Alkyl–Aryl Coupling Catalyzed by Tandem Systems of Pincer-Ligated Iridium Complexes and Zeolites

Long V. Dinh^†, Bo Li^†, Akshai Kumar^†‡, William Schinski^§, Kathleen D. Field^†, Alexander Kuperman^§, Fuat E. Celik^*⊥, and Alan S. Goldman^*†

^† Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, United States

^‡ Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam India

^§ Chevron Energy Technology Company, 100 Chevron Way, Richmond, California 94802, United States

^⊥ Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, United States

ACS Catal., 2016, 6, pp 2836–2841

DOI: 10.1021/acscatal.6b00149

Publication Date (Web): March 28, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acscatal.6b00149

We report that pincer-ligated iridium catalysts for alkane dehydrogenation can operate in tandem with zeolite catalysts for arene–alkene coupling, to effect the overall intramolecular dehydrocoupling of alkyl–H and aryl–H bonds (i.e., the dehydrocyclization of alkyl benzene). Thus, zeolite and soluble iridium cocatalysts in refluxing pentylbenzene (205 °C) gave high yields of 1-methyl-1,2,3,4-tetrahydronaphthalene. Subsequent dehydrogenation and isomerization affords 1- and 2-methylnaphthalene and 2-methyl-1,2,3,4-tetrahydronaphthalene. Total yields of cyclized product as high as 5.4 M (94%) have been obtained, corresponding to 6800 turnovers per mol Ir. Turnover numbers for the tandem-catalyzed dehydrocyclization are much greater than those obtained for simple dehydrogenation by Ir catalysts (to give olefins) in the absence of zeolite.