Enantioselective reduction of <i>N</i>-alkyl ketimines with frustrated Lewis pair catalysis using chiral borenium ions

Mercea, Dan M.; Howlett, Michael G.; Piascik, Adam D.; Scott, Daniel J.; Steven, Alan; Ashley, Andrew E.; Fuchter, Matthew J.

doi:10.1039/c9cc02900a

Cited by 36 publications

(22 citation statements)

References 53 publications

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“…[ 55 ] By using the chiral N ‐heterocyclic carbene (NHC)‐stabilized borenium ion 28b , enantioselective reduction of ketimines is achieved with up to 86% ee . [ 56 ] A new intramolecular N/B FLP catalyst 29 was reported to reduce ketimines with up to 37% ee . [ 25 ] In 2014, the intramolecular chiral P/B ferrocene catalyst 30 was designed for the hydrogenation of bulky imines, achieving max 26% ee .…”

Section: Overviews In Catalysismentioning

confidence: 99%

Frustrated Lewis Pairs: Discovery and Overviews in Catalysis

Zhang

2020

Chin. J. Chem.

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Frustrated Lewis Pairs (FLPs) are derived from simple combinations of Lewis acids (electron acceptors) and Lewis bases (electron donors), in which steric demands prevent from forming classical Lewis acid-base adducts. Since 2006, FLP chemistry has emerged as a novel strategy for the design and application of main-group chemistry and development of new metal-free catalytic processes. This strategy has been applied to stoichiometric reactivity and then extended to catalysis. In this review, we briefly summarize the representative discoveries and developments of FLP chemistry in the field of catalysis, including hydrogenation, hydrosilylation, reduction of CO2, transformations of alkynes to organic derivatives, C-H bond borylation and polymerization. Nan Li (left) was born in Henan, China, in 1988. She received her BS degree from Xinyang University in 2012. She obtained her PhD degree in 2017, supervised by Professor Bing-Tao Guan at Nankai University. Following her graduate research, she moved to the college of chemistry at Peking University as a Postdoctoral Fellow in the laboratory of Professor Zhenfeng Xi and Professor Wen-Xiong Zhang (2017-2019). Wen-Xiong Zhang (right) received his B.Sc. from Hunan Normal University in 1996, his MSc from Guangxi Normal University in 1999, and his PhD from Nankai University with professor Li-Cheng Song in 2003. He carried out postdoctoral research at Peking University with Prof. Zhenfeng Xi and at Riken in Japan with Prof. Zhaomin Hou. In 2007, he joined College of Chemistry at Peking University as an Associate Professor, where he is now a Professor. His research interests include design, synthesis and small molecule activation of rare-earth-metal heterocycles, metal-catalyzed C-N bond activation, and carbodiimide-based organic synthesis to construct N-containing heterocycles.

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Section: Overviews In Catalysismentioning

confidence: 99%

Frustrated Lewis Pairs: Discovery and Overviews in Catalysis

Zhang

2020

Chin. J. Chem.

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“… 8 Important exceptions are “frustrated radical pairs”, which activate substrates via single electron pathways. 9 Recently, the range of LAs displaying FLP-like reactivity has expanded to encompass a number of cationic species (or neutral species that act as surrogates for the active cationic LA) based on B(III), 10 Si(IV), 11 C(IV), 12 N(III), 13 P(V), 14 and Sb(V). 15 , 16 …”

Section: Introductionmentioning

confidence: 99%

Establishing the Role of Triflate Anions in H₂ Activation by a Cationic Triorganotin(IV) Lewis Acid

Sapsford¹,

Csókás

Scott

et al. 2020

ACS Catal.

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Cationic Lewis acids (LAs) are gaining interest as targets for frustrated Lewis pair (FLP)-mediated catalysis. Unlike neutral boranes, which are the most prevalent LAs for FLP hydrogenations, the Lewis acidity of cations can be tuned through modulation of the counteranion; however, detailed studies on such anion effects are currently lacking in the literature. Herein, we present experimental and computational studies which probe the mechanism of H 2 activation using i Pr 3 SnOTf ( 1 -OTf) in conjunction with a coordinating (quinuclidine; qui) and noncoordinating (2,4,6-collidine; col) base and compare its reactivity with { i Pr 3 Sn·base}{Al[OC(CF 3 ) 3 ] 4 } (base = qui/col) systems which lack a coordinating anion to investigate the active species responsible for H 2 activation and hence resolve any mechanistic roles for OTf – in the i Pr 3 SnOTf-mediated pathway.

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“…In 2019, Fuchter's group synthesized a range of chiral borenium ions and applied them in enantioselective hydrosiylation of ketimines. [116] The newly designed FLP catalyst was stabilized by chiral N-heterocyclic carbene (NHC). In the presence of chiral borenium catalyst 70, more than moderate enantioselectivites were obtained for N-alkyl imine substrates (Scheme 30b).…”

Section: Chiral Boron Lewis Acid As Catalystmentioning

confidence: 99%

“…In 2019, Fuchter's group synthesized a range of chiral borenium ions and applied them in enantioselective hydrosiylation of ketimines [116] . The newly designed FLP catalyst was stabilized by chiral N ‐heterocyclic carbene (NHC).…”

Section: Asymmetric Reduction Using Silicon Hydrides Catalyzed By Chiral Lewis and Brønsted Acidsmentioning

confidence: 99%

The Development of Organocatalytic Asymmetric Reduction of Carbonyls and Imines Using Silicon Hydrides

et al. 2021

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The asymmetric reduction of prochiral ketones and ketimines represents one of the most important and practical chemical transformations toward the synthesis of valuable chiral alcohols and amines. Among the existing strategies, organocatalyzed asymmetric reduction of carbonyls and imines using silicon hydrides is attractive due to low-cost, chemical stability, and easy handling in experiments. In this review, we wish to highlight the recent progress made in the past fifteen years in this field. Four catalytic systems of different activation modes are presented and discussed in detail. We aim to help shed light on common features that enable highly enantioselective silicon hydride reductions through organocatalysis and provide the design principles for the development of more effective catalytic systems.

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Enantioselective reduction of N-alkyl ketimines with frustrated Lewis pair catalysis using chiral borenium ions

Abstract: Effective enantioselective reduction of ketimines has been demonstrated by ‘frustrated’ Lewis pair catalysis using an IBiox-stabilised borenium cation.

Cited by 36 publications

References 53 publications

Frustrated Lewis Pairs: Discovery and Overviews in Catalysis

Frustrated Lewis Pairs: Discovery and Overviews in Catalysis

Establishing the Role of Triflate Anions in H₂ Activation by a Cationic Triorganotin(IV) Lewis Acid

The Development of Organocatalytic Asymmetric Reduction of Carbonyls and Imines Using Silicon Hydrides

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Enantioselective reduction of N-alkyl ketimines with frustrated Lewis pair catalysis using chiral borenium ions

Abstract: Effective enantioselective reduction of ketimines has been demonstrated by ‘frustrated’ Lewis pair catalysis using an IBiox-stabilised borenium cation.

Cited by 36 publications

References 53 publications

Frustrated Lewis Pairs: Discovery and Overviews in Catalysis

Frustrated Lewis Pairs: Discovery and Overviews in Catalysis

Establishing the Role of Triflate Anions in H2 Activation by a Cationic Triorganotin(IV) Lewis Acid

The Development of Organocatalytic Asymmetric Reduction of Carbonyls and Imines Using Silicon Hydrides

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Establishing the Role of Triflate Anions in H₂ Activation by a Cationic Triorganotin(IV) Lewis Acid