Derivatives of fused 3-hydroxymethyl-pyran-4-ones as a mobile keto-allyl system

Syntheses of 3-hydroxymethyl-4H,5H-pyrano(3,4-c)(1)benzopyran-4-one, 7, and 3-hydroxy-methyl-4H,5H-(1)benzothiopyrano(4,3-b)pyran-4-one, 8 , from 2,2-difluoro-4-methyl-5H-(1)benzopyrano- and (1)benzothiopyrano(3,4-e)-1,3,2-dioxaborins, 3 and 4 , are reported. Upon treatment with a solution of sodium cyanide, the corresponding mesylates 9 and 10 as well as the chloromethyl derivatives 11 and 12 yielded 3-methyl-4-oxo-4H,5H-pyrano(3,2-c) (1)benzopyran-2-carbonitrile, 13 , and 3-methyl-4-oxo-4H,5H-(1)benzothiopyrano(4,3-b)pyran-2-carbonitrile, 14 , respectively; these nitriles were converted to carboxylic acids 21 and 22 via methyl esters 19 and 20 . Reaction of the mesylate 10 with dimethylamine afforded a normal displacement product 23 . A similar reaction of 12 required longer time and led to the vinylogous amide 24 .