Highly Enantioselective SPINOL-Derived Phosphoric Acid Catalyzed Transfer Hydrogenation of Diverse C=N-Containing Heterocycles

A highly efficient and enantioselective hydrogenation of diversely substituted C=N‐containing heterocyclic compounds such as 3‐aryl‐1,4‐benzoxazines and 2‐arylquinolines was experimentally explored by using 1,1′‐spirobiindane‐7,7′‐diol‐derived chiral phosphoric acids as the catalyst. This method provides straightforward access to the corresponding tetrahydroquinolines and dihydro‐2H‐1,4‐benzothiazines in high yields (85–99 %) with excellent enantioselectivities (91–99 %). The attractive features of this procedure, which include mild reaction conditions, operational simplicity, relatively low catalyst loading (1 mol‐%), and high levels of enantioselectivities, make it a useful approach for the practical synthesis of optically active nitrogen‐containing aromatic heterocycles. Chiral SPINOL‐derived phosphoric acids are highly enantioselective catalysts for the asymmetric transfer hydrogenation of diversely substituted C=N‐containing heterocyclic compounds (SPA = SPINOL‐derived phosphoric acids). The method provides straightforward access to various optically active tetrahydroquinolines and dihydro‐2H‐1,4‐benzothiazines in high yields with excellent enantioselectivities.