Selective Cleavage of Allyl and Propargyl Ethers to Alcohols Catalyzed by Ti(O-i-Pr)4/MX n /Mg

Allyl and propargyl ethers were effectively deallylated or depropargylated to the parent alcohols via a C−O bond cleavage catalyzed by a low-valent titanium reagent (LVT), Ti(O-i-Pr)4/TMSCl/Mg or Ti(O-i-Pr)4/MgBr2/Mg, under mild reaction conditions. Differentiation between the allyl and propargyl ethers was achieved by the reaction in the presence of AcOEt as an additive. The reagent also catalyzed intra- and intermolecular cyclotrimerization reactions of alkynes to substituted benzenes.