Transition metal-catalyzed addition of a mono- and a diboron reagent to unsaturated carbon-carbon bonds provides an efficient and convenient route for the preparation of mono- and diboronic compounds. These compounds are versatile intermediates for the purposes of organic synthesis. Catalytic control of the chemo-, regio- and diastereoselective CB formation enables access to highly selective functionalized molecules by consecutive tandem sequences. Mechanistic insights involving concatenated reactions through boron chemistry are reviewed and discussed with particular emphasis on the role of the catalytic systems, the scope of the substrates and reagents, and the origin of the asymmetric induction. Recent developments in the cascade reaction from borylation or the formation of carbocycles via multiple carborhodation steps triggered by the rhodium-catalyzed intermolecular addition of organoboron are not covered, however, since they have been the object of other reviews .