Intramolecular Heck reaction: A facile sequential one-pot synthesis of 1,2,3,4-tetrahydrobenzo[b][1,6]naphthyridines

A simple and convenient sequential one-pot synthesis of 1,2,3,4-tetrahydrobenzob]1,6] naphthyridines has been developed. The reductive amination of 2-chloro-3-formylquinolines with various amines in the presence of sodium borohydride provided the corresponding secondary amines in high yields. Further, a sequential one-pot reaction involving N-allylation and intramolecular Heck type 6-exo-trig cyclization was performed on the secondary amines to afford a range of desired 1,2,3,4-tetrahydrobenzob]1,6]-naphthyridine derivatives in good to high yields.