Synthesis of benzothiazole from 2-aminothiophenol and benzaldehyde catalyzed by alkyl carbonic acid

Abstract

A simple and green method was developed for the reaction of 2-aminothiophenol and benzaldehyde in the self-neutralizing acidic CO₂-alcohol system to produce benzothiazoles. A series of benzothiazole derivatives were successfully prepared from the condensation and cyclization reaction of 2-aminothiophenol or substituted 2-aminothiophenol with aliphatic, heteroaryl and aryl aldehydes promoted by alkyl carbonic acid under mild conditions. Moreover, the method is also suitable for the synthesis of 2-phenylbenzimidazole and 2-phenylbenzoxazole. Additionally, this reaction system greatly simplified post-processing, which did not need to be neutralized with base and without salt disposal. These advantages make the process more practical, economical, and environmentally friendly. Mechanism investigation indicated that formation of alkyl carbonic acid from CO₂ and methanol is the key intermediate, which provides hydrogen ions to catalyze the reaction of 2-aminothiophenol and benzaldehyde.

Graphical Abstract

Keywords:

• Alkyl carbonic acid
• 2-aminothiophenol
• benzothiazole derivatives
• synthetic method
• benzaldehyde

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

This work was supported by the Program for Grassland Excellent Talents of Inner Mongolia Autonomous Region, the National Natural Science Foundation of China (21865020), the Natural Science Foundation of Inner Mongolia (No. 2019LH02009 and No. 2021ZD02), the Innovation Team of CO₂ Resource Utilization in Universities of Inner Mongolia Autonomous Region, and the Program for Young Talents of Science and Technology at Universities of Inner Mongolia Autonomous Region (2019).