Ring Opening and Recyclization Reactions of 3-Nitrochromone with Some Nucleophilic Reagents

The chemical reactivity of 3-nitrochromone (1) was studied towards some nucleophilic reagents. Reaction of 3-nitrochromone (1) with some carbon nucleophiles revealed existence of ring-opening ring-closure reactions, and the mode of cyclization depends on the nucleophile used. Treatment of 3-nitrochromone (1) with malononitrile and ethyl cyanoacetate produced benzoxocinone derivatives 2 and 3, respectively. Boiling compound 1 with cyanoacetamide and 2-aminoprop-1-ene-1,1,3-tricarbonitrile afforded pyridine derivatives 4 and 5, respectively. Reaction of compound 1 with 1H-benzimidazol-2-ylacetonitrile, 5-amino-2,4-dihydro-3H-pyrazol-3-one, and dimedone led to pyrido[1,2-a]benzimidazole 6, pyrazolo[3,4-b]pyridine 7, and chromenone 8, respectively. Treating 3-nitrochromone (1) with heterocyclic amines gave enaminones 11 and 12 via nucleophilic attack at C-2 position with ring opening. The structures of the newly synthesized products were deduced on the basis of their analytical and spectral data.