1.2.4- Thiadiazolidin-3-ones, 5-

Several examples of 1,2,4-thiadiazolidin-3-one 5,5-dioxides 191-194 were isolated as by-products in the synthesis of sulfonopeptides. These are formed by refluxing in benzene or toluene the corresponding acylazides. These sulfonyl-hydantoins are extremely labile in protic solvents (96T(52)5303). 

An original isomerization of thiadiazolidine-ones into triazolidin-one-thiones has been achieved enzymatically388. The enzymes used were bovine and equine glutathione... 

Another application was investigated by Olson and coworkers (99HCA(82) 2432). 4-Substituted-A-alkyl- and A-aryl-l,2,5-thiadiazolidin-3-ones 247-249 were prepared and evaluated for their MHC class-II inhibitor activity. 

Chiral l,2,5-thiadiazolidin-3-one 5,5-dioxides 250 were synthesized by way of conventional methods, with the intention of introducing them in new pseudonucleosides as aglicone (96T(52)993). The synthetic methodology, in accord with previous reports, gave the l,2,5-thiadiazolidin-3-ones in good overall yield (35-55%). The glycosilation was performed on the protected heterocycles to prevent the condensation involving the N-2 atom, the most acidic reactive site. As expected only one anomer was obtained that is the p-one. 

Alkylation of mesoionic 132 (R = H) with 2-chloromethyl-4-(3-methyl-butyl)-5-methyl-l,2,5-thiadiazolidin-3-one 1,1-dioxide gave a mixture of C-3 and 2-6>-alkylated products 141 and 142 (96USP5512576). 

Reaction of A,A-dimcthylsullamoyl aziridines 323 and 325 with primary amines furnishes substituted 1,2,5-thiadiazolidine 1,1-dioxides 324 and 326, respectively, in a regioselective manner <06SL833>. Aziridine 325 is made from ( I /t,6,S ,Z)-bicyclo[4.2. l]non-3-en-9-one in two steps /V,/V-dimethylsulfamoyl imine formation using dimethylsulfamide and subsequent reaction with trimethylsulfoxonium ylide. The product from the reaction with 4-methoxy-benzyl amine can be subsequently manipulated (debenzylation and derivatization) to give the alternative nitrogen substitution pattern in a controlled manner. 

Treatment of a-amino esters with sulfonamide in the presence of DBLJ at 160°C also affords 2-unsubstituted-l,2,5-thiadiazolidin-3-one 1,1-dioxides 199 in moderate yield <2005SL834>. 

The reaction of 5(4H)-oxazolones (32) and miinchnones with triphenylvinylphos-phonium bromide (33) provides a mild synthesis of substituted pyrroles (34) (Scheme 11). The cycloaddition-elimination reactions of 5-imino-l,2,4-thiadiazolidin-3-ones with enamines and ester enolates produce 2-iminothiazolidines. " Chiral isomtinchnone dipoles show jr-facial diastereoselectivity with IV-phenyl- or A -methyl-maleimide in refluxing benzene. ... 

In 1991 L abbe reported that the 1,2,4-thiadiazolidine (71) and the 1,2,4-dithiazolidine (72) are interconvertible in the presence of electrophilic nitriles and give the 1,2,4-thiadiazoline-5-ones (73) as products (Scheme 18) <9UOC3268>. It is suggested that the reaction goes by a consecutive... 

Bu NHCOCHjNHPh SOCI2 2-r-Butyl-5-phenyl-1,2,5-thiadiazolidin-3-one 1-oxide 77JOC1015... 

L abbe and Verhelst have shown that intermediary thiatriazolines may be trapped with isocyanates to give 5-arylimino-l,2,4-thiadiazolidin-3-ones when isothiocyanate is slowly added (7 days) to a mixture of alkyl azide and isocyanate kept in solution at 80°C <76AG510>. Good to moderate yields were obtained. The suggested intermediacy of thiatriazoline was fully supported by an independent experiment in which authentic 4-methyl-5-phenylimino-l,2,3,4-thiatriazoline (96) was added to butyl isocyanate at RT to give the expected thiazolidine (97) in 95% yield (Equation (9)). 

Fungicidal properties are exhibited by 3-methyl-209 and 3-methyl-thio-5-arylsulfonyl-l,2,4-thiadiazoles,210 5-substituted 3-trichloro-methyl-1,2,4-thiadiazoles,97 2,4-dimethyl-3-thiono-l,2,4-thiadiazoli-din-5-one,164,166,211 and 2,4-dimethyl-l,2,4-thiadiazolidine-3,5-dithi-one.165,166 5-Halogeno-3-halogenoalkyl-l,2,4-thiadiazoles are active against Rhizoctonia aolani,9B... 

A classic example of this reaction is the Dimroth rearrangement, which is initiated thermally or in the presence of base catalysts and can usually occur with the retention or cleavage of the S-S bond depending on the nature of the substituents. The former pathway is typical of 3,5-diimino- and 5-imino-l,2,4-dithiazolidine-3-one derivatives and involves a rupture of one C-N bond, rotation of the N-C-N moiety around the S-C bond, and formation of a new 1,2,4-dithiazolidine derivative. The second pathway occurs when at least one N-substituent is an alkyl group and involves a rupture of the S-S bond, rotation of the N-C-S moiety around the N-C bond, and formation of the 1,2,4-thiadiazolidine derivative (Scheme 14) <1996CHEC-II(4)453>. 

Tetrahydrothiopyran-4-one undergoes a Barton-Kellogg reaction with hydrazine hydrate to give the azine 370. Sequential thiadiazolidine formation, oxidation to the thiadiazoline and extrusion of N2 produces the 4,4 -bis(tetra-hydro-4/7-thiopyranylidene) (Scheme 91) <2000JOC4584>. 

Thiadiazolidines can be obtained from aliphatic aldehydes or ketones and disubstituted hydrazine derivatives (Scheme 29). A typical preparation of a mesoionic compound consists in the reaction of 1-methylthioacylhydrazine and phosgene (Scheme 31a). Syntheses by three-bond formation are rare for example, a one-pot reaction of an aldehyde with hydrazine and sulfur. A typical ring transformation reaction is the irradiation of 1,3,4-oxadiazoles to yield 1,3,4-thiadiazoles. 

The reaction of isocyanates with iminothiatriazolines generated in situ has been employed in the preparation of 5-arylimino-l,2,4-thiadiazolidin-3-ones (49 equation 21). The utility... 

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