Asymmetric Synthesis of Polycyclic Heterocyclic Compounds via Friedel–Crafts Reaction/Cyclization Reaction Catalyzed by Nickel Catalyst
Shujun Tong, Zhifei Zhao, Liangjian Hu, Shiwu Li
Abstract
The first highly enantioselective asymmetric Friedel–Crafts reaction/cyclization reaction of 5-aminopyrazoles with 3-alkenyloxindoles to afford polycyclic heterocyclic compounds bearing an all-carbon quaternary stereocenter catalyzed by a complex of Ni II with the C 2 -symmetric bipyridine- N, N ′-dioxide ligand L 12 has been developed. The relevant products with a wide range of substrates and good functional tolerance were obtained in 89–98% yield with 56–99% ee in the presence of 10 mol % Ni(OTf) 2 and 11 mol % L 12 in DCM at 25 °C. Moreover, an experiment on scaling up the process along with the transformations of the cycloadducts further emphasized the practical application of the synthesis.