Enantioselective Construction of Fused N-Heterocycles via Sequential Annulation and Catalytic Transfer Hydrogenation
Guang-Peng Lu1, Bo-Xuan Yao2, Shao-Fei Ni2
1Key Lab of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Wushan Rd-381, Guangzhou 510641, P.R. China.
Abstract:
Herein, we report the first regio- and enantioselective synthesis of tetrahydropyrido[2,3-b]pyrazines using a chiral iridacycle catalyst. Pyridyl diamines and diketones undergo sequential annulation and asymmetric transfer hydrogenation of the in situ generated pyrido[2,3-b]pyrazine intermediates. This method provides diverse fused N-heterocycles in high yields (up to 95%) and enantioselectivity (98.5:1.5 er), exclusively reducing the pyridyl ring to form the stereocenter at the C6 site. Mechanistic studies reveal that π-π stacking and H-bonding govern the enantioselectivity.
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