Arylthioureas with bromine or its equivalents gives no 'Hugerschoff' reaction product.

The in situ generated aryl-alkyl unsymmetrical thiourea obtained by the reaction of an aryl isothiocyanate with an aliphatic secondary amine on treatment with bromine or its equivalent gave exclusively a product having a thioamido guanidino moiety and not the expected Hugerschoff product 2-aminobenzothiazole. A plausible reaction mechanism has been proposed for this unprecedented transformation and the scope has been extended to various substrates.

The thiocarbonyl 'S' is softer than thiolate 'S': a catalyst-free one-pot synthesis of isothiocyanates in water.

Treatment of the preformed or the in situ generated aryl/alkyl dithiocarbamates triethylammonium salt (ArNHCSS(-).Et(3)NH(+)) with methyl acrylate in an aqueous medium gave solely arylisothiocyanate (ArNCS), whereas the in situ generated aryl dithiocarbamic acid (ArNHCSS(-).H(+)) yielded exclusively the thia-Michael adduct (ArNHCSSCH(2)CH(2)COOMe). This differential reactivity can be explained by two alternative mechanisms which is dependent both on the nature of the counter cation and on the pH of the reaction medium. Irrespective of the counter cations, the thiocarbonyl sulfur (=S) atom, having large orbital-coefficient, is softer compared to the thiol/thiolate sulfur (-SH/S(-)) in a dithiocarbamate salt and the former adds to the Michael acceptor by a 1,4-addition.