Preparation and N.M.R. spectra of 2,5-Diaryl-2,5-di-t-butyl-Δ³-1,3,4-thiadiazoline 1,1-Dioxides

Abstract

The reaction of 1-(4-methoxyphenyl)-2,2-dimethyldiazopropane with sulphur dioxide in benzene at 5? gave a 54% yield of 2,5-di-t-butyl- 2,5-bis(4-methoxyphenyl)-Δ³-1,3,4-thiadiazoline 1,1-dioxide (4a). The n.m.r, spectra of this and the analogous compounds from 1-(4- chlorophenyl)-, and 1-(3,4,5-trimethoxyphenyl)-diazopropane, showed temperature dependence due to restricted rotation of the aryl groups. The energy barriers associated with this process were determined.    Structural factors profoundly influence the course of the reaction of 1-aryldiazoalkanes with sulphur dioxide. For example, 1-adamantyl-1- (4-methoxyphenyl)diazomethane gave no detectable amount of the thiadiazoline derivative, but an almost quantitative yield of 1-(4- methoxybenzoyl)-adamantane.