Reactions of 1,3-Dithietans

Reactions of 1,3-Dithietans.—Monothiobenzil can be generated by photolysis of its dithietan dimer.Dithietanones (121) can be used as thioketen equivalents. Tetrafluoro-l,3-dithietan reacts with oxygen atoms to give CFj, SO, and CFjS as primary products, and with trifluoromethyl hypochlorite to give (122). With tris(trifluoromethyl)methyl hypochlorite it gives (123). The 1,1-dioxides and the 1,1,3,3-tetroxides of tetrafluoro-, tetrachloro-, and tetrabromo-l,3-dithietans have been reported.  

Aldehydes can be converted into their hexafluoroisopropylidene derivatives (124) by reaction with triphenylphosphine and 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietan.  

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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. 

The methodology based on the reaction of 1,3-dithietanes with quadricyclane 67 was applied to the synthesis of polyfluorinated sulfur-containing polycyclic hydrocarbons. The reactions of 2,2,4,4-tetrakis(trifuoromethyl)-l,3-dithietane 66 with quadricyclane 67 under various conditions gave the cycloadduct 68 in high yields (Equation 9) <2005JFC(126)1332>. 

The reaction of 1,3-dithietane 92f substituted with a diethylphosphoryl group with G-nucleophiles is analogous to the previously reported reaction. Its condensation with different C-nucleophiles, such as cyclic and acyclic a-carbonyl-methylenes and a-carbonylhydrazones, gave a number of [2,l-3]fused phosphono-substituted thioxopyranes 97, 100, 103, 107, oxadiazine 109, and thiazine 105 (Scheme 12), which are of potential biological interest <2002PS1885>. 

The vast majority of the compounds of this type are prepared through condensation of aldehydes, primary amines and HjS or variants thereof (Scheme 16). Although other methods exist, e.g., the reaction of 1,3-dithietan-2-ones with aldimines to give systems like (86) <84CB2205>, they have found little general use because the three compounds in the condensation process are so simple. This reaction is extremely simply carried out in one pot to furnish the 1,3,5-dithiazine in acceptable yield. 

Previously difficult substitution reactions of 1,3-dithietan 1,1,3,3-tetroxide (50) are now possible. The formation of the silyl derivative (51) (see Scheme 8), its conversion into the dithieten (52), followed by the addition of electrophiles forms the substitution products. The dithieten (52) can be considered as the first enol ether of a sulphone. The transient benzothiet (53) has been prepared by the thermolysis of (54), its structure having been confirmed by i.r. and photoelectron spectroscopy. ... 

Another reported synthesis of symmetrical spiro-1,3-dithietanes 163a-d substituted with an adamantyl moiety is based on the [2+2] cycloaddition of two molecules of variously substituted adamantane-2-thiones <1997BCJ509>. With methanesulfonic acid as an acidic catalyst, the reaction provided 1,3-dithietanes 163a-d in high yields at ambient temperature. A similar reaction was performed with phosphorus pentachloride as the catalyst (Equation 22 Table 8) <2002AXCo231>. 

Several syntheses of l,3-dithia-2,4-diphosphetane derivatives may be considered as formally proceeding via dimerization through P=S bonds,analogous to the formation of 1,3-dithietanes by dimerization of thiocarbonyl compounds (Section XXXVI.3.A). These reactions include indirect methods involving the addition of elemental sulfur to aminoiminophosphines (e-g., the synthesis of 618) or phenylphosphine and treatment of thiophenol with P4Sio, ° as well as direct... 

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. 

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... 

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... 

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... 

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>. 

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 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,... 

Ab initio calculations have also been carried out <2003JFC(124)99> for the photodimerization reaction of trifluoro-thioacetyl fluoride 13 which affords approximately equal amounts of trans- and >-2,4-difluoro-2,4-bis(trifluoromethyl-1,3-dithietane) 14 (Scheme 1) <1965JOC1375>. The calculations indicate that both dimers are thermodynamically stable relative to the monomer, and of almost equal stability. The Ec and G2gs.is values obtained in the G3(MP2) calculations of the dimers relative to monomers gave 115 and 45 kj mol-1 for cis-14, while the corresponding values for trans-14 were 112 and 44 kj mol-1. For both isomers, the 1,3-dithietane ring was found to be planar <2003JFC(124)99>. 

Photochemical oxidation of the dimer 59 led to an unexpected photochemical oxidation reaction, giving dioxide 60 and its rearrangement to 61. Exposition of the 1,3-dithietane 59 to oxygen and LJV light led to the formation of the stable disulfenate 61, uncommon in the literature. The proposed mechanism for the transformation 59 —> 61 is shown in Scheme 6, but other possibilities are not excluded <2004TL7655>. 

The cyclic disulfone, 1,3-dithietane 1,1,3,3-tetraoxide 83, underwent Knoevenagel and substitution reactions to form a new class of unsaturated disulfenes. Thus, its treatment with isobutyraldehyde in the presence of a catalyst gave 84 bearing unsaturated vinylic moieties, the double bonds of which were resistant to all typical olefin reactions. Deprotonation of 84 and subsequent silylation with C4F9-S02-0SiMe3 yielded 2,4-disilylated product 85 (Scheme 9) <1996CB161>. 

The suggested reaction mechanism assumes an initial nucleophilic attack on the 1,3-dithietane carbon by the a-C-atom of the substituted acetonitriles with subsequent cyclization and transformation of the cyano groups, which lead directly to the observed y-thiapyrones 94 <1998H(47)221>. 

A 2 day reaction of ethyl carbon(isothiocyanatidate) 183 carried out in water furnished the 1,3-dithietane 184 in 75% yield (Scheme 22) <1998EJI1025>. The occurrence of the intermediate 185 has been demonstrated. 

As a modification of this procedure, one can consider the reaction of ketones with sulfurating agents leading to thioketones which next react via a [2+2] cycloaddition to furnish 1,3-dithietanes. Thus the reaction of 1,5-diketones with Lawesson s reagent afforded fused 1,3-dithietanes 186 in high yields (Equation (31) Table 9) <1997BCJ509, 2000JOC1799>. 

Table 9 Reaction of 1,5-diketones with Lawesson s reagent to form fused 1,3-dithietanes 186 (Equation 31)...

A very similar reaction of carbon disulfide with ACV-diethyl prop-l-ynyl amine produced the symmetrically substituted bis-methylidene 1,3-dithietane 189 in only 9% yield (Equation 34) <1998T9849>. 

The reaction of nitroketene dithioacetate with dibromomethane in methanol gave 2-nitromethylene- 1,3-dithietane 190 in 35% yield (Equation 35) <2000AXC1113, 2002SUL207>. 

The reactions of carbon disulfide with compounds 191 under phase-transfer catalysis (PTC) conditions followed by the reaction of the formed intermediate with 5,5-dibromo-3-phenyl-2-thioxo-thiazolidin 4-one 192 gave spiro-1,3-dithietane derivatives 193 (Scheme 23) <1997PS173>. 

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