Dakin Oxidation Research Articles

From lignin-derived monomers to 1,4-cyclohexanediol via a two steps Dakin oxidation and hydrodeoxygenation reaction

Lignin is the largest renewable source of aromatic building blocks in nature and has great potential as a starting material for the production of bulk or functionalized aromatic compounds, providing a suitable alternative to widely used petroleum-derived chemicals. In this work, we present a novel 1,4-cyclohexanediol (CHDO) preparation from lignocellulose. In contrast to conventional methods, this pathway has taken the lignin-degrading monomers as a starting point, and flexibly employs a series of oxidative and catalytic reactions to achieve the preparation of CHDO. The proposed pathway consists of a two-step chemical process to efficiently obtain high yields of CHDO from lignocellulose. The first step is the oxidation of lignin-derived monophenols to p-hydroxyl phenolic compounds using the Dakin oxidation reaction (yield>80 %), and finally the de-functionalization and hydrogenation of the resulting monomers using the hydrodeoxygenation (HDO) reaction.

Heavy Water Microdroplet Surface Enriches the Lighter Isotopologue Impurities.

Water microdroplets promote unusual chemical reactions at the air-water interface. However, the interfacial structure of water microdroplets and its potential influence on chemical processes are still enigmatic. Here, we present evidence of in-droplet fractionation of water isotopologues. Employing a sonic spray, we atomized the heavy water (D2O, 99.9 atom % D) solution of three classes of organic compounds (basic, acidic, and neutral). The analytes were predominantly desorbed from the resulting droplet surface in protonated form rather than deuterated form, as detected by mass spectrometry. This result remained unaltered upon adding formic acid-d2 (DCOOD) to the droplet. Monitoring Dakin oxidation of benzaldehyde at the surface of binary microdroplets composed of 1:1 (v/v) D2O/H218O revealed the preferred formation of phenolate-16O over phenolate-18O. Atmospheric pressure chemical ionization mass spectrometric analysis of the vapor composition in the sprayed aerosol revealed the preferential evaporation of lighter water isotopologue impurities from the surface of heavy water microdroplets. These results indicate the enrichment of lighter water isotopologue impurities (HOD/H2O) on the surface of heavy water microdroplets, implying possible future developments for water isotopologue fractionation using microdroplets.

Oxone-mediated dakin reaction of benzaldehydes to phenols

We report the Dakin reaction using Oxone as a mild and green oxidant. This protocol does not require acidic additives or transition metal catalysts. It effectively operates on salicylaldehyde and benzaldehyde substrates, yielding catechols and phenols in moderate to high yields.

Theoretical study on the reaction mechanism of Dakin oxidation: influence of methoxy groups

Theoretical study on the reaction mechanism of Dakin oxidation: influence of methoxy groups

Peroxodicarbonate - a renaissance of an electrochemically generated green oxidizer.

The direct anodic conversion of alkali carbonates in aqueous media provides access to peroxodicarbonate, which is a safe to use and green oxidizer. Although first reports date back around 150 years, its low concentrations and limited thermal stability have consigned this reagent to oblivion. Boron-doped diamond anodes, novel electrolyser concepts for heat dissipation, and the mixed cation trick allow record breaking peroxodicarbonate concentrations >900 mM. The electrochemical generation of peroxodicarbonate was already demonstrated on a pilot scale. The inherent safety is ensured by the limited stability of the peroxodicarbonate solution, which decomposes under ambient conditions to oxygen and facilitates subsequent downstream processing. This peroxide has, in particular at higher concentrations, an unusual reactivity and seems to be an ideal reagent when peroxo-equivalents in combination with alkaline base are required. The conversions with peroxodicarbonate include the Dakin reaction, epoxidation, oxidation of amines (aliphatic and aromatic) and sulfur compounds, deborolative hydroxylation reactions, and many more. Since the base equivalents also represent the makeup chemical for pulping plants, peroxodicarbonate is an ideal reagent for the selective degradation of lignin to vanillin. Moreover, peroxodicarbonate can be used as a halogen-free bleaching agent. The emerging electrogeneration and use of this green platform oxidizer are surveyed for the first time.

