A Selective and Versatile Synthesis of Substituted Chromones via Addition of Phenols to Dimethyl Acetylenedicarboxylate

Abstract

Despite many published syntheses of chromones, none has been reported to be both selective for chromones and tolerant of ring substitution. The addition of substituted phenols to dimethyl acetylenedicarboxylate is now reported as a versatile high yield initial step in a simple three-step synthesis of chromone 2-carboxylic acids. Triethylamine being used to deprotonate the substituted phenol, the addition to dimethyl acetylenedicarboxylate proceeds under mild conditions and tolerates a wide range of functional groups on the phenol. Although not stereoselective, both fumarate and maleate aryloxy products of this addition can then be cyclized, according to a known method, to chromones without contamination by isomeric coumarins. Thus the addition reaction is a valuable component of a versatile and selective synthesis of substituted chromones.