A Facile and Efficient Deoxygenation of Amine-N-oxides with WCl6/NaI System

Abstract

The deoxygenation of amine-N-oxides to amines is an important transformation in the synthesis of nitrogenous aromatic heterocycles and an area of considerable interest, particularly when a molecule has other reducible or labile moieties. A number of methods have been described for the reduction of amine-N-oxides, including agents such as low-valent titanium, Zn/HCOONH4, InCl3, tributyltinhydride, Pd/C, SmI2, tetrathiomolybdate, indium/NH4Cl, Mo(CO)6. However, many of these methods are deficient in some respects such as relatively severe reaction conditions, low yields, poor selectivity or occurrence of side reactions. Consequently, there is still a need for introducing selective and mild reagents for the deoxygenation of amineN-oxides to amines. In continuation of our efforts towards the development of the low-valent metal reagents for organic transformations, we observed that a combination of WCl6 with sodium iodide could bring about the deoxygenation of amine-N-oxides under mild conditions. The new reducing system was generated by the addition of sodium iodide to a stirred solution of tungsten hexachloride in acetonitrile under nitrogen atmosphere. In this communication, we wish to report an efficient and chemoselective method for the deoxygenation of various amine-N-oxides to the corresponding amines by treatment with WCl6/NaI system in aceto-