Journal of the American Chemical Society
Journal of the American Chemical Society
5 years ago

Mechanism and Origins of Ligand-Controlled Stereoselectivity of Ni-Catalyzed Suzuki–Miyaura Coupling with Benzylic Esters: A Computational Study

Mechanism and Origins of Ligand-Controlled Stereoselectivity of Ni-Catalyzed Suzuki–Miyaura Coupling with Benzylic Esters: A Computational Study
Michael R. Harris, Yuan Gao, K. N. Houk, Luke E. Hanna, Chong-Lei Ji, Shuo-Qing Zhang, Xin Hong, Elizabeth R. Jarvo, Buck L. H. Taylor
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 (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) produces the stereochemically inverted C–C coupling product, while the tricyclohexylphosphine (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 the 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.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b04973

DOI: 10.1021/jacs.7b04973

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.