kresge, A. J.; Tobin, J. B. J. Org. Chem. 1993, 58, 2652–2657.