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Ding B, Xue Q, Wei H, Chen J, Liu ZS, Cheng HG, Cong H, Tang J, Zhou Q. Enantioconvergent synthesis of chiral fluorenols from racemic secondary alcohols via Pd(ii)/chiral norbornene cooperative catalysis. Chem Sci 2024; 15:7975-7981. [PMID: 38817591 PMCID: PMC11134410 DOI: 10.1039/d4sc01004c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 04/18/2024] [Indexed: 06/01/2024] Open
Abstract
An efficient protocol for the asymmetric synthesis of fluorenols has been developed through an enantioconvergent process enabled by Pd(ii)/chiral norbornene cooperative catalysis. This approach allows facile access to diverse functionalized chiral fluorenols with constantly excellent enantioselectivities, applying readily available racemic secondary ortho-bromobenzyl alcohols and aryl iodides as the starting materials.
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Zhou L, Cheng HG, Li L, Wu K, Hou J, Jiao C, Deng S, Liu Z, Yu JQ, Zhou Q. Synthesis of planar chiral ferrocenes via enantioselective remote C-H activation. Nat Chem 2023:10.1038/s41557-023-01176-3. [PMID: 37069268 DOI: 10.1038/s41557-023-01176-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 03/08/2023] [Indexed: 04/19/2023]
Abstract
Planar chiral ferrocenes are widely studied structures in asymmetric catalysis, materials science and medicinal chemistry. Although synthetic methods for 1,2-disubstituted planar chiral ferrocenes are well known, methods for the direct construction of 1,3-disubstituted planar chiral ferrocenes remain elusive. Here we report a modular platform for the construction of planar chirality in 1,3-disubstituted ferrocenes/ruthenocenes via an enantioselective relay remote C-H activation strategy. This method demonstrates a mechanism for remote enantiocontrol via enantiodetermining initial C‒H activation at the C2 position, enabled by a chiral mono-N-protected natural amino-acid ligand, and subsequent relay to the remote C3 position by a bridgehead-substituted norbornene mediator. A wide variety of 1,3-disubstituted planar chiral metallocenes are prepared with high enantioselectivity (96‒99% e.e.). The reaction shows good functional-group tolerance and high step-economy, and aryl iodides/bromides are compatible as coupling partners. The resulting metallocenes can be readily derivatized to yield planar chiral ligands and catalysts for asymmetric catalysis as well as building blocks for other applications.
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Cheng HG, Jia S, Zhou Q. Benzo-Fused-Ring Toolbox Based on Palladium/Norbornene Cooperative Catalysis: Methodology Development and Applications in Natural Product Synthesis. Acc Chem Res 2023; 56:573-591. [PMID: 36716326 DOI: 10.1021/acs.accounts.2c00781] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
ConspectusBenzo-fused skeletons are ubiquitous in agrochemicals, medicines, natural products, catalysts, and other organic function materials. The assembly of these skeletons in an efficient manner is an actively explored field in organic synthesis. Palladium/norbornene (Pd/NBE) cooperative catalysis is a powerful tool for the expeditious assembly of polysubstituted arenes through bis-functionalization of the ortho and ipso positions of aryl iodides in one operation. Owing to the efforts of Lautens, Catellani, and others, an array of Pd/NBE-promoted annulations for the syntheses of diversified benzo-fused rings have been developed. However, these methods have not been broadly applied in total synthesis yet.Our group is interested in efficient and practical total synthesis of biologically active molecules. In the past 7 years, we have been devoted to the development of new annulation strategies for the assembly of common benzo-fused skeletons through Pd/NBE-promoted reactions of aryl iodides with novel bifunctional reagents. In this Account, we summarize our laboratory's systematic efforts in this direction. First, readily available epoxides and aziridines were exploited as versatile bifunctional alkylating reagents, which enables quick assembly of a series of valuable benzo-fused heterocycles, including isochromans, dihydrobenzofurans, 1,3-cis-tetrahydroisoquinolines (THIQs), 1,3-trans-THIQs, etc. Second, a convergent access to 5-7-membered benzo-fused carbocycles (including indanes and tetrahydronaphthalenes) was developed by Pd/NBE-promoted annulation of aryl iodides with simple olefinic alcohol-containing alkylating reagents. Third, a Pd/NBE-promoted annulation between aryl iodides and cyclohexanone-containing amination reagents was developed for the construction of benzo-fused N-containing bridged scaffolds. Thus, we have established a practical and versatile toolbox for the quick assembly of diversified benzo-fused skeletons. These new annulation reactions are of high chemo-, regio-, and stereoselectivities with good step and atom economy. Moreover, they are able to rapidly increase molecular complexity from simple building blocks. Finally, their synthetic value has been demonstrated by immediate adoption in several efficient total syntheses of medicines and complex natural products. Compared to conventional synthetic logics, the Pd/NBE-promoted annulation toolbox allows the development of highly convergent strategies, which significantly improves the overall synthetic efficiency.We believe the results presented in this Account will have significant implications beyond our research. It can be envisaged that new Pd/NBE-promoted annulations as well as new applications in complex total synthesis will be revealed in the near future.
