Hydrogenations with palladium precipitated in the presence of the substrate

Abstract

Catalytic hydrogenation of 2,3-dihydro-2-methyl-9-phenyl-1H-indeno[2,1-c]pyridine (I; R = Me) or of the 2,3,4,9-tetrahydro-analogue [phenindamine (II)] with palladium precipitated in situ afforded smoothly a quantitative yield of stereospecifically pure all-cis-2,3,4,4a,9,9a-hexahydro-2-methyl-9-phenyl-1H-indeno[2,1-c]-pyridine (IV; R = Me). N-Debenzylation also occurs under these conditions. Use of conventional catalysts and conditions gave intractable mixtures.