Synthetic Applications of C–O and C–E Bond Activation Reactions

Merging the Norrish type I reaction and transition metal catalysis: photo- and Rh-promoted borylation of C–C σ-bonds of aryl ketones

“…as aryl sources instead of aryl halides in various cross-coupling reactions and functionalization reactions. 1 On the other hand, the use of aryl ketones as substrates has been a great challenge because cleavage of strong C–C σ-bonds is involved to generate arylmetal species. Although catalytic C–C bond activation reactions of ketones have been developed extensively since the discovery of the Rh-catalyzed hydrogenolysis of the C–C σ-bond α to a carbonyl group in 1994, 2 substrates are mostly limited to small-membered cyclic ketones and well-designed ketones bearing directing groups to facilitate oxidative addition of C–C bonds.…”

Palladium-catalyzed addition of acylsilanes across alkynesviathe activation of a C–Si bond

“…1a, top). 3 Although the cleavage of a C–Si bond can occur using complexes bearing an X-type ligand, the mechanism involves a transmetallation, during which the silicon group is eliminated, thus making it unsuitable for use in carbosilylation reactions (Fig. 1a, bottom).…”

Nickel-catalyzed direct methylation of arylphosphines via carbon–phosphorus bond cleavage using AlMe3

“…Initial formation of phosphine-aluminum adduct 1-AlMe 3 would reduce the electron density of the C(aryl)-P bond in 1, thereby facilitating oxidative addition to a Ni(0) catalyst to form intermediate A. 17 3b). Intermediate B is supported by the observation of a trace amount of Me-Ar F by GC-MS, which is likely formed by reductive elimination from B.…”

“…Initial formation of phosphine-aluminum adduct 1-AlMe 3 would reduce the electron density of the C(aryl)–P bond in 1 , thereby facilitating oxidative addition to a Ni(0) catalyst to form intermediate A . 17 A methyl group on the aluminum center in A is subsequently transferred to nickel via transmetallation to generate the Me–Ni–Ar intermediate B and aluminum phosphide C . 7 The formal nucleophilic attack by a phosphide fragment in C to the methyl group in B via a cyclic transition state TS results in the formation of methylated phosphine 2 and Ar–AlMe 2 D with the regeneration of Ni(0).…”