Donor Amine Salt-Based Continuous in situ-Product Crystallization in Amine Transaminase-Catalyzed Reactions
The unfavorable reaction equilibrium of transaminase-catalyzed reactions is a major challenge for the efficient biocatalytic synthesis of chiral amines. In this study the synthetic utilization of a salt-based, continuous in situ-product crystallization is
Hülsewede, Dennis,Dohm, Jan-Niklas,von Langermann, Jan
Chiral Bronsted Acids Catalyze Asymmetric Additions to Substrates that Are Already Protonated: Highly Enantioselective Disulfonimide-Catalyzed Hantzsch Ester Reductions of NH-Imine Hydrochloride Salts
While imines are frequently used substrates in asymmetric Bronsted acid catalysis, their corresponding salts are generally considered unsuitable reaction partners. Such processes are challenging because they require the successful competition of a catalytic amount of a chiral anion with a stoichiometric amount of an achiral one. We now show that enantiopure disulfonimides enable the asymmetric reduction of N-H imine hydrochloride salts using Hantzsch esters as hydrogen source. Our scalable reaction delivers crystalline primary amine salts in great efficiency and enantioselectivity and the discovery suggests potential of this approach in other Bronsted acid catalyzed transformations of achiral iminium salts. Kinetic studies and acidity data suggest a bifunctional catalytic activation mode.
Wakchaure, Vijay N.,Obradors, Carla,List, Benjamin
supporting information
p. 1707 - 1712
(2020/08/28)
Development of an in situ-Product Crystallization (ISPC)-Concept to Shift the Reaction Equilibria of Selected Amine Transaminase-Catalyzed Reactions
The synthesis of enantiopure amines via amine transaminases involves several challenges including unfavorable reaction equilibria and product inhibition. Described here is a non-catalytic approach to overcome such problems by using an in situ-product crystallization (ISPC) to selectively remove a targeted product amine from an amine transaminase-catalyzed reaction. The continuous removal of the product amine from its reaction solution as a barely soluble salt effectively yields a displacement of the reaction equilibrium towards the products and facilitates a simple downstream processing approach via filtration. The targeted product amine is eventually obtained from the salt, while the counterion compound can be easily recycled.
Hülsewede, Dennis,T?nzler, Marco,Süss, Philipp,Mildner, Andrea,Menyes, Ulf,von Langermann, Jan
p. 2130 - 2133
(2018/05/31)
Rhodium-catalyzed asymmetric hydrogenation of unprotected NH imines assisted by a thiourea
Asymmetric hydrogenation of unprotected NH imines catalyzed by rhodium/bis(phosphine)-thiourea provided chiral amines with up to 97% yield and 95% ee. 1HNMR studies, coupled with control experiments, implied that catalytic chloride-bound intermediates were involved in the mechanism through a dual hydrogen-bonding interaction. Deuteration experiments proved that the hydrogenation proceeded through a pathway consistent with an imine.
Zhao, Qingyang,Wen, Jialin,Tan, Renchang,Huang, Kexuan,Metola, Pedro,Wang, Rui,Anslyn, Eric V.,Zhang, Xumu
supporting information
p. 8467 - 8470
(2014/08/18)
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