Reaction of 2-(trifluoromethyl)chromones with pyridoxal: Formation of 1-benzopyranooxepino- and 1-benzopyranopyranopyridines

Pyridoxal undergoes oxa-Michael initiated ring closure with 2-(trifluoromethyl)chromones giving 11a,13-dihydro-6H-1-benzopyrano[3′,2′:6,7]oxepino[3,4-c]pyridin-6-ones and 6H,11aH-1-benzopyrano[3′,2′:5,6]pyrano[2,3-c]pyridin-6-ones. Participation of alcoholic hydroxy group of pyridoxal in the initial oxa-Michael addition leads to the former product and that of the phenyl hydroxy group to the later one.

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► 2-(Trifluoromethyl)chromones and pyridoxal hydrochloride were reacted in the presence of sodium hydroxide.
► Two novel polyfluoroalkyl-containing heterocyclic systems, 11a,13-dihydro-6H-1-benzopyrano[3′,2′:6,7]oxepino[3,4-c]pyridin-6-ones and 6H,11aH-1-benzopyrano[3′,2′:5,6]pyrano[2,3-c]pyridin-6-ones were synthesized.
► The reaction depends on the pH of the aqueous media.