Intramolekulare 1,3‐dipolare Cycloadditionen von Diarylnitriliminen aus 2,5‐Diaryltetrazolen

Intramolecular 1,3‐Dipolar Cycloadditions of Diaryl‐nitrile‐imines Generated from 2,5‐Diaryl‐tetrazoles Alkenyl‐substituted diaryl‐nitrile‐imines – generated by photolysis or thermolysis of alkenyl‐substituted 2,5‐diaryl‐tetrazoles ‐ undergo a regioselective intramolecular [2 + 3] cycloaddition to yield new heterocyclic compounds, e. g. fused 2‐pyrazolines. With alkinyl derivatives, the corresponding pyrazoles have been formed. UV evidence is given for the intermediate nitrile‐imine at − 190°. The latter can be trapped using an excess of carboxylic acid (UV evidence for a new intermediate at − 120°). In this case, the corresponding rearranged addition product N ′‐acyl‐ N ′‐aryl‐benzohydrazide is isolated in good yield.