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The Corey–Winter olefin synthesis is a series of chemical reactions for converting 1,2-diols into olefins.〔Corey, E. J.; Winter, R. A. E. ''J. Am. Chem. Soc.'' 1963, ''85'', 2677. ()〕〔Corey, E. J.; Hopkiss, P. B. ''Tetrahedron Lett.'' 1982, ''23'', 1979. ()〕 It is named for the American chemist and Nobelist Elias James Corey and the American-Estonian chemist Roland Arthur Edwin Winter.〔Block, E. ''Org. React.'' 1984, ''30'', 457. 〕 Often, thiocarbonyldiimidazole is used instead of thiophosgene as shown above, since thiophosgene has a similar toxicity profile as phosgene, whereas thiocarbonyldiimidazole is a much safer alternative. ==Mechanism== The reaction mechanism involves the formation of a cyclic thiocarbonate from the diol and thiophosgene. The second step involves treatment with trimethyl phosphite, which attacks the sulfur atom, producing S=P(OMe)3 (driven by the formation of a strong P=S double bond) and leaving a carbene.〔Horton, D.; Tindall, Jr., C. G. ''J. Org. Chem.'' 1970, ''35(10)'', 3558-3559. ()〕 This carbene collapses with loss of carbon dioxide to give the olefin. An alternative mechanism does not involve a free carbene intermediate, but rather involves attack of the carbanion by a second molecule of trimethylphosphite with concomitant cleavage of the sulfur-carbon bond. The phosphorus stabilized carbanion then undergoes an elimination to give the alkene, along with an acyl phosphite, which then decarboxylates. The Corey-Winter olefination is a stereospecific reaction: a ''trans''-diol gives a ''trans''-alkene, while a ''cis''-diol gives a ''cis''-alkene as the product. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Corey–Winter olefin synthesis」の詳細全文を読む スポンサード リンク
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