Conjugate addition of nitroalkanes to dimethyl maleate. Regioselective formation of both monoesters of 2-alkylsuccinic acids

Diesters of (E)-2-alkylidenesuccinic acids obtained by conjugate addition of nitroalkanes to dimethyl maleate can be selectively monohydrolyzed at the more reactive carboxyl group to the corresponding half-ester. Alternatively, total hydrolysis to the diacid allows a subsequent selective methyl esterification of the alkanoic carboxyl group to give the other regioisomeric half-ester. 2-Alkylsuccinic monoesters can be finally obtained by catalytic hydrogenation of the unsaturated derivatives.