J.Org. Chem., Vol. 42, No. 10, 1977 1773
Selenium Stabilized Anions 7380-81-6; 15 (Ar = P - C H ~ C ~ H61587-08-4; ~), 15 (Ar = p-H$OC&), 61587-09-5; 15 (Ar = p-C&$02), 61587-10-8; 16, 61587-11-9; 17, 61587-13-1; 18,5633-34-1;19,24104-87-8;d i e t h y l disulfide, 110-81-6; 1,2-dithiane, 505-20-4; bis(p-methylphenyl) disulfide, 103-19-5; bis(pmethoxypheny1) disulfide, 5335-87-5; bis(pnitropheny1) disulfide, 100-32-3.
References and Notes (1) (a) Part 39: L. Field arid C. H. Banks, J. Org. Chem., 40, 2774 (1975). (b) Presented in part at the 25th Southeastern Regional Meeting of the American Chemical Society, Charleston, S.C., Nov 7-9, 1973, Abstract No. 336, and at the 7th Central Regioml Meeting of the American Chemical Society, Morgantown. W.Va., May 28-30, 1975, Abstract No. 85. (c) Abstracted from the Ph.D. Dissertation of H.-K. C., Vanderbilt University, Aug 1976, which gives considerable additional detail. (d) This investigationwas supported by NIH Research Grant AM 11685 awarded by the National Institute of Arthritis, Metabolism, and Digestive Diseases PHSIDHEW, and in part by the Research Council of Vanderbilt University. (2) S. Nakayama, M. Yoshifuji. R. Okazaki, and N. Inamoto, Chern. Cornrnun., 1186(1971). (3) M. Yoshifuji, S. Nakayama, R. Okazaki. and N. Inamoto, J. Chem. SOC., Perkin Trans. 7, 2065 (1973). (4) (a) H. Matsuyama, H. Minato, and M. Kobayashi, Bull. Chem. SOC.Jpn., 46, 2845 (1973): (b) H. Matsuyama, H. Minato, and M. Kobayashi. ibid., 46,3828 (1973).
(5) (a) A. W. Johnson, "Ylid Chemistry", Academic Press, New York, N.Y., 1966; (b) B. M. Trost and L. S. Melvin, Jr., "Sulfur Ylides". Academic Press, New York, N.Y., 1975. (6) (a) R. Kuhn and H. Trischmann, Justus Liebigs Ann. Chem., 611, 117 (1958); (b) For leading references, see L. Field, Synthesis, 101 (1972). (7) We prefer the simplicity and easy visualization of this type of nomenclature for 12, as used by Ando et a1.8 The index name of Chemical Abstracts for 12 is diphenylsulfonium 2-methoxy-1-rnethoxycarbonyl-2-oxoethylide. (8) W. Ando, T. Yagihara, S. Tozune. I. Imai, J. Suzuki, T. Toyama. S. Nakaido, and T. Migita, J. Org. Chem., 37,1721 (1972). (9) For the reasons of ref 7, we prefer this name to the index name of Chemical Abstracts for 14, dimethylsulfonium 2-ethoxy-2-oxoethylide. (10) (a) Y. Hayasi and H. Nozaki, Bull. Chern. SOC.Jpn., 45, 198 (1972); (b) S. Kato, S . Imamura, and M. Mizuta, lnt. J. Sulfur Chem., Part A, 2, 283 (1972). (1 1) (a) E. E. Reid, "Organic Chemistry of Bivalent Sulfur", Vol. 11, Chemical PublishingCo., New York, N.Y.. 1960, pp 24-26; (b) ibid., p 126; (c) ibid., Vol. IV, 1962, pp 43, 79. (12) L. Field and R. B. Barbee, J. Org. Chem., 34, 36 (1969). (13) C. King, J. Org. Chem., 25, 352 (1960). (14) L. F. Fieser and M. Fieser, "Reagents for Organic Synthesis", Vol. I, Wiley, New York, N.Y., 1967. (15) E. J. Corey and M. Chaykovsky, J. Am. Chem. SOC., 87, 1353 (1965). (16) S. Oae, W. Tagaki, and A. Ohno, Tetrahedron, 20, 427 (1964). (17) G. B. Payne, J. Org. Chem., 32, 3351 (1967). (18) B. M. Trost, J. Am. Chem. SOC., 89, 138 (1967). (19) A. W. Johnson and R. T. Amel, J. Org. Chem,, 34, 1240 (1969). (20) K. W. Ratts and A. N. Yao. J. Org. Chem., 31, 1185 (1966).
