Aerobic Oxidation Of Aldehydes Research Articles

Selective aerobic oxidation of aliphatic aldehydes: the critical role of percarboxylate anion on the selectivity

During the aerobic oxidation of aldehydes, peracids accumulate in the reaction mixture and may be decomposed in a non-selective way during workup. Using carboxylate salts, the peracids are selectively transformed into the carboxylic acids in situ.

First Asymmetric Synthesis of Passerini‐Type Condensation Products in Water Using Pregabalin: A Chiral Amino Acid for the Efficient Asymmetric Induction

AbstractThis article describes the use of Pregabalin as a commercially available chiral amino acid in the efficient synthesis of the Passerini‐type condensation products via two‐component condensation of aromatic aldehydes with cyclohexyl isocyanide. All reactions are accompanied with aerobic oxidation of aldehydes in water leading to chiral α‐acyloxycarboxamides with moderate to good enantioselectivities (up to 88 % ee) under green conditions such as nonmetal source. This is the first report of asymmetric synthesis of Passerini products in water.

Radical C-H Acylation of Nitrogen Heterocycles Induced by an Aerobic Oxidation of Aldehydes.

An aerobic radical approach for the synthesis of unsymmetrical heteroaryl ketones is described herein. The reaction involves cross-dehydrogenative coupling between aldehydes and heteroaromatic bases with molecular oxygen (O2 ). The key aspect of the method is the generation of reactive acyl radical via homolytic activation of aldehyde C-H bond using O2 as the sole oxidant. The reaction has a good substrate scope with respect to aldehydes and functionalized nitrogen heterocycles. Based on our mechanistic studies, a radical chain pathway is suggested for the reaction. A synthetic application of the method is demonstrated in the formal synthesis of natural alkaloid (±) angustureine.

Iron‐Catalyzed Aerobic Oxidation of Aldehydes: Single Component Catalyst and Mechanistic Studies

An aerobic oxidation of aldehydes towards carboxylic acids in MeCN using 1 atm of pure oxygen or oxygen in air as the oxidant and a catalytic amount of single component catalyst, Fe(NO3)3·9H2O, has been developed. Carboxylic acids with different synthetically useful functional groups were obtained at room temperature. Two mechanistic pathways have been proposed based on isotopic labeling, NMR monitoring, and control experiments. The practicality of this reaction has been demonstrated by conducting several 50 mmol‐scale reactions using pure oxygen or an air‐flow of ~30 mL/min.

Metal‐Free Aerobic Oxidative Esterification of Aldehydes in the Presence of Cyanide

A metal‐free aerobic oxidative esterification of aldehydes in the presence of cyanide is described. Various aromatic aldehydes and sterically congested alcohols were amenable to this protocol. In addition, this method could be extended to the preparation of thioesters with a thiol in place of an alcohol. Furthermore, the cyanide‐mediated aerobic oxidation of aldehydes was applied to the synthesis of lactones via intramolecular esterification in the absence of an alcohol.

ChemInform Abstract: Aerobic Oxidation of Aldehydes by Visible Light Photocatalysis.

AbstractA highly efficient photolytic oxidation of aliphatic and aromatic aldehydes to the corresponding carboxylic acids is developed using molecular oxygen as oxidant and a fluorinated iridium complex as photocatalyst.

Aerobic oxidation of aldehydes by visible light photocatalysis

An efficient and environmentally benign method for the oxidation of aldehydes to carboxylic acids has been developed. Singlet oxygen, generated by visible light in the presence of a Ru or Ir photocatalyst, reacted with aldehydes to give the corresponding carboxylic acids in excellent yields. The reaction is highly chemo-selective, in which only an aldehyde moiety is reactive even in the presence of other photo-oxidation active sites. This method is an example of an ideal green chemical reaction in the sense that molecular oxygen and visible light are key sources for the transformation.

Insights in the aerobic oxidation of aldehydes

The hydroformylation of olefins (oxo synthesis) is the most important process for the production of higher aldehydes (>C4). The liquid phase oxidation of the latter to carboxylic acids by molecular oxygen or air has been known for more than 150 years and is an industrially important process. However, in the recent literature, several different oxidizing reagents and catalytic processes have been reported for this oxidation but most of them have limitations as they use environmentally unacceptable reagents or unnecessarily sophisticated conditions. Herein, we re-evaluated the air oxidation of aldehydes. We show that under mild conditions (air or oxygen and non-optimized stirring), reactions are transfer limited and thus catalyst has no effect on reaction rate. Using efficient stirring (self-suction turbine), uncatalysed air oxidation of 0.8 M aldehyde is possible in 50 min at room temperature whereas less than 10 min was necessary with 10 ppm Mn(II). Thus, recommendations for avoiding common pitfalls that may rise during the evaluation of new catalysts are made.

ChemInform Abstract: Aerobic Oxidation of Aldehydes under Ambient Conditions Using Supported Gold Nanoparticle Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Aerobic oxidation of aldehydes under ambient conditions using supported gold nanoparticle catalysts

A new, green protocol for producing simple esters by selectively oxidizing an aldehyde dissolved in a primary alcohol has been established, utilising air as the oxidant and supported gold nanoparticles as catalyst. The oxidative esterifications proceed with excellent selectivities at ambient conditions; the reactions can be performed in an open flask and at room temperature. Benzaldehyde is even oxidised at a reasonable rate below −70 °C. Acrolein is oxidised to methyl acrylate in high yield using the same protocol.

Polar Effects in Free‐Radical Reactions. A Novel Homolytic Acylation of Heteroaromatic Bases by Aerobic Oxidation of Aldehydes, Catalyzed by N‐Hydroxyphthalimide and Co Salts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Polar effects in free‐radical reactions. A novel homolytic acylation of heteroaromatic bases by aerobic oxidation of aldehydes, catalysed by N‐hydroxyphthalimide and Co salts

AbstractA new process for the homolytic acylation of protonated heteroaromatic bases is described; an N‐oxyl radical (PINO) generated from N‐hydroxyphthalimide by air oxygen and Co(II) abstracts a hydrogen atom from an aldehyde. The resulting nucleophilic acyl radical adds to a heteroaromatic base, which is then rearo‐matised in a chain process. Quinazoline has an anomalous behaviour, giving 3H‐quinazolin‐4‐one as the only reaction product.