Bipyridine-<i>N</i>,<i>N</i>′-dioxides Catalysts: Design, Synthesis, and Application in Asymmetric Synthesis of 1<i>H</i>-Pyrazolo[3,4-<i>b</i>]pyridine Analogues
Shijie Zhu, Xue Tian, Jichang Liu, Bin Dai, Shiwu Li
Abstract
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.
Topics & Concepts
ChemistryCatalysisPyridineYield (engineering)AdductReactivity (psychology)Combinatorial chemistryBipyridineLigand (biochemistry)Medicinal chemistryEnantioselective synthesisStereochemistryOrganic chemistryReceptorPathologyAlternative medicineMaterials scienceMetallurgyCrystal structureBiochemistryMedicineAsymmetric Synthesis and CatalysisSynthesis and Biological EvaluationCyclopropane Reaction Mechanisms