14645-32-0Relevant articles and documents
Catalytic Enantio- and Diastereoselective Mannich Addition of TosMIC to Ketimines
Franchino, Allegra,Chapman, Jack,Funes-Ardoiz, Ignacio,Paton, Robert S.,Dixon, Darren J.
supporting information, p. 17660 - 17664 (2018/11/10)
Chiral amines bearing a stereocenter in the α position are ubiquitous compounds with many applications in the pharmaceutical and agrochemical sectors, as well as in catalysis. Catalytic asymmetric Mannich additions represent a valuable method to access such compounds in enantioenriched form. This work reports the first enantio- and diastereoselective addition of commercially available p-toluenesulfonylmethyl isocyanide (TosMIC) to ketimines, affording 2-imidazolines bearing two contiguous stereocenters, one of which is fully-substituted, with high yields and excellent stereocontrol. The reaction, catalyzed by silver oxide and a dihydroquinine-derived N,P-ligand, is broad in scope, operationally simple, and scalable. Derivatization of the products provides enantioenriched vicinal diamines, precursors to NHC ligands and sp3-rich heterocyclic scaffolds. Computations are used to understand catalysis and rationalize stereoselectivity.
Organocatalytic asymmetric direct vinylogous Michael addition of α,β-unsaturated γ-butyrolactam to nitroolefins
Choudhury, Abhijnan Ray,Mukherjee, Santanu
supporting information; experimental part, p. 7313 - 7320 (2012/10/07)
The first organocatalytic enantioselective direct vinylogous Michael reaction of α,β-unsaturated γ-butyrolactam to nitroolefins is developed using cinchona alkaloids as the catalysts. Both product enantiomers are accessible with moderate to good enantioselectivity.
Heterogeneous enantioselective hydrogenation of ethyl pyruvate catalyzed by cinchona-modified Pt catalysts: Effect of modifier structure
Blaser,Jalett,Lottenbach,Studer
, p. 12675 - 12682 (2007/10/03)
The effect of the structure of chiral modifiers derived from natural cinchona alkaloids on the enantioselectivity and rate of the Pt/Al2O3-catalyzed hydrogenation of ethyl pyruvate was investigated. The influence of the following structural elements was studied: The cinchonidine versus the cinchonine backbone; effect of the nature and the size of substituents attached to C9; effect of partial hydrogenation of the quinoline ring; effects of changes of the substituent at the quinuclidine moiety. The strongest effects on ee and somewhat less on rate were observed for changes in the O-C9-C8-N part of the cinchona alkaloid and for partial or total hydrogenation of the quinoline rings. The nature of the substituents in the quinuclidine part had a comparably minor influence. The solvent was found to have a significant effect on enantioselectivity and rate. In acetic acid, the best results were obtained with O-methyl-10,11-diydrocinchonidine (ee's up to 93%), whereas dihydrocinchonidine was the most effective modifier in toluene. In agreement with a basic model proposed by Pfaltz, it was concluded that the minimal-requirements for an efficient modifier for the hydrogenation of α-keto esters is the presence of a basic nitrogen center close to one or more stereogenic centers and connected to an aromatic system. The results are in qualitative agreement with mechanistic models based on hydrogen-bonding interactions between an adsorbed modifier molecule and adsorbed ethyl pyruvate or its half-hydrogenated intermediate.