Dual Functionality of Choline Hydroxide for the Dakin Reaction

: A facile synthetic approach to Dakin oxidation utilizing green conditions was demonstrated. A combination of hydrogen peroxide and aqueous choline hydroxide in cooperation with various hydroxyl aryl aldehydes and ketones was used to provide the corresponding dihydric aromatic compounds. The whole procedure was conducted at ambient temperature in an aerobic environment. The scope of ChOH/H2O2 platform was also investigated, showing that the reactivity of the present platform was highly dependent on the position of the hydroxy group of the aromatic ring.

Recent developments in synthesis of catechols by Dakin oxidation

In recent years, Dakin oxidation has evolved primarily around the conversion of ortho- and para-hydroxy benzaldehydes and acetophenones to dihydric phenols, which are found in nature and complex organic materials.

Convenient synthesis of 3-Hydroxyquinolines via dakin oxidation: A short synthesis of Jineol

A convenient synthesis of 3-hydroxyquinolines has been described via unprecedented Dakin oxidation of quinoline-3-carboxaldehydes. Subsequently, application of the methodology to a high yielding synthesis of quinoline alkaloid Jineol (1) is reported.

Heterogeneous Nitrogen‐doped Graphene Catalysed HOO− Generation via a Non‐radical Mechanism for Base‐free Dakin Reaction

AbstractA heterogeneous nitrogen‐doped graphene catalytic pathway for H2O2 activation to generate alkaline hydrogen peroxide (HOO−) through a non‐radical mechanism was reported. Remarkably, the heterogeneous catalytic procedure has been used for the evergreen and environmentally Dakin reaction without using any transition metals, homogeneous bases, ligands, additives or promoters, completely. The study of catalyst structure and catalytic activities indicate that the most active sites are created by the graphitic N atoms at zig‐zag edges of the sheets. In addition, N as dopant element changes the reactivity of the neighbour C atoms, and leads to the formation of carbon‐hydroperoxide (C−(HOOH)) and C−O* (C−O−) transition state species on the graphene surface in catalytic the reaction.magnified image

PEEL EXTRACT ASSOCIATED OXIDATIVE GREEN DAKIN SYNTHESIS OF SOME PHENOLS USING AQUEOUS BANANA EXTRACT CATALYST

The green Dakin reactions can be performed by employing gallic acid as an oxidizing agent. Implementation of gallic acid helps to avoid the usage of catalyst, ligand and any toxic or hazardous oxidizing agent. Gallic acid accelerates the conversion of the atmospheric oxygen into hydrogen peroxide, which helps in the oxidation of aldehydes in situ . Mango peel, potato peel, pomegranate pomace, grape pomace extract contains the rich source of gallic acid that performs the oxidations in a natural feedstock. The best results were obtained by mango peel as well as potato peel extract giving excellent yields with minimum time at room temperature. The ‘aqueous extract of banana’ (AEB), in the said conversion plays a dual role of catalyst and a base. The reported work can be considered as environment-friendly Dakin oxidation, as it is carried out in a neat AEB at room temperature under aerobic conditions with low reaction time and better yield.

Quenching of Salicylaldehyde‐based Luminescence Probe via Dakin Reaction: Approach for Highly Selective Detection of Hydrogen Peroxide

A novel assay for H2O2 based on luminescence quenching is developed from the Dakin reaction between deprotonated salicylaldehyde (D‐SA) and H2O2. Under alkaline condition, the phenolic hydroxyl group of SA is deprotonated, exhibiting good luminescence emission ability (λex = 433 nm, λem = 508 nm). Luminescence of D‐SA is quenched by H2O2 in a concentration‐dependent manner. Good linearity is obtained with a regression coefficient of 0.9989 in the range of 0.3 ~ 150 μM and a detection limit (LOD) is 30 nM. In addition, D‐SA luminescence probe shows good biocompatibility and low cytotoxicity to HeLa cells through MTT assay. The feasibility for in vitro applications is demonstrated through confocal laser scanning microscopy.

