Enantioselective nucleophilic addition of Grignard reagents to N-(2-pyridylsulfonyl)imines in the presence of bis(oxazoline) afforded products with good enantioselectivity. Dynamically induced chirality on the sulfur by coordination of a chiral Lewis acid to a pyridyl nitrogen and one of the sulfonyl oxygens fixes the conformation of the complex and induces enantioselectivity. Since the 2-pyridylsulfonyl
The first method for Strecker reaction (cyanation of imines) of aldimines with TMSCN in the presence of N-heterocyclic carbene prepared from 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride and t-BuOK, as a nucleophilic catalyst, is described.
Strecker reactions of various aldimines as well as ketoimines with TMSCN proceeded smoothly under mild conditions to give the corresponding alpha-amino nitriles and alpha,alpha-disubstituted alpha-amino nitriles, respectively, in good to excellent yields in the presence of nanocrystalline magnesium oxide. The reaction proceeds through hypervalent silicate species by coordination to O2-/O- (Lewis basic site) of nanocrystalline magnesium oxide, proved by Si-29 NMR. (C) 2008 Elsevier Ltd. All rights reserved.
Catalytic Asymmetric Synthesis of Zinc Metallacycles
作者:Hayden D. Bishop、Qiang Zhao、Christopher Uyeda
DOI:10.1021/jacs.3c05885
日期:2023.9.20
Transition-metal-catalyzed reductive coupling reactions of alkynes and imines are attractive methods for the synthesis of chiral allylic amines. Mechanistically, these reactions involve oxidative cyclization of the alkyne and the imine to generate a metallacyclic intermediate, which then reacts with H2 or a H2 surrogate to form the product. As an alternative to this hydrogenolysis pathway, here we