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Ye J, Li L, You Y, Jiao C, Cui Z, Zhang Y, Jia S, Cong H, Liu S, Cheng HG, Zhou Q. Enantioselective Assembly of Ferrocenes with Axial and Planar Chiralities via Palladium/Chiral Norbornene Cooperative Catalysis. JACS AU 2023; 3:384-390. [PMID: 36873690 PMCID: PMC9976344 DOI: 10.1021/jacsau.2c00630] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 01/11/2023] [Accepted: 01/11/2023] [Indexed: 06/18/2023]
Abstract
The preparation of ferrocenes with both axial and planar chiralities poses a considerable challenge. Herein, we report a strategy for the construction of both axial and planar chiralities in a ferrocene system via palladium/chiral norbornene (Pd/NBE*) cooperative catalysis. In this domino reaction, the first established axial chirality is dictated by Pd/NBE* cooperative catalysis, while the latter planar chirality is controlled by the preinstalled axial chirality through a unique axial-to-planar diastereoinduction process. This method exploits readily available ortho-ferrocene-tethered aryl iodides (16 examples) and the bulky 2,6-disubstituted aryl bromides (14 examples) as the starting materials. Five- to seven-membered benzo-fused ferrocenes with both axial and planar chiralities (32 examples) are obtained in one step with constantly high enantioselectivities (>99% e.e.) and diastereoselectivities (>19:1 d.r.).
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Liu ZS, Deng S, Gao Q, Hua Y, Cheng HG, Qi X, Zhou Q. Construction of Axially Chiral Biaryls via Atroposelective ortho-C–H Arylation of Aryl Iodides. ACS Catal 2023. [DOI: 10.1021/acscatal.2c06310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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Zhang X, Wei H, Wei Q, Wu C, Liu C, Cheng HG, Zhou Q. Modular One‐Step Three‐Component Assembly of Isochromans via Palladium/Norbornene Cooperative Catalysis. ASIAN J ORG CHEM 2022. [DOI: 10.1002/ajoc.202200642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Chen R, Jia S, Man Y, Cheng HG, Zhou Q. A Concise Total Synthesis of (±)-Stepharine and (±)-Pronuciferine. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/a-1984-0755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We herein report a concise total synthesis of (±)-stepharine and (±)-pronuciferine using readily available reagents as the starting materials. This synthesis features a three-component Catellani reaction/Au-catalyzed 6-exo-dig cyclization for the assembly of 1-methylene-THIQ scaffold and an oxidative dearomatization for constructing spiro-cyclohexadienone scaffold.
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Yang T, Li X, Deng S, Qi X, Cong H, Cheng HG, Shi L, Zhou Q, Zhuang L. From N-H Nitration to Controllable Aromatic Mononitration and Dinitration-The Discovery of a Versatile and Powerful N-Nitropyrazole Nitrating Reagent. JACS AU 2022; 2:2152-2161. [PMID: 36186553 PMCID: PMC9516713 DOI: 10.1021/jacsau.2c00413] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 08/16/2022] [Accepted: 08/17/2022] [Indexed: 06/16/2023]
Abstract
Nitroaromatics are tremendously valuable organic compounds with a long history of being used as pharmaceuticals, agrochemicals, and explosives as well as vital intermediates to a wide variety of chemicals. Consequently, the exploration of aromatic nitration has become an important endeavor in both academia and industry. Herein, we report the identification of a powerful nitrating reagent, 5-methyl-1,3-dinitro-1H-pyrazole, from the N-nitro-type reagent library constructed using a practical N-H nitration method. This nitrating reagent behaves as a controllable source of the nitronium ion, enabling mild and scalable nitration of a broad range of (hetero)arenes with good functional group tolerance. Of note, our nitration method could be controlled by manipulating the reaction conditions to furnish mononitrated or dinitrated product selectively. The value of this method in medicinal chemistry has been well established by its efficient late-stage C-H nitration of complex biorelevant molecules. Density functional theory (DFT) calculations and preliminary mechanistic studies reveal that the powerfulness and versatility of this nitrating reagent are due to the synergistic "nitro effect" and "methyl effect".
