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Selective Methylative Homologation: An Alternate Route to Alkane Upgrading

Bercaw, John E. and Hazari, Nilay and Labinger, Jay A. and Scott, Valerie J. and Sunley, Glenn J. (2008) Selective Methylative Homologation: An Alternate Route to Alkane Upgrading. Journal of the American Chemical Society, 130 (36). pp. 11988-11995. ISSN 0002-7863.

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InI3 catalyzes the reaction of branched alkanes with methanol to produce heavier and more highly branched alkanes, which are more valuable fuels. The reaction of 2,3-dimethylbutane with methanol in the presence of InI3 at 180−200 °C affords the maximally branched C7 alkane, 2,2,3-trimethylbutane (triptane). With the addition of catalytic amounts of adamantane the selectivity of this transformation can be increased up to 60%. The lighter branched alkanes isobutane and isopentane also react with methanol to generate triptane, while 2-methylpentane is converted into 2,3-dimethylpentane and other more highly branched species. Observations implicate a chain mechanism in which InI3 activates branched alkanes to produce tertiary carbocations which are in equilibrium with olefins. The latter react with a methylating species generated from methanol and InI3 to give the next-higher carbocation, which accepts a hydride from the starting alkane to form the homologated alkane and regenerate the original carbocation. Adamantane functions as a hydride transfer agent and thus helps to minimize competing side reactions, such as isomerization and cracking, that are detrimental to selectivity.

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Labinger, Jay A.0000-0002-1942-9232
Additional Information:© 2008 American Chemical Society. Received April 24, 2008. Web Release Date: August 13, 2008. We thank Professor Enrique Iglesia for useful discussions. This work was supported by BP through the MC^2 program. Supporting Information Available. A complete listing of experimental results (in Excel format), along with an explanatory guide to the Excel tables and details of a labeling experiment. This material is available free of charge via the Internet at
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Issue or Number:36
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ID Code:11803
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Deposited On:30 Sep 2008 02:50
Last Modified:03 Oct 2019 00:22

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