CuH-catalyzed Asymmetric Conjugate Reduction Of P-Quinone Methides

Triarylmethanes are important molecules owing to their high utilities in material science,medicinal chemistry as well as organic synthesis.Despite the methods for the assembly of racemic triarylmethanes were developed,the rapid and efficient access to the optically enriched triarylmethanes remains to be a challenge.Herein,the enantioselective 1,6-conjugate reduction of p-quinone methides catalyzed by copper hydride was realized,achieving a rapid and efficient access to optically enriched triarylmethanes.After screening of chiral ligands such as chiral phosphines,phosphoramidtes and oxazolines,it revealed the chiral oxazolines 2z is the best choice.The reaction conditions such as hydrogen sources(silanes),bases,solvents and temperature were investigated.The methodology was very general independent on the steric hindrance or electronic nature of p-quinone methides.The corresponding triarylmethanes were obtained in up to 99% yield and with up to 92% ee.The reaction can be scaled up to the gram scale without significant erosions in yield and enantioselectivity.Noteworthy,the optically enriched triarylmethanes can be readily transformed to other synthetically versatile compounds using the known methods.