A Tricky Reaction of Inorganic Azide

Aryldiazonium ions and sodium azide react to form aryl azides. We did not mention this reaction in the discussion of the SN reactions of Ar—N2 (Section 5.4) because it belongs, at least in part, to the 1,3-dipolar cycloadditions. 

Ar— N3 + N2. The reaction proceeds following two reaction channels 1,3-dipolar cycloaddition via the intermediate phenylpentazole (right) and via the alternative phenyl-pentazene (left). 

Carruthers, Cycloaddition Reactions in Organic Synthesis, Pergamon, Elmsford, NY, 1990. 

One or More C=C Bond(s) by Pericyclic Processes, in Comprehensive Organic Functional Group Transformations (A. R. Katritzky, O. Meth-Cohn, C. W. Rees, Eds.), Vol. 1, 771, Elsevier Science, Oxford, U. K., 1995. 

Bemardi, M. Olivucci, M. A. Robb, Predicting Forbidden and Allowed Cycloaddition Reactions Potential Surface Topology and Its Rationalization, Acc. Chem. Res. 1990, 23, 405. 

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