Triflic acid-promoted transacylation and deacylation reactions in ionic liquid solvents

Abstract

A convenient process for transacylation by sterically crowded aromatic ketones (namely acetylmesitylene 1, acetyldurene 2, acetylprehnitene 3, acetylpentamethylbenzene 4 and diacetyldurene 5) to activated aromatic compounds such as anisole has been developed using triflic acid (TfOH) as catalyst and employing various room temperature imidazolium ionic liquids as “eco-friendly” solvents under relatively mild conditions (at 70 °C). The yields have been optimized based on the arene to TfOH molar ratios and the reaction temperature. Deacetylation to transacylation product ratios depend on the reaction conditions and increase on raising temperature. In the absence of an activated arene receptor, hindered ketones are efficiently deacetylated by TfOH in the ionic liquid solvents. The simple process employed avoids the use of large excess of AlCl₃ or TFA, and chlorinated or nitrated solvents which were previously utilized to effect this transformation.