Tetrasulfur tetranitride, reaction with

The first reported synthesis of the new class of 10 i heteroaromatic systems was made by Daley, Rees, and Williams <84CC55>. The method of obtaining these compounds was the reaction of tetrasulfur tetranitride, S4N4, with dimethyl ethynedicarboxylate in boiling toluene, which was reported <79JHC1009> however, the incorrect structures of products were proposed. 

The only heterocyclic seven-membered ring system with maximum unsaturation containing six heteroatoms is 1,3A4,5,2,4,6-trithiatriazepine (1). The methoxycarbonyl derivative 2 is a minor product (14%) of the complex reaction of tetrasulfur tetranitride with dimethyl acetylenedicarboxylatc in refluxing toluene, which gives mainly dimethyl l,2,5-thiadiazole-3,4-dicarboxylate (3, 67%) (see Houben-Wcyl, Vol. E8d, pl54ff which includes an experimental procedure). Two other products are the trithiadiazepine 4 (5%, see Section 4.4.1.1.1.) and the 1,2,4-thiadiazole derivative 5 (3%).385... 

The yield of the ester 2 in the reaction of tetrasulfur tetranitride with dimethyl acetylenedicarb-oxylate is increased if the reaction is conducted at lower temperatures. The ester is transformed into the parent trithiatriazepine 1 by hydrolysis, followed by decarboxylation of the resulting acid.417... 

As in the case of Group IVA, combinations with these typical non-metals will not be treated in detail insofar as nitrogen compounds are concerned. Of interest with respect to this review are the highly conducting compounds that are obtained by the room-temperature reaction of tetrasulfur tetranitride with halogens, e.g., (SNBrg4)j. (1, 366,423). 

Aroylformamido-4-aryl-l,2,5-thiadiazoles 156 can also be prepared from aryl dibromomethyl ketones 155 on treatment with tetrasulfur tetranitride at 115 °C (Equation 31) <1995J(P1)253>. These reactions are, however, complex, and the 1,2,4-thiadiazole 157 is often produced as a minor product. 

Unlike the reaction of alkyl aryl ketoximes with tetrasulfur tetranitride <1996CHEC-II(4)355>, the treatment of alkyl methyl ketoximes 189 with tetrasulfur tetranitride antimony pentachloride complex in either benzene or toluene at 50-80°C gave low yields (3-37%) of 3-alkyl-4-methyl-l,2,5-thiadiazoles 190 (Equation 39) <1999H(50)147>. Compounds 190 were volatile and the low yields are in part attributed to their loss as the solvent was removed in vacuo. Suprisingly, only single regioisomers were obtained. 3-Heptanone oxime 191 did, however, give a mixture of two isomers 192 and 193 (Equation 40). 

In a development on the reaction of monohaloalkyl aryl ketoximes with tetrasulfur tetranitride, the introduction of two halogens such as chlorine, bromine, or fluorine at the a-position of alkyl aryl ketoximes significantly improved the yields of thiadiazoles <1998J(P1)109>. The preferential displacement of chlorine over bromine or fluorine allowed the preparation of monobromo- and monofluoro-3-aryl-thiadiazoles 195 from a,a-chlorobromoalkyl- and a,a-chlorofluoro-alkyl aryl ketoximes 194 (Equation 41). 

The reaction of active hydrocarbons, phenols, and related compounds with tetrasulfur tetranitride affords fused thiadiazoles, and this chemistry is well documented in CHEC(1984) <1984CHEC(6)513> and CHEC-II(1996) <1996CHEC-II(4)355>. No recent work has been reported. 

Reactions of arylchloromethyl-p-tolyl sulfoxides with tetrasulfur tetranitride (S4N4) yield 3,5-diaryl-1,2,4,6-thiatriazine 1-oxides <00T7153>. [4+2] Cycloadditions of thiazyl... 

The reactions of l-aryl-2,2,2-trifluoroethanone oximes 378 with tetrasulfur tetranitride (S4N4) in toluene at reflux gave 5-aryl-5-trifluoromethyl-4//-l,3,2,4,6-dithiatriazines 379, l-aryl-2,2,2-trifluoroethylideneaminosulfenamides 380 and sulfur (equation 165) . ... 

Reaction of tetrasulfur tetranitride with aryl and alkyl bromomethyl ketones (288) in refluxing chlorobenzene gives 3,5-diaroyl and 3,5-diacyl-l,2,4-thiadiazoles (98) in yields of 17-60% (Equation (44)) <92JHC1433>. 

The reaction of tetrasulfur tetranitride with phenylacetylene affords the imine (338), which can be oxidized to the monoxide (339). The monoxide (339) then undergoes facile hydrolysis to 3,5-dibenzoyl-1,2,4-thiadiazole (340) probably, by the mechanism shown in Scheme 75 <89CC1134>. 

