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Please login to access the full content or check if you have access via Variation 1: Generation of Nitrene (NH) from Hydrazoic Acid

DOI: 10.1055/sos-SD-009-00047

Zeller, K.-P.Science of Synthesis, (2001968.

Photolysis of hydrazoic acid (HN3) with UV light generates the unsubstituted nitrene (NH) in its first excited state as a singlet species (see also HoubenWeyl, Vol. E16c, pp 93144). In the presence of ethyne in an argon matrix at 4K, ketenimine (H2C=C=NH)[‌10‌] is formed as the only reaction product through a postulated 1H-azirine intermediate.[‌11‌] The gas-phase photolysis of mixtures of hydrazoic acid and acetylene yields fragmentation products of C2H3N species.[‌12‌] From the product analysis the primary formation of 1H-azirine and aminoacetylene has been concluded. Similarly, the photolysis of hydrazoic acid in the presence of but-2-yne in a 12K argon matrix yields dimethylketenimine (5) as the major product (Scheme 2).[‌13‌] Its formation has been rationalized by the intermediate existence of 2,3-dimethyl-1H-azirine (4), which undergoes rapid ring opening and methyl migration. A minor product, also detected by IR spectroscopy, has been tentatively assigned as 4. Performing the reaction in a xenon matrix results in the formation of 1-(methylamino)prop-1-yne as the major product. It has been postulated that in argon the reaction proceeds on the excited singlet reaction surface, providing an immediate route to the 1H-azirine, whereas in a xenon matrix the major part of the reaction takes place on a triplet reaction surface attained by singlettriplet crossover through an external heavy-atom effect.

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