Synthesis and molecular structure of novel 4‐aryloctahydropyrido‐[1,2‐c]pyrimidine derivatives

A series of new 4‐aryloctahydropyrido[1,2‐c]pyrimidine‐1,3‐diones 6a,b,d‐h and j were synthesized by intramolecular cyclization of α‐aryl‐α‐(1‐ethoxycarbonyl‐2‐piperidyl)‐acetamide derivatives 5a,b,d‐h and j . The structures of compounds were determined by ¹H and ¹³C nmr spectroscopy. Nmr and X‐ray diffraction data indicate that the configuration at the C4, C4a stereocenters constitute RR and SS pair.