Hydrogenation of compounds containing an indolizine moiety and of 1-benzylisoquinoline over rhenium heptasulfide

It was shown by hydrogenation of 2,8-diphenylindolizine, benzo[2,3]indolizine, dibenzo[2,3;5,6]indolizine, dibenzo[ 2,3;7,8 ]indolizine, 1-benzylisoquinoline, and 2,3-dimethyl-6-ethyl-4-(4-nitrophenyl)pyridine over Re2S7 (250°C, {Mathematical expression} = 140 atm, 4 h) that the pyridine ring in benzoindolizines is hydrolyzed in preference to the pyrrole ring. Phenyl substituents at the indolizine do not prevent its complete reduction while alkyl substituents make reduction difficult. Annelation of the pyrrole and pyridine rings of indolizine lower the degree of its reduction; a nitro group is reduced to an amino group. © 1991 Plenum Publishing Corporation.