1
|
Tiessler-Sala L, Maréchal JD, Lledós A. Rationalization of a Streptavidin Based Enantioselective Artificial Suzukiase: An Integrative Computational Approach. Chemistry 2024; 30:e202401165. [PMID: 38752552 DOI: 10.1002/chem.202401165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Indexed: 06/06/2024]
Abstract
An Artificial Metalloenzyme (ArM) built employing the streptavidin-biotin technology has been used for the enantioselective synthesis of binaphthyls by means of asymmetric Suzuki-Miyaura cross-coupling reactions. Despite its success, it remains a challenge to understand how the length of the biotin cofactors or the introduction of mutations to streptavidin leads the preferential synthesis of one atropisomer over the other. In this study, we apply an integrated computational modeling approach, including DFT calculations, protein-ligand dockings and molecular dynamics to rationalize the impact of mutations and length of the biotion cofactor on the enantioselectivities of the biaryl product. The results unravel that the enantiomeric differences found experimentally can be rationalized by the disposition of the first intermediate, coming from the oxidative addition step, and the entrance of the second substrate. The work also showcases the difficulties facing to control the enantioselection when engineering ArM to catalyze enantioselective Suzuki-Miyaura couplings and how the combination of DFT calculations, molecular dockings and MD simulations can be used to rationalize artificial metalloenzymes.
Collapse
Affiliation(s)
- Laura Tiessler-Sala
- Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | - Jean-Didier Maréchal
- Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | - Agustí Lledós
- Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193, Barcelona, Spain
| |
Collapse
|
2
|
Kania MJ, Reyes A, Neufeldt SR. Oxidative Addition of (Hetero)aryl (Pseudo)halides at Palladium(0): Origin and Significance of Divergent Mechanisms. J Am Chem Soc 2024. [PMID: 38959060 DOI: 10.1021/jacs.4c04496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
Two limiting mechanisms are possible for oxidative addition of (hetero)aryl (pseudo)halides at Pd(0): a 3-centered concerted and a nucleophilic displacement mechanism. Until now, there has been little understanding about when each mechanism is relevant. Prior investigations to distinguish between these pathways were limited to a few specific combinations of the substrate and ligand. Here, we computationally evaluated over 180 transition structures for oxidative addition in order to determine mechanistic trends based on substrate, ligand(s), and coordination number. Natural abundance 13C kinetic isotope effects provide experimental results consistent with computational predictions. Key findings include that (1) differences in highest occupied molecular orbital (HOMO) symmetries dictate that, although 12e- PdL is strongly biased toward a 3-centered concerted mechanism, 14e- PdL2 often prefers a nucleophilic displacement mechanism; (2) ligand electronics and sterics, including ligand bite angle, influence the preferred mechanism of the reaction at PdL2; (3) phenyl triflate always reacts through a displacement mechanism regardless of the catalyst structure due to the stability of a triflate anion and the inability of oxygen to effectively donate electron density to Pd; and (4) the high reactivity of C-X bonds adjacent to nitrogen in pyridine substrates relates to stereoelectronic stabilization of a nucleophilic displacement transition state. This work has implications for controlling rate and selectivity in catalytic couplings, and we demonstrate application of the mechanistic insight toward chemodivergent cross-couplings of bromochloroheteroarenes.
Collapse
Affiliation(s)
- Matthew J Kania
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Albert Reyes
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Sharon R Neufeldt
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| |
Collapse
|
3
|
Shi Y, Derasp JS, Maschmeyer T, Hein JE. Phase transfer catalysts shift the pathway to transmetalation in biphasic Suzuki-Miyaura cross-couplings. Nat Commun 2024; 15:5436. [PMID: 38937470 PMCID: PMC11211432 DOI: 10.1038/s41467-024-49681-4] [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: 02/26/2024] [Accepted: 06/14/2024] [Indexed: 06/29/2024] Open
Abstract
The Suzuki-Miyaura coupling is a widely used C-C bond forming reaction. Numerous mechanistic studies have enabled the use of low catalyst loadings and broad functional group tolerance. However, the dominant mode of transmetalation remains controversial and likely depends on the conditions employed. Herein we detail a mechanistic study of the palladium-catalyzed Suzuki-Miyaura coupling under biphasic conditions. The use of phase transfer catalysts results in a remarkable 12-fold rate enhancement in the targeted system. A shift from an oxo-palladium based transmetalation to a boronate-based pathway lies at the root of this activity. Furthermore, a study of the impact of different water loadings reveals reducing the proportion of the aqueous phase increases the reaction rate, contrary to reaction conditions typically employed in the literature. The importance of these findings is highlighted by achieving an exceptionally broad substrate scope with benzylic electrophiles using a 10-fold reduction in catalyst loading relative to literature precedent.
