Direct, Redox-Neutral Prenylation and Geranylation of Secondary Carbinol C-H Bonds: C4-Regioselectivity in Ruthenium-Catalyzed C-C Couplings of Dienes to α-Hydroxy Esters

摘要

The ruthenium catalyst generated in situ from Ru_3(CO)_(12) and tricyclohexylphosphine, PCy_3, promotes the redox-neutral C-C coupling of aryl-substituted a-hydroxy esters to isoprene and myrcene at the diene C4-position, resulting in direct carbinol C-H prenylation and geranylation, respectively. This process enables direct conversion of secondary to tertiary alcohols in the absence of stoichiometric byproducts or premeta-lated reagents, and is the first example of C4-regioselectivity in catalytic C-C couplings of 2-substituted dienes to carbonyl partners. Mechanistic studies corroborate a catalytic cycle involving diene-carbonyl oxidative coupling.