Mechanism and Origins of Ligand-controlled Stereoselectivity of Ni-Catalyzed Suzuki-Miyaura Coupling with Benzylic Esters: A Computational Study
| Autor: | Elizabeth R. Jarvo, Yuan Gao, Luke E. Hanna, Kendall N. Houk, Buck L. H. Taylor, Chong-Lei Ji, Shuo-Qing Zhang, Michael R. Harris, Xin Hong |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
inorganic chemicals
Stereochemistry Stereoisomerism 010402 general chemistry Ligands 01 natural sciences Biochemistry Article Catalysis Stereocenter chemistry.chemical_compound Colloid and Surface Chemistry Nickel Benzyl Compounds Molecular Structure 010405 organic chemistry Chemistry Ligand Tricyclohexylphosphine Esters General Chemistry Oxidative addition Transition state 0104 chemical sciences SN2 reaction Quantum Theory Thermodynamics Stereoselectivity |
| Popis: | Nickel catalysts have shown unique ligand control of stereoselectivity in the Suzuki–Miyaura cross-coupling of boronates with benzylic pivalates and derivatives involving C(sp3)–O cleavage. The SIMes ligand produces the stereochemically inverted C–C coupling product, while the PCy3 ligand delivers the retained stereochemistry. We have explored the mechanism and origins of the ligand-controlled stereoselectivity with density functional theory (DFT) calculations. The oxidative addition determines the stereoselectivity with two competing transition states, an SN2 back-side attack type transition state that inverts the benzylic stereogenic center, and a concerted oxidative addition through a cyclic transition state which provides stereoretention. The key difference between the two transition states is the substrate-nickel-ligand angle distortion; the ligand controls the selectivity by differentiating the ease of this angle distortion. For the PCy3 ligand, the nickel-ligand interaction involves mainly σ-donation, which does not require a significant energy penalty for the angle distortion. The facile angle distortion with PCy3 ligand allows the favorable cyclic oxidative addition transition state, leading to the stereoretention. For the SIMes ligand, the extra d-p back donation from nickel to the coordinating carbene increases the rigidity of nickel-ligand bond, and the corresponding angle distortion is more difficult. This makes the concerted cyclic oxidative addition unfavorable with SIMes ligand, and the back-side SN2-type oxidative addition delivers the stereoinversion. |
| Databáze: | OpenAIRE |
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