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Wang HC, You SL. Asymmetric Allylic Amination of Alkyl-Substituted Allylic Carbonates with Pyridones Catalyzed by the Krische Iridium Complex. Org Lett 2024. [PMID: 39331508 DOI: 10.1021/acs.orglett.4c03400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2024]
Abstract
An efficient Ir-catalyzed asymmetric allylic amination reaction of alkyl-substituted allylic carbonates is disclosed. With the Krische iridium complex as the catalyst, asymmetric allylic amination of alkyl-substituted allylic carbonates with pyridones proceeds effectively, affording pyridone derivatives containing a stereocenter α to the nitrogen atom in excellent yields and enantioselectivity (up to 99% yield, 95% ee). This catalytic system broadens the substrate scope of the reaction compared with that of the known catalytic systems. This reaction can also be conducted on a gram scale, further enhancing its potential for synthetic application.
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Affiliation(s)
- Hu-Chong Wang
- New Cornerstone Science Laboratory, State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Shu-Li You
- New Cornerstone Science Laboratory, State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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2
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Tu JL, Huang B. Direct C(sp 3)-H functionalization with aryl and alkyl radicals as intermolecular hydrogen atom transfer (HAT) agents. Chem Commun (Camb) 2024. [PMID: 39268687 DOI: 10.1039/d4cc03383c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/17/2024]
Abstract
Recent years have witnessed the emergence of direct intermolecular C(sp3)-H bond functionalization using in situ generated aryl/alkyl radicals as a unique class of hydrogen atom transfer (HAT) agents. A variety of precursors have been exploited to produce these radical HAT agents under photocatalytic, electrochemical or thermal conditions. To date, viable aryl radical precursors have included aryl diazonium salts or aryl azosulfones, diaryliodonium salts, O-benzoyl oximes, aryl sulfonium salts, aryl thioesters, and aryl halides; and applicable alkyl radical sources have included tetrahalogenated methanes (e.g., CCl3Br, CBr4 and CF3I), N-hydroxyphthalimide esters, alkyl bromides, and acetic acid. This review summarizes the current advances in direct intermolecular C(sp3)-H functionalization through key HAT events with in situ generated aryl/alkyl radicals and categorizes the procedures by the specific radical precursors applied. With an emphasis on the reaction conditions, mechanisms and representative substrate scopes of these protocols, this review aims to demonstrate the current trends and future challenges of this emerging field.
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Affiliation(s)
- Jia-Lin Tu
- Faculty of Arts and Sciences, Beijing Normal University, Zhuhai 519085, China.
- School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
| | - Binbin Huang
- Faculty of Arts and Sciences, Beijing Normal University, Zhuhai 519085, China.
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3
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Aquilina JM, Banerjee A, Morais GN, Chen S, Smith MW. Total Synthesis of (-)-Rauvomine B via a Strain-Promoted Intramolecular Cyclopropanation. J Am Chem Soc 2024; 146:22047-22055. [PMID: 39042605 DOI: 10.1021/jacs.4c07669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
We describe the first total synthesis of the unusual cyclopropane-containing indole alkaloid (-)-rauvomine B via a strategy centered upon intramolecular cyclopropanation of a tetracyclic N-sulfonyltriazole. Preparation of this precursor evolved through two generations of synthesis, with the ultimately successful route involving a palladium-catalyzed stereospecific allylic amination, a cis-selective Pictet-Spengler reaction, and ring-closing metathesis as important bond-forming reactions. The key cyclopropanation step was found to be highly dependent on the structure and conformational strain of the indoloquinolizidine N-sulfonyltriazole precursor, the origins of which are explored computationally through DFT studies. Overall, our synthesis proceeds in 11 total steps and 2.4% yield from commercial materials.
