AlCl3-Mediated Direct Carbon−Carbon Bond-Forming Reaction of α-Hydroxyketene-S,S-acetals with Arenes and Synthesis of 3,4-Disubstituted Dihydrocoumarin Derivatives

A simple and efficient AlCl3-mediated C−C coupling reaction between readily available α-hydroxyketene-S,S-acetals and various arenes via direct substitution of the hydroxy group in alcohols has been developed. On the basis of this C−C coupling reaction, a series of bio- and pharmacologically important 3,4-disubstituted dihydrocoumarins, difficult to obtain by other methods, were prepared in high yields by a sequential Friedel−Crafts alkylation and intramolecular annulation reaction of α-hydroxyketene acyclic-S,S-acetals with phenols under mild conditions.