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Harariya MS, Gogoi R, Goswami A, Sharma AK, Jindal G. Is Enol Always the Culprit? The Curious Case of High Enantioselectivity in a Chiral Rh(II) Complex Catalyzed Carbene Insertion Reaction. Chemistry 2023; 29:e202301910. [PMID: 37665257 DOI: 10.1002/chem.202301910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/04/2023] [Accepted: 09/04/2023] [Indexed: 09/05/2023]
Abstract
The mechanism of Rh2 (S-NTTL)4 catalyzed carbene insertion into C(3)-H of indole is investigated using DFT methods. Since the commonly accepted enol mechanism cannot account for enantioinduction, a concerted oxocarbenium pathway was proposed in an earlier work using a model catalyst. However, after considering the full catalytic system, this study finds that akin to other reactions, here, too, the enol pathway is of lower energy, which now naturally raises a conundrum regarding the mode of chiral induction. Herein, a new water promoted mechanistic pathway involving a metal-associated enol intermediate hydrogen bonding and stereochemical model are proposed to solve this puzzle. It is shown how the catalyst bowl-shaped structure along with substrate-catalyst binding is crucial for achieving high levels of enantioselectivity. A stereodetermining water-assisted proton transfer is proposed and confirmed through deuterium-labeling experiments. The water molecules are held together by H-bonding interactions with the carboxylate ligands that is reminiscent of enzyme catalysis. Although several previous studies have aimed at understanding the mechanism of metal catalyzed carbene insertion reactions, the origin of high stereoinduction especially with chiral metal complexes remains unclear, and till date there is no transition state model that can explain the high enantioselectivity with such chiral Rh complexes. The metal-associated enol pathway is currently underrepresented in catalytic cycles and may play a crucial role in catalyst design. Since the enol pathway is commonly adopted in other metal-catalyzed X-H insertion reactions involving a diazoester, the presented results are not specific to the current reaction. Therefore, this study could provide the direction for achieving high levels of enantioselectivity which is otherwise difficult to achieve with a single metal catalyst.
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Affiliation(s)
- Mahesh S Harariya
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Romin Gogoi
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Anubhav Goswami
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Akhilesh K Sharma
- Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 1643007, Tarragona, 560012, Spain
| | - Garima Jindal
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
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Computational Exploration of Dirhodium Complex-Catalyzed Selective Intermolecular Amination of Tertiary vs. Benzylic C-H Bonds. Molecules 2023; 28:molecules28041928. [PMID: 36838915 PMCID: PMC9959850 DOI: 10.3390/molecules28041928] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 02/14/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
The mechanism and origins of site-selectivity of Rh2(S-tfpttl)4-catalyzed C(sp3)-H bond aminations were studied using density functional theory (DFT) calculations. The synergistic combination of the dirhodium complex Rh2(S-tfpttl)4 with tert-butylphenol sulfamate TBPhsNH2 composes a pocket that can access both tertiary and benzylic C-H bonds. The nonactivated tertiary C-H bond was selectively aminated in the presence of an electronically activated benzylic C-H bond. Both singlet and triplet energy surfaces were investigated in this study. The computational results suggest that the triplet stepwise pathway is more favorable than the singlet concerted pathway. In the hydrogen atom abstraction by Rh-nitrene species, which is the rate- and site-selectivity-determining step, there is an attractive π-π stacking interaction between the phenyl group of the substrate and the phthalimido group of the ligand in the tertiary C-H activation transition structure. By contrast, such attractive interaction is absent in the benzylic C-H amination transition structure. Therefore, the DFT computational results clearly demonstrate how the synergistic combination of the dirhodium complex with sulfamate overrides the intrinsic preference for benzylic C-H amination to achieve the amination of the nonactivated tertiary C-H bond.
