A simple, efficient, and eco-friendly aerobic procedure for synthesis of 2-substituted benzothiazoles catalyzed by facile prepared [N 2222 ][Pro] in a biomass medium (ethyl lactate) has been developed. The reactions afford the target 2-arylbenzothiazoles in good to excellent yields ([80 %) under air condition and was observed without use of chromatography. In addition, this proline-based ionic liquid catalyst can be easily recycled six times without loss of catalytic activity in gram scale synthesis.
Lactic acid is recognised as a biocompatible medium for the chemoselective synthesis of the 1,2-disubstituted benzimidazole scaffold via a direct one-pot cyclocondensation of o-phenylenediamine with aldehydes. Various 1,2-disubstituted benzimidazole derivatives were successfully synthesised with high selectivity with good to excellent yields without any additional catalyst or additive. Most products could be isolated by a simple filtration after completion of the reactions. Satisfactory results were also obtained from multi-gram scale reactions.
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