Oxidative Amidation Of Aromatic Aldehydes Research Articles

Naphthalene Monoanhydride and Perylene Composites for Efficient Photocatalytic Hydrogen Evolution and Metal-Free Heterogeneous Oxidative Amidation.

This study explores the synthesis of two visible light active organic chromophore-based composites using naphthalene monoanhydride (Np) and 1,7-dibromoperylene monoanhydride diester (PMDE). These chromophores feature favorable optical and electronic properties and polyaromatic skeletons with anhydride functionalities that facilitate π-π interactions between the chromophore and polymeric carbon nitride (CN) or covalent connections of chromophores with NH2 groups of CN. Accordingly, heterogeneous chromophore-CN composite photocatalysts namely, Np/CN(c) and PMDE/CN(c) were prepared by adopting in situ calcination (c) and composites Np/CN(a) and PMDE/CN(a) were prepared by ex situ physical adsorption (a) methods. In situ prepared Np/CN(c) and PMDE/CN(c) composites exhibited H2 evolution rates (HER) of 1069 and 705 μmol h-1 g-1, respectively, which are significantly higher than ex situ Np/CN(a) and PMDE/CN(a) composites with HER of 465 and 252 μmol h-1 g-1, respectively. These rates are 10, 7, 4.8, and 2.5 times higher than the bulk-CN, indicating the potential of these composites for efficient photocatalytic H2 evolution. Surface area normalized HER enhancements were 3.8, 5.3, 6.6, and 4.2 times higher for Np/CN(c), PMDE/CN(c), Np/CN(a), and PMDE/CN(a) respectively compared to bulk-CN. These composite photocatalysts exhibited excellent stabilities under prolonged photoirradiation, with H2 evolution consistently increasing with the light exposure time. Additionally, these metal-free heterogeneous composites demonstrated efficient photocatalytic activities towards oxidative amidation of aromatic aldehydes, with up to 80% product yields, establishing the prospects of combining homogeneous and heterogeneous entities in a metal-free active material in solar energy harvesting.

AIEE Active Nanoassemblies of Pyrazine Based Organic Photosensitizers as Efficient Metal-Free Supramolecular Photoredox Catalytic Systems

Pyrazine derivatives DIPY, TETPY and CNDIPY have been designed and synthesized which form fluorescent supramolecular assemblies in mixed aqueous media due to their AIEE and ICT characteristics. Among all the derivatives, the assemblies of TETPY and CNDIPY show strong absorption in the visible region with high absorption coefficients, low HOMO-LUMO gap, and high photostability. Further, the supramolecular nanoassemblies of TETPY and CNDIPY show excellent potential to generate reactive oxygen species (ROS) under the visible light irradiation. Owing to their strong absorption in the visible region and ROS generation ability, the supramolecular nanoassemblies of TETPY and CNDIPY act as efficient photoredox catalytic systems for carrying out (a) oxidative amidation of aromatic aldehydes (b) hydroxylation of boronic acid and (c) oxidative homocoupling of benzylamines under mild conditions such as aqueous media, aerial environment, and natural sunlight as a source of irradiation. All the mechanistic investigations suggest the participation of in-situ generated ROS in the organic transformations upon light irradiation.

Urea‐2,2‐dihydroperoxypropane as a Novel and High Oxygen Content Alternative to Dihydroperoxypropane in Several Oxidation Reactions

AbstractUrea‐2,2‐dihydroperoxypropane (UDHPP)‐ a white crystalline solid oxidant which is formed when urea is recrystallized from dihydroperoxypropane‐ was applied as the terminal oxidant in several oxidative procedures namely epoxidation of α, β‐unsaturated ketones and alkenes, oxidation of sulfides to sulfoxides and sulfones, bayer‐villeger reaction, bromination and iodation of aniline and phenol derivatives, oxidative esterification, oxidative amidation of aromatic aldehydes, thiocyanation of aromatic compounds, and oxidation of pyridines, oxidation of secondary, allylic and benzylic alcohols. All the approaches were carried out under mild conditions and short reaction times and afforded the corresponding products in high yields.

Exploring organic photosensitizers based on hemicyanine derivatives: a sustainable approach for preparation of amide linkages.

Hemicyanine derivatives C1–C4 have been synthesized and show strong absorption in the visible region, good water solubility, efficient intersystem crossing, a high singlet oxygen quantum yield and high ability to transport electrons from the donor to acceptor. These hemicyanine derivatives were utilized as photocatalysts in additive/base free oxidative amidation of aromatic aldehydes in mixed aqueous media under visible light irradiation at low catalytic loading. The hemicyanine derivative C4 exhibited recyclability upto four cycles and reusability upto five cycles in oxidative amidation of aromatic aldehydes. Among all the hemicyanine derivatives, C4 shows a high photocatalytic efficiency due to a high singlet oxygen quantum yield. All the mechanism investigations showed involvement of reactive oxygen species generated by the organic triplet photosensitizer based on hemicyanine derivative for carrying out oxidative amidation of aldehyde. Our results will encourage the design of new “metal free” organic photosensitizers and their application in photocatalysis.

