A-thioketenes

H, 13C and 29Si NMR. Formed by scavenging 173 a solution of organotin(II) compound 72 (see Table 7) with a thioketene. ... 

The carcinogenic properties of hexachlorobutadiene are proposed to result from binding of the sulfenic acid degradation product or a thioketene intermediate to cellular DNA (Dekant et al. 1990b Henschler and Dekant 1990). Cell necrosis is thought to stimulate replication of cells with altered DNA, enhancing tumorigenesis. 

Section II,A,1 3//-Pyrazoles have been prepared from 1,3,3,3-tetra-fluoropropyne and DPD169 and from l-thioalkyl-2-trimethlsiIylethynes with DAP.170 One of the latter alkynes was formed via valence isomerism of a thioketene.170... 

A similar polar cyclization of an enamine and a thioketene derivative is shown in equation (87) (76TL4283), but electron-deficient alkenes and alkynes react in a concerted fashion. Concerted cyclizations may be subdivided into those in which the sulfur atom is part of the enophile or the dienophile. Into the first category fall the dimerizations of a,( - unsaturated thioaldehydes (equation 88) which may be shown to closely follow frontier molecular orbital predictions of regioselectivity (79JOC486). Related to this are the thiochalcones (equation... 

This route is similar to those syntheses starting from mononuclear complexes with a terminal vinylidene ligand (see Scheme 17).54,55 In both cases a thioketene complex is formed as an intermediate, which is then reduced. 

Photolysis of a thiophene anhydride in an argon matrix at 12 K yielded a mixture of a thioketene and a thioaldehyde321 (equation 55). 

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-... 

In the absence of an alkylating agent, a dithiadiazine 163 is formed on protonation <1984BSB405>. Since desaurine is a dimer of a thioketene, we can classify this reaction in this section. Alternatively, this could be seen as a ring transformation. 

The synthesis of poly-dibenzylidene-l,3-dithietane 201 is based on the Wittig reaction of/ -xylcnc-bis(triphcnyl-phosphonium) chloride 199 with carbon disulfide <2001MM346, 2002MM3806>. The phosphonium salt 199 was converted to the ylide 200, which reacted with carbon disulfide, yielding, after methanolysis, a thioketene. The latter was stirred at room temperature for 12 h to provide the polymeric compound 201, bearing 1,3-dithietane moieties in 54% yield (Scheme 25) <2001MM346, 2002MM3806>. 

N-Aryl- and iV,iV-dialkyl-thiobenzamides react with acid chloride phenylhydrazones to give 5-anilino- and 5-dialkylamino-2,4,5-triaryl-l,3,4-thiadiazolines, respectively. Treatment with alcohol gives the corresponding 5-alkoxy-l,3,4-thiadiazoline (Scheme 23a) (76ACS(B)837). A second example of the use of acid chloride phenylhydrazone is its reaction with a thioketene to provide thiadiazolines with a methylene group in the 5-position (Scheme 23b) (66AG(E)970). 

A general synthesis of benzofuran-2-thiolates utilizes 1,2,3-thiadiazoles as cyclization precursors. Upon treatment with base, the heterocycle is deprotonated and extrudes nitrogen to generate an alkynethiolate which can be spectroscopically monitored. This species can take up a proton to form a thioketene that undergoes cyclization to a benzofuranthiolate which is finally alkylated with an alkyl halide (Equation 125) <1997CC1753>. 

The formation of desaurins from ketones, carbon disulfide, and base 1275,1281,1282,1285-1290 believed to involve nucleophilic attack on a thioketene by the dianion of a 1,1-dimercaptoalkene, as shown for the synthesis of 572. Related syntheses involve the use of thiophosgene instead of carbon disulfide and the use of diazoalkanes or phosphonium and sulfonium ylides instead of a ketone and base. Treatment of perfluoroiso-butylene with fluoride ion and elemental sulfur in a dipolar, aprotic solvent ° °° or with sources of anionic sulfur (potassium sulfide, sodium hydrosulfide,potassium thiocyanate,sodium thiosulfate, dithiocarbamate salts, dithiophosphate salts ) give the dimer (573) of bis(trifIuoromethyl)-thioketene. Similarly, other 2,4-bis(methylene)-l,4-dithietanes are obtained by treating 2,2-dichlorovinyl ketones with anionic sulfur re-... 

Theoretical calculations indicate a low stability for 21128 . The above reaction was examined by the technique of flash photolysis and kinetic mass spectrometry and a strong signal for the species C2H2S was observed, with a decay half-life of ca. 2 sec. Indirect, though compelling, evidence was presented to the effect that the signal was not due to a thioketene intermediate, CH2-C-S. Thiirene reacts rapidly with triple bonds to produce thiophenes, viz. 

Photochemical desulfurization of thiocarbonates occurs with [Fe(CO)j] to give mononuclear as well as trinuclear (type 8) carbene complexes (24). A similar reaction affords desulfurization of diphenylcyclopropenethione (22). The thioketene cluster 13 reacts quantitatively, but in a more complicated way, with a thioketene to form a dinuclear vinylidene complex (14). 

Reactions of thioketones with nucleophilic reagents have been studied to some extent. Thiobenzophenone (20) and its 4,4 -substituted derivatives react with cyclopentadienyliron dicarbonyl anion and cyclopentadienyl-molybdenum or -tungsten tricarbonyl anion at room temperature to give fulvenes. Phase-transfer catalysis conditions improve the yields. An electron-transfer mechanism has been proposed for this desulphurization and coupling reaction. An electron-transfer mechanism has also been proposed for the reduction of thiopivalophenone (54) by 1-benzyl-1,4-dihydronicotinamide in acetonitrile. 2,3-Diphenylcyclopropene-thione (55) reacts with 7V-methylarylamines to give the bicyclic thioamides (56). The formation of a thioketen as an intermediate has been suggested. A similar reaction scheme has also been proposed for the reaction of (55) with 3,4-dihydroisoquinoline. ... 

Photochemical elimination of nitrogen from a bicyclic 1,2,3-thiadiazole results in the formation of a thioketen, e.g. (79), instead of a thiiren (see Scheme 4), which is in contrast to the reaction of monocyclic thiadiazoles. When 1,2,3-selenadiazoles are subjected to thermolysis at 500—600 C, they give the selenoketens (80)— (82). The selenoketens have been trapped and characterized at —196 C. 

The reaction of a ketone with a thioalkynolate gives a -thionolactone. The intermediacy of a thioketen has been suggested. ... 

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