An efficient synthesis of phenyl-substituted dibenzonaphthyridines

A one-pot synthesis of 9-chloro-6-methyl-7-phenyldibenzo[b,h][1,6]naphthyridines from 4-chloro-2-methylquinolines is reported. Since the yield of the dibenzonaphthyridine was low, in an alternative method the title compounds were prepared from the 4-chloro-2-methylquinolines via 2-methyl-4-[(4-chlorophenyl)amino]quinolines as intermediates, which provided improved yields.