Current Catalysis - Volume 11, Issue 1, 2022

Alkyne carboxylic acid derivatives are stable, non-toxic, inexpensive, and commercially available. They are prevalent intermediates for various synthetic transformations. In recent years, decarboxylative oxidative alkynylation reactions involving direct C−H bond activation of diverse carbo- and hetero-cycles with alkyne carboxylic acid have attracted more and more interest from the synthetic community. The joy and challenges of direct oxidative decarboxylative alkynylation have been discussed in detail to enlighten this highly emerging area. More emphasis is being placed on the fascinating implementation and advancement of various methods for the formation of C(SP²)-C(SP) bonds. This short review mainly focuses on developments of the decarboxylative oxidative alkynylation reaction, considering the uniqueness of each protocol by highlighting the substrate scope, selectivity, and yields in conjunction with mechanistic insights.

The synthesis of organoboron compounds was accomplished using borylation catalyzed by palladium. This reaction is ubiquitous due to its widespread utility in coupling reactions and allied applications in synthesis. The attraction of borylation in organic synthesis has been attributed to moderate conditions associated with the reactions and tolerance to different types of functional groups. Their applications spread across pharmaceutical, medical, agricultural and other fields. This review summarizes the recent advances in palladium-catalyzed borylation halides and covers literature from (2012-2021).

Iron-catalyzed C–H amination reactions have emerged as a potent tool in synthetic organic chemistry in recent years. These reactions are eco-friendly, highly catalytic efficient, and show good functional group tolerance. The organonitrogen products of the reaction have found wide applications in agricultural chemistry, medicinal chemistry, industrial chemistry, and natural product synthesis. This review focuses on the recent progress in iron-catalyzed C–H amination reactions and covers literature from 2019-2021.

Introduction: Alumina-supported nickel-iron-ruthenium-based catalyst with a high surface area (200 m² g^-1) was synthesized via an impregnation method and tested for dry reforming of methane. Methods: The prepared catalyst was characterized by different analytical techniques, such as Xray diffraction, X-ray fluorescence, N2 sorption, environmental scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). Result: The results revealed that the catalyst contains 2.5 wt.% Ni, 2 wt.% Fe and 1.8 wt.% Ru. Conclusion: The catalytic tests showed that the prepared sample exhibits remarkable catalytic activity towards methane dry reforming, with high conversion of methane and carbon dioxide reaching up to 92% and 89%, respectively, at 800°C.

Background: The 4-thiazolidinone-5-carboxylic acid and its derivatives have diverse applications in agriculture, industrial and pharmaceutical fields. Therefore, the synthesis of this heterocyclic compound attracted much attention from researchers with green chemistry protocols. In this research work, we have introduced the green protocol for the synthesis of 4-thiazolidinone- 5-carboxylic acid by keeping the parameters in mind like cost-effective, environmentally benign, short reaction time and easy work-up procedure. Methods: Initially, we irradiated the mixture of substituted aldehyde, thiosemicarbazide and furan 2-5-dione in the presence of choline chloride-thiourea-based Deep Eutectic Solvent (DES) as a green medium. The reaction optimization was performed in different solvents like ethanol, glycerol, and PEG-400. Results: The DES, which was used as a green solvent, produced an excellent result in context to short reaction time, yield, easy workup, mild reaction condition and cost-effective protocol. All the results are discussed. Conclusion: The DES-mediated synthesis of 4-thiazolidinone-5-carboxylic acid is found to be an excellent protocol, which followed green chemistry principles. This method has specific features like mild reaction conditions, environmentally benign, cost-effective and easy workup procedure.

Background: Phenol and its derivatives exist in water bodies due to the discharge of polluted wastewater from industrial, agricultural, and domestic activities into water bodies. Various industries like pharmaceutical, petrochemical and coal processing industries discharge phenolic compounds into water bodies. Phenol and substituted phenols are quite toxic to humans. Objective: Oxidative destruction of phenol in water was carried out at ambient temperature by using laboratory-synthesized goethite and commercial Fe2O3, TiO2, and MnO2 as catalysts in the presence and the absence ofH2O2. Methods: The reactions were carried out in a batch reactor in 100 mL conical flasks. After mixing the reactants (Phenol and H2O2) and the catalyst in appropriate amounts, the flasks were capped, and the contents were agitated in a water bath shaker (NSW, India) at a constant temperature of 300 K for a predetermined time interval. Results: The results have been characterized in terms of percentage destruction of the Phenol. The catalyst Goethite was able to bring about 15.8 to 23.5% destruction as the reactant-H2O2 mole ratio was increased from 1:1 to 1:20 with a fixed catalyst load of 0.2 gL^-1. The total conversion of phenol increases smoothly with an increase in the reaction time from 60 to 300 min in all cases except Fe2O3, in which case the reaction does not advance after 60 min. Interestingly, the catalyst MnO2, brings about 94.4 % oxidative conversion of phenol with the same loading in the absence of H2O2, i.e., in wet air oxidation. It is also found that a 1:1 mixture of MnO2 + TiO2 gives 100 % conversion for a catalyst load of ≥ 6 gL^-1 in the absence of H2O2. Conclusion: It is found that phenol could be completely oxidized to harmless end products at room temperature. For this purpose, MnO2 has been found to be the most active catalyst among the ones tested, whether H2O2 is present or not in the reaction mixture. The three oxides Fe2O3, goethite and TiO2 can perform better only in the presence of H2O2.

1-(2-aminoethyl)-3-methylimidazolium bromide [Aemim]Br ionic liquid acted as a catalyst as well as a solvent in the Knoevenagel condensation reaction. The extent of products formed with high yield and more flattering for the synthesis of aliphatic and aromatic esters. The [Aemim] Br can be recycled for 6 runs without great loss of activity. Background: The Knoevenagel condensation was one of the fundamental reactions in organic chemistry both at the laboratory and industrial levels. Objective: An effective method for the condensation of a variety of aliphatic and aromatic carbonyl compounds with ethyl acetoacetate and subsequent hydrolysis to corresponding α, β - unsaturated esters in [Aemim]Br was achieved. Methods: The weighed quantity of [Aemim]Br, an aldehyde and ethyl acetoacetate were carried out at 25°C. The reaction commenced instantaneously making the reaction mixture highly viscous. The product was extracted with ether. The combined organic extracts were dried using anhydrous sodium sulphate, evaporated under reduced pressure and assayed on GC. Results: We could achieve to get Knoevenagel condensation with good yield. Conclusion: An effectual procedure for Knoevenagel condensation of a variety of aliphatic and aromatic aldehydes with active ethyl acetoacetate arises smoothly in the presence of [Aemim]Br without any additional solvents. This is the best method that proved an effective green industrial process.