C-H Bond Activation Reaction [Synthetic Reagents]

　Recently, there have been a large number of reports on "C-H bond activation reaction". C-H bond activation is a methodology for directly forming carbon-carbon bonds by activating a carbon-hydrogen bond, which is the most fundamental linkage in organic chemistry. Traditional cross coupling reactions have been one of the most useful synthetic methods for the formation of carbon-carbon bonds. However, the cross coupling reaction requires extra procedures for preparing organic halides (or triflates) compounds, and organic boron or metal compounds. On the other hand, the C-H bond activation can reduce these procedures, thus making this reaction a cost-effective and eco-friendly system.

　C-H bonds generally have relatively high energy, therefore, the formation of a carbon-carbon or carbon-heteroatom bond by dissecting C-H bonds has been believed to be difficult. In 1993, Murai et al. reported the direct addition of C-H bonds of aromatic ketones to olefins in the presence of a catalytic amount of carbonyl(dihydrido)tris(triphenylphosphine)ruthenium(II) [C2251].¹⁾ Since then, numerous examples of C-H bond activation have been reported.