1
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Edelmann S, Lumb JP. A para- to meta-isomerization of phenols. Nat Chem 2024:10.1038/s41557-024-01512-1. [PMID: 38632366 DOI: 10.1038/s41557-024-01512-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 03/18/2024] [Indexed: 04/19/2024]
Abstract
Phenols and their derivatives are ubiquitous in nature and critically important industrial chemicals. Their properties are intimately linked to the relative substitution pattern of the aromatic ring, reflecting well-known electronic effects of the OH group. Because of these ortho-, para-directing effects, meta-substituted phenols have historically been more difficult to synthesize. Here we describe a procedure to transpose phenols that hinges on a regioselective diazotization of the corresponding ortho-quinone. The procedure affords the meta-substituted phenol directly from its more common and accessible para-substituted isomer, and demonstrates good chemoselectivity that enables its application in late-stage settings. By changing the electronic effect of the OH group and its trajectory of hydrogen bonding, our transposition can be used to diversify natural products and existing chemical libraries, and potentially shorten the length and cost of producing underrepresented arene isomers.
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Affiliation(s)
- Simon Edelmann
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, Montreal, Quebec, Canada.
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2
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Azpilcueta-Nicolas CR, Lumb JP. Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters. Beilstein J Org Chem 2024; 20:346-378. [PMID: 38410775 PMCID: PMC10896223 DOI: 10.3762/bjoc.20.35] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 01/29/2024] [Indexed: 02/28/2024] Open
Abstract
Due to their ease of preparation, stability, and diverse reactivity, N-hydroxyphthalimide (NHPI) esters have found many applications as radical precursors. Mechanistically, NHPI esters undergo a reductive decarboxylative fragmentation to provide a substrate radical capable of engaging in diverse transformations. Their reduction via single-electron transfer (SET) can occur under thermal, photochemical, or electrochemical conditions and can be influenced by a number of factors, including the nature of the electron donor, the use of Brønsted and Lewis acids, and the possibility of forming charge-transfer complexes. Such versatility creates many opportunities to influence the reaction conditions, providing a number of parameters with which to control reactivity. In this perspective, we provide an overview of the different mechanisms for radical reactions involving NHPI esters, with an emphasis on recent applications in radical additions, cyclizations and decarboxylative cross-coupling reactions. Within these reaction classes, we discuss the utility of the NHPI esters, with an eye towards their continued development in complexity-generating transformations.
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Affiliation(s)
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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3
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Wang X, Kinziabulatova L, Bortoli M, Manickoth A, Barilla MA, Huang H, Blancafort L, Kohler B, Lumb JP. Indole-5,6-quinones display hallmark properties of eumelanin. Nat Chem 2023:10.1038/s41557-023-01175-4. [PMID: 37037912 DOI: 10.1038/s41557-023-01175-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 03/07/2023] [Indexed: 04/12/2023]
Abstract
Melanins are ubiquitous biopolymers produced from phenols and catechols by oxidation. They provide photoprotection, pigmentation and redox activity to most life forms, and inspire synthetic materials with desirable optical, electronic and mechanical properties. The chemical structures of melanins remain elusive, however, creating uncertainty about their roles, and preventing the design of synthetic mimics with tailored properties. Indole-5,6-quinone (IQ) has been implicated as a biosynthetic intermediate and structural subunit of mammalian eumelanin pigments, but its instability has prevented its isolation and unambiguous characterization. Here we use steric shielding to stabilize IQ and show that 'blocked' derivatives exhibit eumelanin's characteristic ultrafast nonradiative decay and its ability to absorb light from the ultraviolet to the near-infrared. These new compounds are also redox-active and a source of paramagnetism, emulating eumelanin's unique electronic properties, which include persistent radicals. Blocked IQs are atomistically precise and tailorable molecules that can offer a bottom-up understanding of emergent properties in eumelanin and have the potential to advance the rational design of melanin-inspired materials.
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Affiliation(s)
- Xueqing Wang
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Lilia Kinziabulatova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
| | - Marco Bortoli
- Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona, Girona, Spain
| | - Anju Manickoth
- Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona, Girona, Spain
| | - Marisa A Barilla
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
| | - Haiyan Huang
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Lluís Blancafort
- Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona, Girona, Spain.
| | - Bern Kohler
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, Montreal, Quebec, Canada.
