The Formation of a Unique 2D Isonicotinate Polymer Driven by Cu(II) Aerobic Oxidation

The isolation and structural characterization of a unique Cu(II) isonicotinate (ina) material with 4-acetylpyridine (4-acpy) is provided. The formation of [Cu(ina)₂(4-acpy)]_n (1) is triggered by the Cu(II) aerobic oxidation of 4-acpy using O₂. This gradual formation of ina led to its restrained incorporation and hindered the full displacement of 4-acpy. As a result, 1 is the first example of a 2D layer assembled by an ina ligand capped by a monodentate pyridine ligand. The Cu(II)-mediated aerobic oxidation with O₂ was previously demonstrated for aryl methyl ketones, but we extend the applicability of this methodology to heteroaromatic rings, which has not been tested so far. The formation of ina has been identified by ¹H NMR, thus demonstrating the feasible but strained formation of ina from 4-acpy in the mild conditions from which 1 was obtained.

Binuclear O2 activation and hydrogen transfer mechanism for aerobic oxidation of alcohols

Density functional theory calculations reveal a binuclear O₂ activation and hydrogen transfer mechanism with spin-crossovers for aerobic oxidation of alcohols.

Palladium catalyzed chemo- and site-selective C-H acetoxylation and hydroxylation of oxobenzoxazine derivatives

An efficient protocol for the introduction of acetoxy and hydroxy functionalities on unactivated aryl sp2 carbons of oxobenzoxazine derivatives via an ortho-C-H activation reaction using a palladium catalyst has been developed for the first time. Interestingly, this intermolecular C-H functionalization reaction takes place in a facile and simple manner with high chemo- and site selectivity.

A Novel Catalytic role of Molecular Iodine in the Oxidation of Benzylic Alcohols: Microwave-Assisted Reaction

Molecular iodine was used to catalyse the oxidation of several benzylic alcohols to the corresponding ketones under the microwave-irradiated method, and the role of iodine was explored.

Copper-Promoted Functionalization of Organic Molecules: from Biologically Relevant Cu/O2 Model Systems to Organometallic Transformations

Copper is one of the most abundant and less toxic transition metals. Nature takes advantage of the bioavailability and rich redox chemistry of Cu to carry out oxygenase and oxidase organic transformations using O₂ (or H₂O₂) as oxidant. Inspired by the reactivity of these Cu-dependent metalloenzymes, chemists have developed synthetic protocols to functionalize organic molecules under enviormentally benign conditions. Copper also promotes other transformations usually catalyzed by 4d and 5d transition metals (Pd, Pt, Rh, etc.) such as nitrene insertions or C-C and C-heteroatom coupling reactions. In this review, we summarized the most relevant research in which copper promotes or catalyzes the functionalization of organic molecules, including biological catalysis, bioinspired model systems, and organometallic reactivity. The reaction mechanisms by which these processes take place are discussed in detail.

Application of dialkyl azodicarboxylate frameworks featuring multi-functional properties

The application of dialkyl azodicarboxylates as versatile reagents in Mitsunobu, oxidation, electrophilic, amination and carbonylation reactions is reviewed.

Iminium Ion and N-Hydroxyimide as the Surrogate Components in DEAD-Promoted Oxidative Ugi Variant

A practical metal-free oxidative Ugi-type three-component assembly has been achieved efficiently, employing a tertiary-amine-derived iminium ion as an imine surrogate, N-hydroxyimide as an acid surrogate, and DEAD as an oxidant. This dual-surrogate Ugi variant proceeded with a broad substrate scope and desired functional group tolerance, leading to a wide range of N-alkyl- N-acyl aminophthalimide and N-alkyl- N-acylaminosuccinimide derivatives in good isolated yields.

Copper-Catalyzed Aerobic Oxidative Amidation of Benzyl Alcohols

A Cu-catalyzed synthesis of amides from alcohols and secondary amines using the oxygen in air as the terminal oxidant has been developed. The methodology is operationally simple requiring no high pressure equipment or handling of pure oxygen. The commercially available, nonprecious metal catalyst, Cu(phen)Cl₂, in conjunction with di-tert-butyl hydrazine dicarboxylate and an inorganic base provides a variety of benzamides in moderate to excellent yields. The pK_a of amine conjugate acid and electronics of alcohol were shown to impact the selection of base for optimal reactivity. A mechanism consistent with the observed reactivity trends, KIE, and Hammett study is proposed.

Versatile and highly efficient oxidative C(sp3)–H bond functionalization of tetrahydroisoquinoline promoted by bifunctional diethyl azodicarboxylate (DEAD): scope and mechanistic insights

The oxidant–base bifunctionality of DEAD realized highly reliable cross dehydrogenative coupling of tetrahydroisoquinoline derivatives via aminal intermediates.

