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 alpha-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 alpha-hydroxyketene acyclic-S,S-acetals with phenols under mild conditions.