New mechanism for the reaction of amines with zinc dithiocarbamates

✍ Scribed by A. Dirksen; P. J. Nieuwenhuizen; M. Hoogenraad; J. G. Haasnoot; J. Reedijk

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 205 KB
• Volume: 79
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/1097-4628(20010207)79:6<1074::aid-app110>3.0.co;2-l

✦ Synopsis

This article reports a detailed reinvestigation of the reaction of bis(dialkyldithiocarbamato)zinc(II) (ZDAC) with amines. The reaction of primary amines with bis(dimethyldithiocarbamato)zinc(II) (ZDMC) results in the formation of a 1,1,3-trisubstituted thiourea, a 1,3-disubstituted thiourea, dimethylammonium dimethyldithiocarbamate (DMADC), ZnS, and H 2 S. The ratio of formation between the two thiourea products strongly depends on the reaction conditions chosen. A new mechanism is proposed, which involves the formation of an amine-dithiocarbamic intermediate, from which the two most important products, a 1,1,3-trisubstituted and a 1,3-disubstituted thiourea, are formed. Also, direct transformation of the 1,1,3-trisubstituted thiourea into the 1,3-disubstituted thiourea via nucleophilic attack of the primary amine onto the thiocarboxy of the 1,1,3trisubstituted thiourea was found to occur, catalyzed by ZnCl 2 . The reaction of primary amines with ZDACs is catalyzed by elemental sulfur, which has been attributed to sulfur insertion in the zinc-ligand ring of the ZDAC, resulting in a higher reactivity of the ZDAC complex. Finally, when ZDACs are reacted with a secondary amine, no thiourea products are formed and only a mixture of zinc dithiocarbamates is obtained.