posted on 2024-02-15, 11:03authored byZaiqi Han, Xiangqing Feng, Haifeng Du
The
asymmetric hydrogenation of quinoxalines represents one of
the most efficient approaches for the synthesis of optically active
tetrahyroquinoxalines. In this paper, we demonstrate a metal-free
asymmetric transfer hydrogenation of 2-substituted quinoxalines with
regenerable dihydrophenanthridine under H2 using a combination
of chiral phosphoric acid and achiral borane as catalysts. A wide
range of optically active 2-substituted tetrahydroquinoxalines were
produced in high yields with ≤98% ee.