Reactivity of 2H-1,2,3-diazaphosphole derivatives: unexpected formation of indoles and a new indolization reaction

Abstract

2H-1,2,3-Diazaphosphole derivatives (1) react with alkyl halides to give the corresponding 2,3-disubstituted indoles (3) as the major products (30–40% yields). Small amounts (15–20%) of the ring-opened compounds (4) in the two diastereoisomeric Z-configurations are also obtained. During this reaction a cis-(1)⇄trans-(1) isomerization is also observed. Mechanistic explanations of these results have been described and a new general method has been developed for the synthesis of 2,3-disubstituted indoles from ketone arylhydrazones and PCl₃.