1.2.4- Dithiazolidine-, 3- thione

A related cycloaddition/elimination reaction occurs when 5-imino-1,2,4-dithiazolidin-3-ones (300) or -3-thiones (306) are treated with phenylisocyanate to afford 2-phenyl-5-imino-1,2,4-thia-diazolidin-3-ones (307) (Equation (45)) <92JPR685>. 

Isomerization of 5-imino-l,2,4-dithiazolidine-3-thiones (34) into l,2,4-thiadiazolidine-3,5-di-thiones (51) by a Dimroth rearrangement (see Section 4.13.6.1.1) is a reversible process <91JPR107>. The equilibrium position strongly depends on the nature of substituents. When R = R = Me or Pr the equilibrium position is (34) (51) =1 2, with R = R = Et the ratio is 1 9. When R = Ar, R = Aik, the equilibrium is almost wholly shifted to the right. The forward process is usually accelerated by bases, the reverse by acids. When both substituents are Ar no isomerization occurs <91JPR107>. Isomerization of the 3,5-diimino analogue (52) to a monothione isomer (53), accelerated by pyridine, reaches an equilibrium ratio of (52) (53) =1 9 <89BSB879>. 

Fused 5-imino-l,2,4-dithiazolidine-3-thiones and 3-imines (100) take up nucleophiles on one sulfur atom, releasing the XCS structural unit of the heterocycle (Scheme 15) <85JCS(P1)1007>. Nonfused analogues (101) give up one sulfur atom to the nucleophile, the rest of heterocycle closing to form a 1,3-thiazetidine ring (102) (Scheme 16) <87ZC142>. 

Two products are isolated from the reaction of 4-methyl-5-methylimino-l,2,4-dithiazolidine-3-thione (108) with nitriles (Scheme 23) its 1,2,4-thiadiazolidine isomer (109) and a 1,2,4-thia-diazolidine derivative incorporating the nitrile unit (112). A sequence of 1,3-cycloaddition-elim-ination steps via heteropentalene intermediates is proposed for the process <9lJOC3268). 

Amino-1,2,4-dithiazole-5-thione may be used for corrosion inhibition of Cu-)-Zn powder mixture <86Mi 413-03) or for inhibition of polymer ageing <85URPl 142485) A-alkoxy derivatives inhibit corrosion of iron <91URP1650683,82MI413-06,82MI413-07). 1,2,4-Dithiazolidines (247 = H,... 

Substituted thiatriazoline-5-thiones are probably formed in the reaction between alkyl azides and phenyl isothiocyanate.66 In this case the reaction is conducted at 80-100° in the absence of solvent, and the primary products cannot be obtained. With two equivalents of phenyl isothiocyanate, 4-alkyl-3,5 -bis(pheny limino)-1,2,4-dithiazolidines are formed in 29-65% yield [Eq. (20)]. 

This reaction may involve stepwise addition of the two equivalents of PhNCS via a 3-membered ring intermediate, RN—S—C=NPh.66 A thia-ziridine was also suggested by Borsche67 to explain the formation of 4-phenyl-5-phenylimino-l,2,4-dithiazolidine-3-thione from the aluminum chloride-catalyzed decomposition of phenyl azide in carbon disulfide. If a 4-substituted thiatriazoline is formed from phenyl isothiocyanate and the alkyl azide, the reaction may then be formulated as indicated in Eq. (21). This scheme is supported by the recent findings of Neidlein and... 

Only a few examples of a nucleophilic attack at the nitrogen atom of 1,2,4-dithiazolidine derivatives are known. 5-Imino-l,2,4-dithiazolidine-3-thione gives tribenzyl-substituted 5-imino-l,2,4-thiadiazolidine-3-thione with an excess of boiling benzylamine <1996CHEC-II(4)453>. l,2,4-Dithiazolidine-3,5-dione 12 forms the potassium salt 11 under the action of KOH in ethanol or KH in MeCN (Scheme 15) <2000SL1622>. 

This approach to 1,2,4-dithiazolidine derivatives 124 was investigated in detail by L abbe and co-workers on the example of a reaction of 4-alkyl-5-arylimino-l,2,3,4-thiotriazolines 123 and related compounds with isothiocyanates and other heterocumulenes. In these reactions, in addition to compounds 124, l,2,4-thiadiazolidine-3-thiones 125 are formed (Equation 17) <1996CHEC-II(4)453>. 

The heating of 4-o-tolyl-l,3-dithia-2,5-diazolium hexafluoroarsenate 154 with a small excess of o-tolylcyanide 155 in liquid S02 leads to 1,2,4-dithiazolium hexafluoroarsenate 6 in low yield (Equation 24) <1996AXC2148>. The decomposition of the known pesticide, 3,5-dirncthyltctrahydro-2//-1,3,5-thiadiazine-2-thione 156 (DTTT), in water and in salt solutions was studied in detail. 4-Methyl-5-methylimino-l,2,4-dithiazolidine-3-thione 157 and 2,4-dimethyl-l,2,4-thiadiazolidine-3,5-dithione 158 were isolated by HPLC and identified among the noncyclic decomposition products (Equation 25) <1996MI503>. 

