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Thiadiazolines

4-Thiadiazolines.—The cycloaddition of aromatic sulphines to nitril imines is a regiospecific non-stereospecific reaction resulting in the formation of A -l,3,4-thiadiazoline derivatives. Interaction of the sulphines (137) and diphenylnitrilimine [generated in situ by the action of triethylamine on N-a-chlorobenzylidene-N -phenylhydrazine (138) in boiling benzene] gave uniform 1 1 adducts that were identified as the A -l,3,4-thiadiazoline S-oxides (139), the alternative 1,2,3-thiadiazoline structure (141) being conclusively eliminated on the basis of chemical and spectroscopic evidence. The non-stereo specific nature of the reaction was demonstrated and its significance discussed.  [Pg.693]

The S-oxides (139) are readily oxidized to the sulphones (140), which are in turn pyrolysed with loss of sulphur dioxide as shown. This twofold extrusion-process confirms the sites of bond-formation in the original cycloaddition.  [Pg.693]

4-Thiadiazolidine derivatives, amongst other structures, have proved suitable as starting materials for this purpose. Thus, the azo-sulphide (143), accessible by the oxidation of the spirane (142), is converted into the thiiran (145) at 100 °C, but it affords high yields of the bis-cyclohexylidene (146) on thermolysis in the presence of triphenylphosphine. The required [Pg.693]

Bonini, G. Maccagnani, L. Thijs, and B. Zwanenburg, Tetrahedron Letters, 1973,3569. [Pg.693]

The pyrolytic conversion of 2,2,5,5-bis(pentamethylene)-A -l,3,4-thiadia-zoline (143) into the episulphide (145) proceeds, according to kinetic evidence, via the primarily formed ylide (144). Detailed observations, made with cis- and trans-2,5-diethyl (and di-t-butyl)-A -l,3,4-thiadiazoline (148), show that the process proceeds sterically, in agreement with orbital-synunetry considerations, by conrotatory ring-closure [to (149)]. [Pg.694]


Several related derivatives have also been utilized in this type of synthesis. Imino-chloromethanesulfenyl chlorides (184), prepared by the controlled addition of chlorine to isothiocyanates, react with amidines (161) to give 1,2,4-thiadiazolines (185) (71T4117). Chlorocarbonylsulfenyl chloride (186), prepared by the hydrolysis of trichloromethanesulfenyl chloride with sulfuric acid, reacted with ureas, thioureas and guanidines to give 1,2,4-thiadiazolidine derivatives (187) <70AG(E)54, 73CB3391). [Pg.130]

X-Ray crystallographic studies on 1,2,4-thiadiazoles (see Table 1) show the 1,2,4-thiadiazole ring to be essentially planar. The X-ray structure of 4-phenyl-5-(/>-nitrophenyl)-3-(/>-methoxyphenyl)-A2-l,2,4-thiadiazoline 3 shows that the 1,2,4-thiadiazoline ring has a 30° fold around the S(l)-N(4) vector atoms S-l, N-2, C-3, and N-4 are nearly coplanar <1986JCM156>. [Pg.491]

In general, 3-hydroxy-l,2,4-thiadiazoles react with hard nucleophiles (acid chlorides, sulfonyl chlorides) at the oxygen atom, whereas soft nucleophiles (isocyanates, acid anhydrides) react at the N-2 position yielding 1,2,4-thiadiazolin-3-ones. Nucleophiles react at the N-4 position of 5-hydroxy-l,2,4-thiadiazoles <1996CHEC-II(4)307>. There have been no new publications on O-linked substituents since the publication of CHEC-II(1996). [Pg.499]

The thermolysis of 4-benzyl-5-sulfonyliminothiatriazolines 113 in the presence of a variety of nitriles yields 5-imino-1,2,4-thiadiazolines 115. These reactions have been interpreted as proceeding via a thiaziridinimine intermediate 114 (Scheme 14) <1996CHEC-II(4)307>. [Pg.507]