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4
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Halloran MW, Li E, Esguerra KVN, Lumb JP. A Bioinspired Synthesis of 1,4-Benzothiazines by Selective Addition of Sulfur Nucleophiles to ortho-Quinones. J Org Chem 2023; 88:2561-2569. [PMID: 36719706 DOI: 10.1021/acs.joc.2c02463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Herein, we report a bioinspired approach to the synthesis of 1,4-benzothiazines by drawing inspiration from the biosynthesis of pheomelanin pigments (pheomelanogenesis). In this context, general conditions for the regioselective coupling reaction between ortho-quinones and thiols were developed. The mild conditions proved amenable to a wide scope of both thiol and ortho-quinone coupling partners while simultaneously suppressing redox-exchange. The utility of this methodology was demonstrated by a synthesis of 1,4-benzothiazines, following a biomimetic, oxidative cyclization.
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Affiliation(s)
- Matthew W Halloran
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Elizabeth Li
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Kenneth Virgel N Esguerra
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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5
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Azpilcueta-Nicolas CR, Meng D, Edelmann S, Lumb JP. Dearomatization of Biaryls through Polarity Mismatched Radical Spirocyclization. Angew Chem Int Ed Engl 2023; 62:e202215422. [PMID: 36454656 DOI: 10.1002/anie.202215422] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/21/2022] [Accepted: 12/01/2022] [Indexed: 12/03/2022]
Abstract
Dearomatization reactions involving radical cyclizations can facilitate the synthesis of complex polycyclic systems that find applications in medicinal chemistry and natural product synthesis. Here we employ redox-neutral photocatalysis to affect a radical spirocyclization that transforms biaryls into spirocyclic cyclohexadienones under mild reaction conditions. In a departure from previously reported methods, our work demonstrates the polarity mismatched addition of a nucleophilic radical to an electron rich arene, and allows the regioselective synthesis of 2,4- or 2,5-cyclohexadienones with broad functional group tolerance. By transforming biaryls into spirocycles, our methodology accesses underexplored three-dimensional chemical space, and provides an efficient means of creating quaternary spirocenters that we apply to the first synthesis of the cytotoxic plant metabolite denobilone A.
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Affiliation(s)
| | - Derek Meng
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Simon Edelmann
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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6
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Abstract
Catechols are part of many essential chemicals and are valuable, typically nucleophilic intermediates used in synthesis. Here we describe an unexpected transformation in which they play the role of the electrophile in a formal nucleophilic aromatic substitution. We made this discovery while studying a seven-membered dioxepin ring formation during a synthesis of the benzyltetrahydroisoquinoline (S)-cularine. We suggest a chain mechanism for this new transformation that is triggered by molecular oxygen and that propagates an electrophilic ortho-quinone.
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Affiliation(s)
- Zheng Huang
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Xiang Ji
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
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7
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Huang Z, Lumb JP. Mimicking oxidative radical cyclizations of lignan biosynthesis using redox-neutral photocatalysis. Nat Chem 2020; 13:24-32. [PMID: 33349693 DOI: 10.1038/s41557-020-00603-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 11/06/2020] [Indexed: 01/02/2023]
Abstract
Oxidative cyclizations create many unique chemical structures that are characteristic of biologically active natural products. Many of these reactions are catalysed by 'non-canonical' or 'thwarted' iron oxygenases and appear to involve long-lived radicals. Mimicking these biosynthetic transformations with chemical equivalents has been a long-standing goal of synthetic chemists but the fleeting nature of radicals, particularly under oxidizing conditions, makes this challenging. Here we use redox-neutral photocatalysis to generate radicals that are likely to be involved in the biosynthesis of lignan natural products. We present the total syntheses of highly oxidized dibenzocyclooctadienes, which feature densely fused, polycyclic frameworks that originate from a common radical progenitor. We show that multiple factors control the fate of the proposed biosynthetic radicals, as they select between 5- or 11-membered ring cyclizations and a number of different terminating events. Our syntheses create new opportunities to explore the medicinal properties of these natural products, while shedding light on their biosynthetic origin.
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Affiliation(s)
- Zheng Huang
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, Montreal, Quebec, Canada.
