Alkoxymercuration

Alkoxymercuration is a two-step addition reaction of alkenes to alcohols in the presence of mercuric salts, followed by a reductive demercuration. In this process, an alkene reacts with mercuric acetate in an alcohol solvent to form an alkoxymercurial ether intermediate, which after reduction yields an alkyl ether. It is closely related to oxymercuration–demercuration and uses the alcohol as both solvent and nucleophile, delivering ethers in a Markovnikov-like regiochemical outcome without rearrangements.

The mechanism begins with the formation of a mercurinium ion from the alkene and Hg(OAc)2. The alcohol solvent (ROH) then attacks the more substituted carbon of the mercurinium ion, opening the ring and placing the OR group on that carbon. This step yields a beta-alkoxy mercurial intermediate, which, after deprotonation, gives an alkyl mercurial ether. Reductive demercuration, typically with sodium borohydride (NaBH4), removes the mercury and furnishes the corresponding alkyl ether, RO–R′, derived from the original alkene. The overall addition is anti across the double bond.

Scope and limitations include broad substrate compatibility with terminal and internal alkenes, and tolerance of several functional groups. The method provides a convenient route to alkyl ethers from alkenes under relatively mild conditions and avoids carbocation rearrangements common in other etherifications. However, the use of mercury reagents poses toxicity and environmental concerns, requiring careful handling and waste disposal. Safety-focused alternatives have been developed, but alkoxymercuration remains a useful transformation in selected synthetic contexts.