Werner transition‐metal complex (WTMC)‐mediated mild and efficient chemo‐selective acylation of phenols and anilines under solvent‐free condition

Abstract

Werner‐type transition‐metal complexes (WTMC) such as [Co(NH3)5Cl]Cl2, Cu[(NH3)4]SO4, Mn(acac)3, Ni[(NH3)6]Cl2, Ni[(en)3]S2O3, and Hg[Co(SCN)4] efficiently promote the chemoselective acetylation of phenols and anilines under solvent‐free condition. The results of this study clearly shows that the optimal condition for the acetylation of anilines/phenols (1 mmol) (2a–r) with acetic anhydride (1.2 mmol) in the presence of WTMC (1 mmol) and two drops of H3PO4 on heating for 10 min under solvent‐free condition gives the corresponding acetanilides/phenyl acetate (3a–r) in good to excellent yield. Furthermore, the method is simple, efficient, chemoselective, and eco‐friendly under solvent‐free condition for the acetylation of anilines and phenols promoted by WTMC by using acetic anhydrate as the acetylating agent. The simple preparation of the catalyst, easy procedure of the acetylation reaction, and simple work‐up indicate the importance of WTMC for such reactions.