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8
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9
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Affiliation(s)
- Xiang Ji
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Zheng Huang
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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10
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Abstract
We describe a concise synthesis of the pseudodimeric tetrahydroisoqunoline alkaloid (S,S)-tetramethylmagnolamine by a catalytic aerobic desymmetrization of phenols. Desymmetrization reactions increase molecular complexity with high levels of efficiency, but those that do so by aerobic oxidation are uncommon. Our conditions employ molecular oxygen as an oxygen atom transfer agent and a formal acceptor of hydrogen, enabling two mechanistically distinct aromatic C-H oxygenation reactions with high degrees of selectivity.
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Affiliation(s)
- Zheng Huang
- Department of Chemistry , McGill University , 801 Sherbrooke Street West , Montreal , QC H3A 0B8 , Canada
| | - Xiang Ji
- Department of Chemistry , McGill University , 801 Sherbrooke Street West , Montreal , QC H3A 0B8 , Canada
| | - Jean-Philip Lumb
- Department of Chemistry , McGill University , 801 Sherbrooke Street West , Montreal , QC H3A 0B8 , Canada
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11
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Affiliation(s)
- Wenbo Xu
- College of Chemistry, Chemical Engineering and Materials Science, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Normal University, Jinan 250014, China
| | - Zheng Huang
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
| | - Xiang Ji
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
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12
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Abstract
The elucidation of substrate-protein interactions is an important component of the drug development process. Due to the complexity of native cellular environments, elucidating these fundamental biochemical interactions remains challenging. Photoaffinity labeling (PAL) is a versatile technique that can provide insight into ligand-target interactions. By judicious modification of substrates with a photoreactive group, PAL creates a covalent crosslink between a substrate and its biological target following UV-irradiation. Among the commonly employed photoreactive groups, diazirines have emerged as the gold standard. In this Minireview, recent developments in the field of diazirine-based photoaffinity labeling will be discussed, with emphasis being placed on their applications in chemical proteomic studies.
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Affiliation(s)
- Matthew W Halloran
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada
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13
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Affiliation(s)
- Zheng Huang
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
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14
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Abstract
CuIII species have been invoked in many copper-catalyzed transformations including cross-coupling reactions and oxidation reactions. In this review, we will discuss seminal discoveries that have advanced our understanding of the CuI/CuIII redox cycle in the context of C–C and C–heteroatom aerobic cross-coupling reactions, as well as C–H oxidation reactions mediated by CuIII–dioxygen adducts.1 General Introduction2 Early Examples of CuIII Complexes3 Aerobic CuIII-Mediated Carbon–Heteroatom Bond-Forming Reactions4 Aerobic CuIII-Mediated Carbon–Carbon Bond-Forming Reactions5 Bioinorganic Studies of CuIII Complexes from CuI and O2
5.1 O2 Activation5.2 Biomimetic CuIII Complexes from CuI and Dioxygen5.2.1 Type-3 Copper Enzymes and Dinuclear Cu Model Complexes5.2.2 Particulate Methane Monooxygenase and Di- and Trinuclear Cu Model Complexes5.2.3 Dopamine–β-Monooxygenase and Mononuclear Cu Model Complexes6 Conclusion
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15
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16
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Huang Z, Kwon O, Huang H, Fadli A, Marat X, Moreau M, Lumb JP. A Bioinspired Synthesis of Polyfunctional Indoles. Angew Chem Int Ed Engl 2018; 57:11963-11967. [PMID: 29978600 DOI: 10.1002/anie.201806490] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 06/29/2018] [Indexed: 01/25/2023]
Affiliation(s)
- Zheng Huang
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
| | - Ohhyeon Kwon
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
| | - Haiyan Huang
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
| | - Aziz Fadli
- L'Oréal Research and Innovation; Aulnay-sous-Bois France
| | - Xavier Marat
- L'Oréal Research and Innovation; Aulnay-sous-Bois France
| | | | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
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17
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Affiliation(s)
- Zheng Huang
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
| | - Ohhyeon Kwon
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
| | - Haiyan Huang
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
| | - Aziz Fadli
- L'Oréal Research and Innovation; Aulnay-sous-Bois France
| | - Xavier Marat
- L'Oréal Research and Innovation; Aulnay-sous-Bois France
| | | | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A 0B8 Canada
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18
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Esguerra KVN, Lumb JP. Selectivity in the Aerobic Dearomatization of Phenols: Total Synthesis of Dehydronornuciferine by Chemo- and Regioselective Oxidation. Angew Chem Int Ed Engl 2018; 57:1514-1518. [PMID: 29271101 DOI: 10.1002/anie.201710271] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 12/05/2017] [Indexed: 11/11/2022]
Abstract
We describe a selective aerobic oxidation of meta-biaryl phenols that enables rapid access to functionalized phenanthrenes. Aerobic oxidations attract interest due to their efficiency, but remain underutilized in complex molecule settings due to challenges of selectivity. We discuss these issues in the context of Cu catalysis, and highlight the advantages of confining oxygen activation and substrate oxidation to the catalyst's inner-coordination sphere. This gives rise to predictable selectivity that we use for a concise synthesis of the aporphine dehydronornuciferine.
