N-iodoamides. Cyclisation of biphenyl-2-carboxamides

Abstract

The reaction of biphenyl-2-carboxamide and its N-methyl and N-phenyl derivatives with t-butyl hypochlorite–iodine in t-butyl alcohol containing potassium t-butoxide gave phenanthridones, as well as the corresponding 4′-t-butoxy- and 4′-oxoisoindoline-1-spirocyclohexa-2′,5′-dien-3-ones. Both potassium t-butoxide and t-butyl alcohol suppress the iodination of aromatic substrates by iodine monochloride. The role of potassium t-butoxide and t-butyl alcohol in the formation of the isoindoline-1-spirocyclohexa-2′,5′-dien-3-ones and the mechanism of formation of the 4′-ketone from the 4′-t-butoxyisoindoline-1-spirocyclohexa-2′,5′-dien-3-ones are discussed.