Selenium Stabilized Anions. Selenoxide Syn Elimination and Sila-Pummerer Rearrangement of cy-Silyl Selenoxides Hans J. Reich*l and Shrenik K. Shah D e p a r t m e n t of Chemistry, U n i v e r s i t y of Wisconsin, Madison, Wisconsin 53706 Received August 14,1975 Several a - s i l y l selenides (2, 10) have been prepared b y silylation o f a-lithio selenides a n d a l k y l a t i o n o f a - l i t h i o a - s i l y l selenides. O x i d a t i o n o f these selenides t o selenoxides results in competitive selenoxide syn elimination t o give v i n y l silanes (4) a n d sila-Pummerer rearrangement t o give v i n y l selenides (8) a n d carbonyl compounds. T h e r a t i o can b e controlled t o some extent by control o f reaction conditions, but a more pronounced change (favoring syn elimination) can be achieved by m a k i n g t h e arylseleno group more electron withdrawing ( m - t r i f l u o r o m e t h y l phenylselcno instead o f phenylseleno). These m -trifluoromethylphenyl selenides are also deprotonated substant i a l l y more r a p i d l y t o give a - l i t h i o selenides t h a n are p h e n y l selenides. Silaalkene could n o t be produced by selenoxide syn elimination. T h e sila-Pummerer rearrangement has been used t o prepare a - s i l y l ketones.
Functionalized organolithium reagents, in which a-heteroatom substituents serve both to facilitate preparation of the anion by acidifying a hydrogens and to mediate subsequent transformations of products derived from the anion, have become important tools for the synthetic organic chemist. As part of our study of selenium stabilized anions,2 we have developed methods for the generation of several silyl substituted a-lithio selenides, and explored potentially useful synthetic transformations of products derived from them. Of particular interest is the possibility of forming silaalkenes by selenoxide syn elimination, and the competition between selenoxide syn e l i m i n a t i ~ n giving ,~ vinyl silanes, and silaPummerer rearrangement,4 giving carbonyl compounds after hydrolysis. The thermolysis of a-silyl sulfoxides gives only sila-Pummerer products. It was our feeling that the lower activation energy for selenoxide syn elimination38 as compared to sulfoxide elimination might enable the elimination pathway to compete favorably with the sila-Pummerer reaction in the selenium system. We chose selenide 2 for our study. Benzyl phenyl selenide5 was silylated2a to give la, which was in turn deprotonated and methylated to give 221. Oxidation of 2a to the selenoxide 3a was
1.LiN.i-Pr,, -78 "C
ArSeCHzPh
2. MeaiC1
SiMe, l a , Ar = b, Ar =
C,H, m-CF,C,H, CH, Ph
1 LtNEt,
__t
2 Me1
\7
A
ArSe
SiMe,
2
carried out using rn-chloroperbenzoic acid. Decomposition of 3a occurred with a half-life of ca. 30 min a t 0 "C (observed by low-temperature NMR), and gave varying mixtures of products resulting from selenoxide syn elimination (path a) and sila-Plummerer rearrangement (path b), presumably via the ylide 5. The data in Table I show that significant amounts of both path a and path b occur under all conditions tried. The ratio does not respond in a predictable way to changes in reaction conditions such as solvent polarity, temperature, or pH. The partitioning of intermediate 5 to acetophenone (6 and 7) and
1774 J. Org. Chem., Vol. 42, No. 10, 1977 Table I. Products from Decomposition of Selenoxide 3 Products, % 4 6+7 8
Starting material
Reaction conditions
3a 3a 3a 3a 3a 3a 3b 3b
CC14," 80 "c CCl4,Olb80 "C C2C14,b 10c1"C THF,b 25 "C MeOH,asb400C Acetone,"bt'56 "C CCl4," 80 "C THF,b 25 "C
64 55 55 30 51 49 66
58
6 7 10 22 8
20