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Affiliation(s)
- Kenneth Virgel N Esguerra
- Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, Quebec, H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, Quebec, H3A 0B8, Canada
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19
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Esguerra KVN, Lumb JP. Selectivity in the Aerobic Dearomatization of Phenols: Total Synthesis of Dehydronornuciferine by Chemo- and Regioselective Oxidation. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201710271] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke St. W. Montreal Quebec H3A 0B8 Canada
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20
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Esguerra KVN, Lumb JP. Inside Cover: Synthesis of ortho
-Azophenols by Formal Dehydrogenative Coupling of Phenols and Hydrazines or Hydrazides (Chem. Eur. J. 36/2017). Chemistry 2017. [DOI: 10.1002/chem.201701560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke St. W. Montreal Quebec H3A 0B8 Canada
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21
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Affiliation(s)
- Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Kanada
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22
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Lumb JP. Stopping Aerobic Oxidation in Its Tracks: Chemoselective Synthesis of Benzaldehydes from Methylarenes. Angew Chem Int Ed Engl 2017; 56:9276-9277. [PMID: 28605566 DOI: 10.1002/anie.201704160] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Indexed: 11/07/2022]
Abstract
A practical and elegant solution to the long-standing challenge of methylarene partial oxidation has recently been provided by Pappo and co-workers who devised a catalytic aerobic route to benzaldehydes. The solution hinges on the unique hydrogen-bonding capacity of hexafluoroisopropanol, which prevents overoxidation of the aldehyde to the carboxylic acid.
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Affiliation(s)
- Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada
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23
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Glavinović M, Krause M, Yang L, McLeod JA, Liu L, Baines KM, Friščić T, Lumb JP. A chlorine-free protocol for processing germanium. Sci Adv 2017; 3:e1700149. [PMID: 28508082 PMCID: PMC5419701 DOI: 10.1126/sciadv.1700149] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 03/07/2017] [Indexed: 05/16/2023]
Abstract
Replacing molecular chlorine and hydrochloric acid with less energy- and risk-intensive reagents would markedly improve the environmental impact of metal manufacturing at a time when demand for metals is rapidly increasing. We describe a recyclable quinone/catechol redox platform that provides an innovative replacement for elemental chlorine and hydrochloric acid in the conversion of either germanium metal or germanium dioxide to a germanium tetrachloride substitute. Germanium is classified as a "critical" element based on its high dispersion in the environment, growing demand, and lack of suitable substitutes. Our approach replaces the oxidizing capacity of chlorine with molecular oxygen and replaces germanium tetrachloride with an air- and moisture-stable Ge(IV)-catecholate that is kinetically competent for conversion to high-purity germanes.
