Mild, Stereoselective, and Highly Efficient Synthesis of N-Acylhydrazones Mediated by CeCl3·7H2O in a Broad Range of Solvents

In a mild and practical approach, hydrazides and aldehydes underwent condensation reactions that were mediated by cerium(III) chloride to be rapidly converted into N-acylhydrazones. This method uses a minimal catalytic amount of cerium(III), is stereoselective, and offers several unique features, such as compatibility with aryl, heterocyclic, alkenyl, and sensitive functional groups as well as the ability to prepare N-acylhydrazones from highly hindered substrates. More strikingly, cerium(III) efficiently mediated the reaction with less reactive substrates such as diaryl and alkyl aryl ketones, when classical protocols without the catalyst were not effective. This method enables the synthesis of a structurally diverse library of N-acylhydrazones that have applications in synthetic and medicinal chemistry.