Abstract The copper [I]-catalyzed exchange of bromine by methoxide in 5-bromovanillin and in 3, 5-dibromo-4-hydroxybenzaldehyde provides an efficient method for preparing 3, 5- dimethoxy-4-hydroxybenzaldehyde, from which 3, 4, 5-trimethoxybenzaldehyde is obtained by methylation with dimethylsulfate.
