Radical addition reactions. Part II. The addition of ethyl cyanoacetate to conjugated olefins

Abstract

The addition of ethyl cyanoacetate, catalysed by t-butyl peroxide at 155—160°, to a series of conjugated olefins XCH:CHY, namely dimethyl fumarate (X = Y = CO₂Me), methyl crotonate (X = Me, Y = CO₂Me), β-methylstyrene, methyl cinnamate, benzylideneacetone, and cis- and trans-cinnamonitrile (X = Ph, Y = Me, CO₂Me, Ac, or CN, respectively), gives mainly the 1 : 1-adduct, XCHR·CH₂Y (R = CH(CN)·CO₂Et), in the first two cases, and XCH₂·CHRY in the others, in yields of 26, 53, 42, 31, 16, 26, and 20%, respectively. Isomerisation of cis-cinnamonitrile to the trans-isomer under the conditions of the reaction is interpreted as due to the reversibility of the addition step. This, however, does not occur in the addition of butanal to the same nitrile, which gives PhCH₂·CH(CN)·COPrⁿ(40%).