Iron-Catalyzed Aerobic Oxidation Research Articles

One–pot synthesis of 1,2,4-triazole-Fused heterocycles via sequential condensation and iron-catalyzed aerobic oxidation

A one-pot method has been devised for the synthesis of 1,2,4-triazole-fused heterocycles. This method involves the condensation of commercially available (hetero)aromatic/aliphatic aldehydes and 2-hydrazinopyridine derivatives, succeeded by iron-catalyzed oxidation using O2 in air as the oxidant and without using any ligands or additives. The salient merits of this chemistry include broad substrate scope, simple operation, one-pot synthesis, and excellent functional group tolerance, as well as the use of air, a cheap and abundant iron catalyst, and ligand- and additive-free conditions. The efficacy of this synthetic method has been demonstrated through the synthesis of 30 examples of 1,2,4-triazole-fused heterocycles with diverse substituents in moderate to excellent yields. Furthermore, the successful synthesis of an antibacterial agent has been achieved with a satisfactory yield.

Iron-catalyzed aerobic oxidation of silyl ethers to carboxylic acids.

Direct aerobic oxidation of silyl ethers to carboxylic acids has been developed. The mild reaction conditions lead to a broad range of functional group compatibility. Different types of silyl groups have been investigated and selective deprotective oxidation has been realized. The reaction could be conducted under air.

Selective iron-catalyzed aerobic oxidation of alcohols in water to carboxylic acids mediated by additives

The iron catalyst (POM-Fe) could combine with chloride ions to form a supramolecular aggregate FeMo6·Cl, which was used in the oxidation of alcohols to carboxylic acids under mild conditions and can tolerate 40 substrates with moderate to high yield.

Iron-Catalyzed Aerobic Oxidation of Alcohols: Lower Cost and Improved Selectivity

An aerobic oxidation reaction of alcohols toward aldehydes or ketones using catalytic amounts of Fe(NO3)3·9H2O, 4-OH-TEMPO, and NaCl has been developed. Compared with the former catalytic system with TEMPO developed in this group, the new protocol using 4-OH-TEMPO, which is much cheaper on an industrial scale, accomplished the transformation with a higher selectivity, especially for aliphatic alcohols toward aldehydes. α,β-Unsaturated alkynals or alkynones can be efficiently synthesized from propargyl alcohols, which has been much less studied in the literature.

Systematic Evaluation of 2-Arylazocarboxylates and 2-Arylazocarboxamides as Mitsunobu Reagents.

2-Arylazocarboxylate and 2-arylazocarboxamide derivatives can serve as replacements of typical Mitsunobu reagents such as diethyl azodicarboxylate. A systematic investigation of the reactivity and physical properties of those azo compounds has revealed that they have an excellent ability as Mitsunobu reagents. These reagents show similar or superior reactivity as compared to the known azo reagents and are applicable to the broad scope of substrates. p Ka and steric effects of substrates have been investigated, and the limitation of the Mitsunobu reaction can be overcome by choosing suitable reagents from the library of 2-arylazocarboxylate and 2-aryl azocarboxamide derivatives. Convenient recovery of azo reagents is available by one-pot iron-catalyzed aerobic oxidation, for example. SC-DSC analysis of representative 2-arylazocarboxylate and 2-arylazocarboxamide derivatives has shown high thermal stability, indicating that these azo reagents possess lower chemical hazard compared with typical azo reagents.

Studies on Iron-Catalyzed Aerobic Oxidation of Benzylic Alcohols to Carboxylic Acids

A comprehensive study on aerobic oxidation of benzylic alcohols­ to carboxylic acids with a catalytic amount each of Fe(NO3)3·9H2O, TEMPO, and KCl is conducted. Various synthetically useful functional groups are well tolerated in the reaction. Distinct electronic and steric effects are observed in the reaction: electron-withdrawing groups accelerate the reaction while electron-donating groups make the reaction slower, and ortho-substituted substrates react slower than meta-substituted substrates. Several large-scale reactions (100 mmol) are conducted using a slow air flow of 30 mL/min to demonstrate the practicality of this method in an academic laboratory.

