1,2,3,5-Oxathiadiazine 2,2-dioxides

Oxathiadiazine-2,2-dioxides, 1,4,3,5-oxathiadiazine-4,4-dioxides, and l,2,4,5-oxadithiazine-2,2,4,4-tetraoxides formed from cyano compounds and S03 93MI22. 

The crystal structure of the 1,2,3,5-oxathiadiazine 2,2-dioxide (13) has been reported to be triclinic with the space group PI with z = 2 <9lJOU759>. 

The crystal structure of 1,2,3,5-oxathiadiazine-2,2-dioxide 24 was mentioned briefly in CHEC-II(1996) <1996CHEC-II(6)967>. The S-O bond length of 1.632 A is significantly longer than the analogous bond (1.610 A) in the cyclic trimer SO3 and this is consistent with the observation that this bond, rather than the C-O bond, ruptures in reactions of 24 with nucleophiles (see Section 9.14.5) <1997CHE1028>. 

Oxathiadiazine 2,2-dioxides 74 react readily with aqueous acid to produce (depending on substituents and conditions) A -acylamidines 104 or imides 105 (Scheme 8). Reaction of 74 (R = R = aryl) with alcohols in benzene in the presence of a small amount of water affords A -sulfamidines 106 (Scheme 8). Treatment of 74 with amines results in rupture of the C-O bond and formation of products such as 107 and 108 (Scheme 8) <1997CHE1028>. 

At room temperature and below, hydrolysis of oxathiadiazines 111 with water bound to 7-alumina affords 1,2,3,5-oxathiadiazine 2,2-dioxides 24, CX3CO2H, and ammonia (path 1), while at 30-50 °C, elimination of the CX3CO group is accompanied by a rearrangement (path 2) to furnish the 1,2,4,6-thiatriazine 1,1-dioxides 72 (Scheme 9) <2000RJ01229>. 

Pyrimidines. 4,6-Diphenyl-l,2,3,5-oxathiadiazine 2,2-dioxide added to a suspension of ethyl sodiomalonate in dioxane, and heated 1 hr. at 100° after the slightly exothermic reaction has subsided 4-hydroxy-2-6-diphenyl-5-ethoxycarbonylpyrimi-dine. Y 82%. - Various other heterocyclics can be easily prepared from 1,2,3,5-oxathiadiazine 2,2-dioxides. F. e. s. H. Weidinger and H. J. Sturm, A. 716, 143 (1968). 

Cycloadditions The [2+2+2] cycloaddition reaction of olefins with SO3 occurs via a [4+2] cycloaddition of an intermediate dipole with another equivalent of SO3. Benzonitrile also reacts with SO3 at 0 °C to form an ionic intermediate 78, which reacts with another equivalent of benzonitrile to form 4,6-diphenyl-1,2,3,5-oxathiadiazine-2,2-dioxide 79. ... 

Certain nitriles react with the sodium salt of carbomethoxysulfamoyl chloride to afford 6-substituted 2-methoxy-1,4,3,5-oxathiadiazine dioxides 65, whereas A -chlorosulfonyl-N -methyl-N -phenylurea with an excess of... 

Disubstituted l,2,3,5-oxathiadiazine-2,2-dioxides, synthesis, structural features, chemical properties 97KGS1182. 

Diaryl-l,2,3,5-oxathiadiazine 2,2-dioxides (187) are valuable starting reagents which are readily prepared by treatment of the aryl cyanide with sulfur trioxide. Amidines, imidates and trichloroacetonitrile react with (187) to give a wide range of 4,6-diaryl-l,3 5-triazines in 50-90% yields under acidic conditions (equation 108) (63CB2070). 

The oxathiadiazines (106) (73TL2783) and (107) (77ZC222) are ring opened by nucleophilic attack at the sp2 carbons indicated. The oxathiazine dioxide (108) is reduced to the 3,4-dihydro derivative by 0.5 equivalent LAH (72JOC196), although the isomeric chlorooxathiazine dioxide (109). behaves differently towards nucleophiles. Nucleophilic attack at C-6 followed by elimination of SO3 and chloride ion occurs as shown (80AG(E)131). 

Jones and Paisley have reported the ionic and thermal fragmentation of 4,6-diphenyl-l,2,3,5-oxathiadiazine-2,2-dioxide, 26. Thermal decomposition of 26 in the solid state leads to formation of benzonitrile and a brown-colored intractable glass. The major ionic decomposition pathways for 26 are shown in Eq. (17). The failure of 26 to eliminate SO 2 on thermolysis lysis may reflect a heteroatom effect it may also be due to a medium effect with the SO 2 being trapped before it could escape the solid. It should be noted that the only volatile pyrolysis product, benzonitrile, appears as an intense ion, mfe 103, in the mass spectrum of 26. 

