Here, we report highly efficient deoxygenative chlorination of aldehydes and alcohols with a dichloromethyl methyl ether and TiCl 4 system. The method converts various aldehydes and alcohols into the desired geminal dichlorides or chlorides with good to excellent yields (up to 99 %). Combined with a subsequent Rieche formylation step using the same reagent system, this method provides an efficient approach for synthesis of aromatic dialdehydes. This strategy involves deoxychlorination of the aryl aldehydes followed by a second formylation of more activated benzal chloride derivatives. Dialdehydes can be easily obtained by hydrolyzing the corresponding of dichloromethyl derivative.

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