Silylated dithiols, with

It is observed that the synthesis of various polymers by the silylated method is superior to the conventional diamine, diphenol, or dithiol route particularly with respect to higher inherent viscosity or molecular weight of the resulting polymers. 

Long reaction times lead to the disappearance of the blue color of thione 1, related to the addition of a second molecule of hydrogen sulfide to give colorless gem-dithiols 3. Aromatic derivatives (R = Ar) are less prone to further addition of hydrogen sulfide, whereas with aliphatic derivatives (R = alkyl), gem-dithiols are generally the final reaction products and can be isolated and fully characterized.18 gem-Dithiols 3 can be converted into thioacylsilanes 1 by neutralization of the thionation solution with solid sodium hydrogen carbonate. With this procedure, enolizable acylsilanes 2 (R = R CH2) are stereoselectively transformed into Z-a-silyl enethiols 4 (vide infra). 

Other examples of functionalization at C-2 via phosphorus ylides and phosphonate carbanions are described in Section 4.12.11. Utilization of 2-non-phosphorus-containing carbanions was also exemplified. Thus, 2-silicon-substituted 1,3-benzodithioles were synthesized via deprotonation of benzo-l,3-dithiole 245 with -BuLi and subsequent treatment of the resulting anion with trimethylsilyl chloride (TMSCl) to give 2-(trimethylsilyl)-benzo-l,3-dithiole 246 (Scheme 29). The second silyl group was introduced by further deprotonation of 246 ( -BuLi) followed by the reaction with an additional equivalent of TMSCl. Tin-substituted benzo-l,3-dithioles were synthesized in a similar way but the deprotonation of the monostannyl derivative was carried out with LDA (Scheme 29) <1996CL171>. 

Peterson olefination using the a-silyl anion 449 with ketones 450 or 451 provided Tt-extended 1,3-dithioles 452 and 453 in 13% and 6% yields, respectively (Scheme 64) <2004EJ0138>. 

The silyl substituted dithiol (Mc3SiSCF2)2, prepared from the sulphenyl chloride CISC2F4SCI (4) and (Mc3Si)2Hg, reacts with the dichlorides RECI2 (E = P, As) to give the heterocycle, the phosphorus derivative undergoing a Michaelis-Arbuzov rearrangement, but not the arsenic one (equation 12). These heterocycles also result directly from (4) and the bis-silyl phosphine or arsine. ... 

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