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Zhang Y, Lv C, Hu C, Su Z. Mechanistic Study of Asymmetric Alkynylation of Isatin-Derived Ketimine Mediated by a Copper/Guanidine Catalyst. J Org Chem 2022; 87:11693-11707. [PMID: 36001814 DOI: 10.1021/acs.joc.2c01321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this work, we performed a mechanistic study of asymmetric alkynylation of isatin-derived N-Boc ketimine that was first reported by Feng, Liu, and co-workers (Chem. Commun. 2018, 54, 678-681). Guanidine-amide promoted the formation of highly nucleophilic copper acetylene species by abstracting the terminal proton of phenylacetylene with an imine moiety. The guanidinium salt-Cu(I) complex was the most active species in the addition of the C═N bond, in which copper acetylene coordinated to the O atom of the amide moiety, and the isatin-derived ketimine substrate was activated by hydrogen bonding as well as tert-butoxycarbonyl···Cu(I) coordination. Due to weak interaction between Cu(I) and the Ph group in the amide of guanidine, as well as the repulsion between the tert-butyl group in ketimine and the cyclohexyl group in guanidine, the copper acetylene preferred to attack isatin-derived ketimine from the re-face, leading to the S-configuration product with excellent stereoselectivity. The affinity of the counterion for the Cu(I) center in the copper salt affected the deprotonation of phenylacetylene and the formation of guanidinium salt active species. In contrast to CuBr and CuCl, the combination of CuI with aniline-derived guanidine-amide exhibited high catalytic activity and a chiral induction effect, contributing to a high turnover frequency (9.70 × 10-4 s-1) in catalysis and ee%.
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Affiliation(s)
- Yan Zhang
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, P. R. China
| | - Cidan Lv
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, P. R. China
| | - Changwei Hu
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, P. R. China
| | - Zhishan Su
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, P. R. China
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Fang R, Liu K, Kirillov AM, Yang L. DFT Rationalization of Gold(I)-Catalyzed Couplings between Alkynyl Thioether and Nitrenoid Derivatives: Mechanism, Selectivity Patterns, and Effects of Substituents. J Org Chem 2022; 87:7193-7201. [PMID: 35579210 DOI: 10.1021/acs.joc.2c00407] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The present work focuses on a theoretical investigation of mechanistic features, chemoselectivity, regioselectivity, and effect of substituents in the gold-catalyzed reactions of alkynyl thioethers and isoxazoles. The DFT calculations reveal that the nucleophilic attack of isoxazole to a β-position of catalyst-bound ynamide forms a vinyl intermediate. This undergoes cleavage of the N-O isoxazole bond and isomerizes to form an α-imino α'-sulfenyl gold carbene complex with stabilization of the Au-S interaction. For 3,5-dimethylisoxazole, the reaction follows a formal [3 + 2] cycloaddition pathway and a 1,3-H migration to give the pyrrole products. Replacement of 3,5-dimethylisoxazole by 3,5-dimethyl-4-phenylisoxazole leads to the formation of deacylative annulation products and desulfenylated 3-acylated pyrroles. Reactions with 4-methyl-3,5-diphenylisoxazoles induce the formation of N-acylated pyrroles and desulfenylated 3-acylated pyrroles. For the minor pathway, the α-addition and 1,2-S migration result in sulfur-substituted β-keto enamide derivatives. In addition, the unique features of regio- and chemoselectivity were rationalized by the distortion and interaction analysis. Apart from fully rationalizing the experimental results, the theoretical DFT data give an important support for comprehending related types of reaction mechanisms.
