Benzisoxazole core and benzoxazolopyrrolidine via HDDA-derived benzyne with PTIO/DMPO

A novel method for HDDA-derived benzyne trapped by nitrone was developed. This research described a simple and efficient pathway for the synthesis of benzisoxazoles from arynes and PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl), C−C and C−O bonds were formed in a single step without catalyst under mild conditions. The unexpected cleavage of C−N bond contributed to the formation of isoxazole ring, as indicated by DFT studies. Furthermore, we obtained the structure of benzoxazolopyrrolidine when the trapping agent is DMPO (5,5-dimethyl-1-pyrroline N-oxide).