Photolytic and chromium(II)-promoted addition reactions of N-halogenoformamides with alkenes

Abstract

Formamidyl radicals (HCONR) do not intramolecularly abstract hydrogen or cyclise onto aromatic rings, but do add intermolecularly to alkenes. The photolytic addition of N-halogenoformamides to alkenes is inhibited by N-alkylation. However, N-alkyl-N-halogenoformamides add to alkenes in the presence of chromium(II) species. The addition of N-halogenoformamides to alkenes occurs regiospecifically with formamidyl bonding to the less substituted terminus of the alkene. The adducts obtained from N-alkylformamidyls exist as mixtures of rotameric isomers whose configurations have been assigned. The reactivity of the formamidyl radical has been discussed in terms of its conformation and electronic state.