The synthetic utility of magnesium bromide has been investigated, and it has been found that magnesium bromide is effective for the direct conversion of MOM ethers into alkylthiomehyl ethers in the presence of appropriate nucleophiles such as thiophenol and n-butanethiol. Magnesium bromide can be used as a mild and efficient reagent for the selective cleavage of MOM and MTM ethers in the presence of MEM ethers. The selective cleavage of SEM ethers in the presence of tertbutyldimethylsilyl ethers has been also performed successfully with magnesium bromide and n-butanethiol.