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Affiliation(s)
- Martin Glavinović
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Michael Krause
- Department of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada
| | - Linju Yang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University–Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu 215123 China
| | - John A. McLeod
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University–Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu 215123 China
| | - Lijia Liu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University–Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu 215123 China
| | - Kim M. Baines
- Department of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University–Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu 215123 China
| | - Tomislav Friščić
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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McCann S, Lumb JP, Arndtsen BA, Stahl SS. Second-Order Biomimicry: In Situ Oxidative Self-Processing Converts Copper(I)/Diamine Precursor into a Highly Active Aerobic Oxidation Catalyst. ACS Cent Sci 2017; 3:314-321. [PMID: 28470049 PMCID: PMC5408333 DOI: 10.1021/acscentsci.7b00022] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Indexed: 05/11/2023]
Abstract
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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Affiliation(s)
- Scott
D. McCann
- Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Jean-Philip Lumb
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8 Canada
- E-mail:
| | - Bruce A. Arndtsen
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8 Canada
- E-mail:
| | - Shannon S. Stahl
- Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
- E-mail:
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25
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Affiliation(s)
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
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26
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Esguerra KVN, Lumb JP. Synthesis of ortho
-Azophenols by Formal Dehydrogenative Coupling of Phenols and Hydrazines or Hydrazides. Chemistry 2017; 23:8596-8600. [DOI: 10.1002/chem.201701226] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Indexed: 01/13/2023]
Affiliation(s)
| | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke St. W. Montreal Quebec H3A 0B8 Canada
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Lumb JP, Kwon O, Esguerra K, Glazerman M, Petitjean L, Xu Y, Ottenwaelder X. Development of 3,5-Di-tert-butylphenol as a Model Substrate for Biomimetic Aerobic Copper Catalysis. Synlett 2017. [DOI: 10.1055/s-0036-1588761] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
We develop 3,5-di-tertbutylphenol as a strategic substrate for the evaluation of biomimetic Cu2–O2 complexes intended to mimic the activity of tyrosinase. We describe a practical and scalable synthesis and validate its use in an aerobic ortho-oxygenation catalyzed by N,N′-di-tert-butylethylenediamine and [Cu(CH3CN)4]PF6.
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Affiliation(s)
| | | | | | | | | | - Yalun Xu
- Department of Chemistry, McGill University
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Xu B, Hartigan EM, Feula G, Huang Z, Lumb JP, Arndtsen BA. Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201609255] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Boran Xu
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Elizabeth M. Hartigan
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Giancarlo Feula
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Zheng Huang
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Bruce A. Arndtsen
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
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Xu B, Hartigan EM, Feula G, Huang Z, Lumb JP, Arndtsen BA. Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion. Angew Chem Int Ed Engl 2016; 55:15802-15806. [PMID: 27873434 DOI: 10.1002/anie.201609255] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Indexed: 11/06/2022]
Affiliation(s)
- Boran Xu
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Elizabeth M. Hartigan
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Giancarlo Feula
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Zheng Huang
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Bruce A. Arndtsen
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
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31
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Trost BM, Masters JT, Le Vaillant F, Lumb JP. Synthesis of a 1,3-Bridged Macrobicyclic Enyne via Chemoselective Cycloisomerization Using Palladium-Catalyzed Alkyne-Alkyne Coupling. J Org Chem 2016; 81:10023-10028. [PMID: 27648602 DOI: 10.1021/acs.joc.6b01920] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A unique intramolecular Pd-catalyzed alkyne-alkyne coupling is presented. This transformation generates a strained, 1,3-bridged, macrocyclic enyne. The process was readily executed on gram scale, and the structure of the product was elucidated via X-ray crystallographic analysis. A mechanistic rationale for the observed chemoselectivity is provided.
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Affiliation(s)
- Barry M Trost
- Department of Chemistry, Stanford University , Stanford, California 94305-4401, United States
| | - James T Masters
- Department of Chemistry, Stanford University , Stanford, California 94305-4401, United States
| | - Franck Le Vaillant
- Department of Chemistry, Stanford University , Stanford, California 94305-4401, United States
| | - Jean-Philip Lumb
- Department of Chemistry, Stanford University , Stanford, California 94305-4401, United States
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32
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Trost BM, Masters JT, Taft BR, Lumb JP. Asymmetric synthesis of chiral β-alkynyl carbonyl and sulfonyl derivatives via sequential palladium and copper catalysis. Chem Sci 2016; 7:6217-6231. [PMID: 27746892 PMCID: PMC5044515 DOI: 10.1039/c6sc01724j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 06/09/2016] [Indexed: 11/21/2022] Open
Abstract
We present a full account detailing the development of a sequential catalysis strategy for the synthesis of chiral β-alkynyl carbonyl and sulfonyl derivatives. A palladium-catalyzed cross coupling of terminal alkyne donors with acetylenic ester, ketone, and sulfone acceptors generates stereodefined enynes in high yield. These compounds are engaged in an unprecedented, regio- and enantioselective copper-catalyzed conjugate reduction. The process exhibits a high functional group tolerance, and this enables the synthesis of a broad range of chiral products from simple, readily available alkyne precursors. The utility of the method is demonstrated through the elaboration of the chiral β-alkynyl products into a variety of different molecular scaffolds. Its value in complex molecule synthesis is further validated through a concise, enantioselective synthesis of AMG 837, a potent GPR40 receptor agonist.