Collapse
Affiliation(s)
- Yao Shi
- Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
| | - Joshua S Derasp
- Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada.
| | - Tristan Maschmeyer
- Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
| | - Jason E Hein
- Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada.
- Department of Chemistry, University of Bergen, Bergen, Norway.
- Acceleration Consortium, University of Toronto, Toronto, ON, Canada.
| |
Collapse
|
4
|
Yang Y, Wu C, Xing J, Dou X. Developing Biarylhemiboronic Esters for Biaryl Atropisomer Synthesis via Dynamic Kinetic Atroposelective Suzuki-Miyaura Cross-Coupling. J Am Chem Soc 2024; 146:6283-6293. [PMID: 38381856 DOI: 10.1021/jacs.3c14450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
We herein introduce biarylhemiboronic esters as a new type of bridged biaryl reagent for asymmetric synthesis of axially chiral biaryl structures, and the palladium-catalyzed asymmetric Suzuki-Miyaura cross-coupling of biarylhemiboronic esters is developed. This dynamic kinetic atroposelective coupling reaction exhibits high enantioselectivity, good functional group tolerance, and a broad substrate scope. The synthetic application of the current method was demonstrated by transformations of the product and a programmed synthesis of chiral polyarene. Preliminary mechanistic studies suggested that the reaction proceeded via an enantio-determining dynamic kinetic atroposelective transmetalation step.
Collapse
Affiliation(s)
- Yiming Yang
- Department of Chemistry, School of Science, China Pharmaceutical University, Nanjing 211198, P. R. China
| | - Changhui Wu
- Department of Chemistry, School of Science, China Pharmaceutical University, Nanjing 211198, P. R. China
| | - Junhao Xing
- Department of Chemistry, School of Science, China Pharmaceutical University, Nanjing 211198, P. R. China
| | - Xiaowei Dou
- Department of Chemistry, School of Science, China Pharmaceutical University, Nanjing 211198, P. R. China
| |
Collapse
|
5
|
Xie X, Zhang J, Song XQ, Li W, Cao F, Zhou C, Zhu H, Li L. Unveiling Pre-Transmetalation Intermediates in Base-Free Suzuki-Miyaura Cross-Couplings: A Computational Study. Inorg Chem 2024; 63:2606-2615. [PMID: 38267390 DOI: 10.1021/acs.inorgchem.3c03855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2024]
Abstract
The pre-transmetalation intermediates are critically important in Suzuki-Miyaura cross-coupling (SMC) reactions and have become a hot spot of the current research. However, the pre-transmetalation intermediates under base-free conditions have not been clear. Herein, a comprehensive theoretical study is performed on the base-free Pd-catalyzed desulfonative SMC reaction. The fragile coordination feature and the acceleration role of the RuPhos chelate ligand are revealed. The hydrogen-bond complex between the Pd-F complex and aryl boronic acid is identified as an important pre-transmetalation intermediate, which increases the energy span to 32.5 kcal/mol. The controlling factor for the formation of the hydrogen-bond complexes is attributed to the electronegativities of halogen atoms in the metal halide complexes. What is more, other reported SMC reaction systems involving metal halide complexes and aryl boronic acids are reconsidered and suggest that the hydrogen-bond complexes widely exist as stable pre-transmetalation intermediates with influencing the catalytic activities. The earth-abundant Ni-catalyzed desulfonative SMC reaction is further designed and predicted to have a higher activity than the original Pd-catalyzed SMC reaction.
Collapse
Affiliation(s)
- Xiaofeng Xie
- College of Pharmacy, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding, Hebei 071002, P. R. China
| | - Jiejing Zhang
- College of Pharmacy, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding, Hebei 071002, P. R. China
| | - Xue-Qing Song
- College of Pharmacy, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding, Hebei 071002, P. R. China
| | - Wan Li
- College of Pharmacy, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding, Hebei 071002, P. R. China
| | - Fei Cao
- College of Pharmacy, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding, Hebei 071002, P. R. China
| | - Chengyan Zhou
- College of Pharmacy, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding, Hebei 071002, P. R. China
| | - Huajie Zhu
- School of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, P. R. China
| | - Longfei Li
- College of Pharmacy, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding, Hebei 071002, P. R. China
| |
Collapse
|
6
|
Han C, Zhao F, Lu Q, Liu F. Computational Determination of the Mechanism of the Palladium-Catalyzed Domino Reaction of ortho-Iodostyrene, Oxanorbornadiene, and Phenylboronic Acid. J Org Chem 2023; 88:15608-15614. [PMID: 37905531 DOI: 10.1021/acs.joc.3c01522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
The palladium-catalyzed three-component domino reaction of ortho-iodostyrene, 2,3-dicarbomethoxy-7-oxanorbornadiene (ONBD), and phenylboronic acid discovered by the Lautens group provides a convenient method to synthesize indenes derivatives. Herein, density functional theory (DFT) calculations were employed to explore the detailed mechanism of this domino reaction. The computational results suggest that the alkene-insertion-first and the transmetalation-first mechanisms are competitive, and the former mechanism is slightly more favorable because of the difficult intramolecular alkene insertion of the alkyl-PdII-aryl than alkyl-PdII-I complex. Further analysis on substituents of ONBD unveils the impacts of noncovalent interactions and electronic effect on the rate-determining retro-Diels-Alder process. The understanding of this domino reaction has important implications for developing a novel palladium-catalyzed domino reaction with a retro-Diels-Alder strategy.
