Decomposition of tetramethyl-2-tetrazene under acidic conditions

Abstract

Decompositions of tetramethyl-2-tetrazene (TMT) under acidic conditions were investigated by product analysis and by nmr and esr spectroscopic monitors. Photolysis in acetonitrile containing trifluoroacetic acid generated the dimethylaminium radical which added efficiently to an olefinic double bond. Some adducts contained a (CH3)2NCH2— moiety, the immediate precursor of which could be CH2=N(CH3)2+ species. Photolytic addition of TMT to nor-bornenes generated 2-norbornyl radicals that underwent coupling through the exo or endo side to give the dimers. Thermal decomposition in sulfuric acid in the presence of toluene gave N,N-dimethyltoluidines, N-methylphenethylamine, benzyltoluenes, and a plethora of other minor products in addition to a large amount of formylidene methylamine. The last compound was the major product when thermal decomposition of TMT was carried out in trifluoroacetic acid in the presence of toluene or anisol; amination products of aromatic substrates were low and contained only ortho and para isomers. TMT dissolved in these solvents exhibited the esr signal of the stable [Formula: see text] (the tetrazene cation radical) which did not react with cyclohexene. In concentrated sulfuric acid, TMT was decomposed in less than 15 min giving formylidene methylamine and dimethylamine as shown by nmr. In trifluoroacetic acid, the esr signal of tetramethylhydrazine cation radical [Formula: see text] emerged after the TMT solution was irradiated; no dimethylaminium radical signal could be detected. The relationship of [Formula: see text] and [Formula: see text] with formation of the observed products remains unclear.