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Affiliation(s)
- Barry M Trost
- Department of Chemistry , Stanford University , Stanford , CA 94305-5080 , USA .
| | - James T Masters
- Department of Chemistry , Stanford University , Stanford , CA 94305-5080 , USA .
| | - Benjamin R Taft
- Department of Chemistry , Stanford University , Stanford , CA 94305-5080 , USA .
| | - Jean-Philip Lumb
- Department of Chemistry , Stanford University , Stanford , CA 94305-5080 , USA .
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33
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Affiliation(s)
- Zheng Huang
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
| | - Jean-Philip Lumb
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal Quebec H3A 0B8 Canada
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Huang Z, Lumb JP. A Catalyst-Controlled Aerobic Coupling of ortho-Quinones and Phenols Applied to the Synthesis of Aryl Ethers. Angew Chem Int Ed Engl 2016; 55:11543-7. [PMID: 27513295 DOI: 10.1002/anie.201606359] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Indexed: 01/08/2023]
Abstract
ortho-Quinones are underutilized six-carbon-atom building blocks. We herein describe an approach for controlling their reactivity with copper that gives rise to a catalytic aerobic cross-coupling with phenols. The resulting aryl ethers are generated in high yield across a broad substrate scope under mild conditions. This method represents a unique example where the covalent modification of an ortho-quinone is catalyzed by a transition metal, creating new opportunities for their utilization in synthesis.
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Affiliation(s)
- Zheng Huang
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada.
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35
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Glavinović M, Qi F, Katsenis AD, Friščić T, Lumb JP. Redox-promoted associative assembly of metal-organic materials. Chem Sci 2016; 7:707-712. [PMID: 28791114 PMCID: PMC5530005 DOI: 10.1039/c5sc02214b] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 10/08/2015] [Indexed: 11/30/2022] Open
Abstract
We develop an associative synthesis of metal-organic materials that combines solid-state metal oxidation and coordination-driven self-assembly into a one-step, waste-free transformation. The methodology hinges on the unique reactivity of ortho-quinones, which we introduce as versatile oxidants for mechanochemical synthesis. Our strategy opens a previously unexplored route to paramagnetic metal-organic materials from elementary metals.
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Affiliation(s)
- Martin Glavinović
- Department of Chemistry , McGill University , 801 Sherbrooke St. West Montreal , Quebec H3A 0B8 , Canada . ; ; ; Tel: +514-398-4889
| | - Feng Qi
- Department of Chemistry , McGill University , 801 Sherbrooke St. West Montreal , Quebec H3A 0B8 , Canada . ; ; ; Tel: +514-398-4889
| | - Athanassios D Katsenis
- Department of Chemistry , McGill University , 801 Sherbrooke St. West Montreal , Quebec H3A 0B8 , Canada . ; ; ; Tel: +514-398-4889
| | - Tomislav Friščić
- Department of Chemistry , McGill University , 801 Sherbrooke St. West Montreal , Quebec H3A 0B8 , Canada . ; ; ; Tel: +514-398-4889
| | - Jean-Philip Lumb
- Department of Chemistry , McGill University , 801 Sherbrooke St. West Montreal , Quebec H3A 0B8 , Canada . ; ; ; Tel: +514-398-4889
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36
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Huang Z, Askari MS, Esguerra KVN, Dai TY, Kwon O, Ottenwaelder X, Lumb JP. A bio-inspired synthesis of oxindoles by catalytic aerobic dual C-H functionalization of phenols. Chem Sci 2015; 7:358-369. [PMID: 29861988 PMCID: PMC5952266 DOI: 10.1039/c5sc02395e] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 10/05/2015] [Indexed: 11/30/2022] Open
Abstract
We report a bio-inspired approach to the synthesis of oxindoles, which couples the energetic requirements of dehydrogenative C–N bond formation to the reduction of oxygen.