Mechanism of Copper/Azodicarboxylate-Catalyzed Aerobic Alcohol Oxidation: Evidence for Uncooperative Catalysis

Cooperative catalysis between Cu(II) and redox-active organic cocatalysts is a key feature of important chemical and enzymatic aerobic oxidation reactions, such as alcohol oxidation mediated by Cu/TEMPO and galactose oxidase. Nearly 20 years ago, Markó and co-workers reported that azodicarboxylates, such as di-tert-butyl azodicarboxylate (DBAD), are effective redox-active cocatalysts in Cu-catalyzed aerobic alcohol oxidation reactions [Markó, I. E., et al. Science 1996, 274, 2044], but the nature of the cooperativity between Cu and azodicarboxylates is not well understood. Here, we report a mechanistic study of Cu/DBAD-catalyzed aerobic alcohol oxidation. In situ infrared spectroscopic studies reveal a burst of product formation prior to steady-state catalysis, and gas-uptake measurements show that no O2 is consumed during the burst. Kinetic studies reveal that the anaerobic burst and steady-state turnover have different rate laws. The steady-state rate does not depend on [O2] or [DBAD]. These results, together with other EPR and in situ IR spectroscopic and kinetic isotope effect studies, reveal that the steady-state mechanism consists of two interdependent catalytic cycles that operate in sequence: a fast Cu(II)/DBAD pathway, in which DBAD serves as the oxidant, and a slow Cu(II)-only pathway, in which Cu(II) is the oxidant. This study provides significant insight into the redox cooperativity, or lack thereof, between Cu and redox-active organic cocatalysts in aerobic oxidation reactions.

Mechanistic insight into the aerobic oxidation of benzyl alcohol catalyzed by the CuII–TEMPO catalyst in alkaline water solution

The benzyl alcohol oxidation to benzaldehyde in the alkaline water solution catalyzed by Cu^II/L–TEMPO catalyst is investigated by density functional method. The favorable mechanisms and the role for the water ​have also been predicted.

Copper oxide as efficient catalyst for oxidative dehydrogenation of alcohols with air

Well-defined CuO nanoparticles are presented as catalysts in a new noble metal-free and green reaction protocol for carbonyl compound synthesis.

Copper Catalysts for Aerobic Oxidation of Alcohols

Inspired by reactions catalyzed by galactose oxidase, a copper-containing enzyme, extensive studies were carried out on copper-based catalysts for alcohol oxidation using O2 as the terminal oxidant. Significant advances have been made towards the development of homogeneous and heterogeneous copper catalysts. These advances over the past decades are reviewed.

Room temperature synthesis of a novel gamma-MnO2 hollow structure for aerobic oxidation of benzyl alcohol

A novel gamma-MnO(2) hollow structure has been synthesized at room temperature using a simple chemical reaction between MnSO(4) and KMnO(4) in aqueous solution without using any templates, surfactants, catalysts, calcination and hydrothermal processes. The synthesized gamma-MnO(2) hollow structure was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET analysis. It was found that the hollow structure consisting of short gamma-MnO(2) nanorods with diameters of 5-10 nm and lengths of 50-100 nm could form when the MnSO(4)/KMnO(4) mole ratio was equal to or larger than 2.3. The excess amount of Mn(2+) in solution was observed to promote the crystallization of gamma-MnO(2) nanorods and the formation of the gamma-MnO(2) hollow structure. In addition, the evolution of microstructure and morphology of the products obtained with a MnSO(4)/KMnO(4) mole ratio of 2.3 at different reaction times revealed that the hollow structure was formed via an Ostward ripening process. Furthermore, the obtained gamma-MnO(2) hollow structure was found to exhibit a better catalytic performance than conventional gamma-MnO(2) in the aerobic oxidation of benzyl alcohol to benzaldehyde, demonstrating its possible application in alcohol oxidation.

A Novel Environmentally Benign Method for the Selective Oxidation of Alcohols to Aldehydes and Ketones

In the presence of [Ru(terpyridine)(2,6-pyridinedicarboxylate)], aliphatic and benzylic alcohols are oxidized to the corresponding aldehydes or ketones with high selectivity by using hydrogen peroxide as the oxidant. There is no need for the addition of co-catalysts or organic solvents. By applying an optimized reaction protocol, high catalyst productivity (turnover number>10,000) and activity (turnover frequency up to 14,800 h(-1)) has been achieved.

Transition-metal- and organic-solvent-free: a highly efficient anaerobic process for selective oxidation of alcohols to aldehydes and ketones in water

A new system, I2-KI-K2CO3-H2O, selectively oxidized alcohols to aldehydes and ketones under anaerobic condition in water at 90 degrees C with excellent yields. The process is green, mild and inexpensive.