4 years ago

Mechanisms and Origins of Chemo- and Regioselectivities of Ru(II)-Catalyzed Decarboxylative C–H Alkenylation of Aryl Carboxylic Acids with Alkynes: A Computational Study

Mechanisms and Origins of Chemo- and Regioselectivities of Ru(II)-Catalyzed Decarboxylative C–H Alkenylation of Aryl Carboxylic Acids with Alkynes: A Computational Study
Jing-Lu Yu, Shuo-Qing Zhang, Xin Hong
The mechanisms and chemo- and regioselectivities of Ru(II)-catalyzed decarboxylative C–H alkenylation of aryl carboxylic acids with alkynes were investigated with density functional theory (DFT) calculations. The catalytic cycle involves sequential carboxylate-directed C–H activation, alkyne insertion, decarboxylation and protonation. The facile tether-assisted decarboxylation step directs the intermediate toward the desired decarboxylative alkenylation, instead of typical annulation and double alkenylation pathways. The decarboxylation barrier is very sensitive to the tether length, and only the seven-membered ring intermediate can selectively undergo the designed decarboxylation, suggesting a tether-dependent chemoselectivity. This tether-dependent chemoselectivity also applies to the alkyl tethers. In addition, the polarity of solvent is found to control the chemoselectivity between the decarboxylative alkenylation and [4 + 2] annulation. Solvent with low polarity (toluene) favors the decarboxylation pathway, leading to the decarboxylative alkenylation. Solvent with high polarity (methanol) favors the ionic stepwise C–O reductive elimination pathway, leading to the [4 + 2] annulation. To understand the origins of regioselectivity with asymmetric alkynes, the distortion/interaction analysis was applied to the alkyne insertion transition states, and led to a predictive frontier molecular orbital model. The asymmetric alkynes selectively use the terminal with the larger HOMO orbital coefficient to form the C–C bond in the insertion step.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b00714

DOI: 10.1021/jacs.7b00714

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.