The synthesis of biologically active 2‐substituted benzimidazoles and benzothiazoles was developed using Zn(L‐Pro)2 as catalyst in ethanol at room temperature in an aerobic oxidative cyclization reaction involving o‐phenylenediamine and 2‐aminothiophenol with various substituted aldehydes. This process offers a quick and eco‐friendly way to synthesize a variety of pharmacologically important benzothiazoles and benzimidazoles.
Microwave irradiated C–S cross-coupling reaction to synthesize 5-aryllthiobenzo-2,1,3-thiadiazole derivatives from a variety of benzene thiols with 5-bromo-2,1,3-benzothiadiazole, catalyzed by Cu(I) iodide and potassium carbonate as a cost-effective base in DMF, was conducted, affording excellent yields of the desired products. Microwave conditions assisted in the development of C–S cross-coupling reaction with higher yields.
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.
Buchwald precatalyst (XantPhos Pd-G3) was employed for the first time in a C-S cross-coupling reaction involving 2-(4-bromo phenyl) benzothiazole or 5-bromo-2,1,3-benzothiadiazole with various benzene thiols in DMF, K2CO3 as a base, under microwave irradiation at 80 oC, 200W. Good to excellent yields of the desired products were obtained under microwave conditions. Other significant benefits of this synthetic approach are low catalyst loading, short reaction times, and eco-friendly conditions. Additionally, we have successfully synthesized 29 compounds, some of which are new in this protocol.
Synthesis of bis-arylsulfenyl-benzo-2,1,3-thiadiazoles was accomplished using a Pd-G3 XantPhos as a simple and inexpensive catalyst. Numerous benzene thiols reacted well with 4,7-dibromo-benzo-2,1,3-thiadiazole in DMF, using K2CO3 as the base, obtaining high product yields in a short reaction time. Furthermore, all the synthesized compounds showed remarkable fluorescent properties with emission wavelengths in the visible range. Due to their unique properties, they might be used as image probes in fluorescence microscopy. The study found that these compounds have a wide range of potential applications in the area of sensors, as well as other photophysical properties.
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