Chiral Amine Synthesis – Recent Developments and Trends for Enamide Reduction, Reductive Amination, and Imine Reduction

Nugent, Thomas C.; El-Shazly, Mohamed

doi:10.1002/adsc.200900719

Cited by 845 publications

(365 citation statements)

References 408 publications

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“…[5] The hydrosilylation reaction is a widely employed method for accessing enantiomerically enriched amines, [6] and it is extremely useful from an industrial perspective, as it affords chiral products by using typically very cheap reducing agents. [7] Several groups have used the organocatalytic strategy for the hydrosilylation of ketoimines. [8] Among the most successful Lewis bases used to activate HSiCl 3 are the picolinamides, simply synthesized by connecting picolinic acid to a chiral carbon skeleton.…”

Section: Introductionmentioning

confidence: 99%

Cinchona‐Derived Picolinamides: Effective Organocatalysts for Stereoselective Imine Hydrosilylation

et al. 2014

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Picolinamide-cinchona organocatalysts for the successful enantioselective reduction of ketomines were developed. For the first time, a new type of chiral Lewis base, a cationic species, is reported to efficiently organocatalyze the addition of trichlorosilane to imines. Excellent yields with good to high enantioselectivities (up to 91 %) were obtained in the reduction of differently substituted substrates. Noteworthy,

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Section: Introductionmentioning

confidence: 99%

Cinchona‐Derived Picolinamides: Effective Organocatalysts for Stereoselective Imine Hydrosilylation

et al. 2014

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“…The phosphinyl group is very attractive since its removal from the reduction products can be conveniently achieved under mild acidic conditions, leading to the free primary amines [22,23]. N-phosphinyl imines have found a variety of synthetic applications in asymmetric processes [10,24,25]. For instance, the preparation of chiral amines can be achieved by stereoselective reduction of N-phosphinyl ketimines through different synthetic approaches such as hydrogenation [26][27][28], hydrosilylation [29][30][31][32][33], Meerwein-Schmidt-PonndorfVerley (MSPV) reaction [34] or the use of boron [35] and aluminium hydrides [36].…”

Section: Open Accessmentioning

confidence: 99%

“…In addition, chiral amines have been extensively used as resolving agents [1][2][3][4], starting materials for the preparation of therapeutic drugs [5] and chiral auxiliaries in asymmetric synthesis [6][7][8]. Due to this, synthetic chemists have made great efforts in order to implement efficient procedures for the preparation of chiral amines [9,10] among which the reduction of iminic substrates plays a capital role. In recent…”

Section: Introductionmentioning

confidence: 99%

Chiral β-Amino Alcohols as Ligands for the Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of N-Phosphinyl Ketimines

2012

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Some chiral β-amino alcohols have been evaluated as potential ligands for the ruthenium-catalyzed asymmetric transfer hydrogenation (ATH) of N-phosphinyl ketimines in isopropyl alcohol. The ruthenium complex prepared from [RuCl 2 (p-cymene)] 2 and (1S,2R)-1-amino-2-indanol has shown to be an efficient catalyst for the ATH of several N-(diphenylphosphinyl)imines, affording the reduction products in very good isolated yields and enantiomeric excesses up to 82%. The inherent rigidity of the indane ring system present in the ligand seems to be very important to achieve good enantioselectivities.

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“…[1] Among such entities are homopropargyl amines, used in the total synthesis of a number of natural products. [2] Several investigations have adopted the chiral auxiliary strategy; the desired products are obtained in high diastereoselectivity as trimethylsilyl-substituted alkynes.…”

mentioning

confidence: 99%

A Robust, Efficient, and Highly Enantioselective Method for Synthesis of Homopropargyl Amines

et al. 2012

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Catalytic protocols that generate a-branched amines efficiently and enantioselectively facilitate the preparation of many important biologically active molecules. [1] Among such entities are homopropargyl amines, used in the total synthesis of a number of natural products. [2] Several investigations have adopted the chiral auxiliary strategy; the desired products are obtained in high diastereoselectivity as trimethylsilyl-substituted alkynes. [3] In contrast, the corresponding catalytic protocols are scarce. The first relevant report included three examples of reactions of allenyl stannanes with a glyoxylate-derived tosylimine, [4] affording homopropargyl sulfonamides in 34-96% yield and 55:45-93:7 enantiomeric ratio (e.r.). [5] A notable recent advance entails enantioselective additions of a readily available allenylboron to tosylimines catalyzed by a Ag-phosphine catalyst to furnish a wider range of products and higher enantioselectivity (87:13 to more than 98:2 e.r.). Nonetheless, reactions of substrates that do not bear an aryl substituent proved to be less efficient, those of enolizable alkyl-substituted tosylimines were not reported and, as with the aforementioned initial development, removal of the tosyl unit requires strong reducing conditions. [6][7][8] Herein, we present a broadly applicable and efficient catalytic method for enantioselective synthesis of homopropargyl amides (Scheme 1); acid hydrolysis generates the parent amines. Transformations are performed with 0.25-2.0 mol% of a chiral N-heterocyclic carbene (NHC) complex of copper, derived from a readily available chiral imidazolinium salt and CuCl or the more robust CuCl 2 ·2H 2 O, both of which are commercially available. Aryl-, heteroaryl-, alkenyl-, as well as alkyl-substituted N-phosphinoyl imines can serve as substrates. Additions proceed to completion in seven hours or less, delivering homopropargyl amides in 65% to more than 98% yield and 92:8 to more than 98:2 e.r. The Cu-catalyzed process is amenable to gram-scale operations, and can be performed in a common fume hood without the need for strictly anhydrous and/or oxygen-free conditions. We began by probing the capacity of chiral C 1 -symmetric imidazolinium salt [9] 3a (Scheme 2), effective for reactions of allylborons with N-phosphinoyl imines, [10] in serving as the ** Financial support was provided by the NIH (GM-57212). We are grateful to Dr. B. Li for securing X-ray structures and to Frontier Scientific, Inc. for gifts of the allenylboron reagent. We thank Boston College Research Services for providing access to computational facilities.

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Chiral Amine Synthesis – Recent Developments and Trends for Enamide Reduction, Reductive Amination, and Imine Reduction

Cited by 845 publications

References 408 publications

Cinchona‐Derived Picolinamides: Effective Organocatalysts for Stereoselective Imine Hydrosilylation

Cinchona‐Derived Picolinamides: Effective Organocatalysts for Stereoselective Imine Hydrosilylation

Chiral β-Amino Alcohols as Ligands for the Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of N-Phosphinyl Ketimines

A Robust, Efficient, and Highly Enantioselective Method for Synthesis of Homopropargyl Amines

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