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Bai M, Jia S, Zhang J, Cheng HG, Cong H, Liu S, Huang Z, Huang Y, Chen X, Zhou Q. A Modular Approach for Diversity‐Oriented Synthesis of 1,3‐trans‐Disubstituted Tetrahydroisoquinolines: Seven‐Step Asymmetric Synthesis of Michellamines B and C. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ding B, Xue Q, Cheng HG, Zhou Q, Jia S. Recent Advances in Catalytic Nonenzymatic Kinetic Resolution of Tertiary Alcohols. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/a-1712-0912] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
AbstractThe kinetic resolution (KR) of racemates is one of the most widely used approaches to access enantiomerically pure compounds. Over the past two decades, catalytic nonenzymatic KR has gained popularity in the field of asymmetric synthesis due to the rapid development of chiral catalysts and ligands in asymmetric catalysis. Chiral tertiary alcohols are prevalent in a variety of natural products, pharmaceuticals, and biologically active chiral compounds. The catalytic nonenzymatic KR of racemic tertiary alcohols is a straightforward strategy to access enantioenriched tertiary alcohols. This short review describes recent advances in catalytic nonenzymatic KR of tertiary alcohols, including organocatalysis and metal catalysis.1 Introduction2 Organocatalysis2.1 Peptide Catalyst2.2 Chiral Phosphoric Acid Catalyst2.3 Chiral Lewis Base Catalyst2.4 Chiral Quaternary Ammonium Salt Catalyst3 Metal Catalysis3.1 Mixed La-Li Heterobimetallic Catalyst3.2 Rh Catalyst3.3 Hf Catalyst3.4 Pd Catalyst3.5 Cu Catalyst3.6 Ag Catalyst4 Conclusion and Outlook
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Cheng HG, Zhou Q, Yang Z, Chen R, Cao L, Wei Q, Wang Q. Eight-Step Asymmetric Synthesis of (–)-Berkelic Acid. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/a-1799-0459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
AbstractWe herein report an eight-step asymmetric synthesis of (–)-berkelic acid. This work features a sequential Catellani-type reaction/oxa-Michael addition with epoxides as dual-functionalized alkylating reagents for synthesizing the isochroman framework, a one-pot, acid-catalyzed deprotection/spiroacetalization process for the construction of a tetracyclic core intermediate, and a late-stage Ni-catalyzed reductive coupling reaction for the installation of the side chain. Remarkably, during the deprotection/spiroacetalization process, four new stereocenters are created with high stereocontrol from a single existing chiral center.
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Shen Z, Zhou L, Wu C, Zhou Q, Cheng HG. Palladium-catalyzed [4+3] annulation of 2-bromobiphenyls and epoxides for the assembly of dihydrodibenzo[b,d]oxepines. Org Biomol Chem 2022; 20:8869-8872. [DOI: 10.1039/d2ob01720b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A palladium-catalyzed [4+3] annulation of 2-bromobiphenyls and epoxides for the construction of dihydrodibenzo[b,d]oxepines is reported. This approach involves direct C–H and C–O bond activation followed by a ring annulation and...
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Wu C, Liu ZS, Shang Y, Liu C, Deng S, Cheng HG, Cong H, Jiao Y, Zhou Q. Withdrawal: Asymmetric Alkenyl Catellani Reaction for the Construction of C-N Axial Chirality. Angew Chem Int Ed Engl 2021; 60:17248. [PMID: 34033193 DOI: 10.1002/anie.202105669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Accepted Article version of the above article, published online on 25 May 2021 in Wiley Online Library (wileyonlinelibrary.com), has been withdrawn by agreement between the corresponding author, the journal′s Executive Committee, and Wiley‐VCH GmbH, Weinheim. The withdrawal has been agreed upon due to significant conceptual similarities with another of the authors' recently published articles, which was not disclosed during the peer review process.