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Affiliation(s)
- Jake M Aquilina
- Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390, United States
| | - Ankush Banerjee
- Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390, United States
| | - Gabriel N Morais
- Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390, United States
- Department of Chemistry and Biochemistry, Oberlin College, 119 Woodland St., Oberlin, Ohio 44074, United States
| | - Shuming Chen
- Department of Chemistry and Biochemistry, Oberlin College, 119 Woodland St., Oberlin, Ohio 44074, United States
| | - Myles W Smith
- Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390, United States
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Arachchi MK, Schaugaard RN, Schlegel HB, Nguyen HM. Scope and Mechanistic Probe into Asymmetric Synthesis of α-Trisubstituted-α-Tertiary Amines by Rhodium Catalysis. J Am Chem Soc 2023; 145:19642-19654. [PMID: 37651695 PMCID: PMC10581542 DOI: 10.1021/jacs.3c04211] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Asymmetric reactions that convert racemic mixtures into enantioenriched amines are of significant importance due to the prevalence of amines in pharmaceuticals, with about 60% of drug candidates containing tertiary amines. Although transition-metal catalyzed allylic substitution processes have been developed to provide access to enantioenriched α-disubstituted allylic amines, enantioselective synthesis of sterically demanding α-tertiary amines with a tetrasubstituted carbon stereocenter remains a major challenge. Herein, we report a chiral diene-ligated rhodium-catalyzed asymmetric substitution of racemic tertiary allylic trichloroacetimidates with aliphatic secondary amines to afford α-trisubstituted-α-tertiary amines. Mechanistic investigation is conducted using synergistic experimental and computational studies. Density functional theory calculations show that the chiral diene-ligated rhodium promotes the ionization of tertiary allylic substrates to form both anti and syn π-allyl intermediates. The anti π-allyl pathway proceeds through a higher energy than the syn π-allyl pathway. The rate of conversion of the less reactive π-allyl intermediate to the more reactive isomer via π-σ-π interconversion was faster than the rate of nucleophilic attack onto the more reactive intermediate. These data imply that the Curtin-Hammett conditions are met in the amination reaction, leading to dynamic kinetic asymmetric transformation. Computational studies also show that hydrogen bonding interactions between β-oxygen of allylic substrate and amine-NH greatly assist the delivery of amine nucleophile onto more hindered internal carbon of the π-allyl intermediate. The synthetic utility of the current methodology is showcased by efficient preparation of α-trisubstituted-α-tertiary amines featuring pharmaceutically relevant secondary amine cores with good yields and excellent selectivities (branched-linear >99:1, up to 99% enantiomeric excess).
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Affiliation(s)
- Madhawee K Arachchi
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Richard N Schaugaard
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - H Bernhard Schlegel
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Hien M Nguyen
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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Stivala CE, Zbieg JR, Liu P, Krische MJ. Chiral Amines via Enantioselective π-Allyliridium- C, O-Benzoate-Catalyzed Allylic Alkylation: Student Training via Industrial-Academic Collaboration. Acc Chem Res 2022; 55:2138-2147. [PMID: 35830564 PMCID: PMC9608351 DOI: 10.1021/acs.accounts.2c00302] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
ConspectusCyclometalated π-allyliridium-C,O-benzoate complexes discovered in the Krische laboratory display unique amphiphilic properties, catalyzing both nucleophilic carbonyl allylation and electrophilic allylation of diverse amines as well as nitronates. Given the importance of chiral amines in FDA-approved small-molecule drugs, a collaboration with medicinal chemists at Genentech that included on-site graduate student internships was undertaken to explore and expand the scope of π-allyliridium-C,O-benzoate-catalyzed allylic amination and related processes. As described in this Account, our collective experimental studies have unlocked asymmetric allylic aminations of exceptionally broad utility and scope. Specifically, using racemic branched alkyl-substituted allylic acetate proelectrophiles, primary and secondary aliphatic or aromatic amines, including indoles, engage in highly regio- and enantioselective allylic amination. Additionally, unactivated nitronates were found to be competent nucleophilic partners for regio- and enantioselective allylic alkylation, enabling entry to β-stereogenic α-quaternary primary amines. Notably, these π-allyliridium-C,O-benzoate-catalyzed allylic substitutions, which display complete branched regioselectivity in