N-Iodo-amides: cyclisation of substituted biphenyl-2-carboxamides

Abstract

Homolysis of N-iodo-amides leads to 2′-, 3′-, and 4′-substituted biphenyl-2-carboxamidyl radicals which cyclise intramolecularly to give γ- and δ-lactams in parallel processes. The proportion of Ar₁-5 and Ar₂-6 cyclised products is in accord with the steric and electronic effects of the substituents. 4′-Iodo-4′-methoxy-N-methyl-3-oxoisoindoline-1-spiro-1′-cyclohexa-2′,5′-dienes have been identified as spiro-intermediates in the cyclisation of N-methyl-4′-methoxybiphenyl-2-carboxamide.