Electrophilic Substitution at Azomethine Carbon Atoms. Reaction of Aromatic Aldehyde Hydrazones with Trifluoroacetic Anhydride

Article abstract of DOI:10.1021/jo00236a026

Reaction of dimethylhydrazones of aromatic aldehydes with trifluoroacetic anhydride at room temperature affords high yields of products bearing trifluoroacetyl groups.These electrophilic substitution reactions generally occur on the azomethine carbon, although competitive N-acylation is observed in highly electron-rich systems.Use of diisopropylhydrazones suppressed this N-acylation completely, leading to high yields of C-acylated products.The trifluoroacetyl hydrazones can be cyclized thermally to imidazole and oxadiazine derivatives and can be converted into 1-trifluoromethyl 1,2-diketones by acid hydrolysis.