Haval-Argade contrathermodynamic rearrangement of alkylidenesuccinimides to alkylmaleimides via the corresponding isoimides: a general approach to alkyl and dialkyl substituted maleimides

A simple and efficient access to alkyl and dialkyl substituted maleimides has been demonstrated via the new contrathermodynamic rearrangement of (E)-alkylidenesuccinimides to alkylmaleimides. The (E)-alkylidenesuccinimides obtained from the Wittig-condensation of N-arylmaleimide with aliphatic aldehydes on regioselective hydrolysis furnished the corresponding (E)-alkylidenesuccinanilic acids in 95-98% yields. The β-alkylidenesuccinanilic acids on treatment with cyanuric chloride in the presence of triethylamine gave the corresponding β-alkylisomaleimides in 78-80% yields via the β-alkylideneisosuccinimides with the exocyclic to endocyclic carbon-carbon double bond migration. The kinetically controlled products alkylisomaleimides in refluxing acetic acid furnished the thermodynamically controlled alkylmaleimides in 98% yield. The Wittig condensation of alkyl substituted isomaleimides/maleimides with aliphatic aldehydes gave the desired dialkyl substituted maleimides in high yields. A conversion of α-methylenesuccinanilic acids to α-methylisomaleimides has also been described, with 90% yield.