PREPARATION AND PHOTOLYSIS OF DIARYL ESTERS OF ACETYLENEDICARBOXYLIC ACID

Two diaryl acetylenedicarboxylates 1a,b have been prepared in moderate yields by direct reaction of acetylenedicarboxylic acid with the corresponding phenols catalyzed by sulfuric or p-toluenesulfonic acids and also through acetylenedicarbonyl chloride. The accompanying by-products have been characterized. Attempted esterification using N,N'-dicyclohexylcarbodiimide as condensing agent gives an asymmetric ester amide 11a and a substituted uracil 12a. Photolysis of the aryl esters 1a,b in benzene solution affords the benzocoumaran-3-ones 14a,b. In the case of 1b, minor amounts of a polycyclic condensed 4-chromanone 17b have also been observed. These results show that the nature of the substituent attached at the beta-position of the C = C triple bond plays an important role in the cyclization of o-hydroxyaryl ethynyl ketones.