Collapse
Affiliation(s)
- Chunyu Han
- College of Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Fengyue Zhao
- College of Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Qianqian Lu
- College of Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Fang Liu
- College of Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| |
Collapse
|
7
|
Olding A, Ho CC, Lucas NT, Bissember AC. Pretransmetalation Intermediates in Suzuki-Miyaura Cross-Couplings: Synthesis of C sp3-, C sp2- and C sp-Organopalladium(II) Boronates. Inorg Chem 2023; 62:5054-5057. [PMID: 36946982 DOI: 10.1021/acs.inorgchem.3c00198] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
Organopalladium(II) boronates represent fundamental pretransmetalation intermediates in Suzuki-Miyaura cross-couplings. These species are typically kinetically unstable, making them particularly elusive. In this study, a range of unprecedented, kinetically stable alkyl-, alkenyl-, allenyl-, and alkynylpalladium(II) boronates were prepared from various Csp3, Csp2, and Csp electrophiles via a simple, general method. The structures of these complexes were secured by X-ray crystallography, and the chemical competence of a number of these intermediates in transmetalation was demonstrated.
Collapse
Affiliation(s)
- Angus Olding
- School of Natural Sciences─Chemistry, University of Tasmania (UTAS), Hobart, Tasmania 7001, Australia
| | - Curtis C Ho
- School of Natural Sciences─Chemistry, University of Tasmania (UTAS), Hobart, Tasmania 7001, Australia
| | - Nigel T Lucas
- Department of Chemistry, University of Otago, Dunedin, Otago 9054, New Zealand
| | - Alex C Bissember
- School of Natural Sciences─Chemistry, University of Tasmania (UTAS), Hobart, Tasmania 7001, Australia
| |
Collapse
|
8
|
Mohammadi L, Hosseinifard M, Vaezi MR. Stabilization of Palladium-Nanoparticle-Decorated Postsynthesis-Modified Zr-UiO-66 MOF as a Reusable Heterogeneous Catalyst in C-C Coupling Reaction. ACS OMEGA 2023; 8:8505-8518. [PMID: 36910943 PMCID: PMC9996586 DOI: 10.1021/acsomega.2c07661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 02/03/2023] [Indexed: 06/18/2023]
Abstract
Here we prepared a highly efficient and reusable catalyst by a step-by-step postsynthesis modification of UiO-66-NH2 metal-organic frameworks (MOFs) with nitrogen-rich organic ligands and used it as support for the preparation of UiO-66-NH2@cyanuric chloride@2-aminopyrimidine/PdNPs. The catalytic performance's results of UiO-66-NH2@cyanuric chloride@2-aminopyrimidine/PdNPs, UiO-66-NH2/PdNPs, and UiO-66-NH2@cyanuric chloride/PdNPs indicate high efficiency of the modulation of the microenvironment of the palladium NPs. The addition of N-rich organic ligands through postsynthesis modification caused a unique structure of the final composite in favor of the progress of the C-C coupling reaction. Various techniques, including FT-IR, XRD, SEM, TEM, EDS, and elemental mapping, were used to characterize UiO-66-NH2@cyanuric chloride@2-aminopyrimidine/PdNPs, indicating its successful preparation. Three C-C coupling reactions, including the Suzuki, Heck, and Sonogashira coupling reactions, were promoted using the produced catalyst. As a result of the postsynthesis modification (PSM), the proposed catalyst displays improved catalytic performance. In addition, the suggested catalyst was highly recyclable up to ten times without leaching of PdNPs.
