Borylation and Silylation

The products, especially the C-B compounds, are useful for subsequent transformations. The C-B bond of arylboranes may also be oxidized to give a phenol. A one-pot 3-selective borylation-Suzuki coupling was 

---

Reaction of alkenes with boryl and silyl groups c/r-located at the C=C bond with alcohols is known to proceed in two different ways <1973S309, 1986JOM(310)151> by protolytic cleavage of the B-C bond and by complexation... 

The borylation and silylation of arenes and alkanes with borane and silane reagents are exceptions. 

More recently, a copper-bifluoride complex has been described, starting once again from the alkoxide species. Subsequently, [Cu(NHC)2] [HF2] complexes were developed (Figure 8.2) [91]. Both complexes were highly air stable in the solid state and moderately stable in solution compared to their analog [Cu(F) (IPr)] [92]. Remarkably, catalytic activity was observed in several transformations such as the reduction of ketones, the 1,4-conjugated borylation and silylation, and the diastereoselective allylation. 

Hartwig [117] published a timely review on the subject of arene C-H borylations and silylations in... 

Hartwig, J. F. Borylation and silylation of C-H bonds a platform for diverse C-H bond functionalizations. Acc. Chem. Res. 2012,45, 864-873. 

Notwithstanding the extremely rich and diverse reactivity presented above, all the examples presented thus far feature the addition of an NHC catalyst onto an sp carbon. Several reactions have been developed in the last ten years describing the activation of heteroatom o bonds by NHCs [8cj. The concept can be well illustrated by the recent work of Hoveyda and coworkers, who reported boryl and silyl conjugate additions to a,P-unsaturated carbonyls (Scheme 18.35) [124]. In both cases, addition of the NHC onto a trivalent boron atom activated the B-heteroatom bond. The use of Cj-symmetric imidazolinium salt 169 in the sUyl conjugate addition led to P-silyl ketones, esters, and aldehydes in good to high enantioselectivity. 

Activation of Boryl and Silyl Derivatives Catalyzed by NHCs... 

Boryl and silyl conjugate additions, according to Hoveyda and coworkers. 

---