A New Carbocation Formation via Lewis Acid-Catalyzed C–O Bond Cleavage of N -Tosyl Carbamates

A novel Lewis acid-catalyzed C–O bond cleavage of N-tosyl carbamates derived from secondary benzyl alcohols has been developed. In the presence of catalytic FeCl3, these carbamates undergo rapid C–O bond cleavage to generate reactive benzylic carbocation intermediates, which are efficiently intercepted by exogenous nucleophiles. The resulting intermolecular Friedel–Crafts alkylations and annulations proceed under mild conditions at 25 °C within 5 min to 5 h, affording diverse products in up to 96% yield. Control experiments demonstrate that the incorporation of N-tosylisocyanate substantially enhances the efficiency of benzylic alcohol activation under the present conditions. This method provides a rapid and versatile approach to diverse benzylic functionalization products from readily accessible secondary benzyl alcohols.