AgOTf-Promoted Transetherification of p-Methoxybenzyl Ethers with Allyl and Benzyl Bromides

Conventional transetherification involves activation of the ether C-O bond, enabling either C-O/O-H bond metathesis with alcohols or C-O/C-O metathesis with other ethers. Here, we report an alternative approach based on an unusual C-O/C-Br bond metathesis. Silver triflate (AgOTf) promotes the transetherification of p-methoxybenzyl ethers (PMB-OR2 ) with allyl or benzyl bromides (R 1 -Br), selectively affording unsymmetrical ethers (R 1 -O-R 2 ). The reaction tolerates a wide range of functional groups that are incompatible with the strong bases required for Williamson ether synthesis. Furthermore, the method enables a three-component process involving R¹-Br, R²-Br, and PMBOH, where PMBOH acts as an "oxygen linker" through a sequential etherification/transetherification process. Mechanistic studies indicate a cationic pathway proceeding via a trialkyl oxonium intermediate.