The dithiazolidine ring is of moderate stability, depending on its substitution. Some dithiazolidine derivatives, obtained by 1,3-dipolar cycloaddition of the thionc-.S -imide 113 and thiones 114, are indefinitely stable at room temperature as compounds 115 (R1, R2 = Ar). Others decomposed during recrystallization affording the corresponding imines 118, and some, such as the sterically crowded 115 (R1, R2 = 2-adamantyl), are so unstable that they spontaneously decompose, affording hexafluorothioacetone 116 and finally the more stable compound 117 (Scheme 16) <1998EJ0459>. 

In CHEC-II(1996), the formation of 1,4,2-dithiazolidine derivatives 212 (R = Ar) from the sterically crowded thione 203 and arylazides (R = Ar) was reported. Nitrogen is evolved from the initially formed thiatriazoline cycloadduct 210 and the in situ-formed thiocarbonyl-A-imide 211 is trapped by the superdipolarophilic thione 203 (Scheme 28) <1996CHEC-II(4)532, 1993HCA2147>. Some new examples of this reaction have appeared. Thus, methyl azidoacetate and the thione 203 afford the corresponding dithiazolidine 212 (R = CH2COOMe)... 

PJC880>. Even in cases of three-component reactions, that is, the thione, arylazides, and, as third component, a reactive C=C dipolarophile, the dithiazolidine derivatives 212 are also formed (although in moderate yields) C1995HCA1067, 1995HCA1298>. 

Thermolysis of 3-benzyl-5-tosylimino-l,2,3,4-thiatriazoline (49) in the presence of thione (50) furnished 1,2,4-dithiazolidine-5-imine (51) in moderate yield. These results have been interpreted in terms of an unstable thiaziridineimine intermediate (48) which is trapped by the C=S compound in a regiospecific manner as depicted in Scheme 9 (76JHC883). Thermolysis without the presence of the thione (50) leads to the isolation of the sulfonyl carbodiimide (52). 

For the l,2,4-dioxazol-3-one (65 R1 = Ar, X = Z = 0) (72JPR145), nucleophilic addition by secondary amines occurs at the ring C=N to give the adduct (90), and while I gives a high yield of benzamide, the site of attack in this case is less clear. In contrast, the l,2,4-dithiazole-3-thione (30) is attacked by arylamines at the thione carbon with extrusion of sulfur, in a reaction analogous to that in Scheme 15. A similar reaction occurs with the isomeric 1,2,4-dithiazolidine derivatives (41 X = 0, S) (72IJC1138). 

Disubstituted 5-imino-l,2,4-dithiazolidine-3-thiones (317) with a 5-alkylimino group rearranged when boiled in triethylamine in the presence of ethanol to give 318 (91JPR107) (Scheme 98). 

There exist some unsaturated five-membered cyclic disulfides which are remarkably stable, among them the l,2-dithia-4-cyclopentene-3-thiones and 3,5-diimino-l,2,4-dithiazolidines, the so-called trithiones and thiurets, respectively. Here, the S—S 3px-interaction is either absent, or compensated by conjugative stabilization of the rings. Kehl and Jeffrey (149) have... 

The interconvertibility of 1,2,4-dithiazoles and 1,2,4-thiadiazoles has been known for a long time. Examples of such reactions have been encountered in the study of isoperthiocyanic acid (3-imino-l,2,4-dithiazolidine-5-thione) and its analogs (the thiurets , isothiocyanate oxides and sulfides ), and their elucidation has not been as easy matter.1,3 The interpretation of these, and of novel conversions of 1,2,4-dithiazoles to 1,2,4-thiadiazoles has more recently been greatly aided by the application of physical methods, including X-ray analyses. Since the reactions are not all of one kind, it has been expedient to describe them in two separate Sections, among the syntheses of type A and type C, respectively. 

Cl i,Hi 2N2S, 3-Phenyl-2-phenylimino-l,3-thiazetidine, 44B, 362 Cl Hi2 80283, 4-(6-Methoxy-3-pyridinyl)-5-[(6-methoxy-3-pyridinyl)-imino]-l,2,4-dithiazolidine-3-thione, 46B, 406 Cl nH, 2N11S, 5-Imino-4-phenyl-3-phenylamino-4H-l,2,4-thiadiazoline, 44B, 363... 

Several thioureas have been synthesized by ring-opening reactions of heterocyclic compounds such as l,3-dithiolan-2-thiones, 5-arylimino-l,2,4-dithiazolidine-3-thiones, benzoxazole-2-thiones, and 3,1-benzo-thiazine-4-thione derivatives. Similarly, the action of triphenylphosphine on 5-amino-l,2,4-dithiazolo-3-thiones gave thiocarbamoyl isothiocyanates (304). Other thioureas have been obtained by thermolytic decarbonylation of 2-amino-5(4H)-thiazolones and by treatment of 4,5,6,7-tetrahydro-cyclopenta-l,3-dioxin-4-one" and 3-nitrophthalic anhydride with thiourea. ... 

Amino-3Yi 1,2,4 dithiazole-3-thione, 9CI. Isoperthiocyanic acid. 3-Imino l,2,4-dithiazolidine-5-thione. Xanthan hydride [6846-35-1]... 

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