Practical Phosphomolybdate-Catalyzed Hydroboration of Carbon-Carbon Triple and Double Bonds

Organoboron compounds are important intermediates in contemporary organic synthesis, but their radical synthetic strategy remains challenging due to their inherent instability. Polyoxometalate clusters (POMs) have emerged as an important class of catalysts because of their multiple active sites, high stability, and catalytic activity. Herein, we report a Keggin polyoxometalate (PMo₁₂O₄₀^3-) cluster for the radical hydroboration of alkynes and alkenes. Mechanistic studies show that an intervalence charge transfer transition (IVCT) from Mo^V to Mo^VI enables the generation of boryl-centered radicals under mild conditions. This work demonstrates the phosphomolybdate clusters featuring unique multiple Mo sites and strong electron reservoir properties, which promotes efficient C-B bond forming reactions. The catalyst is compatible with a variety of alkynes and alkenes and functional groups for delivering hydroborated products in green solvents. Moreover, the application of this method is also showcased by the gram-scale synthesis, catalyst recycling, and further modifications of the product.