Generation and selected reactions of chlorinated thiocarbonyl S-imides*

N-Aryl-1,1,1-trichloromethanesulfenamides ArNH-SCCl₃ easily undergo dehydrochlorination upon treatment with potassium hydroxide in ethanolic solution. The intermediate thiocarbonyl S-imides formed thereby behave differently depending on the type of the N-aryl group. The sterically crowded N-(2,6-dimethylphenyl)- and -N-(2,4,6-trimethylphenyl)-1,1,1-trichloromethanesulfenamides yield the corresponding sulfur N,N'-diaryldiimides via a multi-step reaction, whereas the less crowded 2-methylphenyl and 4-methylphenyl derivatives undergo a regioselective 'head-to-head' dimerization leading to 5,5,6,6-tetrachloro-1,4,2,3-dithiadiazinanes in high yields. An identical reaction course is observed in the case of the 4-methoxy- and 4-bromoaniline derivatives. A diradical mechanism is postulated to explain the 'head-to-head' dimerization pathway.