Exploring benzylic -C(sp)-boron-silicon and boron-tin centers as a synthetic platform

A stepwise build-up of multi-substituted C sp 3 carbon centers is an attractive, conceptually simple, but often synthetically challenging type of disconnection. To this end, this report describes how gem -α,α-dimetalloid-substituted benzylic reagents bearing boron/silicon or boron/tin substituent sets are an excellent stepping stone towards diverse substitution patterns. These gem -dimetalloids were readily accessed, either by known carbenoid insertion into C-B bonds or by the newly developed scalable deprotonation/metallation approach. Highly chemoselective transformations of either the C-Si (or C-Sn) or the C-B bonds in the newly formed gem -C sp 3 centers have been achieved through a set of approaches, with a particular focus on exploiting the synthetically versatile polarity reversal in organometalloids by λ 3 -aryliodanes. Of particular note is the metal-free arylation of the C-Si (or C-Sn) bonds in such gem -dimetalloids via the iodane-guided C-H coupling approach. DFT calculations show that this transfer of the (α-Bpin)benzyl group proceeds via unusual [5,5]-sigmatropic rearrangement and is driven by the high-energy iodine( iii ) center. As a complementary tool, the gem -dimetalloid C-B bond is shown to undergo a potent and chemoselective Suzuki-Miyaura arylation with diverse Ar-Cl, thanks to the development of the reactive gem -α,α-silyl/BF 3 K building blocks. This work explores divergent reactivity of the benzylic gem -boron-silicon and boron-tin double nucleophiles, including the arylation of the C-B bond with Ar-Cl, along with a complementary oxidative λ 3 -iodane-guided arylation of the C-Si/Sn moiety.