N-Acetylation of methyl hydrazones with acetic acid in presence of PdCl₂

Abstract

All reagents were used as purchased from commercial suppliers without further purification. The 1H-NMR spectra were recorded on an 400 MHz instrument using solvent as an internal standard (CDCl3-d1). Column chromatography was performed on silica gel (60-mesh). TLC was carried out on 0.2 mm silica gel 60 F254 analytical aluminum plates HRMS spectra were recorded using by THERMO ITQ900 LC/MS spectrometer with ESI method.Infrared (IR) spectra were recorded in the range of 4000-600 cm-1 via ATR diamond. Melting points were measured using melting point apparatus and are uncorrected. General procedure for the synthesis of 3a-3iPalladium(II) chloride (17.3 mg, 10 mol %) was added to a solution of methyl hydrazone derivative (1)(1 eqv) in toluene (15 mL). Acetic acid (2) (1.2 eqv) was then added and the resulting mixture was heated at reflux temperature for 18 h under N2 atmosphere. After complete conversion (monitored by TLC) the reaction mixture was filtered and then evaporated. The residue was eluted with ethyl acetate to give acetylated hydrazone derivatives (3), which were chromatographed on silica gel (20 g). (E) N-methyl-N'-(phenylmethylene)acetohydrazide (3a)