Practical Site-selective Oxidation of Glycosides with Pd(OAc)2/Neocuproine

Abstract

Palladium-catalyzed oxidation of the secondary C3 hydroxy group in glycopyranosides has set its mark in the selective modification of unprotected carbohydrates. The pre-formed catalyst [(neocuproine)PdOAc]2(OTf)2 oxidizes besides monosaccharides also di-, and oligosaccharides. Here, we provide a more convenient protocol for this reaction in which the Pd-catalyst is formed in situ from Pd(OAc)2 and neocuproine in methanol at 50 °C. Together with a simplified product isolation, this protocol is applied to a series of mono- and disaccharides and has been applied on 10-gram scale. The protocol is also valuable as a screening method to determine whether more extensive studies using the pre-formed catalyst are worthwhile.