l-Phenylalanine Triflate as Organocatalyst for Divergent ­Approaches to Trisubstituted Hexahydroimidazo[1,2-a]pyridine and 1,4-Diazepane Derivatives

The convergent synthesis of two biologically significant classes of trisubstituted hexahydroimidazo[1,2- a ]pyridine and 1,4-diazepane derivatives from readily available aromatic aldehydes, ketones, and ethane-1,2-diamine is reported. This protocol is promoted by the highly effective l -phenylalanine triflate catalyst through intermolecular annulation, and tolerates a variety of functional groups with excellent yields.