1.3.2.4.6- Dithiatriazine

The polyazapolysulfur ring system 1,3,2,4,6-dithiatriazine 15 is obtained by reacting 1-aryl-2,2,2-trifluoroethanone oximes with tetrasulfur tetranitride in refluxing toluene. However, the yield is only moderate <%JHC295>. 

The NH groups of sulfonamide functions are also readily alkylated. The 1,2,6-thiadiazine dioxide (74) gives the 2-methyl derivative on treatment with iodomethane in acetone in the presence of potassium carbonate <65CI(L)182). The 1,3,2,4,6-dithiatriazine (75) forms a silver salt (64MI22800), and reaction of the salt with iodomethane gives the expected TV-methyl compound. 

Thiadiazines can also be prepared from [3 + 3] condensations involving sulfur diimides. Thus reaction of bis(lV-tosyl)sulfur diimide (69TL4117) with 1,3-diaminopropane gives the thiadiazine (18). Bis(trimethylsilyl)sulfur diimide reacts with CSI to give a 1,3,2,4,6-dithiatriazine (74CB1,.74ZN(B)799) (Scheme 27). 

Considerable interest has been shown in the reaction of 1,3,5-trichlorotrithiatriazine with nucleophiles in order to prepare new heterocyclic S—N systems. Most of the preparative routes to dithiatriazines involve the reactions of nitriles with thiazyl chloride monomer or dimer.18 20,22 However, these methods generally lead to a mixture of products.The silylated imidamide 1 was found to be a mild selective reagent in the reaction with trichlorotrithiatriazine 2.23 Thus, 7-phenyl-l A4, 3/l4-,5/l l-trithia-2,4,6,8,9-pentaazabicyc]o[3.3.1 ]nona-1(9),2,3,5,7-pcn-taene (3) can be prepared in dichloromethane solution from silylated benzimidamide 1 and trichlorotrithiatriazine 2. The molecule8 can be described in terms of a 1,3,2,4.6-dithiatriazine bridged by a N-S-N fragment across the 1,3-sulfur atoms. 

Dithiatriazine Oligomers and Chlorine, Bromine or Xenon(II) Fluoride... 

The reduction of 5-(trifluoromethyl)dithiatriazine 6a with zinc dust in liquid sulfur dioxide at room temperature gives the five-membered radical 7 in 26% yield. At 0 °C the same procedure gives the 1,3,2,4,6-dithiatriazine oligomer.20 The 1,3-dibromo compound 6b decomposes to radical 7 with elimination of bromine and nitrogen.14... 

The 1,3,2,4,6-dithiatriazines (7) are also formally 8ti electron systems, and are thus antiaromatic. The formation of the dimer on reducing the dichloro compounds is attributed to the coupling of the triplet states of (7) to achieve a singlet ground state <85JA7710,92IC1417>. 

The reactions of the non-5-chlorinated 1,3,2,4,6-dithiatriazines are, in fact, reactions of the dimers. These undergo addition reactions with alkenes to give adducts (85CC929,85MCLC447,861C47, 86IC2119,91CB39>. 

Dithiatriazines are also obtained by reacting S3N3CI3 with amidine salts. For example, reaction with A,A-dimethylguanidinium hydrochloride provides 5-dimethylamino-l,3-dichloro-1,3,2,4,6-dithiatriazine (62) in low yield <83ZN(B)347>. 

Trichlorotrithiatriazine and cyanogen chloride gives 1,3,5-trichloro-1,3,2,4,6-dithiatriazine (26% yield). This reacts slowly with excess cyanogen chloride to give l,3,5-trichloro-l,2,4,6-thiatriazine and trichloro-l,3,5-triazine <93CB260l>. 

A bicyclic 5-phenyl-1,3,2,4,6-dithiatriazine derivative (63) is obtained by the slow addition of a solution of iV,A,iV -tris(trimethylsilyl)benzamidine in dichloromethane to S3N3CI3 in dichloro-methane at 0°C <85JA7710>. 

The crystal structure of 1,3,2,4,6-dithiatriazine 21 (Ar = Ph) was reported to be triclinic with space group P Z. This molecule is nonplanar and not aromatic <1996JHC295>. 

The 1,3,2,4,6-dithiatriazine 21 (Ar=Ph) is inert to concenttated hydrochloric acid and TFA in dichloromethane at room temperature and does not react with 4-biphenylcarbonyl chloride in the presence of triethylamine <19%JHC295>. 

The 1,3,2,4,6-dithiatriazines 21 were prepared in moderate yields (17-37%) from 2,2,2-trifluoroacetophenone oximes by treatment with tetrasulfur tetranitride in refluxing toluene. The aminosulfenamides 128 and sulfur were also formed as by-products (see Equation 3) <1996JHC295>. 

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