Thiadiazolines are readily cleaved at the N—S bond by reducing agents under very mild conditions. Thus the diethylamino derivative (41) is reduced with HjS in pyridine/triethylamine to... [Pg.316]

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... [Pg.319]

The condensation of 5-amino-3-methyl-l,2,4-thiadiazole (118) with aliphatic or aromatic nitriles yields 1 1 adducts, which are, according to their H NMR spectra, equilibrium mixtures of (119) and (120) (Scheme 28) <82AHC(32)285>. These adducts are produced by a bond switch at the n-hypervalent sulfur in (121). X-ray analysis of the adduct formed from the reaction of (118) with chloroacetonitrile showed the adduct to exist as (122) in the crystals <81AX(B)185>. Further examples of this type of bond switch at rc-hypervalent sulfur are observed in the reaction of 5-imino-1,2,4-thiadiazolines with various electrophilic reagents (Section 4.08.6.1). [Pg.325]

The final step in the synthesis of the thiadiazole nucleoside (178) is achieved by prolonged treatment of (179) with methanolic sodium methoxide (Equation (25)) <82AHC(32)285). Reaction of the A"-1,2,4-thiadiazoline (180) with dry HCl in methanol leads to the 2-carbamoyl compound (181). When (180) is treated with a mixture of free amines and amine hydrochlorides in the ratio of 2 1 in refluxing ethanol, 2-amidino-3-imino-5-methylthio derivatives (182) are formed in good yield (Scheme 42) <84CHEC-i(6)463>. [Pg.333]

Aqueous solutions of methyl isothiocyanate are slowly oxidized in air to give 2,4-dimethyl-1,2,4-thiadiazoline-3,5-thione (71) <82AHC(32)285>. When mixtures of alkylisothiocyanates and alkyl-isocyanates are chlorinated, 3-oxathiadiazolium salts (198) are formed via an intermediate iminochloromethylsulfenyl chloride (199). Hydrolysis of these salts yields 2,4-dialkyl-1,2,4-thia-diazolidin-3,5-diones (200) (Scheme 45) <80USP4183816>. [Pg.335]

The addition of arylthioureas to benzoylisothiocyanate affords good yields of 5-aryl-1-benzoyl-2-thiobiurets (246). Treatment of (246) with acidic hydrogen peroxide gives 5-benzoylamino-3-oxo-1,2,4-thiadiazolines (247) in high yields (Scheme 55) <81S232>. [Pg.339]

The reaction of arylthioamides (248) with phenylisocyanate affords the arenethiocarboxamide (249), which can be benzylated to give (250) and then converted into 5-aryl-3-oxo-2-phenyl-1,2,4-thiadiazoline (251) on treatment with bromine in chloroform. Alternatively, (249) can be transformed into (251) by direct oxidation with bromine (Scheme 56) <85IJC(B)977>. [Pg.340]

Reaction of alkyl or aryl isocyanates with benzimidazolinethione (254) affords the iV-carbamyl derivative (255). Treatment of (255) with bromine in triethylamine gives the benzimidazolo[l,2-r/]-1,2,4-thiadiazoline (256) (Scheme 58). A related thioanalogue (258) was obtained by a similar process from the A-thiocarbomyl derivative (257) (Equation (35)) <83X2311). [Pg.341]

In contrast, the reaction of SchifFs bases (276) with aryl nitrile sulfides yields 1,2,4-thiadiazolines (277) in very low yields (2-5%) (Equation (42)) <86JCR(S)156>. [Pg.343]

