Radical reactions of vinyl epoxides have received little attention' despite their synthetic usefulness,2 and we are unaware of any studies of n-Bu3Sn radical addition to vinyl epoxides, which serves as a starting point for the generation of allylic or alkyl radicals via translocation of radical sites.3 We wish to report novel sequential radical reactions of vinyl epoxides utilizing 1 ,5-n-Bu3Sn group or ]$hydrogen atom transfer from carbon to oxygen, depending on the structural nature of vinyl epoxides.Although very little is known on 1,Stransfers of heteroatoms bearing d orbitals3 such as organo~ilicon~ and organotin groups,$ the ease of a 1,5-n-Bu3Sn group transfer to an alkoxy radical is anticipated on the basis of three factors. First, the C-Sn bond is much weaker than the C-H bond and an alkoxy radical would abstract a I,5-n-Bu3Sn group rather than a hydrogen atom. Second, 1,5-n-Bu3Sn abstraction should be facile because of the presence of the a-vinyl group. Third, a favorable geometry for 1,5-n-Bu3Sn transfer is realized with 2. The reaction of the vinyl exo epoxide 1 with n-Bu3SnH occurred smoothly, yielding initially the alkoxy radical 2 bearing allyltin moiety. I,5-n-Bu3Sn transfer in 2 proceeded rapidly and cleanly, yielding the allylic radical 3 which underwent cyclization as shown in Scheme I.The radical reaction of a vinyl exo epoxide6 was carried out by the addition of a 0.05 M benzene solution of n-Bu3SnH (1.2 (1) Huyser, E. S.; Munson, L. R. J . Org. Chem. 1965,30, 1436. Stogryn, E. L.; Gianni. M. H. Tetrahedron Lett. 197O,II, 3025. Suzuki, A.; Miyaura, N.; Itoh, M.; Brown, H. C.; Holland, G. W.; Negishi, EA. J. Am. Chem. Soc. 1971,93,2792. Murphy, J. A.; Patterson, C. W.; Wooster, N. F. Tetrahedron Lett. 1988, 29, 955. (2) For recent reports, see: Trost, B. M.; Sudhakar, A. R. J . Am. Chem. SOC. 1988, 110, 7933. Oshima, M.; Yamazaki, H.; Shimizu, I.; Nisar, M.; Tsuji, J. J . Am. Chem. SOC. 1989, 111, 6280 and references cited therein.(3) Reviews: Beckwith, A. L. J.; Ingold, K. U. Rearrangements in Ground and Excited Stares; de Mayo, P., Ed.; Academic Press: New York, 1980; Vol. 1, Chapter 4. Freidlina, R. Kh.; Terent'ev, A. B. Adu. Free Radical Chem. 1980, 6, 1 . (4) As far as we are aware, 1,5-TMS transfer has not been reported. According to our preliminary experiment (i -ii), 1.5-TMS transfer from benzylic carbon to oxygen did not occur, indicative of a strong preference for 1,s-H transfer over 1,S-TMS transfer, probably due to the stabilizing effect of the TMS group (Miura, K.; Oshima, K.; Utimoto, K. Tetrahedron Lett. 1989,30,4413). A similar phenomenon has been recently observed by Curran (Snieckus, V.; Cuevas, J.-C.; Sloan, C. P.; Liu, H.; Curran, D. P. J. Am. Chem. SOC. 1990, 112, 896). n.BySnD TMS Ph -i OH I/, 68% ( 5 ) For one example of 1,5-n-Bu3Sn transfer from enoxyl oxygen to alkoxy oxygen, see: Davies, A. G.; Tie, M.-W. J. Orgatwmet. Chem. 1978, 155, 25. (6) Vinyl exo epoxides (h,Ib,lc) were prepared from cyclohexanone in seven steps (LDA, allyl bromide/LDA, HCHO MsCl pyridine, DBU/...
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