Access to Enantiopure Triarylmethanes and 1,1-Diarylalkanes by NHC-Catalyzed Acylative Desymmetrization

We present herein an unprecedented, efficient and enantioselective synthesis of triarylmethanes and 1,1-diarylalkanes through N-heterocyclic carbene-catalyzed acylative desymmetrization of bisphenols. This method utilizes readily available substrates, reagents and a simple procedure to deliver the valuable products in excellent enantiopurity. DFT calculations reveal that the selectivity is governed by the C-C bond cleavage step of the tetrahedral intermediate leading to the ester product. A transition state model featuring a combination of intramolecular hydrogen bond and steric effect is developed to explain the enantioselectivity.