Fischer indole synthesis of 3-acyl- and 3-alkoxy-carbonylindoles

Abstract

N-Benzyl-N-phenylhydrazine derivatives of 1,3-diketones and 1,3-ketoesters undergo normal Fischer cyclisations to indoles, but no method could be found for the subsequent removal of the N-protecting group. No method could be found for the indolisation of N-aroyl-N-phenylhydrazine derivatives of dimedone with retention of the N-protecting group, though heating in tetralin did effect the electrocyclic step of the Fischer sequence and the formation of a carbon–carbon bond.