An easy access to highly versatile gem-silylboronate synthons is achieved by means of a new olefination reagent, HC(Bpin) (SiMe ). Subsequent silicon or boron-based selective functionalization allows for the modular and stereocontrolled synthesis of all-carbon tetrasubstituted alkenes. A particular attraction of this approach is the iododesilylation reaction, which becomes a pivotal tool for C-Si functionalization.

The synthesis of spiroheterocyclic structures with a pendant methylene boronate substituent has been accomplished to promote further functionalization. A Cucatalyzed borylative ring closing C−C coupling of an alkenyl halide is the key step toward the synthesis of [m.n]-spirocycles (m,n = 3−5). Computational studies on the mechanism reproduced all the experimental trends and explain the enhanced reactivity of systems leading to strained smaller rings. The optimized protocol also gives access to dispirocycle scaffolds, fully characterized by X-ray diffraction.

The adduct [MeO → Bpin-Bpin](-) efficiently mediates the β-boration of α,β-unsaturated imines formed in situ. The use of chiral phosphines as additives, and in particular the chiral phosphine (S)-MeBoPhoz, enables the catalytic asymmetric reaction to proceed with higher enantioselectivity than the analogue copper(I) mediated reaction.

Diboron reagents can be activated both, from a metal or free-metal context, and consequently the addition of boryl units to unsaturated substrates proceeds sometimes with complementary selectivity. We highlight here the power of boron chemistry to functionalize molecules and provide new routes towards challenging compounds.