Collapse
Affiliation(s)
- Leila Mohammadi
- Department
of Nano Technology and Advanced Materials, Materials and Energy Research Center, Karaj, Iran
| | | | - Mohammad Reza Vaezi
- Department
of Nano Technology and Advanced Materials, Materials and Energy Research Center, Karaj, Iran
| |
Collapse
|
9
|
Olding A, Ho CC, Lucas NT, Canty AJ, Bissember AC. Pretransmetalation Intermediates in Suzuki–Miyaura C–C and Carbonylative Cross-Couplings: Synthesis and Structural Authentication of Aryl- and Aroylnickel(II) Boronates. ACS Catal 2023. [DOI: 10.1021/acscatal.2c05657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Affiliation(s)
- Angus Olding
- School of Natural Sciences−Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Curtis C. Ho
- School of Natural Sciences−Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Nigel T. Lucas
- Department of Chemistry, University of Otago, Dunedin, Otago 9054, New Zealand
| | - Allan J. Canty
- School of Natural Sciences−Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Alex C. Bissember
- School of Natural Sciences−Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia
| |
Collapse
|
10
|
Lin Z, Cai Y, Zhang Y, Zhang H, Xia H. Heterocyclic Suzuki-Miyaura coupling reaction of metalla-aromatics and mechanistic analysis of site selectivity. Chem Sci 2023; 14:1227-1233. [PMID: 36756314 PMCID: PMC9891379 DOI: 10.1039/d2sc05455h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/29/2022] [Indexed: 01/03/2023] Open
Abstract
Pd-catalyzed Suzuki-Miyaura cross-coupling is one of the most straightforward and versatile methods for the construction of functionalized arenes and heteroarenes but site-selective cross-coupling of polyhalogenated (hetero)arenes containing identical halogen substituents remains a challenging problem. Herein, we report a new candidate for heterocyclic Suzuki-Miyaura coupling reaction. This candidate has been applied in organometallic systems by combining classical aryl boronic acid reagents with non-classical heteroarenes. Experimental and computational studies of the mechanism of the reactions were performed, with an emphasis on the identity of the reactive species in the oxidative addition step and the nature of the precise site selectivity. The influence of both the aromaticity of the metalla-aromatic substrates and the steric and electronic properties of the halogenated sites are studied in detail.
Collapse
Affiliation(s)
- Zuzhang Lin
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 China
| | - Yapeng Cai
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 China
| | - Yaowei Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 China
| | - Hong Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 China
| | - Haiping Xia
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 China .,Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology Shenzhen 518055 China
| |
Collapse
|
11
|
Firsan S, Sivakumar V, Colacot TJ. Emerging Trends in Cross-Coupling: Twelve-Electron-Based L 1Pd(0) Catalysts, Their Mechanism of Action, and Selected Applications. Chem Rev 2022; 122:16983-17027. [PMID: 36190916 PMCID: PMC9756297 DOI: 10.1021/acs.chemrev.2c00204] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Monoligated palladium(0) species, L1Pd(0), have emerged as the most active catalytic species in the cross-coupling cycle. Today, there are methods available to generate the highly active but unstable L1Pd(0) catalysts from stable precatalysts. While the size of the ligand plays an important role in the formation of L1Pd(0) during in situ catalysis, the latter can be precisely generated from the precatalyst by various technologies. Computational, kinetic, and experimental studies indicate that all three steps in the catalytic cycle─oxidative addition, transmetalation, and reductive elimination─contain monoligated Pd. The synthesis of precatalysts, their mode of activation, application studies in model systems, as well as in industry are discussed. Ligand parametrization and AI based data science can potentially help predict the facile formation of L1Pd(0) species.
Collapse
Affiliation(s)
- Sharbil
J. Firsan
- Science
and Lab Solutions−Chemistry, MilliporeSigma, 6000 North Teutonia Avenue, Milwaukee, Wisconsin53209, United States
| | - Vilvanathan Sivakumar
- Merck
Life Science Pvt Ltd, No-12, Bommasandra-Jigani Link Road, Industrial Area, Bangalore560100, India
| | - Thomas J. Colacot
- Science
and Lab Solutions−Chemistry, MilliporeSigma, 6000 North Teutonia Avenue, Milwaukee, Wisconsin53209, United States,
| |
Collapse
|
12
|
Norman JP, Larson NG, Neufeldt SR. Different Oxidative Addition Mechanisms for 12- and 14-Electron Palladium(0) Explain Ligand-Controlled Divergent Site Selectivity. ACS Catal 2022; 12:8822-8828. [PMID: 37601556 PMCID: PMC10438894 DOI: 10.1021/acscatal.2c01698] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In cross-coupling reactions, dihaloheteroarenes are usually most reactive at C─halide bonds adjacent to a heteroatom. This selectivity has been previously rationalized. However, no mechanistic explanation exists for anomalous reports in which specific ligands effect inverted selectivity with dihalopyridines and -pyridazines. Here we provide evidence that these ligands uniquely promote oxidative addition at 12e- Pd(0). Computations indicate that 12e- and 14e- Pd(0) can favor different mechanisms for oxidative addition due to differences in their HOMO symmetries. These mechanisms are shown to lead to different site preferences, where 12e- Pd(0) can favor oxidative addition at an atypical site distal to nitrogen.
Collapse
Affiliation(s)
| | | | - Sharon R. Neufeldt
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| |
Collapse
|