Additive‐Free Isomerization of Allylic Alcohols to Ketones with a Cobalt PNP Pincer Catalyst1. Issue 33 (13th May 2019)

• Record Type: Journal Article
• Authors: Spiegelberg, Brian; Dell'Acqua, Andrea; Xia, Tian; Spannenberg, Anke; Tin, Sergey; Hinze, Sandra; de Vries, Johannes G.
• Is Part Of: Chemistry. Volume 25:Issue 33(2019)
• Page Start: 7820
• Page End: 7825
• Publication Date: 2019-05-13
• Subjects: allylic alcohols -- cobalt catalysts -- isomerization -- ketones -- pincer ligands; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201901148
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Catalytic isomerization of allylic alcohols in ethanol as a green solvent was achieved by using air and moisture stable cobalt (II) complexes in the absence of any additives. Under mild conditions, the cobalt PNP pincer complex substituted with phenyl groups on the phosphorus atoms appeared to be the most active. High rates were obtained at 120 °C, even though the addition of one equivalent of base increases the speed of the reaction drastically. Although some evidence was obtained supporting a dehydrogenation–hydrogenation mechanism, it was proven that this is not the major mechanism. Instead, the cobalt hydride complex formed by dehydrogenation of ethanol is capable of double‐bond isomerization through alkene insertion–elimination. Abstract : A powerful cobalt drive : Cobalt PNP pincer complexes were found to be efficient catalysts for the isomerization of allylic alcohols to ketones. The catalyst with phenyl groups on the phosphorus atoms was highly active in the absence of a base. A broad variety of substrates were successfully converted. The mechanism proceeds through alkene insertion in the cobalt–hydride bond followed by beta‐hydride elimination.