When thiocarbonyl and ot-diazocarbonyl compounds are combined, acyl-substituted thiocarbonyl ylides 158 are generated from a nonisolable 3-acyl-1,2,4-thiadiazoline 157 (Scheme 8.36). In addition to giving acylthiiranes 159 and 1,3-dithiolanes 160, dipoles 158 can also 1,5-cyclize to produce 1,3-oxathioles 161. Acyl-thiocarbonyl ylides derived from diazoketones [e.g., HC(0)C(N2)R, R = Ph, f-Bu (219,220) 2-diazocyclohexanone (221)] produce 1,3-oxathioles [e.g., 162 (220), Scheme 8.36], while those derived from diazoesters (218,222,223) lead to thiiranes by 1,3-cyclization. Ylides derived from a-diazocarboxamides form 1,3-oxathioles (e.g., 163) and thiiranes (e.g., 159, R = f-Bu, R = NMePh, R = R" = Ph), depending on the nature of the substituents (220). A related 1,5-cyclization of an aminomethyl-thiocarbonyl ylide formed from dimethyl 3-anilino-2-diazobutanedioate was also reported (224). [Pg.574]

The scope of the synthesis is greatly widened by the preliminary preparation of the N-halogenoamidines (56), preferably in situ subsequent displacement of halogen by thiocyanate results in the formation of the desired 5-amino-1,2,4-thiadiazoles (58) in good yields (50-80%).6,79, 80 The use of formamidine affords the parent, 5-amino-1,2,4-thiadiazole (58 R = H) while use of AT-methylformamidine (59) leads to 5-imino-4-methyl-Zl4-1,2,4-thiadiazolines (60).81... [Pg.135]

Methylamino-l,2,4-thiadiazole (195) (but not its 3-phenyl homolog) arises irreversibly171 by isomerization of 5-imino-4-methyl-1,2,4-thiadiazoline (193) in ethanol on prolonged storage or brief heating.81, 171 The structure is confirmed by its alternative synthesis from 201.6 Further methylation (of 195) (to 194, and 194 + 196 when R = Ph) follows the general scheme.81... [Pg.167]

Urea, 3-oxo-A4-1,2,4-thiadiazolin-5-yl-synthesis, 6, 592 Urea, thio-cyclic derivatives toxicity, 1, 138-139 toxicity, 1, 139 Urethane foam catalysts, 1, 405-406 Urethanes... [Pg.920]


See other pages where Thiadiazolines is mentioned: [Pg.864]    [Pg.864]    [Pg.864]    [Pg.920]    [Pg.98]    [Pg.159]    [Pg.159]    [Pg.105]    [Pg.309]    [Pg.309]    [Pg.310]    [Pg.310]    [Pg.310]    [Pg.310]    [Pg.310]    [Pg.317]    [Pg.319]    [Pg.320]    [Pg.339]    [Pg.347]    [Pg.478]    [Pg.487]    [Pg.145]    [Pg.174]    [Pg.198]    [Pg.122]    [Pg.864]    [Pg.196]   
See also in sourсe #XX -- [ Pg.197 ]




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1,2,4-Thiadiazolines 4- alkyl-5-imino

1,2,4-Thiadiazolines 5- amino-3-imino

1.2.3- Thiadiazoline

1.2.4- Thiadiazolines, reaction with acetylenic

1.2.5- Thiadiazolin-3-ones, synthesis

1.3.4- Thiadiazolines, fragmentations

1.3.4- Thiadiazolines, olefin formation

1.3.4- Thiadiazolines, ring-chain tautomerism

2,2-Diphenyl-l,3,4-thiadiazoline

2-Imino-l,3,4-thiadiazoline

2-Imino-l,3,4-thiadiazoline Aminothiadiazole

3- Amino-4-methyl-1,2,4-thiadiazoline

A2-1,3,4-Thiadiazolines

A3-1,3,4-Thiadiazoline

A3-1,3,4-Thiadiazolines

A3-l ,3,4-Thiadiazoline

Thiadiazoles and Thiadiazolines

Thiadiazolin-3-ones, tautomerism

Thiadiazoline 1,1-dioxides

Thiadiazoline, derivs

Thiadiazolines, synthesis

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