Rapid and Simple Microwave-Assisted Synthesis of Benzoxazoles Catalyzed by [CholineCl][Oxalic Acid]

Microwave irradiation has been used to enhance the reaction yields and selectivities for organic transformation. In this paper, microwave irradiation (MW) was investigated for the environmentally benign synthesis of benzoxazoles through the cyclization of 2-aminophenols and benzaldehydes using deep eutectic solvent (DES) as a catalyst. The [CholineCl][oxalic acid] was easily synthesized from choline chloride with oxalic acid and used without further purification. [CholineCl][oxalic acid] catalyzed the synthesis of benzoxazoles to produce the desired product in a good to excellent conversion and selectivity under MW irradiation. The presence of [CholineCl][oxalic acid] helps to promote the rapid heating transfer from microwave irradiation into the reaction mixture. The [CholineCl][oxalic acid] can be recovered and reused several times without a considerable degradation in catalytic activity.

Automated summary

This paper investigates the environmentally friendly synthesis of benzoxazoles through the cyclization of 2-aminophenols and benzaldehydes using deep eutectic solvent (DES) as a catalyst under microwave irradiation. [CholineCl][oxalic acid] was synthesized and used as a catalyst, and it exhibited good conversion and selectivity. The presence of [CholineCl][oxalic acid] promoted the rapid heating transfer from microwave irradiation and it can be reused multiple times without significant degradation in catalytic activity.