Oxidation of 1,1-disubstituted hydrazines with benzeneseleninic acid and selenium dioxide. Facile preparation of tetrazenes

Abstract

Various 1,1-disubstituted hydrazines were oxidized with benzeneseleninic acid in methanol, generally producing the corresponding tetrazenes in high yield. Studies of the by-products of the reaction, of the effects of protic vs. aprotic solvents, and trapping experiments suggest that N-aminonitrenes are unlikely intermediates in this oxidation. An alternative mechanism involving a Pummerer-like reaction of seleninamides derived from the hydrazines is proposed. Tetrazene formation fails when the hydrazine precursor contains an aryl or p-toluenesulfonyl substituent, or when it is highly hindered. Selenium dioxide may be employed as the oxidant instead of the seleninic acid, but is generally less efficacious in achieving high tetrazene yields.