Carbonyl azides thermal decomposition

The thermal or photolytic decomposition of carbonyl azides in the presence of dipole acceptors such as acetylenes provides a valuable method for the construction of oxazoles. Thus the reaction of ethyl azidoformate with either diphenyl- or diethylacetylene produces mainly the 2-ethoxy-oxazole (77 ).166 166 The reaction involves the 1,3-dipolar cycloaddition of carbethoxy nitrene (76b) to the alkyne to give the oxazole (77). On the... 

Allophanyl hydrazide is a white, crystalline, nonhygro-scopic compound which melts at 166° with decomposition. It is soluble in water, methanol, and ethanol (at their boiling points) to the extents of 14, 3, and 1.4 g./lOO ml. of solvent, respectively. It is a weak base, KB = 10-n. Melting points and formulas of typical salts are tabulated below. The compound is thermally unstable when heated at 110° for an extended period of time. As a typical hydrazine derivative, allophanyl hydrazide forms allophanyl hydrazones with carbonyl compounds. Among these, the water-insoluble benzaldehyde derivative (m.p. 208 to 209°) is easily prepared. Allophanyl hydrazide can also be treated with nitrous acid to give the water-insoluble azide, NH2CONHCON3, melting with decomposition at 193°. 

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