Solvent‐Free and under Vacuum O ‐Benzylation of Carboxylic Acids by Using a Rotary Evaporator

Abstract A rapid benzylation of carboxylic acids was achieved under vacuum conditions and assisted by a rotary evaporator using p‐toluenesulfonic acid as a catalyst. Unlike the conventional method that utilizes the Dean‐Stark setup, which typically takes several hours or longer, benzylation was completed in 30 minutes without a solvent. Furthermore, this method avoids using BnBr or acyl halide as starting material and generates water as the only byproduct. This protocol is featured by its high yield, high atom economy, fast reaction, broad substrate scope, and easy operation. The rotary evaporator is commonly seen in chemistry labs, and there is great potential for exploring rotavap‐assisted organic synthesis.