Tetrahedron

Cycloadditions of two thiocarbonyl ylides with α, β-unsaturated esters and nitriles: steric course and mechanism

R Huisgen, G Mloston, H Giera, E Langhals

文献索引：Huisgen, Rolf; Mloston, Grzegorz; Giera, Henry; Langhals, Elke Tetrahedron, 2002 , vol. 58, # 3 p. 507 - 519

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被引用次数: 43

摘要

In the probably concerted cycloadditions of the sterically hindered thiocarbonyl ylide 1 with fumaronitrile, maleonitrile, and dimethyl fumarate, the dipolarophile configuration is retained whereas retention/inversion 99: 1 for dimethyl maleate (51 times less reactive than fumarate) signals a small involvement of a two-step pathway. The latter becomes dominant when two acceptor groups stabilize the anionic terminus of a zwitterionic intermediate. ...