Huang Y, Hayashi T * National University of Singapore, Singapore
Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation
of Diarylmethylamines with Arylboroxines.
J. Am. Chem. Soc. 2015;
137: 7556-7559
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.
