Ruthenium Catalyzed Hydrohydroxyalkylation of Isoprene with Heteroaromatic Secondary Alcohols: Isolation and Reversible Formation of the Putative Metallacycle Intermediate

Abstract

Heteroaromatic secondary alcohols react with isoprene to form products of hydrohydroxyalkylation in the presence of ruthenium(0) catalysts generated from Ru3(CO)12 and tricyclohexylphosphine, enabling direct conversion of secondary to tertiary alcohols in the absence of premetallated reagents or stoichiometric byproducts. The putative oxaruthenacycle intermediate has been isolated, characterized and reversible metallacycle formation has been demonstrated.

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

“…66–68 Mechanistic studies corroborate a catalytic mechanism involving diene-carbonyl oxidative coupling to form an oxaruthenacycle. The transfer of hydrogen from the secondary alcohol reactant mediates transfer hydrogenolysis to release the products of C-C coupling and regenerate the activated ketone to close the catalytic cycle.…”

“…41,69 Beyond α-hydroxy esters, 66 these conditions are applicable to 3-hydroxy-2-oxindoles 67 and secondary alcohols substituted by certain heteroaromatic moieties. 68 In the latter case, the putative oxaruthenacycle intermediate was isolated, characterized and reversible metalacycle formation was demonstrated through experiments involving diene exchange.…”

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

“…[66][67][68] Mechanistic studies corroborate a catalytic mechanism involving diene-carbonyl oxidative coupling to form an oxaruthenacycle. The transfer of hydrogen from the secondary alcohol reactant mediates transfer hydrogenolysis to release the products of C-C coupling and regenerate the activated ketone to close the catalytic cycle.…”

Metal-catalyzed reductive coupling of olefin-derived nucleophiles: Reinventing carbonyl addition

“…Ruthenium(0) catalysis enables reductive coupling of dienes with activated ketones from the secondary alcohol oxidation level via hydrogen auto-transfer (36-38) (Figure 7). Mechanistic studies corroborate a catalytic mechanism involving diene-carbonyl oxidative coupling to form an oxaruthenacycle.…”

“…The regioselectivity of C-C coupling at the diene C4-position is unique among diene-carbonyl reductive couplings. Beyond α-hydroxy esters (36), this process applies to 3-hydroxy-2-oxindoles (37) and heteroaryl substituted secondary alcohols (38). In the latter case, the oxaruthenacycle intermediate was isolated and characterized and reversible metalacycle formation was established through experiments involving diene exchange.…”