An unusual preparation of triazoles proceeding through an amidrazone intermediate (278 Scheme 123) is the transformation of 4,6-diphenyl-l,2,3,5-oxathiadiazine 2,2-dioxide (279) with hydrazines to 3,5- or 1,3,5-triaryltriazoles (280) (63CB2070) in yields of around 90%. 

Section III deals with 1,2,5-thiadiazole 1,1-dioxides and fused systems. Other six-membered rings, such as thiatriazines and oxathiadiazines are gathered in Section IV, and Section V deals with miscellaneous compounds. Finally, in Section VI, the biological properties and other applications are described. 

Two more complicated ring-contraction reactions, both yielding 4-amino-3-oxothiadiazoline 1,1-dioxides, are known. Disselnkoetter reported (71GEP1961864) that the reaction of 1,4,3,5-oxathiadiazine 127 with hydrogen cyanide produced imino derivatives 128, which were easily hydrolyzed to the corresponding oxo derivatives 89b by acid treatment (Scheme 49). The course of the reaction may involve addition of cyanide ion, decarboxylation of the resulting carbamic acid, and a nucleophilic attack at the carbonitrile group, as shown in Scheme 49. 

These heterocycles include thiatriazine 1,1-dioxides, which have been the most studied six-membered heterocycles containing other heteroatoms besides the sulfamide moiety. The herbicidal activity claimed in a number of patents for 1,2,4,6-thiatriazine 1,1-dioxides has prompted the preparation and study of several of its derivatives. The less reported oxathiadiazine 4,4-dioxides and dithiadiazine 1,1-dioxides are also included in this section. 

This fragmentation is apparently thermodynamically controlled, with the equilibrium favoring the cyclized compound 65 (80JOC72I). Reaction of 65 and ynamines afford thiadiazine derivatives 68 and 69 (Section II,C,l,d). 2,6-Dichloro-l,4,3,5-oxathiadiazine 4,4-dioxide (202) decomposes above 100°C (Section IV,C,2) to give CSI and cyanogen chloride. 

Diaryl-l,2,3,5-oxathiadiazine 2,2-dioxides 3, obtained by the cyclization of two equivalents of an aryl cyanide with sulfur trioxide,22 react with a variety of imido derivatives to form 6-substituted 2,4-diaryl-1,3,5-triazines 4 in yields ranging from 25 to 92%.23-25 The reactions are carried out between 20 and 160°C, and in most cases are complete in a short time. 

It is known that the 1,3,2,4,5-dioxadithiazine 2,2,4,4-tetraoxide plus base system reacts via sulfonylimidates with nitriles to give l,4,3,5-oxathiadiazine-4,4-dioxides (69) (Scheme 14)... 

Heating the 2,4,6-trisubstituted-l,2,3,5-oxathiadiazine 2-oxide 111 (X = Cl, NR2 = piperidino or pyrrolidine) at 60 °C in benzene, toluene, or chloroform with an equimolar amount of water resulted in conversion to the salts 26 (Scheme 10). This process apparently involves initial hydrolysis of the trichloroacetamide fragment followed by an unusual substitution of the piperidino or pyrrolidino moiety by the CCI3 group with concomitant loss of CO2. Treatment of salts 26 with sulfuric acid affords the 1,2,4,6-thiatriazine 1,1-dioxide 112 which revert to salts 26 with piperidine or pyrrolidine <2002RJ01702>. 

The 2,6-disubstituted-l,4,3,5-oxathiadiazine 4,4-dioxides 62 readily undergo hydrolysis to give the acyclic compounds 113 in almost quantitative yield (Scheme 11) <2000RJ01523, 2002RJ0889>. 

Reactions of 2,6-di(trihalomethyl)-substituted 1,4,3,5-oxathiadiazine 4,4-dioxides 62 with substituted cyanamides in aromatic solvents (benzene, toluene, chlorobenzene, benzonitrile) furnish stable complexes 27 including 1,4,3,5-oxathiadiazine 4,4-dioxide, symmetric triazine, and solvent (or no solvent) in a ratio of 2 2 1. The molecules involved in the complexes are joined by intramolecular (van der Waals) forces into a unified, energetically favorable supra-molecular system (Scheme 15) <2005RJ0289>. 

An unexpected transformation of 2,4,6-trisubstituted 1,2,3,5-oxathiadiazine 2-oxide derivative 18 on alumina, yielding 1,2,4,5-thiatriazine 1,1-dioxide derivatives 19, has been reported . 

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