Phosphorous Acid-Catalyzed Alkylation of Phenols with Alkenes.

A H3PO3 catalyzed alkylation of phenols with alkenes is achieved in a facile, efficient, and highly selective manner. The reaction shows a unique selectivity, i.e., excellent regioselectivity, thorough suppression of over-alkylation, without alkylation of simple phenyl ring, and can selectively prepare ortho-, meta-, or para-alkylated phenol derivatives with good to excellent yields. This merit along with mild reaction conditions, sensitive functional group tolerance, and scale-up synthesis, as well as late-modification of phenolic bioactive compounds make it an ideal and practical alternative for the modification of phenols.