Enantioselective Synthesis Of Chiral Triarylmethanes Via Indole Imine Methides

Triarylmethanes play an important role in the pharmaceutical arena or dye precursors.However,although the classical approach to synthesize achiral triarylmethanes has been reported,the asymmetric synthesis of triarylmethanes remains challenging.Herein we describe the synthesis of enantioenriched triarylmethanes by indole methanol or 2-vinyl indole and indole via two different approaches under the catalysis of chiral phosphoric acid,which is described as the following two parts:(1)Chiral transfer strategy for the asymmetric synthesis of triarylmethanesWe successfully developed a reaction to synthesize a series of chiral triarylmethanes with indole structure via a methylene indoleimine intermediate with good functional group tolerance which was up to 90% yield and up to 90% ee.The substrates were indole methanol derivatives with the catalysis of chiral phosphoric acid.Nonlinear effect and kinetic experiments were studied to describe the reaction mechanism better.The results suggested that only one molecule of phosphoric acid participated in the reaction in each catalytic cycle,and the reaction contained a dynamic kinetic resolution mechanism.(2)The direct alkene addition strategy for the asymmetric synthesis of quaternary triarylmethanesEnantioenriched quaternary triarylmethanes were successfully synthesized with up to 95% yield and up to 98% ee.The substrates were2-vinyl indole derivatives with the catalysis of chiral phosphoric acid.The wide substrate scope of the mild catalysis process indicated that various functional groups were well tolerated.