Recyclable nickel-catalyzed C–H/O–H dual functionalization of phenols with mandelic acids for the synthesis of 3-aryl benzofuran-2(3H)-ones under solvent-free conditions

Herein, we developed a protocol for the efficient synthesis of 3-aryl benzofuran-2(3H)-ones under solvent-free conditions from phenols and mandelic acids using Ni(OTf)2 as a catalyst. A diverse range of mandelic acids and phenols undergo C–H/O–H bond dual functionalization to generate products in moderate to good or excellent yields. The nickel catalyst can be easily recycled in a test of three runs at the scale of 10 mmol without significant decline in the product yield. It was demonstrated that the yield of the desired product could be increased, for example, in the synthesis of the antioxidant Irganox HP-136 to a scale of 166 g.