Thermisch und photochemisch induzierte intramolekulare, 1,3‐dipolare Cycloadditionen von 5‐(2‐Allyloxyphenyl)‐2‐phenyltetrazol. Vorläufige Mitteilung. 54 Mitteilung über Photoreaktionen

Abstract

Thermal and Photochemically Induced Interamolecular 1,3‐Dipolar Cycloaddition Reactions of 5‐(2‐Allyloxyphenyl)‐2‐phenyltetrazole The title compound 5 is easily obtained by a recently described procedure ( Scheme 2 ). The tetrazole 5 reacts at 165–170° or on irradiation at room temperature to yield 2‐phenyl‐3,3a‐dihydrochromano[4,3‐ c ]pyrazole ( 7 , Scheme 3 ), which probably arises by intramolecular [3+2]‐cycloaddition of the intermediate nitrilimine. Dehydrogenation of 7 with chloranil leads to 2‐phenylchromano[4,3‐ c ]pyrazole ( 8 , Scheme 3 ).