Copper(II) bromide as an efficient catalyst for acetal to bisarylmethyl ether interconversion

Acetals are conveniently and regioselectively transformed into monoprotected diols in the presence of bis(methoxyphenyl)methyl cation source and copper bromide in acetonitrile. The new reagent BMPMOiPr proved to be the most efficient for transprotection with 1,3-dioxolanes and 1,3-dioxanes.