Recyclization Reactions of 2-Methylchromone-3-Carbonitrile with Active Methylene Nucleophiles: Synthesis and Reactions of 4-Methylchromeno[2,3-b]Pyridines.

The chemical reactivity of 2-methylchromone-3-carbonitrile (1) was investigated toward a diversity of active methylene nucleophiles. Ring-opening followed by recyclization reactions of compound 1 with some active methylene nitriles afforded 2-amino-3-substituted-4-methylchromeno[2,3-b]pyridin-5-ones. Also, reactions of carbonitrile 1 with some active methylene ketones produced 2,4-dimethylchromeno [2,3-b]pyridin-5-ones. Annulated chromeno[2,3-b]pyrazolo[4,3-e]pyridine, chromeno[2,3-b][1,3]thiazolo[5,4-e]pyridine and chromeno[2,3-b]quinoline were efficiently synthesized from reaction of carbonitrile 1 with some cyclic methylene compounds. Heteroannulated chromeno[3′,2′:5,6]pyrido[2,3-d]pyrimidines and chromeno[2,3-b][1,8]naphthyridines were synthesized from reaction of compound 2 with formic acid, formamide, and malononitrile, cyanoacetamide, respectively. Chromeno[2′,3′:6,5]pyrido[2,3-b][1,8]naphthyridine 17 was synthesized from reaction of compound 2 with malononitrile dimer. Structures of the newly synthesized products were deduced based on their analytical and spectral data. [ABSTRACT FROM AUTHOR]