2-[(Neopentyl glycolato)boryl]phenyl Triflates and Halides for Fluoride Ion-Mediated Generation of Functionalized Benzynes

2-[(Neopentyl glycolato)boryl]phenyl tri-fluoromethanesulfonates (triflates) and halides have been developed as new benzyne precursors, which generate benzynes at 120 degrees C in the presence of a fluoride ion. There are two major features of these types of precursors. First, they generate benzynes bearing various reactive functional groups, such as carbonyl, cyano, bromo, and primary amino groups. Second, these precursors were directly synthesized through either the palladium-catalyzed Miyaura borylation of 2-iodophenol derivatives or ortho-selective iodination of the corresponding boronic acids as key steps without using any protecting groups. The in-situ-generated benzynes underwent [4+2], (3+2), and [2+2] cycloadditions to give the benzo-fused multicyclic compounds while maintaining such functional groups. In particular, 4-aminobenzyne was generated for the first time and underwent the Diels-Alder reaction with the free primary amino group remaining intact.