The Reactien of Hydroxybenzaldehydes with Phenylacetic Acid

Abstract

The condensation reaction of p-, m- and o-hydroxybenzaldehydes ([2], [7] and [12]) with phenylacetic acid [1] in the presenee of Et3N-Ac2O was studied.By the reaction of either [2] or [7] with [1], the isomers of both trans- and cis-α -phenyl(P- or m-) acetoxycinnamic acids, ([3A], [3B] or [8A], [8B]), were obtained respectively. On the other hand, the reaction of [12] with [1] gave trans-α -phenyl-o-acetoxycinnamic acid [13A] and 3-phenylcoumarine [15].When the trans acids were heated under reflux in Et3N-Ac2O, [3A] and [8A] were converted into the equilibrium mixture of trans and cis isemers, respeetively, but [13A] was changed to [15].Each acetoxy acid except [3B] was hydrelyzed to the corresponding hydroxy acid by treatment with aqueous NaOH, but the cis acid [3B] was converted into trans-p-hydroxy acid [4A].