Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines

The reaction of racemic diarylmethylamines, (Ar(1)Ar(2)CHNR2), where Ar(1) is substituted with a 2-hydroxy group, with arylboroxines (Ar(3)BO)3 in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar(1)Ar(2)CH*Ar(3)) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through o-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents.