Thermische und photochemisch induzierte intramolekulare, 1,3‐dipolare Cycloadditionen von 4‐Phenyl‐3‐(2‐allylphenyl)‐sydnon. Vorläufige Mitteilung. 53. Mitteilung über Photoreaktionen

Abstract

Thermal and photochemically induced intramolecular 1,3‐dipolar cycloaddition reactions of 4‐phenyl‐3‐(2‐allylphenyl)‐sydnone The title compound 9 was synthesised in the usual way, starting from 2‐allylaniline and ethyl 2‐bromo‐2‐phenylacetate, via the nitrosaminacid 8 ( Scheme 2 ). 9 reacts at room temperature with its potential azomethinimine‐function in an intramolecular [3+2]‐cycloaddition to give the tricyclic compound 11 ( Scheme 2 ). On irradiation, 9 yields the dihydro‐3 H ‐pyrazolo[2,3‐ a ]indole 10 which probably arises by intramolecular [3+2]‐cycloaddition of the corresponding intermediate nitrilimine.