Organocatalyst for the Oxidative Homocoupling of Grignard Reagents

Highly fluorinated cyclopentene derivative (1) was developed by Korenaga et al. and can be used for oxidative homocoupling of Grignard reagents. By using 1 as a catalyst, oxidative homocouplings of aryl Grignard reagents, vinyl Grignard reagents and benzyl Grignard reagents proceed in high yields. In this reaction, 1 functions as a four-electron oxidant initially and is converted into the anion species 2 with dimerization of four molecules of the Grignard reagent. Subsequently, an air oxidation of 2 affords a radical species 3, which catalyzes dimerization of a Grignard reagent with regeneration of the anion species 2 to complete the catalytic cycle. In this way, 1 is expected to be used as a green catalyst for homocoupling of Grignard reagents using air as a co-oxidant.