Direct Conversion of Aryl/Alkyl Methyl Halides Into Aldehydes Using Commercially Available Ru(II) Complexes

The conversion of methyl halides into aldehydes often involves the nucleophilic substitution reaction of methyl halides with hydroxide to form alcohols, followed by the conversion of alcohols into aldehydes using a stoichiometric amount of oxidizing agents. The above transformation is also achieved by the Sommelet reaction that avoids the formation of an alcohol intermediate and employs the eco-friendly hexamethylenetetramine as the reagent. The Sommelet reaction works in the presence of a large amount of Brønsted acid, which hampers the sustainability of the reaction. Herein, our group reported three different catalyst systems developed from commercially available Ru complexes namely, [Ru(p-cymene)Cl₂]₂, [Ru(benzene)Cl₂]₂, and [Ru(1,5-cod)Cl₂]_n for the efficient conversion of aryl/alkyl methyl halides into corresponding aldehydes in very good to excellent yields while using hexamethylenetetramine as the reagent. All three developed catalyst systems were efficient for the facile conversion of aryl and alkyl methyl halides into aromatic and aliphatic aldehydes. The synthetic methodology was also extended for the synthesis of dialdehydes as well for the gram-scale synthesis of both napthaldehyde and succinaldehyde.