Rate and stereoselectivity changes during hydrogenation of N-heterocycles

High diastereoselectivities. were obtained in the heterogeneous catalytic h ydrogenation of chiral pyrrole and pyridine derivatives with complete conve rsion, in non-acidic medium. The products of the hydrogenations, secondary and tertiary amines act as catalyst modifiers, increasing the d.e. values i n the last period of the reactions.