New route to unbranched alkenyl and alkyl arenes

A new catalytic reaction combines arenes with α-olefins to selectively make unbranched alkenyl and alkyl arenes, complementing the industrial pathways that lead to corresponding branched alkyl arenes. The products could add to the diversity of compounds available for making soaps, detergents, fuel and lubricant additives, polymer precursors, and flavors and fragrances. The reaction was developed by T. Brent Gunnoe of the University of Virginia and coworkers (J. Am. Chem. Soc. 2017, DOI: 10.1021/jacs.7b01165). The researchers use a rhodium salt catalyst without an added ligand and a Cu(II) oxidant to functionalize benzene, toluene, and other arenes with α-olefins such as propylene and 1-hexene to form unbranched alkenyl arenes. The products can be hydrogenated to make unbranched alkyl arenes, which are not accessible by the acid-catalyzed routes traditionally used industrially to make alkyl arenes. One challenge for the reaction is the high cost of rhodium, but Gunnoe believes recovering and recycling the metal could keep the expense reasonable.