Studies On The Oxidation Of Aromatic Aldehyde Hydrazones And Aldazines With Organo-iodine (III) Reagents

The organo-iodine (III) reagents are widely used in modern organic syntheis fortheir properties of easy-preparation and less-toxicity compared with classic transitionmetal oxidants. Here we will report some research work with bis(trifluoroacetoxy)-iodobenzene as an oxidant.Hydrazine hydrate was used to prepare acetylhydrazine, trifluoroacetylhydrazine,benzoic acid hydrazide, p-fluoro Benzoic acid hydrazide, p-methoxy benzoic acidhydrazide, o-bromo benzoic acid hydrazide, nicotinic acid hydrazide,furan-2-carboxylic acid hydrazide, hydrazine-carboxylic acid methyl ester,benzenesulfonyl hydrazine, p-methylbenzenesulfonyl hydrazine andp-chlorobenzenesulfonyl hydrazine. The preparation of aromatic aldehydeN-acylhydrazones and N-sulfonylhydrazones was achieved by the condensation ofaromatic aldehydes with acylhydrazines or sulfonyl hydrazines. In addition, aldazineswere prepared from aldedehydes and hydrazine hydrate.2,5-Disubstituted-1,3,4-oxadiazoles were directly obtained from aromaticaldehyde N-acylhydrazones through the oxidation with bis(trifluoroacetoxy)iodobenzene at room temperature. The oxidation rules of aromatic aldehydeN-acetylhydrazones, N-trifluoroacetylhydrazones, N-benzoylhydrazones,N-substituted hydrazones, N-heterocyclyl hdyrazones, and carbomethyoxyhydrazoneswere investigated.It is the first report that 2,5-disubstituted-1,3,4-oxadizoles were obtained fromaldazine oxidation in DMSO at room temperature. The reaction of symmetric andunsymmetric aldazines proceeded well and the yields were lower when aldazinescontained nitro and hydroxyl group but higher with electron-donating moieties in themolecular. The reaction mechanism was proposed and testified.Aromatic aldehyde arylsulfonyl hydrazones are oxidized bybis(triluoroacetoxy)iodobenzene in acetone at room temperature. The products wereN-aroyl-N'-arylsulfonyl-hydrazines determined by Nuclear Magnetic Resonance,Infrared spectra, and comparative expeirements. The relationship between the yeildsand the structure of the starting materials was studied and the reaction mechanism wasproposed.o-Nitro aryl aldehyde arylsulfonyl hydrazones were oxidized bybis(trifluoroacetoxy) iodobenzene at room temperature and the products were1-arylsulfonyl-benzo[c]isoxazol-3-ones testified by Hydrogen, Carbon NuclearMagnetic Resonance and single crystal X-ray diffraction. It was the first time thatbenzo[c]isoxazol-3-one was prepared via oxidation.