Rh‐Catalyzed Chemo‐ and Enantioselective Hydrogenation of Allylic Hydrazones

Hu, Qiupeng; Hu, Yanhua; Liu, Yang; Zhang, Zhenfeng; Liu, Yangang; Zhang, Wanbin

doi:10.1002/chem.201605579

Cited by 35 publications

(11 citation statements)

References 79 publications

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“…Weakly coordinating N -protecting groups, such as Ts and Boc, failed delivering the expected products. Rewardingly, with Bz and Ac groups, chemo- and enantioselective hydrogenation took place, affording the chiral allylic hydrazine with high yield and enantioselectivity together with a small amount of the over-reduced byproduct . The corresponding chiral amines are hence easily accessible via reductive cleavage.…”

Section: Substrate’s Design: Activated Iminescontrasting

confidence: 71%

“…Rewardingly, with Bz and Ac groups, chemo-and enantioselective hydrogenation took place, affording the chiral allylic hydrazine with high yield and enantioselectivity together with a small amount of the overreduced byproduct. 111 The corresponding chiral amines are hence easily accessible via reductive cleavage. The best results in terms of reactivity and stereoinduction were achieved with The reaction occurs under high hydrogen pressure, whereas both conversion and enantioselectivity decreased at lower pressure.…”

Section: ■ Iridium-based Catalystsmentioning

confidence: 99%

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Metal-Catalyzed Asymmetric Hydrogenation of C═N Bonds

et al. 2020

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This review recaps the achievements in the field of metal-catalyzed asymmetric direct hydrogenation of nonactivated and activated imines. A summary of the reported catalytic systems with the corresponding reactivity, selectivity, and limitations are given including a discussion about the effects of some reaction conditions on the enantioselectivity of imine hydrogenation. An analysis of proposed imine hydrogenation mechanisms is discussed.

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Section: Substrate’s Design: Activated Iminescontrasting

confidence: 71%

Section: ■ Iridium-based Catalystsmentioning

confidence: 99%

Metal-Catalyzed Asymmetric Hydrogenation of C═N Bonds

et al. 2020

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“…Another significant problem concerns the racemization of α‐stereogenic aldehydes in acidic or basic medium. During the course of our research endeavors related to AH reactions, we have successfully achieved chemo‐ and enantioselectivity by utilizing conjugated substrates bearing an amido directing group and an electron‐rich bisphosphine‐Rh catalytic system in a neutral medium . Inspired by these results, we envisaged that α‐stereogenic aldehydes could be prepared using similar strategies (Scheme ).…”

Section: Introductionmentioning

confidence: 78%

Chemo‐ and Enantioselective Hydrogenation of α‐Formyl Enamides: An Efficient Access to Chiral α‐Amido Aldehydes

et al. 2019

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In order to effectively synthesize chiral α‐amino aldehydes, which have a wide range of potential applications in organic synthesis and medicinal chemistry, a highly chemo‐ and enantioselective hydrogenation of α‐formyl enamides has been developed, catalyzed by a rhodium complex of a P‐stereogenic bisphosphine ligand. Under different hydrogen pressures, the chiral α‐amido aldehydes and β‐amido alcohols were obtained in high yields (97–99 %) and with excellent chemo‐ and enantioselectivities (up to >99.9 % ee). The hydrogenation can be carried out on a gram scale and with a high substrate/catalyst ratio (up to 20 000 S/C), and the hydrogenated products were further converted into several important chiral products. Computations of the catalytic cycle gave a clear description for the R/S pathways, provided a reasonable explanation for the enantioselectivity, and revealed several other specific features.

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“…In continuation of our research on rhodium‐catalyzed asymmetric hydrogenation reactions, we have developed a chemo‐ and enantioselective hydrogenation of aryl‐alkenyl hydrazones assisted by an amido directing group . Using a similar strategy, we herein report the chemo‐ and enantioselective hydrogenation of alkynyl‐aryl hydrazones for the efficient synthesis of chiral propargylamine derivatives (Scheme ).…”

Section: Methodsmentioning

confidence: 99%

Rhodium‐Catalyzed Chemo‐ and Enantioselective Hydrogenation of Alkynyl‐Aryl Hydrazones

Fan

Jiang

et al. 2018

Adv Synth Catal

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As an update of our continuous interest in the hydrogenation of hydrazones, a chemo-and enantioselective hydrogenation of alkynyl-aryl hydrazones was developed using a rhodium complex [Rh((R,Sp)-JosiPhos)(cod)]SbF 6 as the catalyst and benzoic acid as an additive. Directed by a pnitrobenzamido group, the chiral propargyl hydrazines, which can be easily converted to chiral propargylamines of significant importance and potential use, were obtained with good yields, excellent chemoselectivities and good to excellent enantioselectivities. Although the enantioselectivity of the reaction and the substrate/catalyst ratio require further refinement, the reported methodology provides an alternative route for the efficient preparation of chiral propargylamines. Chiral propargylamines are versatile intermediates for the synthesis of numerous important pharmaceuticals and bioactive compounds. Thus, their asymmetric catalytic syntheses have attracted much attention. The asymmetric synthesis of such compounds can be realized via construction of CÀC and CÀN bonds or through reduction of C=C and C=N bonds. The asymmetric addition of terminal alkynes to imines is one of the most studied methodologies for the synthesis of chiral propargylamines. [1] Additionally, the asymmetric addition of alkyl or aryl reagents to alkynyl imines has also been investigated. [2] The asymmetric amination of propargylic esters provides another route to the target products. [3] However, these methodologies are not practical for large scale application due to low reaction activity, the need for a high catalyst loading and difficulties encountered when scaling up the reactions. On the other hand, asymmetric hydrogenation, [4] as the most practical process for its high efficiency, environmental friendliness, and low economic cost, has also been applied to the synthesis of chiral propargylamines. However, there is only one example concerning the reduction of an a-alkynyl enaminde to give the corresponding methyl-substituted chiral propargylamine. [5] To the best of our knowledge, an alternative route that employs the asymmetric hydrogenation of a-alkynyl imines has not been previously studied. The absence of such a methodology is related to the difficulty in developing reactions that are both highly chemo-and enantioselective. [6] In continuation of our research on rhodiumcatalyzed asymmetric hydrogenation reactions, [7] we have developed a chemo-and enantioselective hydrogenation of aryl-alkenyl hydrazones assisted by an amido directing group. [7c] Using a similar strategy, we herein report the chemo-and enantioselective hydrogenation of alkynyl-aryl hydrazones for the efficient synthesis of chiral propargylamine derivatives (Scheme 1).Firstly, a number of N-NHBz-substituted alkynylaryl hydrazones 1-Silyl bearing terminal silyl groups were prepared and tested in the asymmetric hydrogenation using [Rh(cod) 2 ]SbF 6 /(R,R)-QuinoxP* as the catalytic system (Table 1). Compared to C-based

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Rh‐Catalyzed Chemo‐ and Enantioselective Hydrogenation of Allylic Hydrazones

Cited by 35 publications

References 79 publications

Metal-Catalyzed Asymmetric Hydrogenation of C═N Bonds

Metal-Catalyzed Asymmetric Hydrogenation of C═N Bonds

Chemo‐ and Enantioselective Hydrogenation of α‐Formyl Enamides: An Efficient Access to Chiral α‐Amido Aldehydes

Rhodium‐Catalyzed Chemo‐ and Enantioselective Hydrogenation of Alkynyl‐Aryl Hydrazones

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