The synthesis of bifunctional thioureas and the corresponding thiourea S,S,S-trioxides has been examined. Two methods for the synthesis of the bisthioureas were employed. One involved the treatment of a diamine with silicon tetraisothiocyanate in benzene. The second involved treatment of the amine with ammonium thiocyanate in dilute acid. This latter synthesis was superior because of the ease of its use, the high yields obtained, and the purity of the products. Though this synthesis worked well for the preparation of phenylene-l,4-bis(thiourea), it yielded only bisthiocyanate salts in the synthesis of aliphatic thioureas. The oxidation of the bisthioureas was carried out using peracetic acid or hydrogen peroxide to give the corresponding thiourea S,S,S-trioxides.
Webb '89, Dan, "Synthesis and Nucleophilic Reactions of Bifunctional Thiourea S,S,S-Trioxides" (1989). Honors Projects. Paper 30.