Reactions of Some Cyclopropylethylenes with TCNE. A Remarkable Effect of Spiro-Activation in the Cycloaddition

Article abstract of DOI:10.1021/jo00277a024

Previously, mono-, di-, and trisubstituted vinylcyclopropanes 1 have been shown to react with TCNE to give a cyclobutane derivative 2 (type I reaction).However, it was observed that the introduction of a spiro-linked fluorene group to the three-membered ring, as in 5, 7, and 8, resulted in a total change of the reaction pathway to produce a vinylcyclopentane derivative (type II reaction), which was formerly observed to occur only in the reaction of tetrasubstituted ethylene 3.The results may be rationalized in terms of the SET initiation of the reaction, which is supposed to be ascribed to the spiro-activation.The chemical behavior of various substrates (5-9 and 15) as well as their relative reactivities are discussed.