Preferential Incorporation of a Cyclopropyl .SIGMA. Bond Over an Ethylenic .PI. Bond in the TCNE Cycloaddition of 1,2-Dicyclopropylethylene. Occurrence of the Type-II Reaction in Some Disubstituted Substrates.

概要

論文の詳細を見る
Among the two types of cycloadditions known to take place in the reactions of cyclopropyl-substituted ethylenes (1) with tetracyanoethylene (TCNE) (type-1 gives a cyclobutane derivative (2) and type-II yields a vinylcyclopentane derivative (3), the type-II reaction has been practically limited to occur in reactions of tetrasubstituted substrates. However, some disubstituted substrates, namely cis- and trans-1,2-dicyclopropylethylene (4 and 5), were found to produce a mixture of 2 (R1=R2 or R3=H, R2 or R3=cyclo-Pr) and 3 (R1=R2 or R3=H, R2 or R3=cyclo-Pr). In acetonitrile at 80°C, 2 predominated in the reactions of both 4 and 5, but 3 became the major adduct in 1,2-dichloroethane or benzene. The other 1,2-disubstituted ethylenes, such as 1-cyclopropylpropene, 1-cyclopropyl-3-methyl-1-butene and 1-cyclopropyl-3,3-dimethyl-1-butene, produced a small amount of 3 in solvents of low polarity; the type-II, however, has never become a major process. Parent vinylcyclopropane failed to give the type-II adduct in all of the solvents examined. Participation of the cyclopropyl σ bond in the reaction with TCNE is thus shown to have a scope wider than that presumed previously; hence, both the type-I and the type-II processes may be the two principal modes of the reaction of 1 with TCNE.
公益社団法人日本化学会の論文