Transformation of Alkynes into Chiral Alcohols via TfOH-Catalyzed Hydration and Ru-Catalyzed Tandem Asymmetric Hydrogenation

Liu, Sensheng; Liu, Huan; Liu, Qixing; Lv, Jiaqi

doi:10.1021/acs.orglett.8b00034

Cited by 36 publications

(12 citation statements)

References 61 publications

(24 reference statements)

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“…All the analytical data were in accord with those reported in the literature. [31] General procedure of hydrosilylation of 1-phenylcyclohexene 7. To a J.…”

Section: Methodsmentioning

confidence: 99%

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Chiral Bis(oxazoline) Ligand‐Supported Alkyl Aluminum Cations

et al. 2022

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Alkyl aluminum cations have shown high Lewis acidity and capability of catalyzing challenging organic transformations, however, the related chiral catalyst is scarcely documented. Herein, we report the generation of a series of weakly solvated or Lewis base‐stabilized alkyl aluminum cationic complexes bearing chiral bis(oxazoline) ligands. The increase of steric hindrances at the ligand backbone and the aluminum center were found to significantly increase the complex stability. In the Gutmann–Beckett experiment and fluoride ion affinity calculation, these complexes display Lewis acidity greater than B(C6F5)3 and the reported tetra‐coordinate aluminum cation. Preliminary catalytic studies revealed that the aluminum cation catalysts can effectively promote hydroboration of ketone and hydrosilylation of un‐activated olefin, despite only poor ee values were obtained.

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“…All the analytical data were in accord with those reported in the literature. [31] General procedure of hydrosilylation of 1-phenylcyclohexene 7. To a J.…”

Section: Methodsmentioning

confidence: 99%

“…13 C{ 1 H} NMR (CDCl 3 ): δ 159.1, 138.1, 126.8, 114.0, 70.1, 55.4, 25.2. HPLC analysis: [31] OD−H column (220 nm), method: nHex:IPA=95 : 5, flow 1.0 mL/min, t R =11.79 min, t S =12.69 min. All the analytical data were in accord with those reported in the literature [31] …”

Section: Methodsmentioning

confidence: 99%

Chiral Bis(oxazoline) Ligand‐Supported Alkyl Aluminum Cations

et al. 2022

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“…As an alternative to metal catalytic methods, metal-free catalyzed alkyne hydration reactions have also been developed in the presence of acids (Scheme c), where proton from acids initiated vinyl cation intermediates that were further attacked by water and rearranged into ketones (Scheme S1). A diversity of Brønsted acids have been reported to hydrate alkynes, including H 2 O, H 2 SO 4 , p -TsOH, TfOH, HCOOH, CF 3 COOH, and CF 3 SO 3 H . By functionalizing the sulfonic acid group with imidazole-based ionic liquids, the hydration reaction of alkynes can proceed at relatively low temperature (∼60 °C), and the Brønsted acid ionic liquids can be reused as catalysts without catalytic loss .…”

Section: Introductionmentioning

confidence: 99%

Accelerated Metal-Free Hydration of Alkynes within Milliseconds in Microdroplets

Zheng

Jin

Liu

et al. 2021

ACS Sustainable Chem. Eng.

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Conversion of alkynes into ketones by hydration is one of the most fundamental organic addition reactions. Traditional methods for alkyne hydration suffer from usage of toxic and costly metals, excessive acids, harsh conditions, and long reaction times, bringing about an urgent desire to explore more efficient and green protocols to complete this transformation. A metal-free efficient protocol for the accelerated hydration of alkynes in microdroplets was successfully developed in this work to overcome these drawbacks. The hydration process was finished under room temperature using only 18 mol % sulfuric acid as the catalyst and acetonitrile as the solvent. Complete conversions were feasible on the low millisecond time scale in microdroplets for a wide range of alkynes bearing functional groups, including electron-withdrawing groups and electron-donating groups. This is in sharp contrast to trace amounts of ketones or none in 20 min in bulk phase. Compared to the bulk reaction under the same conditions, the reactions in microdroplets are accelerated by 4 to 5 orders of magnitude as seen by the increase in measured rate constants. Further, the accelerated microdroplet hydration can be scaled up to an acetophenone amount of 57.2 ± 0.1 mg min −1 (3.43 ± 0.01 g h −1 ) by using 2 mol L −1 phenylacetylene sprayed at 300 μL min −1 . The microdroplet protocol offers several advantages including ultrahigh acceleration, complete conversion, mild reaction conditions (metal, light, and heat free), and minimal post purification, as well as a wide substrate scope, making it attractive for green and sustainable chemistry.

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“…Recently, several typical examples of the one-pot synthesis of chiral alcohols from alkynes ( Supplementary Table S3 ) has been reported, mainly focusing on the combination of different types of hydrations and enantioselective reductions. These include the use of excess formic acid as a solvent-mediated hydration coupled with Rh-catalyzed asymmetric transfer hydrogenation (ATH), ( Li et al, 2013 ), noble metallic/ligand catalysts such as [(iPr)AuX] (X = NTf 2 or BF 4 ), ( Ye et al, 2015 ; Xia et al, 2017 ), [(iPr)AuCl], ( Li et al, 2015 ), Co-Salen ( Wang et al, 2014 ), and Co-Porphyrin ( Lu et al, 2015 ) mediated hydration coupled with Rh-catalyzed ATH, and TfOH-catalyzed hydration coupled with Rh-mediated asymmetric hydrogenation (AH) ( Liu et al, 2018a ) or ATH ( Liu et al, 2018b ). Despite the great developments that have been made in the one-pot synthesis of enantiopure alcohols from alkynes, most of the reactions should be conducted under high temperatures ( Li et al, 2013 ), high pressure, ( Liu et al, 2018a ), and/or in acidic media which require a large amount of NaOH for pH adjustment.…”

Section: Introductionmentioning

confidence: 99%

Integrated Cobaloxime and Mesoporous Silica-Supported Ruthenium/Diamine Co-Catalysis for One-Pot Hydration/Reduction Enantioselective Sequential Reaction of Alkynes

et al. 2021

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This study developed a cost-efficient hydration/asymmetric transfer hydrogenation (ATH) process for the one-pot synthesis of valuable chiral alcohols from alkynes. During this process, the initial homogeneous cobaloxime-catalyzed hydration of alkynes was followed by heterogeneous Ru/diamine-catalyzed ATH transformation of the in-situ generated ketones, which provided varieties of chiral alcohols in good yields with up to 99% ee values. The immobilized Ru/diamine catalyst could be recycled at least three times before its deactivation in the sequential reaction system. This work shows a general method for developing one-pot asymmetric sequential catalysis towards sustainable organic synthesis.

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Transformation of Alkynes into Chiral Alcohols via TfOH-Catalyzed Hydration and Ru-Catalyzed Tandem Asymmetric Hydrogenation

Cited by 36 publications

References 61 publications

Chiral Bis(oxazoline) Ligand‐Supported Alkyl Aluminum Cations

Chiral Bis(oxazoline) Ligand‐Supported Alkyl Aluminum Cations

Accelerated Metal-Free Hydration of Alkynes within Milliseconds in Microdroplets

Integrated Cobaloxime and Mesoporous Silica-Supported Ruthenium/Diamine Co-Catalysis for One-Pot Hydration/Reduction Enantioselective Sequential Reaction of Alkynes

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