[Cp*IrCl2]2 catalyzed hydroborations of alkenes using a bulky dioxaborocine

4,8-Di-tert-butyl-2,10-dimethyl-12H-dibenzo[d,g][1,3,2]dioxaborocine (1) has been prepared in high yield by the addition of H3B·SMe2 to 6,6′-methylene(2-tert-butyl-4-methylphenol). Dioxaborocine 1 is a relatively stable solid that reacts with a variety of aliphatic alkenes in the presence of catalytic amounts of [Cp*IrCl2]2 to give the terminal hydroboration products. Analogous reactions with vinylarenes, however, afford the corresponding alkenylboronate esters along with equal amounts of the hydrogenation products. Boron products have been characterized by a number of physical and analytical methods, including single-crystal X-ray diffraction studies.