Opportune gem-Silylborylation of Carbonyl Compounds: A Modular and Stereocontrolled Entry to Tetrasubstituted Olefins.

An easy access to highly versatile gem-silylboronate synthons is achieved by means of a new olefination reagent, HC(Bpin)2 (SiMe3 ). 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.

Asymmetric metal free ß-boration of α,ß-unsaturated imines assisted by (S)-MeBoPhoz.

The adduct [MeO → Bpin-Bpin](-) efficiently mediates the ß-boration of α,ß-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.