Behavior of some 2(3H)-furanones bearing a chromone moiety as alkylating agents

Abstract

4-OXO-4H-chromen-3-carboxaldehyde (2) condensed with 3-aroylpropionic acids(1a-c) in the presence of thionyl chloride/N,N- dimethylformamide mixture as a cyclodehydrating agent to yield5-aryl-3-chromonyllmethylene-2(3H)-furanones3a-c as mixtures of (E) and (Z) stereoisomers.These furanones treated with the Lewis acid AlCl3 in benzene, toluene and chlorobenzene to furnish4,4-diaryl-1-(3-chromonyl)buta-1,3-diene-2-carboxylic acids 4a-fas mixtures of geometrical (E,E- and E,Z-) stereoisomers via an intermolecular alkylation mode. The unfavored intramolecular alkylation is explained on the basis of the decreased electron density at C2 of the chromone moiety causing the attack of the intermediate carbocation on this position becomes difficult.