Efficient and selective oxidation of aldehydes with dioxygen catalysed by vanadium-containing heteropolyanions

Abstract

The heteropolyacids "H 3þn [PMo 12en V n O 40 ]$aq" (denoted as HPA-n; n ¼ 2, 3, 8) catalyse the oxidation of aldehydes to carboxylic acids in the presence of dioxygen with very good yields. The effect on the catalytic activity of various parameters such as the precursors, solvent, temperature or catalyst/substrate ratio was examined. The process is particularly selective for linear and aromatic aldehydes. The oxidation of adipaldehyde with dioxygen in mild conditions, in the presence of HPA-2 as a catalyst, leads to the formation of adipic acid together with a significant amount of other byproducts. Thus, several modifications of the catalytic systems have been carried out to improve their selectivity. The effect of cocatalysts was investigated and, among the species tested, complex Ni(acac) 2 was found to be the most efficient yielding 60% of adipic acid.

K-10 montmorillonite: An efficient and reusable catalyst for selective oxidation of aldehydes in the presence of dioxygen

“…The reaction is prolonged with substrates containing electron-donating substituents in the aromatic ring (Table 4, entries, 6-9). These observations clearly show that such active electrondonating groups do not allow smooth oxidation of aldehydes to carboxylic acids because these types of aldehydes can also act as radical scavengers 27 . Previous work 55 showed that irons salts are efficient catalysts precursors for the oxidation of aldehydes.…”

“…The oxidation of trans-cinnamaldehyde and citronellal were evaluated under the oxidative conditions of our catalytic system. These substrates contain aldehyde functionality together with an epoxidizable olefinic double bond 27 .…”

“…Although many reagents are known to oxidize alcohols to aldehydes or ketones 20,21 , the next step of oxidation from the aldehyde to acid is relatively much more difficult to achieve using a very mild procedure and ensuing good yields 22 . Various oxidants such as t-BuOOH 23 , H2O2 3,18,24 , and molecular oxygen [25][26][27] are applied in the catalytic oxidation of aldehydes to the corresponding carboxylic acids. However, despite the merits of these procedures, they might have various disadvantages such as harsh reaction conditions, the excessive requirement for reagents or catalysts, prolonged reaction time, tedious work-up procedures, non-reusability of the catalysts, and low yields of products.…”

Vanadium-Substituted Phosphomolybdic Acids for the Aerobic Cleavage of Lignin Models—Mechanistic Aspect and Extension to Lignin

“…Sometimes, H 3+x PV x are also considered as the precursors of in situ-formed pervanadyl cations that would be the true catalysts as suggested by Bregeault et al [50] and El Amrani et al [51], characterized by a higher redox potential than parent H 3+x PV x [29] and therefore may be more effective for oxidation, including aerobic cleavage. Such ejection is accompanied by the formation of an unstable lacunary polyoxometalate (POM) that generates a phosphomolybdate anion.…”

Selective Catalytic Oxidation of Aldehydes by a Molybdenum System

“…Nevertheless, it is worthy to note that the α-positions of ethers can be easily attacked by molecular oxygen (scheme1). Moreover, THF is not friendly for the environmental point of view, and thus must be handled under strict safety conditions 22 .…”