Palladium-Catalyzed trans- and cis-Carboboration of Alkynes Tethered to Chloroborane with Organozirconium Reagents: Ligand-Dependent Complementary Stereoselectivity

摘要

There are increasing demands for organoboronic acid derivatives in synthetic organic chemistry because they exhibit remarkable reactivities upon appropriate activation, while being stable, storable, and nonpoisonous. Their applications are spreading over the pharmaceutical and material sciences in recognition of the unique properties of organoboron compounds. Therefore, development of efficient methods for the synthesis of stereodefined, functionalized organoboronic acids is highly desirable. Catalytic borylation reactions have gained much attention with respect to efficiency, selectivity, and functional group compatibility. Recent efforts have focused on the additions of boron-element bonds across carbon-carbon multiple bonds, such as diboration and silaboration. Our attention has been focused on the development of catalytic carboboration reactions, in which B-C and C-C bonds are formed concurrently. We have so far reported two distinctive classes of carboborations, i.e., direct and trans-metalative carboborations.