A series of 3-acyl and 3-aroyl-4-substituted 1,2,5-thiadiazoles 82 have been synthesised by reaction of 3,S-disubstituted isoxazoles 81 with tetrasulfur tetranitride antimony pentachloride (S4N4.SbCl5) in toluene at 90 C to reflux temperature. Compounds 82 are produced regioselectively and a plausible mechanism for their formation discussed. Under the same conditions, 3,4-dialkyl and 5-alkyl(aryl)-isoxazoles furnished chloroketones of type 83 <98JCS(P1)2175>. 

This compound is prepared by the reaction of tetrasulfur tetranitride with sulfur. An autoclave, fitted with a magnetic stirrer and capable of being heated to 100°, is used as the reaction vessel. A mixture of 24 g. of tetrasulfur tetranitride and 50 g. of sulfur is suspended or, respectively, dissolved in 380 ml. of pure carbon disulfide. The mixture is heated in the autoclave for 2 hours at 110° and then cooled rapidly. It is then filtered from the polythiocyanogen which is formed under these conditions, and the residue washed well with carbon disulfide. These washings are added to the original filtrate, and this is then evaporated in vacuum. The red residue after removal of carbon disulfide is distilled in high vacuum with a bath temperature of 60 to 65°, whereupon dark red crystals separate in the receiver (f.p. 23°). It is found that the best yields are obtained when the walls of the autoclave are soiled from a previous preparation, in which case about 4 g. of tetrasulfur dinitride is usual. 

Thionyl fluoride can be prepared by the reaction of thio-nyl chloride with metal fluorides such as zinc(II) fluoride1 and arsenic (III) fluoride,2 and with metal fluorosulfites.3 It is also obtained by the action of hydrogen fluoride upon a mixture of tetrasulfur tetranitride and copper(II) oxide4 and by the reaction of hydrogen fluoride with thionyl chloride in the absence of6 or in the presence of6 antimony(V) fluoride as catalyst. Another method and the simplest on a laboratory scale involves the reaction of antimony(III) fluoride with thionyl chloride in the presence of antimony ) chloride as catalyst.7 This last procedure is described below. 

Tetrasulfur tetranitride undergoes a number of interesting reactions. Hydrolysis of the compound in basic solution produces NH3 as the nitrogen product in accord with nitrogen having the higher electronegativity ... 

Where possible, carry out reactions with tetrasulfur tetranitride in an inert solvent, either in solution or as a suspension. The use of an inert solvent is particularly recommended for reactions with strong nucleophiles or electrophiles.5... 

In exploratory reactions do not use more than 0.1 g and keep reaction temperatures down to a minimum and below 100°. Reactions with metal carbonyls are especially hazardous.6,7 A total of up to about 10 g can be used in a well-tested preparation of a compound of known stability, but it is advisable to add the tetrasulfur tetranitride in portions of not more than 0.5 g and to allow each portion to react before adding more. 

Diazoalkanes react with tetrasulfur tetranitride to give red crystalline l,3/l 5, 5,2,4-trithiadiazines (85), a new ring system with an almost planar ring. Thus, addition of ethereal diazomethane to S4N4 in dichloromethane at room temperature affords, after 0.5 h, the 1,3,5,2,4-trithiadiazine in 37% yield. Similar reaction of S4N4 with aryldiazomethanes gives open chain compounds as major... 

Kim and Kong " isolated 2-aroyI-5-aryIoxazoIes 617 together with 2-aroyl-5-arylimidazoles 618 from reaction of arylglyoxals with tetrasulfur tetranitride (S4N4) (Scheme 1.168). 

Molecular orbital calculations have been widely used both for the investigation of the structure and the aromaticity of these seven-membered heterocycles as well as for the determination of the reaction pathways. A qualitative analysis based on MNDO and ab initio molecular orbital calculations has been reported <87JCS(P1)1579,87JCS(P2)i669> for the cycloaddition of several alkynes to tetrasulfur tetranitride with the formation of trithiadiazepines and 1,2,5-thiadiazoles (see heme 28). 

The first l,3A 5, 5,2,4,6-trithiatriazepine (17) was described in <84CC55) and after that in following papers by Rees and co-workers. Schemes of the syntheses and some properties of this class of compounds are given in a series of reviews. Formation of the trithiatriazepine upon the interaction of tetrasulfur tetranitride with alkynes requires a more complex pathway for the reaction mechanisms. A concise route is shown in Scheme 29 with slight modification this route also leads to the trithiadiazepine <87JCS(P1)203>. 

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