1.3- Dithietanes reactions

Peseke treated the 1,3-dithietane (desaurin) (162) with sodium azide in aqueous ethanol and obtained a product believed to be a thiatriazolinylidenecyanoacetate <81ZC102>. Attempts to isolate the free acid were unsuccessful as upon acidification of the solution of the salt, nitrogen evolution took place and the hitherto unknown 2/7,5//-l,4-dithia-2,5-diazine (164) was formed (Scheme 34). According to L abbe et al. the 1,3-dithietane reaction product is best formulated with a negatively... 

Perfluoroisobutylene and potassium sulfide give 2,4-bis[hexafluoroisopro-pylidene]-l,3-dithietane and a small amount of the bis(perfluoro-tcrr-butyl)trisul-fide. The trisulfide is the result of a reaction of the nascent perfluoro-rerr-butyl carbanion with sulfur. The same products in different yields are obtained with sulfur and cesium fluoride [i] (equation 2). 

The benzo-fused 1,3-dithietane 6, from which the formation of two dithiiranes (7 and 8) is possible depending on the course of the reaction, only gave the alkylaryldithiirane 7 in 59% yield by treatment with NaOCl-NaC104 (97BCJ509). Tliis is suggestive of the intermediate formation of the more stable, diaryl-substituted carbocation 9 and not the other counterpart 10. 

Tire reaction of 1,3-dithietanes 14 with OXONE produced dithiirane 1-oxides 15 directly (95TL1867). Dithiirane 1-oxides 15 would be formed through the initially formed 1,3-dithietane oxides. 

Tile 1,3-dithietaiie 11a, when heated, rearranged quantitatively into a disulfide 111. Tlie reaction may involve a dithietane 112 as an intermediate, although a [3,3] sigmatropic rearrangement of 113 could equally explain the formation of 111 (90JOC2421). 

Photochemical reaction of the ester 114 afforded the alkene 115 and three products derived from 115. A mechanism, involving dimerization of 114 leading to a dithietane intermediate 116, was proposed. Trapping of active sulfur species, generated from 116, with dienes was also described (75CB630). 

Tlie following are the typical reactions of the dithietane 73. Treatment of 73 with PI13P led to the loss of one sulfur and the formation of the rearrangement products 121 and 122. Treatment with PhS resulted in the formation of 123, whereas brief exposure to NaBFL, followed by trapping with Mel led to the novel episulhdes 124 and 125 and the alkene 126. 

H321). Tliese radical cations exist in a nonplanar conformation. With fra s-3,4-dimethyl substituents, the barrier to ring flip was estimated to be >5 kcal/mol. In connection with reactions of thiirane with the thiirane radical cation, ab initio calculations were reported on the 1,2-dithietane radical cation (93JA12510). 

The 1,3-dithietane tetroxides (7b) readily undergo tetra-a-halogenation275 with either Br2 or Cl2, but not with I2. Partial a-halogenation in this series can be accomplished indirectly by starting from either 2,4-bis(trimethylsilyl)- or 2,4-bis(t-butyldimethyl-silyl)-l, 3-dithietane tetroxides (275) as shown in equation 103275. In all of the above reactions one takes advantage of the highly acidic a-hydrogens and, consequently, the... 

The preparation and investigation of the thietane oxide system (5a) is largely associated with stereochemical and conformational studies . The investigation of the thietane dioxides (5b) is substantially related to the chemistry of sulfenes , the [2 -I- 2] cycloaddition of which with enamines is probably the method of choice for the synthesis of 5b . The study of the thiete dioxide system (6) evolved, at least in part, from the recognition that the unstable thiete system 183 can be uniquely stabilized when the sulfur in the system is transformed into the corresponding sulfone , and that the thiete dioxide system is very useful in cycloadditions and thermolytic reactions. The main interest in the dithietane oxides and dioxides (7) appears to lie in the synthetic challenge associated with their preparation, as well as in their unique structural features and chemical behavior under thermolytic conditions . ... 

Raasch, and Schaumann and co-workers, have studied the reactions of bis (trifluoromethyl)thioketene (83 R1 = CF3) with alkenes, with thioketones, and with carbodiimides or Schiff-base imines. The products were, respectively, thietans, 1,3-dithietans (84 R1 = CF3), and 1,3-thiazetidines (85 R1 = CF3) (from the carbodiimide).114,115 With phenyl azide the 1,2,3,4-thiatriazoline (86 R = CF3) is formed subsequent pyrolysis yields2,l-benzisothiazole.114... 

The 1,2-dithiete 34 has been prepared <98JOC8192> and X-ray crystal structure determination shows the ring to be planar as had previously been shown for sterically hindered 1,2-dithietes <98BCJ1181>. Prolonged reaction of (alkylthio)chloroacetylenes (RSC i CCl) with NaiS in DMSO yields 1,3-dithietanes 35 <99SUL57>. 

A number of routes to thiocarbonyl fluoride that do not involve tetrafluoro-dithietane have been developed. In one (50), phosgene is chlorinated to give tri-chlorosulfenyl chloride, which is converted to chlorodifluorosulfenyi chloride by reaction with antimony trifluoride, and the fluorinated compound is then dehalogenated by reaction with tin. 

With slight modification, the methods used to prepare fluorothioacyl fluorides can also be used for synthesis of fluorothioketones. Hexafluorothioacetone, the member of this class that has been studied most extensively, is readily obtained by high-temperature reaction of hexafluoropropylene and sulfur (53). The thio-ketone is a deep-blue liquid, bp 8° C, that dimerizes on standing to 2,2,4,4-tetrakis-(trifluoromethyl)-l,3-dithietane. 

A recent study (57) indicates the disulfide can also be formed by reaction of hexafluoropropylene with potassium fluoride and sulfur. It appears that the key intermediate in this reaction is the anion (CF3)2CFSe. 2,2,4,4-Tetrakis(tri-fiuoromethyi)-l,3-dithietane and (CF3)2CFSCF=C(CF3XCF2)2CF3 are also said to be formed. 

Further evidence of facile substitution on sulfur is shown by the reaction with trifluoromethyl hypochlorite. The sulfurane is stable to 100 °C where it reverts to 1,3-dithietane and peroxide (Scheme 30) (77JA4194). 

The 1,4-diazepine system has also been synthesized by the reactions of 1,2-diamines with various other reagents, e.g. ketene dimers (68CRV747, p. 778) 1,3-diynes <74AHC(17)1, p. 5), bis(cyanomethylene)-l,3-dithietanes (76T483). 

The reactions of perfluorinated cyclic sulfides, e.g. perfluorotetrahydrothiophene, per-fluoro-l,3-dithietane, and perfluoro-l,4-dithiane. proceed in a similar way.98... 

The reaction of carbon disulfide with a-functional phosphonates [(Rl0)2P(0)CH2X] in the presence of bases gives di-thiolates which, on treatment with gem-dihalides (R2CHBr2), yield (46) (94MI409). 1,3-Dithietanes (47) on reaction with hydrazides (RCONHNH2) yield the 1,3,4-oxadiazoles (48) (94H185,... 

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