A Predictive Model for the Pd-Catalyzed Site-Selective Oxidation of Diols.

A predictive model, shaped as a set of rules, is presented that predicts site-selectivity in the mono-oxidation of diols by palladium-neocuproine catalysis. For this, the factors that govern this site-selectivity within diols and between different diols have been studied both experimentally and with computation. It is shown that an electronegative substituent antiperiplanar to the C-H bond retards hydride abstraction, resulting in a lower reactivity.

Formation of substituted dioxanes in the oxidation of gum arabic with periodate.

Renewable polysaccharide feedstocks are of interest in bio-based food packaging, coatings and hydrogels. Their physical properties often need to be tuned by chemical modification, by oxidation using periodate, to introduce carboxylic acid, ketone or aldehyde functional groups. The reproducibility required for application on an industrial scale, however, is challenged by uncertainty about the composition of product mixtures obtained and of the precise structural changes that the reaction with periodate induces.

Oxidative Cleavage of Alkene C=C Bonds Using a Manganese Catalyzed Oxidation with HO Combined with Periodate Oxidation.

A one-pot multi-step method for the oxidative cleavage of alkenes to aldehydes/ketones under ambient conditions is described as an alternative to ozonolysis. The first step is a highly efficient manganese catalyzed epoxidation/-dihydroxylation of alkenes. This step is followed by an Fe(III) assisted ring opening of the epoxide (where necessary) to a 1,2-diol.

Regioselective Manipulation of GlcNAc Provides Allosamine, Lividosamine, and Related Compounds.

Palladium-catalyzed oxidation of isopropyl N-acetyl-α-d-glucosamine (GlcNAc) is used to prepare the rare sugars allosamine, lividosamine, and related compounds with unprecedented selectivity. The Passerini reaction applied on 3-keto-GlcNAc provides an entry into branching of the carbon skeleton in this compound.

Regioselective Carbohydrate Oxidations: A Nuclear Magnetic Resonance (NMR) Study on Selectivity, Rate, and Side-Product Formation.

Palladium/neocuproine catalyzed oxidation of glucosides shows an excellent selectivity for the C3-OH, but in mannosides and galactosides, unselective oxidation was initially observed. For further application in more-complex (oligo)saccharides, a better understanding of the reaction, in terms of selectivity and reactivity, is required. Therefore, a panel of different glycosides was synthesized, subjected to palladium/neocuproine catalyzed oxidation and subsequently analyzed by qNMR.

C3 Epimerization of Glucose, via Regioselective Oxidation and Reduction.

Palladium-catalyzed oxidation can single out the secondary hydroxyl group at C3 in glucose, circumventing the more readily accessible hydroxyl at C6 and the more reactive anomeric hydroxyl. Oxidation followed by reduction results in either allose or allitol, each a rare sugar that is important in biotechnology. Also, N-acetylglucosamine is selectively oxidized at C3.

Regioselective oxidation of unprotected 1,4 linked glucans.

Palladium-catalyzed alcohol oxidation allows the chemo- and regioselective modification of unprotected 1,4 linked glucans. This is demonstrated in the two-step bisfunctionalization of 1,4 linked glucans up to the 7-mer. Introduction of an anomeric azide is followed by a highly regioselective mono-oxidation of the terminal C3-OH functionality.

Deuteration enhances catalyst lifetime in palladium-catalysed alcohol oxidation.

The catalyst palladium/2,9-CD3-phenanthroline has a 1.8 times higher turnover number than its non-deuterated counterpart in the aerobic alcohol oxidation of methyl glucoside and allows the regioselective oxidation with dioxygen as the terminal oxidant.

Pd-diimine: a highly selective catalyst system for the base-free oxidative Heck reaction.

Pd(OAc)(2)/3 is an efficient catalyst system for the base-free oxidative Heck reaction that outperforms the currently available catalysts for the more challenging substrates studied. The catalyst system is highly selective, and works at room temperature with dioxygen as the oxidant.