Domino reactions between 3-(6-methylchromonyl)acrylonitrile and nucleophilic reagents

The chemical reactivity of electron deficient chromone–linked acrylonitrile [3-(6-methylchromonyl)acrylonitrile (1)] was studied towards some active methylene nitriles and active methylene ketones. Reaction of compound 1 with malononitrile, cyanoacetamide, ethyl cyanoacetate, malononitrile dimer and acetoacetanilide afforded 5-cyanomethylchromeno[4,3-b]pyridines 2–4 and 9. Compound 1 reacted with 1H-benzimidazol-2-ylacetonitrile producing pyrido[1,2-a]benzimidazole derivative 5. Benzonitrile derivatives 6–8 were efficiently synthesized from the reaction of compound 1 with acetylacetone, ethyl acetoacetate and diethylmalonate. In these reactions a diversity of products has been synthesized through a domino process, including Michael addition, retro-Michael with γ-pyrone ring opening followed by different types of recyclization (RORC). Structures of the new synthesized products were deduced on the basis of their analytical and spectral data, and the reaction mechanisms are discussed.