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Liu ZS, Xie PP, Hua Y, Wu C, Ma Y, Chen J, Cheng HG, Hong X, Zhou Q. An axial-to-axial chirality transfer strategy for atroposelective construction of C–N axial chirality. Chem 2021. [DOI: 10.1016/j.chempr.2021.04.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Shang Y, Wu C, Gao Q, Liu C, Li L, Zhang X, Cheng HG, Liu S, Zhou Q. Diversity-oriented functionalization of 2-pyridones and uracils. Nat Commun 2021; 12:2988. [PMID: 34016986 PMCID: PMC8137914 DOI: 10.1038/s41467-021-23058-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 04/09/2021] [Indexed: 11/28/2022] Open
Abstract
Heterocycles 2-pyridone and uracil are privileged pharmacophores. Diversity-oriented synthesis of their derivatives is in urgent need in medicinal chemistry. Herein, we report a palladium/norbornene cooperative catalysis enabled dual-functionalization of iodinated 2-pyridones and uracils. The success of this research depends on the use of two unique norbornene derivatives as the mediator. Readily available alkyl halides/tosylates and aryl bromides are utilized as ortho-alkylating and -arylating reagents, respectively. Widely accessible ipso-terminating reagents, including H/DCO2Na, boronic acid/ester, terminal alkene and alkyne are compatible with this protocol. Thus, a large number of valuable 2-pyridone derivatives, including deuterium/CD3-labeled 2-pyridones, bicyclic 2-pyridones, 2-pyridone-fenofibrate conjugate, axially chiral 2-pyridone (97% ee), as well as uracil and thymine derivatives, can be quickly prepared in a predictable manner (79 examples reported), which will be very useful in new drug discovery.
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Gao Q, Wu C, Deng S, Li L, Liu ZS, Hua Y, Ye J, Liu C, Cheng HG, Cong H, Jiao Y, Zhou Q. Catalytic Synthesis of Atropisomeric o-Terphenyls with 1,2-Diaxes via Axial-to-Axial Diastereoinduction. J Am Chem Soc 2021; 143:7253-7260. [PMID: 33961421 DOI: 10.1021/jacs.1c02405] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Herein, we report a modular and convergent strategy for the assembly of atropisomeric o-terphenyls with 1,2-diaxes via palladium/chiral norbornene cooperative catalysis and axial-to-axial diastereoinduction. Readily available aryl iodides, 2,6-substituted aryl bromides, and potassium aryl trifluoroborates are used as the building blocks, laying the foundation for diversity-oriented synthesis of these scaffolds (46 examples). Other features include the unique axial-to-axial diastereoinduction mode, construction of two axes in a single operation, and step economy. DFT calculations are performed to rationalize the axial-to-axial diastereoinduction process. Synthetic utilities of this method in preparation of atropisomeric oligophenyls, chiral catalysts, and ligands are demonstrated.
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Cheng HG, Yang Z, Chen R, Cao L, Tong WY, Wei Q, Wang Q, Wu C, Qu S, Zhou Q. A Concise Total Synthesis of (-)-Berkelic Acid. Angew Chem Int Ed Engl 2021; 60:5141-5146. [PMID: 33252181 DOI: 10.1002/anie.202014660] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/27/2020] [Indexed: 12/19/2022]
Abstract
Reported here is a concise total synthesis of (-)-berkelic acid in eight linear steps. This synthesis features a Catellani reaction/oxa-Michael cascade for the construction of the isochroman scaffold, a one-pot deprotection/spiroacetalization operation for the formation of the tetracyclic core structure, and a late-stage Ni-catalyzed reductive coupling for the introduction of the lateral chain. Notably, four stereocenters are established from a single existing chiral center with excellent stereocontrol during the deprotection/spiroacetalization process. Stereocontrol of the intriguing deprotection/spiroacetalization process is supported by DFT calculations.
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Cao L, Hua Y, Cheng HG, Zhou Q. C–H hetero-functionalization of arenes through palladacyclopentane-type intermediates. Org Chem Front 2021. [DOI: 10.1039/d0qo01350a] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In this review article, we summarized recent advances in C–H hetero-functionalization of arenes through palladacyclopentane-type intermediates.
