Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion

Xu, Boran; Hartigan, Elizabeth M.; Feula, Giancarlo; Huang, Zheng; Lumb, Jean‐Philip; Arndtsen, Bruce A.

doi:10.1002/anie.201609255

Cited by 61 publications

(40 citation statements)

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“…[16] Inspired by the research described above, we herein report that we have achieved the first coppercatalyzed cascade bicyclization reactions between oalkynylphenyl isothiocyanates and propargylamine derivatives (Scheme 1c), despite the fact that amines are unstable to oxidants. [17] Unlike previously reported reactions of similar substrates, these reactions afforded 2-(1H-indol-1-yl)-4,5-dihydrothiazoles rather than fused-ring compounds. [10] Furthermore, the reactions could also generate 2-(1H-indol-1-yl)thiazol-5-yl aryl ketones when molecular oxygen was present.…”

Section: Abstract: Biologically Active; Copper; Cyclization; Heterocymentioning

confidence: 65%

One‐Pot Copper‐Catalyzed Cascade Bicyclization Strategy for Synthesis of 2‐(1H‐Indol‐1‐yl)‐4,5‐dihydrothiazoles and 2‐(1H‐Indol‐1‐yl)thiazol‐5‐yl Aryl Ketones with Molecular Oxygen as an Oxygen Source

et al. 2018

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An atom-economical method for synthesizing N-heterocyclic indoles from readily available o-alkynylphenyl isothiocyanates and propargylamine derivatives is reported. This method involves a copper-catalyzed cascade bicyclization process consisting of an intramolecular 5-exo-dig hydrothiolation reaction and an intramolecular hydroamination reaction and, depending on whether or not molecular oxygen is present, selectively affords Z-isomers of 2-(1H-indol-1-yl)-4,5-dihydrothiazoles or 2-(1H-indol-1-yl)thiazol-5-yl aryl ketones in satisfactory yields. Mechanistic studies indicate that molecular oxygen acts as the oxygen source for the ketone moiety in the products.

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Section: Abstract: Biologically Active; Copper; Cyclization; Heterocymentioning

confidence: 65%

One‐Pot Copper‐Catalyzed Cascade Bicyclization Strategy for Synthesis of 2‐(1H‐Indol‐1‐yl)‐4,5‐dihydrothiazoles and 2‐(1H‐Indol‐1‐yl)thiazol‐5‐yl Aryl Ketones with Molecular Oxygen as an Oxygen Source

et al. 2018

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“…The excess O 2 consumption, together with precedents for Cu-catalyzed dehydrogenation of secondary amines, 48−51 raised the possibility that the DBED ligand could be converted to a mono- or diimine derivative under the reaction conditions. Aliquots of the reaction mixture withdrawn at regular intervals were worked up in a manner that allowed analysis of the DBED ligand (see Figures S2–S4).…”

Section: Resultsmentioning

confidence: 99%

Second-Order Biomimicry: In Situ Oxidative Self-Processing Converts Copper(I)/Diamine Precursor into a Highly Active Aerobic Oxidation Catalyst

et al. 2017

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A homogeneous Cu-based catalyst system consisting of [Cu(MeCN)4]PF6, N,N′-di-tert-butylethylenediamine (DBED), and p-(N,N-dimethylamino)pyridine (DMAP) mediates efficient aerobic oxidation of alcohols. Mechanistic study of this reaction shows that the catalyst undergoes an in situ oxidative self-processing step, resulting in conversion of DBED into a nitroxyl that serves as an efficient cocatalyst for aerobic alcohol oxidation. Insights into this behavior are gained from kinetic studies, which reveal an induction period at the beginning of the reaction that correlates with the oxidative self-processing step, EPR spectroscopic analysis of the catalytic reaction mixture, which shows the buildup of the organic nitroxyl species during steady state turnover, and independent synthesis of oxygenated DBED derivatives, which are shown to serve as effective cocatalysts and eliminate the induction period in the reaction. The overall mechanism bears considerable resemblance to enzymatic reactivity. Most notable is the “oxygenase”-type self-processing step that mirrors generation of catalytic cofactors in enzymes via post-translational modification of amino acid side chains. This higher-order function within a synthetic catalyst system presents new opportunities for the discovery and development of biomimetic catalysts.

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“…11 In synthetic chemistry, copper-catalyzed or -mediated aerobic hydroxylations have been intensively studied and have led to a number of important synthetically useful oxidation reactions that have been applied in numerous industrial settings. 12,13 …”

Section: Introductionmentioning

confidence: 99%

Copper-Catalyzed Vinylogous Aerobic Oxidation of Unsaturated Compounds with Air

et al. 2018

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A mild and operationally simple copper-catalyzed vinylogous aerobic oxidation of β,γ- and α,β-unsaturated esters is described. This method features good yields, broad substrate scope, excellent chemo- and regioselectivity, and good functional group tolerance. This method is additionally capable of oxidizing β,γ- and α,β-unsaturated aldehydes, ketones, amides, nitriles, and sulfones. Furthermore, the present catalytic system is suitable for bisvinylogous and trisvinylogous oxidation. Tetramethylguanidine (TMG) was found to be crucial in its role as a base, but we also speculate that it serves as a ligand to copper(II) triflate to produce the active copper(II) catalyst. Mechanistic experiments conducted suggest a plausible reaction pathway via an allylcopper(II) species. Finally, the breadth of scope and power of this methodology are demonstrated through its application to complex natural product substrates.

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Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion

Cited by 61 publications

References 50 publications

One‐Pot Copper‐Catalyzed Cascade Bicyclization Strategy for Synthesis of 2‐(1H‐Indol‐1‐yl)‐4,5‐dihydrothiazoles and 2‐(1H‐Indol‐1‐yl)thiazol‐5‐yl Aryl Ketones with Molecular Oxygen as an Oxygen Source

One‐Pot Copper‐Catalyzed Cascade Bicyclization Strategy for Synthesis of 2‐(1H‐Indol‐1‐yl)‐4,5‐dihydrothiazoles and 2‐(1H‐Indol‐1‐yl)thiazol‐5‐yl Aryl Ketones with Molecular Oxygen as an Oxygen Source

Second-Order Biomimicry: In Situ Oxidative Self-Processing Converts Copper(I)/Diamine Precursor into a Highly Active Aerobic Oxidation Catalyst

Copper-Catalyzed Vinylogous Aerobic Oxidation of Unsaturated Compounds with Air

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