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

13 October 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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.

Keywords

olefin isomerization
iridium
pincer
crown ether
switchable catalysis
responsive catalysis

Supplementary materials

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Camp SwitchableRegioselectivity SI ChemRxiv Submission
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215c5b
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218c6a
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315c5b
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318c6a
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318c6b
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Na118c6a
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218c6b
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