Iron-Catalyzed Aerobic Oxidation and Annulation Reaction of Pyridine and α-Substituted Allenoate toward Functionalized Indolizine.

An iron-catalyzed reaction of pyridine and α-substituted allenoate has been disclosed. The present strategy incorporates the aerobic oxidation into annulation involving substituted allenoate, thus providing a new access to functionalized indolizine.

Iron-Catalyzed Aerobic Oxidation of (Alkyl)(aryl)azinylmethanes

An iron-catalyzed aerobic oxidation of (alkyl)(aryl)azinylmethanes has been developed leading to tertiary alcohols in moderate to good yields. Hock rearrangement was identified as a major side reaction leading to a complex mixture of undesired products. Addition of thiourea sometimes allows inhibiting this side reaction and steers the reaction towards the desired products.

Synthesis of Benzimidazoles via Iron-Catalyzed Aerobic Oxidation Reaction of Imine Derivatives with o-Phenylenediamine

A simple and efficient protocol for preparing benzimidazoles via Fe(NO3)3 · 9H2O-catalyzed aerobic oxidation reaction of imine derivatives with o-phenylenediamine. This process uses air as an economical and green oxidant, tolerates a wide range of substrates, and affords the targeted benzimidazoles in moderate to excellent yields.

Iron-Catalyzed Aerobic Oxidation of Allylic Alcohols: The Issue of C═C Bond Isomerization

An aerobic oxidation of allylic alcohols using Fe(NO3)3·9H2O/TEMPO/NaCl as catalysts under atmospheric pressure of oxygen at room temperature was developed. This eco-friendly and mild protocol provides a convenient pathway to the synthesis of stereodefined α,β-unsaturated enals or enones with the retention of the C-C double-bond configuration.

ChemInform Abstract: Recyclable Mitsunobu Reagents: Catalytic Mitsunobu Reactions with an Iron Catalyst and Atmospheric Oxygen.

Aerobic recycling: A catalytic amount of a hydrazine reagent is sufficient to promote Mitsunobu reactions in the presence of triphenylphosphine, an iron catalyst, and air. The active form of the catalyst, an azo species, can be readily generated by iron-catalyzed aerobic oxidation. MS = molecular sieves, Pc = phthalocyanine.

Recyclable Mitsunobu Reagents: Catalytic Mitsunobu Reactions with an Iron Catalyst and Atmospheric Oxygen

Aerobic recycling: A catalytic amount of a hydrazine reagent is sufficient to promote Mitsunobu reactions in the presence of triphenylphosphine, an iron catalyst, and air. The active form of the catalyst, an azo species, can be readily generated by iron-catalyzed aerobic oxidation. MS = molecular sieves, Pc = phthalocyanine.

Synthesis of β-hydroxyphosphonates by iron-catalyzed oxidative addition of phosphonyl radicals to alkenes

Phosphorohydrazidates have been shown to work as radical precursors by iron-catalyzed aerobic oxidation to generate corresponding phosphonyl radicals. Generated radicals cause intermolecular addition to various alkenes in the presence of molecular oxygen to give β-hydroxyphosphonate compounds in good yield.

Numerical Modeling of Sulfur and Nitrogen Chemistry in a Narrow Cold-Frontal Rainband: The Impact of Meteorological and Chemical Parameters

Abstract To better understand the impact of various meteorological and chemical parameters on chemical deposition from winter storms, the chemistry and microphysics of a narrow cold-frontal rainband and its associated stratiform region were examined with a two-dimensional numerical cloud model. The peak precipitation was associated with the lifting at the leading edge of the cold front. However, the peak sulfate deposition occurred behind the primary updraft, where melting graupel was the dominant source of precipitation, and in the leading rainband. The peak nitrate deposition occurred behind the main updraft and at the leading edge of the main updraft. Sulfur dioxide, aerosol nitrate, and peroxyacetylnitrate were transported to higher altitudes, while aerosol sulfate, nitric acid, and hydrogen peroxide were depleted by the storm. Examination of the pathways for oxidizing aqueous sulfur dioxide showed that iron-catalyzed aerobic oxidation was an important mechanism for converting sulfur dioxide to sulfat...