Abstract
Pyrolytic cleavage of the azo-bridge of diethyl azodicarboxylate (Ia) at 200∼210° was studied and was shown to give diethyl oxalate (VI), tetraethyl hydrazine-N1, N1, N2, N2-tetra-carboxylate (VIII), triethyl hydrazine-N1, N1, N2-tricarboxylate (IX), diethyl hydrazine-N1, N2-dicarboxylate (X), and carbon dioxide, proving formation of the ethoxycarbonyl radical (III) as an important transitionally formed intermediate of the reaction. A homolytic mechanism with the diradical (IV) and ethoxycarbonyl radical (III) as intermediates was tentatively sug-gested for the reaction. Surprisingly, Ia, when treated with alumina or silica gel at room temperature, gave almost same pattern of products obtained by the pyrolysis, yielding VIII, IX, X and carbon dioxide. A photolysis of Ia on a tungsten lamp also gave IX, X, and carbon dioxide.