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Affiliation(s)
- Ran Fang
- Key Laboratory of Chemical Additives for China National Light Industry, College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an 710021, P. R. China
| | - Kunyang Liu
- Key Laboratory of Chemical Additives for China National Light Industry, College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an 710021, P. R. China
| | - Alexander M Kirillov
- Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisbon 1049-001, Portugal
| | - Lizi Yang
- College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
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Guanidine-Amide-Catalyzed Aza-Henry Reaction of Isatin-Derived Ketimines: Origin of Selectivity and New Catalyst Design. Molecules 2021; 26:molecules26071965. [PMID: 33807341 PMCID: PMC8037019 DOI: 10.3390/molecules26071965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/29/2021] [Accepted: 03/29/2021] [Indexed: 12/05/2022] Open
Abstract
Density functional theory (DFT) calculations were performed to investigate the mechanism and the enantioselectivity of the aza-Henry reaction of isatin-derived ketimine catalyzed by chiral guanidine–amide catalysts at the M06-2X-D3/6-311+G(d,p)//M06-2X-D3/6-31G(d,p) (toluene, SMD) theoretical level. The catalytic reaction occurred via a three-step mechanism: (i) the deprotonation of nitromethane by a chiral guanidine–amide catalyst; (ii) formation of C–C bonds; (iii) H-transfer from guanidine to ketimine, accompanied with the regeneration of the catalyst. A dual activation model was proposed, in which the protonated guanidine activated the nitronate, and the amide moiety simultaneously interacted with the ketimine substrate by intermolecular hydrogen bonding. The repulsion of CPh3 group in guanidine as well as N-Boc group in ketimine raised the Pauli repulsion energy (∆EPauli) and the strain energy (∆Estrain) of reacting species in the unfavorable si-face pathway, contributing to a high level of stereoselectivity. A new catalyst with cyclopropenimine and 1,2-diphenylethylcarbamoyl as well as sulfonamide substituent was designed. The strong basicity of cyclopropenimine moiety accelerated the activation of CH3NO2 by decreasing the energy barrier in the deprotonation step. The repulsion between the N-Boc group in ketimine and cyclohexyl group as well as chiral backbone in the new catalyst raised the energy barrier in C–C bond formation along the si-face attack pathway, leading to the formation of R-configuration product. A possible synthetic route for the new catalyst is also suggested.
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Cao J, Zhu SF. Catalytic Enantioselective Proton Transfer Reactions. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20200350] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Jin Cao
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, P. R. China
| | - Shou-Fei Zhu
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, P. R. China
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Gao C, Cao T, Kirillov AM, Fang R, Yang L. Rationalization of the mechanism and chemoselectivity of versatile Au-catalyzed reactions of diazoesters with allyl-functionalized sulfides, selenides, amines, or ethers by DFT. Org Chem Front 2021. [DOI: 10.1039/d1qo00920f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The origin of chemoselectivity and the mechanism of the title reactions were fully rationalized by density functional theory (DFT).
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Affiliation(s)
- Caicai Gao
- Key Laboratory of Chemical Additives for China National Light Industry, College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an 710021, P. R. China
| | - Teng Cao
- Key Laboratory of Chemical Additives for China National Light Industry, College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an 710021, P. R. China
| | - Alexander M. Kirillov
- Centro de Química Estrutural and Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
- Research Institute of Chemistry, Peoples’ Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya st., Moscow, 117198, Russian Federation
| | - Ran Fang
- Key Laboratory of Chemical Additives for China National Light Industry, College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an 710021, P. R. China
| | - Lizi Yang
- College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
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Fang R, Feng Z, Kirillov AM, Yang L. Density Functional Theory Study of the Metal-Catalyzed Cycloaddition of Indolyl-Allenes: Possible Reaction Pathways, Stereoselectivity, and Regioselectivity. Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00080] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Ran Fang
- College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi’an 710021, P. R. China
- State Key Laboratory of Applied Organic Chemistry and Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
| | - Zhitao Feng
- State Key Laboratory of Applied Organic Chemistry and Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
| | - Alexander M. Kirillov
- Centro de Quı́mica Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
- Peoples’ Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya st., Moscow 117198, Russia
| | - Lizi Yang
- College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi’an 710021, P. R. China
- State Key Laboratory of Applied Organic Chemistry and Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
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Wang H, Zeng T, Li X, Wang S, Xiao W, Liu L, Chang W, Li J. Cocatalyst-controlled divergent cascade cycloaddition reaction of arylalkynols and dioxopyrrolidienes: access to spiroketals and oxa-bridged eight-membered cyclic ethers. Org Chem Front 2020. [DOI: 10.1039/d0qo00464b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A cocatalyst-controlled divergent cascade cycloaddition reaction was developed for the synthesis of two different complex oxygen-containing heterocyclic compounds from arylalkynols and dioxopyrrolidienes in the presence of Au(i) catalyst.
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Affiliation(s)
- Hongkai Wang
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Tianlong Zeng
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Xinhong Li
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Songmeng Wang
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Weiguo Xiao
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Lingyan Liu
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Weixing Chang
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Jing Li
- The State Key Laboratory and Institute of Elemento-Organic Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
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