cis-Fused hexahydro-4aH-indeno[1,2-b]pyridines: transformation of bridgehead ester group and conversion to tricyclic analogues of NK-1 and dopamine receptor ligands

The bridgehead ester group of cis-fused methyl 2-oxo-9b-phenyl-1,2,3,4,5,9b-hexahydro–4aH-indeno[1,2-b]pyridine-4a-carboxylates obtained via an intramolecular Ritter reaction, was transformed into acid, alcohol, aldehyde, and amine groups. Further elaboration afforded conformationally constrained tricyclic analogues of NK-1 antagonists and a bicyclic dopamine receptor ligand.