The Nafion-H Catalysed Cyclization of α-Carbomethoxy-α-Diazoacetanilides. Synthesis of 3-Unsubstituted-2-Indolinones.

Article abstract of DOI:10.1016/S0040-4020(01)80781-X

Diazoanilides of type 4 were found to undergo Nafion-H catalysed cyclization onto the aromatic ring and concomitant decarboxylation, under optimal conditions, to give 3-unsubstituted 2-indolinones 5 in moderate yields.Diazoanilides that possess electron-donating substituents in the aromatic moiety gave higher yields of 5 and, in one case, the presence of an electron-withdrawing group in the aromatic moiety did not impede the cyclization.In the case of the diazoanilides that possess a N-butenyl group, preferential 1,3-dipolar cycloaddition of the diazo unit onto the butenyl double bond occurred to give an unstable 1-pyrazoline which was converted, by loss of nitrogen accompanied by hydrogen migration, to dihydro-2-pyridinone derivatives.It was also found that substituents ortho to the amido group and/or the site of cyclization sterically retarded the cyclization.