Synthesis of 3-(trifluoromethyl)benzo[c][1,6]naphthyridines from substituted 4H-pyran-4-ones via 4-amino-5-aryl-2-(trifluoromethyl)pyridin

The cyclization of acylated 4-amino-5-aryl-2-(trifluoromethyl)pyridines und er the action of P2O5/POCl3 smoothly afforded 3-(trifluoromethyl)benzo[c][1 ,6]naphthyridines in good yields. Intermediate aminopyridines were synthesi zed in a two-step sequence from the corresponding 4H-pyran-4-ones, which we re prepared by reaction of 2-acetyl-2-aryloxiranes and 4-dimethylamino-3-(4 -methoxyphenyl)-3-buten-2-one with ethyl trifluoroacetate under basic condi tions. (C) 2000 Elsevier Science Ltd. All rights reserved.