The Direct and Enantioselective Organocatalytic α‐Oxidation of Aldehydes.

Brown, Sean P.; Brochu, Michael P.; Sinz, Christopher J.; MacMillan, David W. C.

doi:10.1002/chin.200402077

Cited by 12 publications

(16 citation statements)

References 2 publications

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“…Herein, we reported the application of ketone catalysis in the asymmetric enamine-based α-hydroxylation with hydrogen peroxide. Though enamine-based α-oxygenation has been extensively explored, the successful examples relied on preactivated reagents such as oxaziridines, nitrosobenzenes, benzoyl peroxide and singlet oxygen [22][23][24][25] . Catalytic direct enamine hydroxylation with hydrogen peroxide has not been achieved 26 .…”

Section: Introductionmentioning

confidence: 99%

“…entry 20). Cyclic ketoesters showed divergent behavior, while smaller rings (n= 4, 5, 6) such as cyclopentanone or cyclohexanone did not show the expected reactivity, the larger cyclic ketoesters (n = 7, 12) reacted smoothly to give the desired products in high enantioselectivity with slightly diminished reactivity (entries[21][22][23][24]. A gram-scale hydroxylation reaction of β-ketoester 1a was performed to probe the practicability with 10 mol% catalyst loading and comparable isolated yield and enantioselectivity were obtained in 8 h (Table 2, entry 1).β-Ketoamides are versatile structural motifs in biologically active compounds and their direct oxidative transformations are challenging because of their oxidative compatibility.…”

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confidence: 99%

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Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

Cai

et al. 2021

J. Am. Chem. Soc.

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Carbonyl and amine are yin and yang in organocatalysis that mutually activate and transform each other. As intrinsically reacting partners, carbonyl and amine tend to condensate, depleting their individual activity when employed as catalysts. Though widely established as prominent catalytic strategies, aminocatalysis and carbonyl catalysis seems not coexist well and a cooperative amine/carbonyl dual catalysis remains virtually unknown. Here we report a cooperative primary amine and ketone dual catalysis in the asymmetric αhydroxylation with H2O2. Besides participating in the typical enamine catalytic cycle, the chiral primary amine catalyst was found to work cooperatively with a ketone catalyst to activate H2O2 via an oxaziridine intermediate derived from in-situ generated ketimine intermediate. The resulted enamine-oxaziridine coupling then facilitated highly-controlled hydroxylation of β-ketocarbonyls that are not possible with other catalytic methods. The dual catalytic approach allows for highly enantioselective α-hydroxylation of a broad range of β-ketocarbonyls. Particularly, late-stage hydroxylation for peptidyl amide or chiral esters can also 2 be achieved with high stereoselectivity. With its operational simplicity and mild conditions, this cooperative amine/ketone catalysis provides a new strategy in catalytic activation of H2O2 and expands the domain of typical amine and carbonyl catalysis to include those challenging transformations.

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

Cai

et al. 2021

J. Am. Chem. Soc.

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“…An ethyl ketone (2t) is also workable with 59% yield and 96% ee (entry 20). Cyclic ketoesters showed divergent behavior, while smaller rings (n= 4, 5, 6) such as cyclopentanone or cyclohexanone did not show the expected reactivity, the larger cyclic ketoesters (n = 7, 12) reacted smoothly to give the desired products in high enantioselectivity with slightly diminished reactivity (entries [21][22][23][24]. A gram-scale hydroxylation reaction of β-ketoester 1a was performed to probe the practicability with 10 mol% catalyst loading and comparable isolated yield and enantioselectivity were obtained in 8 h (Table 2, entry 1).…”

Section: Resultsmentioning

confidence: 99%

Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

Cai¹,

Xu²,

Li³

et al. 2020

Preprint

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Carbonyl and amine are yin and yang in organocatalysis that mutually activate and transform each other. As intrinsically reacting partners, carbonyl and amine tend to condensate, depleting their individual activity when employed as catalysts. Though widely established as prominent catalytic strategies, aminocatalysis and carbonyl catalysis seems not coexist well and a cooperative amine/carbonyl dual catalysis remains virtually unknown. Here we report a cooperative primary amine and ketone dual catalysis in the asymmetric α-hydroxylation with H2O2. Besides participating in the typical enamine catalytic cycle, the chiral primary amine catalyst was found to work cooperatively with a ketone catalyst to activate H2O2 via an oxaziridine intermediate derived from in-situ generated ketimine intermediate. The resulted enamine-oxaziridine coupling then facilitated highly-controlled hydroxylation of β-ketocarbonyls that are not possible with other catalytic methods. The dual catalytic approach allows for highly enantioselective α-hydroxylation of a broad range of β-ketocarbonyls. Particularly, late-stage hydroxylation for peptidyl amide or chiral esters can also be achieved with high stereoselectivity. With its operational simplicity and mild conditions, this cooperative amine/ketone catalysis provides a new strategy in catalytic activation of H2O2 and expands the domain of typical amine and carbonyl catalysis to include those challenging transformations.

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“…Extensive control experiments show that L-proline is adsorbed on both inner and outer surface of the MWCNTs, and its loading content is confirmed by the thermogravimetric analysis (TGA), elemental analysis, and catalytic performance. The catalytic efficiency and recycling capacity of the obtained L-proline/MWCNTs catalyst are investigated in the typical catalytic reactions, including Aldol reaction [30,31], Mannich reaction [32], Michael reaction [33], α-oxyamination reaction [34,35], and Knoevenagel condensation [36,37].…”

Section: Of 10mentioning

confidence: 99%

On the Exceptionally High Loading of L-Proline on Multi-Wall Carbon Nanotubes

Liang

Huang

et al. 2020

Catalysts

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L-proline is directly loaded on the multi-wall carbon nanotubes (MWCNTs) with exceptionally high loading content of 67 wt.%. The obtained L-proline/MWCNTs catalyst is on par with the catalytic activity of free L-proline, even after 7 rounds of recycling and reusing. The excellent activity of L-proline/MWCNTs in typical Aldol reaction, Mannich reaction, Michael reaction, α-oxyamination reaction, and Knoevenagel condensation shows a broad applicability of the composite catalyst in different reactions and solvent systems. We believe that the unusual loading mode may open a window for designing heterogenized organo-catalysts.

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The Direct and Enantioselective Organocatalytic α‐Oxidation of Aldehydes.

Cited by 12 publications

References 2 publications

Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

On the Exceptionally High Loading of L-Proline on Multi-Wall Carbon Nanotubes

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