Synthesis of 3-(Trifluoromethyl)benzo[c][1,6]naphthyridines from Substituted 4H-Pyran-4-ones via 4-Amino-5-Aryl-2-(trifluoromethyl)pyridines

The cyclization of acylated 4-amino-5-aryl-2-(trifluoromethyl)pyridines under the action of P2O5/POCl3 smoothly afforded 3-(trifluoromethyl)benzo[c][1,6]naphthyridines in good yields. Intermediate aminopyridines were synthesized in a two-step sequence from the corresponding 4H-pyran-4-ones, which were prepared by reaction of 2-acetyl-2-aryloxiranes and 4-dimethylamino-3-(4-methoxyphenyl)-3-buten-2-one with ethyl trifluoroacetate under basic conditions.