α-C(sp3)-H Acetalization of Cyclic and Aliphatic Ethers Mediated by N-Bromoamides.

A facile and catalyst-free method for the α-C(sp3)-H acetalization of cyclic and aliphatic ethers mediated by N-bromoamide DBDMH is reported. The reaction proceeds under mild conditions and exhibits a broad substrate scope. Common ethers, such as THF and Et2O, as well as a variety of functionalized alcohols, were efficiently transformed, affording the corresponding acetals in high yields. The developed protocol was further applied to the synthesis of the fragrances Cyanophyll and Efetaal, highlighting its practical utility. Mechanistic studies indicate that the impurities in commercial DBDMH such as molecular bromine and acids were crucial for the high reaction efficiency.