Ultrasound-promoted intramolecular direct arylation in a capillary flow microreactor.

An intramolecular direct arylation of various aryl bromides was performed using ultrasonic irradiation and a continuous flow capillary microreactor. The present procedure provided a higher functional group tolerance, ligand-free, milder reaction conditions and a shorter reaction time for the direct arylation compared with the conventional methods. The ultrasonic irritation not only greatly promoted the conversion and selectivity of the direct arylation, but also solved the clogging problem of the microreactor for solid-forming reaction and made the reaction run smoothly.