Generation of Ethynyl Azides

Although this review is by no means comprehensive, it should give an impression of the great number of feasible syntheses of the title compounds and their possibilities of reactions. The unique combination of C,C double or triple bonds and the azido group often allows not only the common reactions of these parts but also specific transformations into a variety of very different products. Much attention was paid to the results of the last 20 years, but it was tried to mention all important facts about the chemistry of the title compounds including also their history. 

At the latest during the last two decades, it turned out that vinyl azides are not only compounds for experts in organic chemistry but also very useful and general tools in synthetic chemistry. Although these azides are known for about hundred years, efficient approaches, developed in the last 45 years, were necessary to supply the starting materials, which have been utilized to show the versatility of vinyl azides. This is demonstrated by reactions induced by thermolysis, photolysis, cycloaddition, or attack by electrophiles or 

Most probably, the rapid electrocyclic ring closure of allenyl azides was responsible for the fact that the chemistry of these azides was discovered so lately. This cyclization of azidoallenes allowed to create cascade reactions for the synthesis of functionalized NH-l,2,3-tiiazoles. 

Since 1910, many groups have tried to generate ethynyl azides, but these species have proved to be the Yetis within the azides even today. However, latest results have shown that 1-azidoalk-l-ynes can be trapped by 1,3-dipolar cycloaddition although they lost dinitrogen very rapidly to produce cyanocarbenes. 

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