Thioketene dimer

Many thioketene dimers crack at high temperature to give monomers, which then give normal [2 + 2] additions (Scheme 119) (70JOC3470). 

Some thiones dimerize to 1,3-dithietanes (75BSF(2)1670). Thioketenes dimerize spontaneously a-keto thioketenes give desaurins (cf. Scheme 31) (76BAU1913). 

Keywords Dithiafulvene -Conjugated polymer Dendrimer Polyrotaxane Thioketene dimer... 

Conjugated Polymers with Thioketene Dimer Unit. 100... 

There is a long standing interest in the chemistry and the properties of cyclic compounds containing sulfur atom in modern material chemistry due to their redox chemistry. In particular, the focus has been on dithiole derivatives, e.g., dithiafulvenes and tetrathiafulvalenes, since the finding of metallic conductivity and low temperature superconductivity in radical cation salts. The quite low oxidation potentials of 1,4-dithiin compounds have been reported, recently [109]. On the other hand, thioketene dimers (2,4-bis(alkyli-dene)-l,3-dithietane) have been known for more than 100 years and synthesized by various methods [110-115]. The structure of these dimer compounds is similar to that of the redox-active sulfur compounds therefore, the potential electronic property of the thioketene dimer moiety is considerably attractive with the aim of application to a new and better -donor. 

We have reported the first electroactivity of a thioketene dimer compound [116]. The CV measurement of 2,4-dibenzylidene-l,3-dithietane (31), which was prepared by a basic dimerization of phenylthioketene derived from ben-zyltriphenylphosphonium chloride, showed irreversible two-step oxidation peaks at 0.25 and 0.61 V vs Ag/Ag+, indicating that 31 acts as a stronger electron donor than 2,6-bisphenyl-l,4-dithiafulvene (30) and TTF (2). The dimer (31) can form a 1 1 CT complex with TCNQ in DMSO. Cycloaddition polymerization of bisthioketene derived from p-xylenebis(triphenylphosphoni-um chloride) gave a -conjugated polymer (32) with thioketene dimer unit in the main chain (Scheme 12). This polymer was the first polymer contain-... 

A series of silyl and disilyl substituted thioketene dimers (2,4-diylidene-1,3-dithietane), including polymers, have been synthesized (33, 34) [117]. HOMO-LUMO calculation by PM3 semi-empirical molecular orbital method predicted an intramolecular CT from the thioketene dimer to the Si-Si bond in disilyl thioketene dimer (33a) and no electronic interaction between the... 

Fig. 3A-D UV-vis spectra of thioketene dimers A 33a in CHC13 B 33b in CHC13 C 34a in CH3CN D 34b in CH3CN...

Thioketene dimers crack at high temperatures into monomers, which then undergo [Z + Z] cycloadditions (Scheme 101) <1970JOC3470>. 

Its structure as determined by an X-ray investigation is shown in Fig 21. It may be understood as a dimer of the assumed phosphathio-ketene intermediate. The cycloaddition of the phosphathioketene corresponds to the behavior of unsubstituted carbaketenes (146) and so is different from that of the phosphaketenes described earlier, while thioketenes dimerize to 1,3-dithietanes (147,148). An asymmetric retro ring cleavage can be initiated if l-thia-3-phosphetane is irradiated by a mercury lamp generating carbon disulfide and the 1,3-diphosphaallene [Eq. (78)] (117, p. 33). 

Sulfur may react with alkenes either by addition to the C=C double bond or by substitution of H by S with the elimination of H2S. In both cases polysulfanes are formed. Octafluoroisobutene, (CF3)2C=CF2, reacts at 60-70 °C in dimethylformamide (DMF) and in the presence of cesium fluoride with elemental sulfur to give the thioketene dimer (5) and the trisulfane (6) (yield 21 % and 3 5% based on the alkene). Use of KF instead of CsF also produced some tetrasulfane analogous to (6). ... 

The thioketen dimers (264) have been converted into dithiadiazines (265) by treatment with methanolic sodium azide followed by concentrated hydrochloric acid. ... 

Dithiocarboxylic acids (118) can be converted into 1,3-dithietans (119) by acid chlorides,iodine, HCl, DCCI, or upon standing for a long time, and they are formally thioketen dimers. The cycloaddition of two C=S groups yields thioketen dimers and (120) from methyl isothiocyanate. Derivatives (121) are prepared by the reaction of dithiocarboxylic acids (118) with phosgene. ... 

The reaction of diphenylmethylene phosphorane with carbon disulfide affords polymeric diphenylthioketenes . In a similar reaction fiuorenylidene triphenylphosphorane affords the corresponding thioketene dimer . An exchange reaction is observed in the reaction of... 

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