Reactions of 4-hydroxy-6-methyl-2-pyrone and 6-substituted 4-hydroxycoumarins with αβ-unsaturated acyl chlorides

Abstract

Reactions of 4-hydroxy-6-methyl-2-pyrone and 6-substituted 4-hydroxycoumarins with αβ-unsaturated acyl chlorides were carried out in pyridine or in tetrachloroethane containing titanium(IV) chloride. In the case of reactions carried out in pyridine, the ratio of two isomers formed was related to the substituents at the β-position of the αβ-unsaturated acyl chlorides and at the 6-position of the 4-hydroxycoumarin. A mechanism for these reactions is discussed.