Intramolecular Photocycloaddition Reactions in the 2-(4-Pentenyl)-5-aryl-Substituted Tetrazole System

Article abstract of DOI:10.1021/jo00143a016

Irradiation of 2-(4-pentenyl)-5-aryl-substituted tetrazoles with UV light results in the loss of nitrogen and formation of a nitrile imine intermediate.This reactive 1,3-dipole undergoes an intramolecular 1,3-dipolar cycloaddition reaction to produce a bicyclopyrazoline ring.The primary photochemical process occurs from the n<*>?^* excited singlet state.The effect of substituents on the para position of the 5-phenyl group of the tetrazole ring was examined.A kinetic investigation, involving Stern-Volmer plots and relative reactivity studies, shows that there is amarked leveling of the rate profile associated with these internal cycloadditions when compared with their bimolecular counterparts.The high degree of order already present in the transition state for these intramolecular nitrile imine cycloadditions could account for the leveling of the rate profile.