Anion effect of 5-ethylisoalloxazinium salts on flavin-catalyzed oxidations with H2O2

The anion effect of the 5-ethylisoalloxazinium salts on their catalytic activity was investigated for the oxidation of sulfide with aq H2O2 in order to design more practical and safer flavinium salt catalysts that can replace the conventional perchlorate salt. The anions forming stronger conjugated acids were found to accelerate the catalytic sulfoxidation. The riboflavin-derived isoalloxazinium triflate salt was chosen as a readily accessible flavin with an efficient catalytic activity. In fact, the isoalloxazinium triflate 1b is an excellent organocatalyst for the chemoselective oxidations of a sulfide to a sulfoxide, Bayer–Villiger reaction of a cyclobutanone to a γ-butyrolactone, Dakin reaction of an arylaldehyde to a phenol, and oxidation of an aldehyde to a carboxylic acid using aq H2O2 as a terminal oxidant under mild conditions.

ChemInform Abstract: H2O2 in WEB: A Highly Efficient Catalyst System for the Dakin Reaction.

AbstractVarious phenols are synthesized in high yields via Dakin oxidation of substituted hydroxylated benzaldehydes using neat water extract of banana as an all‐in‐one mixture of solvent, catalyst, ligand, base, additive, promoter etc.

ChemInform Abstract: One‐Pot Synthesis of Tryptanthrin by the Dakin Oxidation of Indole‐3‐carbaldehyde.

AbstractThe alkaloid tryptanthrin (IIa) is further converted into the natural products phaitanthrin A (IXa), phaitanthrin B (IXb), and cruciferane (X).

A new avenue to the Dakin reaction in H2O2–WERSA

We have developed a novel protocol to realize the Dakin reaction in H2O2–WERSA at room temperature and the system does not require activation, toxic ligand, additive/promoter, transition metal catalyst, base, organic solvent and so on.

ChemInform Abstract: Acceleration of the Dakin Reaction by Trifluoroacetic Acid.

AbstractTrifluoroacetic acid is shown to accelerate the Dakin reaction and the use of SeO2 is essential for the reaction either as carbonyl activator or as a participator in the reaction by intermediately forming peroxyselenic acid.

H2O2in WEB: a highly efficient catalyst system for the Dakin reaction

Without using any transition metal catalyst, ligand, base, toxic or hazardous reagent, additives/promoters and organic solvent, Dakin reactions have been successfully carried out by using H2O2in neat ‘Water Extract of Banana’ (WEB) at room temperature under aerobic conditions in very short reaction times.

ChemInform Abstract: A Mild Oxidation of Deactivated Naphthalenes and Anthracenes to Corresponding para‐Quinones by N‐Bromosuccinimide.

Abstract A new method to synthesize 1,4-naphthoquinone and 9,10-anthraquinone from naphthalene and anthracene functionalized with either –CHO or –COOH groups, using N-bromosuccinimide (NBS) in aqueous N,N-dimethylformamide at 75–80 °C, has been developed. Further, –CN and –CONH2 functionalized naphthalenes and anthracenes can also be transformed into respective para-quinones in a one pot reaction, after successive acid hydrolysis and subsequent reaction with NBS. We believe that the present finding may serve as a valuable alternative to the classical approaches for the synthesis of polycyclic quinones from polyaromatic carbaldehydes through Dakin oxidation followed by further oxidation of the resulting hydroquinone by heavy metal oxides.

One-pot synthesis of tryptanthrin by the Dakin oxidation of indole-3-carbaldehyde

A one-pot approach to indolo[2,1-b]quinazolines from indole-3-carbaldehydes through the Dakin oxidation was developed. It was shown that the reaction proceeded through the condensation of indole-3-carbaldehydes with isatoic anhydrides, derived in situ from indole-3-carbaldehydes by the Dakin oxidation, and further oxidation/cyclization steps.

Acceleration of the Dakin Reaction by Trifluoroacetic Acid

An acceleration of the Dakin reaction caused by addition of trifluoroacetic acid is described. The modified protocol converts aromatic aldehydes to the corresponding phenols within 4 hours at room temperature by means of hydrogen peroxide in acidic medium. This acceleration is attributed to the stability of hydrogen peroxide in an acidic medium. This modified protocol provides alternative and easy access to important phenolic precursors that have been used in the synthesis of various natural products.