Thiophosgene dimer

Synthesis.—In the course of their investigations in the field of simple trithiocarbonates, Gattow and his co-workers have prepared the cyclic trithiocarbonates (284) and (285) by reactions involving the action of methylene iodide on potassium trithiocarbonate, and the treatment of hydrogen trithiocarbonate with dimeric thiophosgene, respectively. The... 

The syntheses of perhalogenated dithiethanes and their oxidation products (214-219) have been recently reported247. The method is based on the photochemical dimerization of thiophosgen or its fluoro- and bromo-analogues followed by partial oxidation with trifluoroperacetic acid to the desired sulfoxides (or sulfones)248 as shown in equation 84. 

As indicated above, the most important of the thiocarbonyl compounds is thiocarbonyl fluoride, CF2=S. It has been synthesized by a number of routes (43), the most convenient of which for laboratory investigation is dimerization of thiophosgene followed by conversion of the dimer to 2,2,4,4-tetrafluoro- i, 3-dithietane (I) and thermal cracking of the dithietane (44). 

A sterically hindered (2,4,6-tri-t-butylphenyl)[bis(trimethylsilyl)]phosphine (9), whose crystal structure has been reported84, was utilized to form a 1-phosphabuta-l,3-diene (equation 67)36. Mes -substituted phosphaketene was obtained from the reaction of 9 with phosgene (equation 68)4. Reaction of 9 with thiophosgene afforded dimeric phosphathioketene, [Mes P=C=S]2 (equation 69)85. A."V3-Dithioxophosphorane was also isolated by introduction of the bulky substituent (equation 70)86. 

The most simple member of this class of compounds is thiocarbonyl fluoride [257, 258], which is obtained from the thiophosgene dimer 8.94A, and then pyrolysis of 8.94B, to the corresponding fluoro monomer [233] (Figure 8.94). 

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-... 

An early electron diffraction study of thiophosgene, CSCI2, assumed C-S, 1 -63 A, which could profitably be checked. The dimer, produced by photolysis of CSCI2, has the structure and the compounds with the empirical formulae... 

Aminoacetophenones (265) when reacted with thiophosgene in a mixture of chloroform, water, and calcium carbonate form the corresponding isothiocyanates (266), but these spontaneously cyclize to afford 4-methylene-3,l-benzoxazine-2-thiones (267) which rearrange under the reaction conditions to yield 4-methylene-3,l-benzothiazin-2-ones (268). These products then slowly dimerize to 4-(3,l-benzothiazine-4-yl)methylene-3,l-benzothiazines (269) (Scheme 51) <9UHC1091>. 

Thiocarbonyl fluoride, 9, is prepared in good yield by pyrolysis of 6 at ca. 600°C in the vapor phase or by carrying out the reaction of sulfur and tetrafluoroethylene at higher temperatures. A cleaner synthesis involves fluorination of thiophosgene dimer to tetrafluoro-l,3-dithietane, 10, followed by cracking of 10 to two molecules of 9 (7). 

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