Rhodium-Catalyzed Asymmetric Arylation of Diarylmethylamines

Key words

rhodium - diarylmethylamines - arylation

Significance

Triarylmethanes are an important class of compounds that are useful in medicinal chemistry and materials science. Reports on their asymmetric synthesis include cross-coupling (B. L. H. Taylor et al. Angew. Chem. Int. Ed. 2013, 51, 7790), selective oxidation (B. F. Shi et al. Angew. Chem. Int. Ed. 2008, 47, 4882) and Friedel–Crafts reaction (M.-H. Zhuo et al. Org. Lett. 2014, 16, 1096). The authors report a rhodium-catalyzed 1,4-addition strategy of an o-quinone methide generated in situ for the synthesis of chiral triarylmethanes.

Comment

A variety of triarylmethanes were generated using this strategy. Substitution of all three aryl groups were tolerated well, giving good to excellent enantioselectivities. One limitation was noted: the enantioselectivity was reduced for substrates with ortho-substitution on Ar¹. The final products could also be deoxygenated through triflation followed by palladium-catalyzed hydrogenolysis.