Tetraalkylthiuram disulfides

Arylsulfenyl derivatives 151 were obtained from mesoionic 150 with diaryl disulfides in the presence of K2CO3 when air was bubbled through the reaction mixture (99M1147). u / yJro-(2-Hydroxy-4-oxo-4/7-pyrido[l,2-u]pyrimidinium)hydroxide (R = H) afforded 3-dialkylaminothiocarbo-nylthio derivatives 152 in the reaction of tetraalkylthiuram disulfides under similar conditions. 

Industrial work has been concentrating on the search for alternative processes for the production of tetraalkylthiuram disulfides 325). 

Their synthesis can also be carried out as a two-phase electrolysis, using ammonium salts 326). Sulfenamides can be produced by oxidizing tetraalkylthiuram disulfides in the presence of amines 321 ... 

Tetraalkylthiuram disulfides are used as vulcanization enhancers, fungicides, and seed treatment agents. Commercial production is still performed by means of oxidation with Cl2. Although their electrochemical synthesis avoids the production of NaCl, which is inevitable in the other processes, it is currently not being employed in industry. 

The preparation of disulfides can be achieved by reacting the thiol or its salts with aqueous hydrogen peroxide358 under alkaline conditions. However, the pH needs to be closely monitored, since if too high, the disulfide selectivity will drop.359 Dialkyl dithiocarbamates can be oxidized to tetraalkylthiuram disulfides (Figure 3.92).360... 

The tetraalkylthiuram disulfides were mentioned for the first time by Tobolsky et al. [53]. We can find them classified in the Polymer Handbook [54] as disulfides (bis dialkylthiocarbanoyle) . 

The reaction of ReCl(CO)5 with tetraalkylthiuram disulfides (benzene reflux, 7 h) produces complexes of the formula Re(CO)(S2CNR2)3 (R = Me, Et) with oxidative addition of the S-S bond". ... 

Tetraalkylthiuram disulfides, R2NC(S)S-S(S)CNR2, are oxidized forms of the di-alkyldithiocarbamate ions R2NC(S)Sa Thiuram disulfides possess pronounced oxidative properties and can easily oxidize and stabilize polyvalent cations in high oxidation states (Ni(III), Cu(III), Ag(II), etc.) as well as coordinate these metal ions in the molecular form [18,19]. Therefore, it should always be kept in mind that complexation of polyvalent cations with dialkyldithiocarbamate anions can be accompanied by a redox equilibrium of the following type ... 

In this chapter, some of these uses are explored in greater detail. Goodyear and Hancock in 1847 discovered that, when natural rubber was heated with a small amount of sulfur, the physical properties of the resultant rubber were improved the material became tougher and more resistant to changes in temperature. This process of vulcanisation is also useful for the treatment of synthetic rubbers, and as well as sulfur, many sulfur donors such as symmetrical diphenylthiourea, tetraalkylthiuram disulfides (1) and 2-mercaptobenzothia-zole (2) (Figure 1) can be used.1 These compounds act as accelerators of the process of polymerisation of the diene monomers in synthetic rubbers for this purpose, the additional presence of zinc oxide and preferably a carboxylic acid, e.g. stearic acid, is required. 

Ihe efficiency of crosslinking is increased by including accelerators (e.g., tetraalkylthiuram disulfide, zinc dialkyldithiocarbamate) and activators (e.g., ZnO plus stearic acid) which inhibit the formation of long polysulfide crosslinks, vicinal crosslinks and intramolecular cyclic sulfide structures. 1,4-Poly-l,3-dienes are also crosslinked by heating with -nitrosobenzene, phenolic resins or maleimides for applications requiring improved thermal stability. 

The photochemically and thermally induced iniferter properties of the tetraalkylthiuram disulfides during free radical polymerization were also exploited to end functionalize PMMA and PSt (Scheme 3.6). Table 3.4 summarizes the functional iniferters used for obtaining telechelic polymers. 

---