Hydroarylation of Olefins with Complexes Bearing d ⁸ Metal Centers

Mechanistic Interrogation of Alkyne Hydroarylations Catalyzed by Highly Reduced, Single-Component Cobalt Complexes

“…Chelation-assisted C–H activations allow selective functionalization of unreactive C–H bonds, thereby accessing atom-economical, late-stage molecular modifications without the installation of wasteful cross-coupling partners. − In this context, hydroarylation has emerged as an attractive method to form C–C bonds via the addition of activated aryl C–H bonds across olefins or alkynes. In the past two decades, catalyst development for such reactions has been aided by mechanistic investigations. ,− The first report of olefin hydroarylation from the Murai group , described RuH 2 (CO)­(PPh 3 ) 3 as the pre-catalyst, and more recent advances in hydroarylations are based on pre-catalysts bearing a metal center with a square-planar d 8 or octahedral d 6 configuration (e.g., Rh, − Ir, − Pd, and Pt − ).…”

“…Chelation-assisted C–H activations allow selective functionalization of unreactive C–H bonds, thereby accessing atom-economical, late-stage molecular modifications without the installation of wasteful cross-coupling partners. − In this context, hydroarylation has emerged as an attractive method to form C–C bonds via the addition of activated aryl C–H bonds across olefins or alkynes. In the past two decades, catalyst development for such reactions has been aided by mechanistic investigations. ,− The first report of olefin hydroarylation from the Murai group , described RuH 2 (CO)­(PPh 3 ) 3 as the pre-catalyst, and more recent advances in hydroarylations are based on pre-catalysts bearing a metal center with a square-planar d 8 or octahedral d 6 configuration (e.g., Rh, − Ir, − Pd, and Pt − ). Significantly, mechanistic studies with these second- and third-row transition metal catalysts implicate a rate-limiting C–H addition. − By comparison, far fewer first-row transition metal hydroarylation catalysts have been identified, despite recent efforts to exploit the high abundance and low costs of Fe, Co, , and Ni. − Future catalyst designs should rely on mechanistic information that is largely non-existent, and notably, first-row metals often engage in mechanisms that are distinctly different from those of heavier transition metals. ,, …”

Olefin Hydroarylation Catalyzed by a Single-Component Cobalt(-I) Complex

“…Recent developments in metal-mediated C–H bond activation chemistry have enabled new catalytic transformations to generate value-added products. − Late-stage C–H functionalizations present attractive alternatives to molecular elaboration methods such as cross-coupling, which require sacrificial, costly, and often toxic reagents. In particular, olefin and alkyne hydroarylations have provided atom-economical routes for formation of C–C bonds. − The Murai group , described the first hydroarylation precatalyst, RuH 2 (CO)­(PPh 3 ) 3 , and subsequent developments involving heavier, late-transition metal catalysts (i.e., with Rh, − Ir, − Pd, − and Pt − ) illustrated the synthetic value of hydroarylation as a convenient transformation for C–H bond diversification. However, given the low abundance and high cost of such metals, it is important to develop efficient catalysts based on environmentally benign first-row metals.…”