A Synthetically Useful Source of Alkyl and Acyl Radicals
Alkyl and acyl xanthates are useful precursors of alkyl and acyl radicals. With acyl xanthates, the radical chain process can be initiated by visible light, and capture of the intermediate acyl radical leads to various carbonyl derivatives. In some cases, the acyl radical extrudes carbon monoxide to give an alkyl radical which in turn can be trapped by an electrophilic olefin. Alkyl xanthates in contrast require U.V. lighting but the reaction sequence can sometimes be initiated with visible light if small amounts of S-benzoyl-O-ethyl xanthate are incorporated into the medium.
KeywordsVisible Light Copper Powder Carbonyl Derivative Acyl Radical Ethyl Xanthate
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- 1.D. Forrest and K.U. Ingold, J. Amer. Chem. Soc., 1978, 100, 3868; J.C. Scaiano and K.U. Ingold, J. Amer. Chem. Soc., 1976, 98, 4727 and references therein; J.C. Scaiano, J. P.-A Tremblay and K.U. Ingold, Can. J. Chem., 1976, 54, 3407; D. Forrest, K.U. Ingold, and D.H.R. Barton, J. Phys. Chem., 1977, 87, 915.CrossRefGoogle Scholar
- 4.P. Delduc, C. Tailhan, and S. Z. Zard, J. Chem. Soc., Chem. Commun., 1988, 308.Google Scholar
- 6.D. H. R. Barton and S. W. McCombie, J. Chem. Soc., Perkin Trans. 1, 1975, 1574; D. H. R. Barton, W. B. Motherwell, and A. S. Stange, Synthesis, 1981, 743; W. Hartwig, Tetrahedron, 1983, 39, 2609.Google Scholar
- 7.B. Giese, “Radicals in Organic Synthesis: Carbon-Carbon Bond Formation”, Pergamon Press, Oxford, 1986.Google Scholar
- 9.D. H. R. Barton, M. V. George, and M. Tomoeda, J. Chem., Soc., 1962, 1967.Google Scholar
- 11.For recent synthetic work on acyl radicals, see: E. J. Walsh Jr., J. M. Messinger II, D. A. Grudoski, and C. A. Allchin, Tetrahedron Lett., 1980, 21, 4409; P. Gottschalk and D. C. Neckers, J. Org; Chem., 1985, 50, 3498; D. J. Coveney, V. F. Patel, and G. Pattenden, Tetrahedron Lett., 1987, 28, 5949; V. Patel and G. Pattenden, Tetrahedron Lett., 1988, 29, 707.Google Scholar