ルテニウム触媒を用いる配位性官能基近傍の炭素-水素結合のケイ素化およびホウ素化

抄録

During the past few years, considerable attention has been devoted to the functional-group-directed functionalization of C-H bonds through nearby heteroatom coordination to the metal center of the catalyst. We found that 1,1,1,3,5,5,5-heptamethyltrisiloxane promoted the Ru-catalyzed intermolecular dehydrogenative coupling. The C(sp²)-H silylation of aromatic compounds, such as aryloxazolines, arylimines, arylpyridines, and benzamides, took place at ortho-positions of the benzene ring. In the case of 2-alkyloxazolines, the C(sp³)-H silylation took place site-selectively at methyl C(sp³)-H bonds located γ to the nitrogen atom of oxazolyl groups. Based on DFT calculations and KIE experiments, we proposed a catalytic cycle involving the rate-determining C(sp³)-Si bond formation step. Also, we have developed a Ru-catalyzed N(sp²)-directed C(sp²)-H borylation using pinacolborane. DFT calculations and KIE experiments suggest that the catalytic cycle should involve oxidative addition of the C(sp²)-H bond, the rate-determining σ-bond metathesis of pinacolborane with the ruthenium hydride complex, and reductive elimination of the C(sp²)-B bond.