Nitrogen-containing heterocycles are fundamentally important to the function of pharmaceuticals, agrochemicals and materials. Herein, we report a bio-inspired approach to the synthesis of oxindoles, which couples the energetic requirements of dehydrogenative C–N bond formation to the reduction of molecular oxygen (O2). Our method is inspired by the biosynthesis of melanin pigments (melanogenesis), but diverges from the biosynthetic polymerization. Mechanistic analysis reveals the involvement of CuII-semiquinone radical intermediates, which enable dehydrogenative carbon–heteroatom bond formation that avoids a catechol/quinone redox couple. This mitagates the deleterious polarity reversal that results from phenolic dearomatization, and enables a high-yielding phenolic C–H functionalization under catalytic aerobic conditions. Our work highlights the broad synthetic utility and efficiency of forming C–N bonds via a catalytic aerobic dearomatization of phenols, which is currently an underdeveloped transformation.
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Affiliation(s)
- Zheng Huang
- Department of Chemistry , McGill University , Montreal , QC H3A 0B8 , Canada .
| | - Mohammad S Askari
- Department of Chemistry and Biochemistry , Concordia University , Montreal , QC H4B 1R6 , Canada .
| | | | - Tian-Yang Dai
- Department of Chemistry , McGill University , Montreal , QC H3A 0B8 , Canada .
| | - Ohhyeon Kwon
- Department of Chemistry , McGill University , Montreal , QC H3A 0B8 , Canada .
| | - Xavier Ottenwaelder
- Department of Chemistry and Biochemistry , Concordia University , Montreal , QC H4B 1R6 , Canada .
| | - Jean-Philip Lumb
- Department of Chemistry , McGill University , Montreal , QC H3A 0B8 , Canada .
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Abstract
Controlling product selectivity during the catalytic aerobic oxidation of phenols remains a significant challenge that hinders reaction development. This work provides a mechanistic picture of a Cu-catalyzed, aerobic functionalization of phenols that is selective for phenoxy-coupled ortho-quinones. We show that the immediate product of the reaction is a Cu(II)-semiquinone radical complex and reveal that ortho-oxygenation precedes oxidative coupling. This complex is the resting state of the Cu catalyst during turnover at room temperature. A mechanistic study of the formation of this complex at low temperatures demonstrates that the oxygenation pathway mimics the dinuclear Cu enzyme tyrosinase by involving a dinuclear side-on peroxodicopper(II) oxidant. Unlike the enzyme, however, the rate-limiting step of the ortho-oxygenation reaction is the self-assembly of the oxidant from Cu(I) and O2. We provide details for all steps in the cycle and demonstrate that turnover is contingent upon proton-transfer events that are mediated by a slight excess of ligand. Finally, our knowledge of the reaction mechanism can be leveraged to diversify the reaction outcome. Thus, uncoupled ortho-quinones are favored in polar, coordinating media, highlighting unusually high levels of chemoselectivity for a catalytic aerobic oxidation of a phenol.
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Affiliation(s)
- Mohammad S Askari
- Department of Chemistry and Biochemistry, Concordia University , Montreal, QC H4B 1R6, Canada
| | | | - Jean-Philip Lumb
- Department of Chemistry, McGill University , Montreal, QC H3A 0B8, Canada
| | - Xavier Ottenwaelder
- Department of Chemistry and Biochemistry, Concordia University , Montreal, QC H4B 1R6, Canada
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40
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Xu B, Lumb JP, Arndtsen BA. A TEMPO-Free Copper-Catalyzed Aerobic Oxidation of Alcohols. Angew Chem Int Ed Engl 2015; 54:4208-11. [DOI: 10.1002/anie.201411483] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Indexed: 11/08/2022]
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Abstract
Lignan natural products comprise a broad spectrum of biologically active secondary metabolites. Their structural diversity belies a common biosynthesis, which involves regio- and chemoselective oxidative coupling of propenyl phenols. Attempts to replicate this oxidative coupling have revealed significant challenges for controlling selectivity, and these challenges have thus far prevented the development of a unified biomimetic route to compounds of the lignan family. A practical solution is presented that hinges on oxidative ring opening of a diarylcyclobutane to intercept a putative biosynthetic intermediate. The effectiveness of this approach is demonstrated by the first total synthesis of tanegool in 4 steps starting from ferulic acid, as well as a concise synthesis of the prototypical furanolignan pinoresinol.
