Palladium Catalyzed Conversion of Aryl Triflates to Acyl-DMAP Salts: A Mild and Versatile Approach to Carbonylations

Abstract

The use of metal catalysis to form potent acylating agents offers an important avenue to broaden the applicability of carbonylation reactions. However, the often disfavored reductive elimination of these reactive products presents a challenge, and has made these often high temperature, high pressure reactions and limited in their scope. Herein, we describe a mild and versatile palladium catalyzed carbonylative method to generate electrophilic acyl-DMAP (4-dimethylaminopyridine) salts by exploiting an alternative feature of these reactions: the counterion. In this, the weakly coordinating triflate anion is found to strongly destabilize Pd(II) toward irreversible reductive elimination of the reactive products, while ligand design can allow the rapid activation of aryl or vinyl triflates. Together, this provides a route to carry out palladium catalyzed carbonylations under exceptionally mild conditions, with low catalyst loading (0.5 mol % Pd), and with broadly available C(sp 2 )-triflate reagents. Coupling their formation with the addition of nucleophiles can be used to assemble a variety of products by carbonylation reactions, including those with palladium reactive functionalities.