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9.5.1.2.1.1.1 Variation 1: Generation of α-Imino Carbenes from 1H-1,2,3-Triazoles

DOI: 10.1055/sos-SD-009-00047

Zeller, K.-P.Science of Synthesis, (2001971.

The elimination of dinitrogen from unsubstituted 1,2,3-triazole in the gas phase requires unexpectedly high temperatures (see also HoubenWeyl, Vol. E8d, p 385ff and Vol. E16c, p 317ff).[‌8‌,‌24‌,‌25‌] At temperatures above 870K the formation of acetonitrile, the most stable isomer of the C2H3N ensemble, has been detected by photoelectron spectroscopy.[‌25‌] The decomposition temperature can be lowered to 550K by copper(I) oxide catalysis. Under these conditions, 2H-azirine (2) is formed predominantly, which by increasing the temperature rearranges into acetonitrile. On the other hand, it has been reported that, by combined flash pyrolysis/matrix isolation, ketenimine (H2C=C=NH) and small amounts of hydrogen cyanide N-methylide (HCN+CH2) can be detected by IR spectroscopy.[‌8‌] From these conflicting results it is difficult to draw any conclusion on the thermal fragmentation mechanism and the possible involvement of intermediate 1H-azirine. Photolysis (λ=222nm) yields two products which have been assigned as hydrogen cyanide N-methylide and aminoacetylene.[‌8‌]

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References