Isoindoles from 2,5-disubstituted pyrroles

Abstract

The self-condensation of 2,5-dimethylpyrrole in acidic media gives 1,3,4,7-tetramethyl-1H-isoindole (tautomeric with 1,3,4,7-tetramethylisoindole) in high yield. The condensation of hexane-2,5-dione with 2,5-dialkyl- and 1,2,5-trialkyl-pyrroles is a useful route to certain isoindoles, the spectroscopic properties of which are recorded. The 2,5-disubstitution pattern of the pyrrole is essential if a more favourable condensation at the α-position is to be avoided: thus hexane-2,5-dione and pyrrole itself give a mixture of 4,7-dimethylindole and 5,8-dimethylindolizine.