Oxidative Esterification Of Aldehydes Research Articles

Highly Dispersive Gold Nanoclusters Confined within Micropores of Defective UiO-66 for Highly Efficient Aldehyde Oxidation at Mild Conditions.

The oxidative esterification of aldehydes under mild conditions remains a significant challenge. This study introduces a unique defective UiO-66 to achieve gold nanoclusters (AuNCs) for efficient aldehyde oxidation under mild conditions. The construction and characterization of these materials are thoroughly investigated by techniques of XRD, SEM and TEM images, FT-IR, Raman, and XPS spectrum, emphasizing the unique microporous in defective UiO-66 are conducive to the fabrication of AuNCs. The catalytic performance of the prepared materials in aldehyde oxidation reactions is systematically evaluated, demonstrating the remarkable efficiency of dispersed Au@UiO-66-25 with high-content (9.09 wt%) Au-loading and ultra-small size (~2.7 nm). Moreover, mechanistic insights into the catalytic process under mild conditions (70 °C for 1 h) are provided, elucidating the determination of defective UiO-66 in the confined fabrication of AuNCs and subsequent furfural adsorption, which underlie the principles governing the observed enhancements. This study establishes the groundwork for the synthesis of highly dispersed and catalytically active metal nanoparticles using defective MOFs as a platform, advancing the catalytic esterification reaction of furfural to the next level.

Cytosine Palladium Complex Supported on Ordered Mesoporous Silica as Highly Efficient and Reusable Nanocatalyst for One-Pot Oxidative Esterification of Aldehydes

The synthesis of esters is one of the most fundamental and significant subjects in organic chemistry and chemical industry because they are used in high-value products such as cosmetics, biofuel, pharmaceuticals, surfactants, and food ingredients. In this study, an efficient, economic, sustainable, and green protocol for oxidative esterification reaction has been developed. A one-pot direct transformation of aliphatic, aromatic, and unsaturated aldehydes into esters in the presence of oxygen has been carried out over mesoporous organosilica-supported palladium nanocatalyst (Pd-Cyt@SBA-15) under ambient conditions. Pd-Cyt@SBA-15 efficiently catalyzed selectively large-scale conversion of aldehydes into esters in high yields and large turnover numbers (TON = 98,000). Pd-Cyt@SBA-15 nanocatalyst demonstrated excellent reusability and stability and could be recycled up to ten times without loss of significant reactivity. ICP-AES analysis showed that no leaching of active palladium species occurred during the recycling process of the heterogeneous Pd-Cyt@SBA-15 nanocatalyst.

N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading.

We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N‐heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α‐ and β‐substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N‐Mes‐/N‐2,4,6‐trichlorophenyl 1,2,4‐triazolium salt, and benzoic acid as co‐catalyst, was developed. A whole series of α/β‐substituted aliphatic aldehydes/enals hitherto not amenable to NHC‐catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid‐induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.

N‐Heterocyclic Carbene/Carboxylic Acid Co‐Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading

AbstractWe report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N‐heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α‐ and β‐substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N‐Mes‐/N‐2,4,6‐trichlorophenyl 1,2,4‐triazolium salt, and benzoic acid as co‐catalyst, was developed. A whole series of α/β‐substituted aliphatic aldehydes/enals hitherto not amenable to NHC‐catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid‐induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.

Direct access to α-acyloxycarbonyl compounds and esters via oxidative esterification of aldehydes under visible light

An efficient synthesis of α-acyloxycarbonyl compounds and esters from aldehydes and α-bromocarbonyl compounds/benzyl bromide derivatives via photoredox catalysis has been developed.

Development of highly efficient and durable reduced graphene oxide decorated with Ag/Co3O4 nanocomposite towards photocatalytic C[sbnd]H activation

We report herein, an in-situ synthesis of Ag/Co3O4 anchored on reduced graphene oxide (rGO) nanocomposite. The Ag/Co3O4 -rGO is considered to be a simple, recyclable and durable photocatalyst for hydroxylation of benzene and oxidative esterification of aldehyde via CH activation using visible light irritation. One-pot hydrothermal synthesis route was explored via homogeneous chemical precipitation using urea as both hydroxylation agent and reducing agent for graphene oxide. The polyethylene glycol also served as a surfactant and well as the reducing agent for Ag (I). It was observed that 2−10 nm sized Ag-nanoparticles supported on 20–60 nm-sized Co3O4 decorated along with the surface of reduced graphene oxide. The as-synthesized nanocomposite efficiently catalyzed hydroxylation of benzene reaction with 99 % conversion of benzene and 96 % phenol selectivity. Similarly, the esterification of aldehyde could be achieved with 86 % aldehyde conversion under room temperature.

Oxidative Esterification of Aldehydes and Alcohols Catalyzed by Camphor-Based Imidazolium Salts

Sixteen new camphor-based imidazolium salts have been synthesized with renewable camphorsulfonic acid as the starting material. The chemical shifts of the characteristic proton of C2 on the imidazolium ring (N−C=N) were discussed thoroughly and all of these imidazolium salts exhibit good thermal stability. Furthermore, the excellent catalytic performance of the synthesized imidazolium salts were observed in the oxidative esterification between aromatic or aliphatic aldehydes containing electron-withdrawing or electron-donating groups on aromatic ring and primary or secondary alcohol by air as the sole oxidant.

Cobalt-catalyzed direct transformation of aldehydes to esters: the crucial role of an enone as a mediator

An oxidative esterification of aldehydes with alkanols catalyzed by an in situ generated low-valent cobalt system has been developed using an enone as a mild oxidant.

