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

Catalytic Dehydrogenative C–C Coupling by a Pincer-Ligated Iridium Complex

Catalytic Dehydrogenative C–C Coupling by a Pincer-Ligated Iridium Complex
William D. Jones, William W. Brennessel, Miles Wilklow-Marnell, Karsten Krogh-Jespersen, Bo Li, Tian Zhou, Alan S. Goldman, Thomas J. Emge
The pincer-iridium fragment (iPrPCP)Ir (RPCP = κ3-2,6-C6H3(CH2PR2)2) has been found to catalyze the dehydrogenative coupling of vinyl arenes to afford predominantly (E,E)-1,4-diaryl-1,3-butadienes. The eliminated hydrogen can undergo addition to another molecule of vinyl arene, resulting in an overall disproportionation reaction with 1 equiv of ethyl arene formed for each equivalent of diarylbutadiene produced. Alternatively, sacrificial hydrogen acceptors (e.g., tert-butylethylene) can be added to the solution for this purpose. Diarylbutadienes are isolated in moderate to good yields, up to ca. 90% based on the disproportionation reaction. The results of DFT calculations and experiments with substituted styrenes indicate that the coupling proceeds via double C–H addition of a styrene molecule, at β-vinyl and ortho-aryl positions, to give an iridium(III) metalloindene intermediate; this intermediate then adds a β-vinyl C–H bond of a second styrene molecule before reductively eliminating product. Several metalloindene complexes have been isolated and crystallographically characterized. In accord with the proposed mechanism, substitution at the ortho-aryl positions of the styrene precludes dehydrogenative homocoupling. In the case of 2,4,6-trimethylstyrene, dehydrogenative coupling of β-vinyl and ortho-methyl C–H bonds affords dimethylindene, demonstrating that the dehydrogenative coupling is not limited to C(sp2)–H bonds.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b03433

DOI: 10.1021/jacs.7b03433

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.