PIFA-Mediated oxidative cyclization of 1-aroyl-N-arylcyclopropane-1-carboxamides and their application in the synthesis of pyrrolo[3,2-c]quinolinones

An efficient ring-closing reaction was developed for the synthesis of spirocyclopropane quinolinediones from 2,2-disubstituted 2-benzoylacetamides in the presence of [bis-(trifluoroacetoxy)iodo]benzene (PIFA). This reaction proceeds at room temperature in the absence of a metal catalyst to provide spirocyclopropane quinolinediones in good to excellent yields. Furthermore, these compounds were readily converted to the corresponding pyrrolo[3,2-c]quinolinones to provide tricyclic ring structures similar to those found in the natural products martinellic acid and martinelline via an intermolecular amine ring-opening cyclization reaction.