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Cheng HG, Zhou Q. Turning constraint into opportunity: development of a four-component Catellani reaction. Sci Bull (Beijing) 2020; 65:1961-1963. [PMID: 36659050 DOI: 10.1016/j.scib.2020.08.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Cheng HG, Pu M, Kundu G, Schoenebeck F. Addition to “Selective Methylation of Amides, N-Heterocycles, Thiols, and Alcohols with Tetramethylammonium Fluoride”. Org Lett 2020; 22:4581. [DOI: 10.1021/acs.orglett.0c01524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Gao Q, Liu ZS, Hua Y, Zhou S, Cheng HG, Zhou Q. Alkyl Tosylates as Alkylating Reagents in the Catellani Reaction. SYNTHESIS-STUTTGART 2020. [DOI: 10.1055/s-0039-1690801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
A cooperative catalytic system involving a Pd/XPhos complex and inexpensive 5-norbornene-2-carbonitrile that enables the use of alkyl tosylates as alkylating reagents in the Catellani reaction has been developed. This mild, scalable protocol is compatible with a range of readily available functionalized aryl iodides and alkyl tosylates, as well as terminating olefins (45 examples, up to 97% yield).
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Cheng HG, Pu M, Kundu G, Schoenebeck F. Selective Methylation of Amides, N-Heterocycles, Thiols, and Alcohols with Tetramethylammonium Fluoride. Org Lett 2020; 22:331-334. [PMID: 31834810 DOI: 10.1021/acs.orglett.9b04400] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We herein disclose the use of tetramethylammonium fluoride (TMAF) as a direct and selective methylating agent of a variety of amides, indoles, pyrroles, imidazoles, alcohols, and thiols. The method is characterized by operational simplicity, wide scope, and ease of purification. Our computational studies suggest a concerted methylation-deprotonation as the preferred reaction pathway.
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Cheng HG, Zhou Q, Wu C. Epoxides as Dual-Functionalized Alkylating Reagents in Catellani Reactions for the Assembly of Heterocycles. Synlett 2020. [DOI: 10.1055/s-0039-1690779] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Reported is a cooperative catalytic system consisting of a complex of Pd with dicyclohexyl(2′,4′,6′-triisopropylbiphenyl-2-yl)phosphine (XPhos) and the potassium salt of 5-norbornene-2-carboxylic acid that permits the use of epoxides as dual-functionalized alkylating reagents in Catellani-type reactions for the assembly of heterocycles. Salient features of this research include readily available substrates, use of the potassium salt of 5-norbornene-2-carboxylic acid as a catalytic mediator as well as a base, and excellent regioselectivity for the cleavage of epoxides. This mild, chemoselective, scalable, atom- and step-economic protocol offers a straightforward approach for the assembly of isochroman and 2,3-dihydrobenzofuran scaffolds.
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Wu C, Yang X, Shang Y, Cheng HG, Yan W, Zhou Q. Synthesis of Benzofused Dioxabicycle Scaffolds via a Catellani Strategy. Org Lett 2019; 21:8938-8942. [PMID: 31670522 DOI: 10.1021/acs.orglett.9b03228] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reported is a modular strategy for the preparation of the unique benzofused dioxabicycle scaffolds involving a Catellani reaction of aryl iodides, epoxides, and terminal alkynes and an oxa-cyclization. This is a mild, scalable, chemoselective, and atom-economical protocol, compatible with various functionalized aryl iodides, epoxides, and terminal alkynes. With the ability to build up the molecular complexity rapidly and efficiently from feedstock chemicals, this method will have wide applications in organic synthesis.
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Chen S, Wang P, Cheng HG, Yang C, Zhou Q. Redox-neutral ortho-C-H amination of pinacol arylborates via palladium(ii)/norbornene catalysis for aniline synthesis. Chem Sci 2019; 10:8384-8389. [PMID: 31803416 PMCID: PMC6839810 DOI: 10.1039/c9sc02759a] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 07/22/2019] [Indexed: 12/28/2022] Open
Abstract
A palladium(ii)/norbornene cooperative catalysis enabled redox-neutral ortho-C-H amination of pinacol aryl- or heteroarylborates for the synthesis of structurally diverse anilines is reported. This method is scalable, robust (tolerance of air and moisture), phosphine ligand-free, and compatible with a wide range of functionalities. These practical features make this reaction amenable for industry. A plethora of synthetically very useful halogenated anilines, which often cannot be prepared via other transition-metal-catalyzed aminations, are readily produced using this method. Particularly, the orthogonal reactivity between pinacol arylborates and aryl iodides is demonstrated. Preliminary deuterium-labeling studies reveal a redox-neutral ipso-protonation mechanism of this process, which will surely inspire the future development of this field. Overall, the exceptionally broad scope (47 examples) and reliability of this procedure, together with the wide availability of pinacol arylborates, make this chemistry a valuable addition to the existing methods for aniline synthesis.
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