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Selecting Double Bond Positions with a Single Cation- Responsive Iridium Olefin Isomerization Catalyst

preprint
submitted on 12.10.2020 and posted on 13.10.2020 by Andrew M. Camp, Matthew R. Kita, Thomas P. Blackburn, Henry M. Dodge, Chun-Hsing Chen, Alexander Miller

The catalytic transposition of double bonds holds promise as an ideal route to alkenes with value as fragrances, commodity chemicals, and pharmaceuticals; yet, selective access to specific isomers is a challenge, requiring independent development of different catalysts for different products. In this work, a single cation-responsive iridium catalyst is developed for the selective production of either of two different internal alkene isomers. In the absence of salts, a single positional isomerization of 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity and stereoselectivity. The same catalyst, in the presence of Na+, mediates two positional isomerizations to produce 3-alkenes. The synthesis of new iridium pincer-crown ether catalysts based on an aza-18-crown-6 ether proved instrumental in achieving cation-controlled selectivity. Experimental and computational studies guided the development of a mechanistic model that explains the observed selectivity for various functionalized 1-butenes, providing insight into strategies for catalyst development based on non-covalent modifications.

Funding

CHE-1553802

CHE-1828183

CHE-0922858

CHE-1726291

History

Email Address of Submitting Author

ajmm@email.unc.edu

Institution

University of North Carolina at Chapel Hill

Country

United States

ORCID For Submitting Author

0000-0001-9390-3951

Declaration of Conflict of Interest

no conflict of interest

Exports