Pd/RHA and Pd/BPA as Eco-Friendly Heterogeneous Catalysts: Microwave-Assisted C–S Cross-Coupling Reaction in DMF

Abstract

First time, Pd-Rice Husk Ash (Pd/RHA) and Pd-Banana Peel Ash (Pd-BPA) were used as eco-friendly catalysts in the C–S cross-coupling reaction of 5-bromo-2,1,3-benzothiadiazole with various benzene thiols in DMF under microwave irradiation at 75 °C, 200 W (100 psi) for 15–25 min. These catalysts were produced from agro-industrial wastes, such as rice husk ash and banana peel ash. These can be recycled and reused up to five catalytic cycles without loss of catalytic efficiency.

Nucleophilic Aromatic Substitution of Heteroaryl Halides with Thiols

“…It was remarkable that reaction at room temperature was seen in the case of 5-bromobenzo­[ c ]­[1,2,5]­thiadiazole, while this coupling reaction with thiols under the catalysis of Pd complexes was specially investigated in a recent paper to examine the fluorescent properties of related coupling products . Our observation demonstrated that no catalyst was needed for this transformation ( 7l ).…”

Pyrrolidinium Acetate (PyrrIL) as a Green and Recyclable Catalyst: Synthesis of 2-Phenyl Benzimidazoles and 2-Phenyl Benzothiazoles under Solvent-Free Conditions at Room Temperature

“…The above-mentioned reports contain drawbacks, such as the use of hazardous reagents, solvents, expensive catalysts, prolonged reaction times, high temperatures, and harsh reaction conditions, as well as the formation of unwanted products. The methodologies employing green catalysts, such as non metal salts, heterogeneous recyclable catalysts, or ionic liquids, [44][45][46][47][48][49][50][51] and green solvents, or solvent-free or microwave or ultrasonic conditions [52][53][54] , are desirable to promote sustainable ecofriendly research. [55][56][57] In this regard, ionic liquids (ILs) have shown promising results in a variety of synthetic processes because of their great selectivity and catalytic efficiency.…”