Chlorodifluoromethane-triggered formation of difluoromethylated arenes catalysed by palladium

Difluoromethylated aromatic compounds are of increasing importance in pharmaceuticals, agrochemicals and materials. Chlorodifluoromethane (ClCF 2 H), an inexpensive, abundant and widely used industrial raw material, represents the ideal and most straightforward difluoromethylating reagent, but introduction of the difluoromethyl group (CF 2 H) from ClCF 2 H into aromatics has not been reported. Here, we describe a direct palladium-catalysed difluoromethylation method for coupling ClCF 2 H with arylboronic acids and esters to generate difluoromethylated arenes with high efficiency. The reaction exhibits a remarkably broad substrate scope, including heteroarylboronic acids, and was used for difluoromethylation of a range of pharmaceuticals and biologically active compounds. Preliminary mechanistic studies revealed that a palladium difluorocarbene intermediate is involved in the reaction. Although numerous metal–difluorocarbene complexes have been prepared, the catalytic synthesis of difluoromethylated or difluoromethylenated compounds involving metal–difluorocarbene complexes has not received much attention. This new reaction therefore also opens the door to understand metal–difluorocarbene complex catalysed reactions. Chlorodifluoromethane (ClCF 2 H), an inexpensive and abundant industrial raw material, represents an ideal and straightforward reagent for introducing the difluoromethyl group. However, efficient approaches for activation of the typically inert ClCF 2 H are limited. Now, ClCF 2 H is employed via a difluorocarbene pathway for palladium-catalysed difluoromethylation of arylboronic acids with broad substrate scope.