N-Heterocyclic Carbene-Catalyzed Oxidative Esterification of Aldehydes: Facile Access to α-Acyloxyacetates and Cyanomethyl Esters

<i>N</i>-Heterocyclic Carbene-Catalyzed Oxidative Esterification of Aldehydes: Facile Access to <i>α</i>-Acyloxyacetates and Cyanomethyl Esters

Iron‐Nitrate‐Catalyzed Oxidative Esterification of Aldehydes and Alcohols with N‐Hydroxyphthalimide: Efficient Synthesis of N‐Hydroxyimide Esters

An Fe(NO3)3·9H2O‐catalyzed cross‐dehydrogenative coupling reaction between N‐hydroxyphthalimide (NHPI) or N‐hydroxysuccinimide (NHSI) and aldehydes or alcohols in air is described. This transformation represents an efficient approach to the preparation of N‐hydroxyimide ester derivatives in moderate to excellent yields, and has a wide substrate scope.

Palladium‐Catalyzed Aerobic Oxidative Cross‐Esterification of Aldehydes with Alcohols

AbstractIn this work, a palladium‐catalyzed oxidative esterification of aldehydes with alcohols was developed by using oxygen as the terminal oxidant. Various aldehydes and alcohols were selectively converted into their corresponding esters in good yields.

Oxidation of Aromatic Aldehydes to Esters: A Sulfate Radical Redox System.

A mild oxidative esterification of various aromatic aldehydes by sulfate radical redox system was presented. In the reaction pathway exploration, the transiency of MeOSO3- was disclosed, which was generated from esterification between the in situ generated HSO4- and MeOH, a rate-limiting step in the process. More importantly, the selectivity-controlling step was represented by the subsequent nucleophilic displacement between MeOSO3- and aldehydes. The ionic oxidant 1a ((NH4)2S2O8) with more N-H numbers in the cation, as compared with 1c ((n-Bu4N)2S2O8) and 1d ((PyH)2S2O8), has better performance in the oxidative esterification of aldehydes.

Bu4NI‐Catalyzed and tBuOOH‐Oxidized Esterification of Aldehydes with Alkyl Halides in Water

AbstractThe importance of esters has stimulated significant efforts to develop efficient methods for their synthesis. In this study, an oxidative esterification of aldehydes with alkyl halides by using tert‐butyl hydroperoxide as an oxidant, Bu4NI as catalyst, and water as solvent is presented. Notably, this novel esterification protocol is suitable for both aromatic and aliphatic aldehydes, primary and secondary alkyl halides to give ester products with broad structural diversity. Through an intramolecular version of this novel esterification process, an alternative synthetic approach toward the biologically interesting isobenzofuran‐1(3 H)‐one was also realized. Compared with literature procedures, the synthetic strategies developed herein showed advantages such as direct use of commercially available and economical starting materials, wide substrate scope, good tolerance of functional groups, sustainable oxidant, and no need of an inert atmosphere or dry solvents.

Gold nanoparticle-decorated graphene oxide: Synthesis and application in oxidation reactions under benign conditions

Gold nanoparticles (∼13nm, 4wt% Au) dispersed on reduced graphene oxide (Au/rGO) surface were prepared via the reduction of gold (III) chloride using sodium citrate on reduced graphene oxide support. The chemical, morphological, and size analyses of Au/rGO by XRD, XPS, TEM, HR-TEM/EDS, AAS, and Raman spectroscopy revealed that the hybrid material comprised of a well-defined rGO support decorated with gold nanoparticles. The ensuing catalyst was evaluated for the oxidation of ethyl benzenes (yields up to 95%) and oxidative esterification of aldehydes (73–97%) using oxygen as an environmentally friendly oxidant in good to excellent yields; reusable and recyclable catalyst displayed high activity without the use of toxic organic solvents.

Oxidative Esterification of Aldehydes with Urea Hydrogen Peroxide Catalyzed by Aluminum Chloride Hexahydrate

Oxidative Esterification of Aldehydes with Urea Hydrogen Peroxide Catalyzed by Aluminum Chloride Hexahydrate

Titanium Superoxide Catalyzed Oxidative Esterification of Aldehydes

Titanium Superoxide Catalyzed Oxidative Esterification of Aldehydes

Cetyltrimethylammonium Bromide Promoted Size-Tuning Synthesis of Rod-Like V&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;5&lt;/SUB&gt; Nanoparticles and Their Catalytic Studies in Oxidative Esterification of Aldehydes

Cetyltrimethylammonium Bromide Promoted Size-Tuning Synthesis of Rod-Like V&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;5&lt;/SUB&gt; Nanoparticles and Their Catalytic Studies in Oxidative Esterification of Aldehydes

Oxidative esterification of aldehydes with alcohols using imidazolium perrhenate catalysts

Four imidazolium perrhenates were synthesized, characterized and used as efficient catalysts for the oxidative esterification of benzaldehydes with alcohols. The perrhenates showed high catalytic activity toward oxidative esterifications, whereas good yields could be obtained for a series of aldehyde and alcohol substrates. The results indicate that the steric effects of functional groups on the aromatic ring play important roles in the formation of esters. Moreover, the alkyl structures of the alcohols also dramatically affect the product yields.

PTFE supported gold nanoparticles as photocatalysts for oxidative esterification of aldehydes

Fast and mild visible light photocatalytic conditions for oxidative esterification of aldehydes using H2O2and the AuNP/PTFE catalyst.

Oxidative Esterification of Aldehydes on Reduced Graphene Oxide-Supported Co3O4

Key words aldehydes - oxidation - esterification - cobalt oxide - nanoparticles - catalyst supports