Bipyridine- N , N '-dioxides Catalysts: Design, Synthesis, and Application in Asymmetric Synthesis of 1 H -Pyrazolo[3,4- b ]pyridine Analogues.

A novel type of highly efficient chiral C 2-symmetric bipyridine- N , N '-dioxides ligand application in catalyzing Michael addition/Cyclization of 5-aminopyrazoles with α,β-unsaturated 2-acyl imidazoles has been developed, affording the corresponding adducts in 85-97% yield with up to 99% enantioselectivity under mild conditions with a lower catalyst loading and broad scope. Remarkably, this protocol exhibits advantages in terms of reactivity and enantioselectivity, giving the fact that as low as 2.2 mol % of L1 and 2.0 mol % of Ni(OTf) 2 can promote the title reaction on gram scale to afford the desired product with excellent enantioselectivity.