Propargylic C-H activation using a Cu(II) 2-quinoxalinol salen catalyst and tert-butyl hydroperoxide

The oxidation of alkynes to alpha,beta-acetylenic carbonyls was achieved using only 1 mol% of a Cu(II) 2-quinox-alinol salen catalyst with tert-butyl hydroperoxide. These reactions proceed under mild conditions (70 degrees C) with excellent selectivity, producing yields up to 78%, and were used on a variety of alkyne substrates to produce the desired corresponding alpha,beta-acetylenic ketones. In addition, these reactions can be run under aqueous conditions using a sulfonated version of the 2-quinoxalinol salen with good yields, reducing the need for volatile organic solvents. (C) 2018 Elsevier Ltd. All rights reserved.