reactions of alkyl-substituted allyl electrophiles, complement the scope of corresponding iridium phosphoramidite-catalyzed allylic aminations, which require aryl-substituted allyl electrophiles to promote high levels of branched regioselectivity. Computational, kinetic, ESI-CID-MS, and isotopic labeling studies were undertaken to understand the mechanism of these processes, including the origins of regio- and enantioselectivity. Isotopic labeling studies suggest that C-N bond formation occurs through outer-sphere addition to the π-allyl. DFT calculations corroborate C-N bond formation via outer-sphere addition and suggest that early transition states and distinct trans effects of diastereomeric chiral-at-iridium π-allyl complexes render the reaction less sensitive to steric effects, accounting for complete levels of branched regioselectivity in reactions of hindered amine and nitronate nucleophiles. Reaction progress kinetic analysis (RPKA) reveals a zero-order dependence on allyl acetate, a first-order dependence on the catalyst, and a fractional-order dependence on the amine. As corroborated by ESI-CID-MS analysis, the 0.4 kinetic order dependence on the amine may reflect the intervention of cesium-bridged amine dimers, which dissociate to form monomeric cesium amide nucleophiles. Hence, the requirement of cesium carbonate (vs lower alkali metal carbonates) in these processes may reside in cesium's capacity for Lewis acid-enhanced Brønsted acidification of the amine pronucleophile. Beyond the development of catalytic processes for the synthesis of novel chiral amines, the present research was conducted by graduate students who benefited from career development experiences associated with training in both academic and industrial laboratories.
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Affiliation(s)
- Craig E Stivala
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Jason R Zbieg
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Peng Liu
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Michael J Krische
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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Jung WO, Mai BK, Yoo M, Shields SWJ, Zbieg JR, Stivala CE, Liu P, Krische MJ. Kinetic, ESI-CID-MS and Computational Studies of π-Allyliridium C,O-Benzoate-Catalyzed Allylic Amination: Understanding the Effect of Cesium Ion. ACS Catal 2022; 12:3660-3668. [PMID: 36092640 PMCID: PMC9456326 DOI: 10.1021/acscatal.2c00470] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The mechanism of π-allyliridium C,O-benzoate-catalyzed allylic amination was studied by (a) reaction progress kinetic analysis (RPKA), (b) tandem ESI-MS analysis, and (c) computational studies involving density functional theory (DFT) calculations. Reaction progress kinetic analysis (RPKA) reveals a zero-order dependence on allyl acetate, first-order dependence on catalyst and fractional-order dependence on amine. These data corroborate rapid ionization of the allylic acetate followed by turnover limiting C-N bond formation. To illuminate the origins of the 0.4 kinetic order dependence on amine, ESI-MS analyses of quaternary ammonium-labelled piperazine with multistage collision induced dissociation (CID) were conducted that corroborate intervention of cesium-bridged amine dimers that dissociate to form monomeric cesium amide nucleophiles. Computational data align with RPKA and ESI-CID-MS analyses and suggest early transition states mitigate the impact of steric factors, thus enabling formation of highly substituted C-N bonds with complete levels of branched regioselectivity. Specifically, trans-effects of the iridium complex facilitate nucleophilic attack at the more substituted allyl terminus trans to phosphorus with enantioselectivity governed by steric repulsions between the chiral bisphosphine ligand and the π-allyl of a dominant diastereomer of the stereogenic-at-metal complex. Beyond defining aspects of the mechanism of π-allyliridium C,O-benzoate-catalyzed allylic amination, these data reveal that a key feature of cesium carbonate not only lies in its enhanced basicity, but also its capacity for Lewis-acid enhanced Brønsted acidification of amines.
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Affiliation(s)
- Woo-Ok Jung
- University of Texas at Austin, Department of Chemistry, Austin, TX 78712, USA
| | - Binh Khanh Mai
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Minjin Yoo
- University of Texas at Austin, Department of Chemistry, Austin, TX 78712, USA
| | - Samuel W J Shields
- University of Texas at Austin, Department of Chemistry, Austin, TX 78712, USA
| | - Jason R Zbieg
- Discovery Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, USA
| | - Craig E Stivala
- Discovery Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, USA
| | - Peng Liu
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Michael J Krische
- University of Texas at Austin, Department of Chemistry, Austin, TX 78712, USA
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