Metal Free Friedel-Crafts Di-acetylation of Resorcinol in Acetic Acid

Abstract

Conventionally, the metal catalyst used for Friedel-Crafts acetylation is poisonous and the acetylating agent is not readily available. Herein, methane sulfonic acid is developed to perform Friedel-Crafts diacetylation of aromatics instead of metal catalyst. Furthermore, acetic acid is employed as acetylating agent to replace acetic anhydride. By this approach, 4,6-diacetylresorcinol, known as an indispensable intermediate in superior fiber polybenzoxazole synthesis, is prepared in high yield from resorcinol. The results obtained by ¹H NMR, FT-IR and HPLC analysis indicate that methane sulfonic acid is an efficient catalyst for Friedel-Crafts acetylation and acetic anhydride can be avoid by replacement with acetic acid, in which phosphorus pentoxide is helpful to improve conversion of desired product.