Oxidative Amidation of Aromatic Aldehydes on Silver/Graphitic Carbon Nitride

Oxidative Amidation of Aromatic Aldehydes on Silver/Graphitic Carbon Nitride

Synthesis of Ag/g‐C3N4 Composite as Highly Efficient Visible‐Light Photocatalyst for Oxidative Amidation of Aromatic Aldehydes

AbstractIn this contribution, an Ag/g‐C3N4 nanocomposite was synthesized and utilized as highly efficient and green photocatalyst for organic reactions under visible light irradiation. A layered, porous g‐C3N4 was synthesized following a modified solvothermal‐roasting process by using melamine and cyanuric chloride as precursor. Silver nanoparticles (NPs) were well anchored on g‐C3N4 nanosheets, which were prepared by a facile impregnation–roasting method. The inexpensive, stable g‐C3N4 coupled with the localized surface plasmon resonance (LSPR) effect of Ag NPs exhibited high photocatalytic activities toward aerobic oxidative amidation of aromatic aldehydes under visible light irradiation. Good to excellent yields were achieved for various substrates under the light of a 25 W compact fluorescent light (CFL) bulb in air. The operationally easy procedure provides an economical, green, and mild alternative for the formation of amide bonds.magnified image

ChemInform Abstract: Iron‐Catalyzed Direct Synthesis of Amides from Methylarenes.

AbstractThe convenient one‐pot synthesis of carboxylic amides involves the in situ generation of N‐chloroamines followed by oxidative amidation of aromatic aldehydes derived from methylarenes upon treatment with tBuOOH.

ChemInform Abstract: N‐Heterocyclic Carbene‐Catalyzed Oxidative Amidation of Aldehydes with Amines.

AbstractThe oxidative amidation of aromatic aldehydes in presence of NBS as oxidant furnishes the products in good yields.

N‐Heterocyclic Carbene‐Catalyzed Oxidative Amidation of Aldehydes with Amines

AbstractThe N‐heterocyclic carbene (NHC)‐catalyzed oxidative amidation of aromatic aldehydes with amines in the presence of N‐bromosuccinimide (NBS) as an oxidant has been developed for the synthesis of amides. This amidation strategy is tolerant to both the electronic and the steric nature of the aryl aldehydes employed. The present methodology was extended to chiral amino acid derivatives to generate the corresponding amides in good yields and excellent ee values (>98%).magnified image

Phenazinium salt-catalyzed aerobic oxidative amidation of aromatic aldehydes.

Amides are prevalent in organic synthesis. Developing an efficient synthesis that avoids expensive oxidants and heating is highly desirable. Here the oxidative amidation of aromatic aldehydes is reported using an inexpensive metal-free visible light photocatalyst, phenazine ethosulfate, at low catalytic loading (1-2 mol %). The reaction proceeds at ambient temperature and uses air as the sole oxidant. The operationally easy procedure provides an economical, green, and mild alternative for the formation of amide bonds.

ChemInform Abstract: Oxidative Amidation of Aromatic Aldehydes with Amine Hydrochloride Salts Catalyzed by Silica‐Coated Magnetic Carbon Nanotubes (MagCNTs@SiO2)‐Immobilized Imine—Cu(I).

AbstractThe title catalyst can be easily separated due to its magnetic property and recycled without significant loss of its catalytic activity in five successive runs.

Oxidative amidation of aromatic aldehydes with amine hydrochloride salts catalyzed by silica‐coated magnetic carbon nanotubes (MagCNTs@SiO2)‐immobilized imine–Cu(I)

Mesoporous silica‐coated magnetic carbon nanotubes were prepared; their surface functionalization, followed by reaction with CuI, were carried out to develop a Cu‐grafted functionalized mesoporous material. This system is able to catalyze oxidative amidation of aromatic aldehydes with amine hydrochloride salts, generating amide derivatives in moderate to good yields. Magnetic properties of this catalyst led to easy separation as well as providing significant recyclability. Copyright © 2013 John Wiley & Sons, Ltd.

ChemInform Abstract: Direct Oxidative Amidation of Aromatic Aldehydes Using Aqueous Hydrogen Peroxide in Continuous Flow Microreactor Systems.

A practical and economical protocol has been developed for the direct oxidative amidation of aromatic aldehydes with secondary amines to synthesize amides in a single operation under mild conditions within 15–40 min. The utilization of aqueous hydrogen peroxide affords a clean synthetic route. No catalysts or promoting reagents are required.

Direct oxidative amidation of aromatic aldehydes using aqueous hydrogen peroxide in continuous flow microreactor systems

A practical and economical protocol has been developed for the direct oxidative amidation of aromatic aldehydes with secondary amines to synthesize amides in a single operation under mild conditions within 15–40 min. The utilization of aqueous hydrogen peroxide affords a clean synthetic route. No catalysts or promoting reagents are required.