A Bench-Stable Homodinuclear Ni<sub>2</sub>−Schiff Base Complex for Catalytic Asymmetric Synthesis of α-Tetrasubstituted <i>anti</i>-α,β-Diamino Acid Surrogates
Catalyticasymmetric direct Mannich-type reactions of α-substituted nitroacetates using a new bench-stable homodinuclear Ni2−Schiff base 1b complex are described. The Ni2−1b complex gave Mannich products, precursors for anti-α,β-diamino acids with an α-tetrasubstituted carbon stereocenter, in >99−91% ee. The Ni2−1b complex was also applicable to direct Mannich-type reactions of malonates and β-keto
Conventional chiralligands rely on the use of a covalently constructed, single chiral molecule embedded with coordinative functional groups. Here, we report a new strategy for the design of a chiralligand for asymmetric transition-metal catalysis; our approach is based on the development of an achiral cationic ammonium–phosphine hybrid ligand paired with a chiral binaphtholate anion. This ion-paired
A catalyticasymmetricsynthesis of nitrogen-containing gem-bisphoshonates is described. A Lewis acid-Bronsted base bifunctional homodinuclear Ni 2 ―Schiff base complex promoted catalytic enantioselective conjugate addition of nitroacetates to ethylidenebisphosphonates, giving products in up to 93% ee and 94% yield. Transformation of the product into a chiral α-amino ester with a gem-bisphosphonate
描述了含氮双膦酸盐的催化不对称合成。路易斯酸-布朗斯台德碱双功能同双核 Ni 2 -希夫碱配合物促进硝基乙酸酯催化对映选择性共轭加成到亚乙基双膦酸酯,得到高达 93% ee 和 94% 产率的产物。还描述了将产物转化为具有双膦酸酯部分的手性 α-氨基酯。
Ozone-Mediated Amine Oxidation and Beyond: A Solvent-Free, Flow-Chemistry Approach
作者:Eric A. Skrotzki、Jaya Kishore Vandavasi、Stephen G. Newman
DOI:10.1021/acs.joc.1c00768
日期:2021.10.15
Ozone is a powerful oxidant, most commonly used for oxidation of alkenes to carbonyls. The synthetic utility of other ozone-mediated reactions is hindered by its high reactivity and propensity to overoxidize organic molecules, including most solvents. This challenge can largely be mitigated by adsorbing both substrate and ozone onto silica gel, providing a solvent-free oxidation method. In this manuscript
The ratio of chiral Bronsted acid to ammonium–phosphine hybrid ligand in the in situ preparation of ion-paired chiral ligands was found to have a notable effect on the stereocontrolling ability of the corresponding palladium complex. The use of supramolecular palladium complexes generated from palladium metal, ammonium phosphine, and a chiral phosphoric acid in a ratio of 1:2:3 enabled an excellent