DIPHENYLTHIIRENE 1-OXIDE - SYNTHESIS, CHARACTERIZATION, AND REACTIVITY

The synthesis of 2,3-diphenylthiirene 1-oxide (7) by treatment of (±)-α,α’-dibromodibenzyl sulfoxide (5) with tri-ethylamine in methylene dichloride solution is described. The sulfoxide 5 was obtained by careful oxidation of the free radical bromination product of dibenzyl sulfide, (±)-α,α’-dibromodibenzyl sulfide (4), by means of m-chloroperbenzoic acid. The structure of 7 was established by oxidation to the corresponding well-known sulfone (1, R = C6H5). Photolysis of 7 at 30°C gave diphenylacetylene. Thermolysis of 7 appeared to be accompanied by ring expansion to the corresponding oxathiete derivative 10 as evidenced by the isolation of benzil. Reaction of 7 with hydroxylamine gave a mixture of α-benzil dioxime (18) and deoxybenzoin oxime (17). Treatment of 7 with phenyldiazomethane gave 3,4,5-triphenylpyrazole (14) and excess phenylmagnesium bromide led to the formation of phenyl triphenylvinyl sulfide (15). Synthesis of the m-and p-fluoro derivatives of 7 as well as the corresponding sulfones and ketones 20 followed by examination of their F NMR spectra provided evidence for conjugative effects increasing in the order thiirene oxide < thiirene dioxide < cyclopropenone. © 1979, American Chemical Society. All rights reserved.