Ultrasound Irradiation Promoted Catalyst-Free Construction of Formamidine Framework Using Isocyanide as Building Blocks.

Reactions of isocyanides with 2-mercaptobenzothiazole and 2-mercaptobenzoxazole afforded a series of compounds containing formamidine framework in moderate to high yields. These organic transformations were performed under mild and catalyst-free conditions. In addition to promoting the reactions, the use of ultrasound irradiation also allowed the process to be carried out under air atmosphere. A possible reaction mechanism was proposed based on the experimental results.