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Affiliation(s)
- Anna K F Albertson
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC, H3A 0B8 (Canada)
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44
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Affiliation(s)
- Kenneth Virgel N. Esguerra
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Yacoub Fall
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Laurène Petitjean
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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45
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Abstract
The importance of aromatic C-O, C-N, and C-S bonds necessitates increasingly efficient strategies for their formation. Herein, we report a biomimetic approach that converts phenolic C-H bonds into C-O, C-N, and C-S bonds at the sole expense of reducing dioxygen (O2) to water (H2O). Our method hinges on a regio- and chemoselective copper-catalyzed aerobic oxygenation to provide ortho-quinones. ortho-Quinones are versatile intermediates, whose direct catalytic aerobic synthesis from phenols enables a mild and efficient means of synthesizing polyfunctional aromatic rings.
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Affiliation(s)
- Kenneth Virgel N Esguerra
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC, H3A 0B8 (Canada)
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46
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47
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Trost BM, Masters JT, Lumb JP, Fateen D. Asymmetric synthesis of chiral cycloalkenone derivatives via palladium catalysis. Chem Sci 2014; 5:1354-1360. [PMID: 24761221 PMCID: PMC3992253 DOI: 10.1039/c3sc53250j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 01/13/2014] [Indexed: 12/04/2022] Open
Abstract
The palladium-catalyzed oxidative desymmetrization of meso dibenzoates yields γ-benzoyloxy cycloalkenones in good yields and with excellent levels of enantioselectivity. These compounds serve as precursors to a broad range of substituted cycloalkenones, including well-established synthetic building blocks and elaborated cycloalkanone derivatives. The ability to prepare both enantiomers of the oxidative desymmetrization products enables a unified strategy toward stereochemically diverse epoxyquinoid natural products.
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Affiliation(s)
- Barry M. Trost
- Department of Chemistry , Stanford University , Stanford , CA 94305-4401 , USA .
| | - James T. Masters
- Department of Chemistry , Stanford University , Stanford , CA 94305-4401 , USA .
| | - Jean-Philip Lumb
- Department of Chemistry , Stanford University , Stanford , CA 94305-4401 , USA .
| | - Dahlia Fateen
- Department of Chemistry , Stanford University , Stanford , CA 94305-4401 , USA .
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48
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Trost BM, Taft BR, Masters JT, Lumb JP. A new strategy for the synthesis of chiral β-alkynyl esters via sequential palladium and copper catalysis. J Am Chem Soc 2011; 133:8502-5. [PMID: 21557627 DOI: 10.1021/ja203171x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A new strategy for the synthesis of chiral β-alkynyl esters which relies on sequential Pd and Cu catalysis is reported. Terminal alkynes bearing aryl, alkyl, and silyl groups can be employed without prior activation yielding a wide range of important chiral building blocks. The reaction sequence utilizes a robust Pd(II)-catalyzed hydroalkynylation of ynoates with terminal alkynes providing geometrically pure ynenoates which are readily reduced by CuH. In contrast to previous reports, where additions to ynenoates proceed with marginal preference for the 1,6-pathway, this conjugate reduction occurs with high 1,4-selectivity yielding β-alkynyl esters with excellent levels of enantioselectivity. Importantly, the method tolerates a wide range of functionality, including allylic carbonates and carbamates, and thus allows for rapid elaboration of the β-alkynyl esters into a variety of chiral, substituted heterocycles.
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Affiliation(s)
- Barry M Trost
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
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Abstract
A robust route to 2,4-disubstituted pyrrole heterocycles relying upon a cascade reaction is reported. The reaction benefits from operational simplicity: it is air and moisture tolerant and is performed at ambient temperature. Control over the reaction conditions provides ready access to isopyrroles, 2,3,4-trisubstituted pyrroles, and 3-substituted pyrollidin-2-ones.
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Affiliation(s)
- Barry M Trost
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States.
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50
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Affiliation(s)
- Jean-Philip Lumb
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Jamin L. Krinsky
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Dirk Trauner
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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