The Synthesis of 1,2,4-Trioxan-5-ones

Several 3,6-substituted 1,2,4-trioxan-5-ones have been prepared in good yield by condensing aldehydes and ketones with trimethylsilyl α-[(trimethylsilyl)peroxy]alkanoates in the presence of trimethylsilyl trifluoromethane sulfonate as catalyst.     

Efficient synthesis of 5-substituted-4,5-dihydro-1,2,4-triazin-6-ones and 5-substituted-1,2,4-triazin-6-ones

Treatment of methyl α-(dimethylarninomethyleneamino)carboxylates 1 (from α-amino acids and dimethylformamide dimethylacetal) with hydrazine gives 5-substituted-4,5-dihydro-1,2,4-triazin-6-ones 2 , which are smoothly dehydrogenated to 5-substituted-1,2,4-triazin-6-ones 3 with potassium permanganate in acetone/acetic acid.     

Thermolysis of 3-phenyl-5-arylamino-1,2,4-oxadiazole and thiadiazole derivatives

Thermal reactions of 3-phenyl-5-arylamino-1,2,4-oxadiazoles I and II were investigated. Neat heating at ca. 250°C for 6 hours afforded H₂O, benzonitrile, arylcyanamides, arylamines, azobenzene, benzimidazole derivatives, and 3,3′-diphenyl-5,5′-bis[1,2,4-oxadiazolyl]. Analogous results were obtained by the thermolysis of 3-phenyl-5-anilino-1,2,4-thiadiazole III at ca. 200°C for 2 hours. In addition to H₂S, NH₃, and HNCS, phenyl isothiocyanate and thiocarbanilide were obtained. Thermolysis of III in quinoline as a radical trap gave analogous resuLts but also 2-anilinoquinoline. A free-radical mechanism has been suggested to account for the identified products. © 1997 John Wiley & Sons, Inc.     

Thermolysis of N-allylic 1,2,4-triazoles

A number of 4-allylic substituted 3,5-diphenyl-4H-1,2,4-triazoles were thermolyzed at 315–320° in evacuated glass ampoules. The main reaction in the melt was rearrangement to the corresponding 1-substituted triazoles, which appeared to proceed via competing S_N2 and S_N2′ mechanisms. The allylic systems were observed to undergo [2,3]-allyl walk reactions between the 1- and 2-ring positions. Allyl to vinyl isomerization also took place. Substitution of the allylic moiety increased the rate of reaction but decreased the rate of isomerization of allylic to the vinylic substituted triazoles. The 4-vinyl substituted triazoles were inert under the reaction conditions. Some triazoles were converted into substituted pyridines. This was proposed to proceed via nitrogen extrusion and formation of a 1,3-dipolar intermediate (nitrile ylide) which added intramolecularly to the allyl moiety and subsequently aromatized to the pyridine.     

Facile Synthesis of Dihydro-1,2,4-benzotriazepin-5-ones

Summary. Direct interaction between model anilines and an 1,3-dipolar nitrile imine, derived from 2-[N′-(1-chloro-2-oxopropylidine)hydrazine]benzoic acid, yielded the respective acyclic amidrazones. The latter adducts underwent CDI-induced cyclocondensation involving the hydrazone–NH terminus and the activated carboxy group to produce the corresponding dihydro-1,2,4-benzotriazepin-5-ones.     

Synthesis of novel silylated 1,2,4-triazin-5-ones

The reaction of various α-silyl-α-keto esters with thiosemicarbazide at 50 °C in ethyl acetate was found to give α-silyl-substituted thiosemicarbazone-acetic acid esters in good yield. These may then be converted to their corresponding silyl-substituted 1,2,4-triazin-5-ones by cyclization under basic conditions.     

Facile Synthesis of Dihydro-1,2,4-benzotriazepin-5-ones

Direct interaction between model anilines and an 1,3-dipolar nitrile imine, derived from 2-[N′-(1-chloro-2-oxopropylidine)hydrazine]benzoic acid, yielded the respective acyclic amidrazones. The latter adducts underwent CDI-induced cyclocondensation involving the hydrazone–NH terminus and the activated carboxy group to produce the corresponding dihydro-1,2,4-benzotriazepin-5-ones.     

The infrared spectra of fused 1,2,4-triazin-5-ones

The IR spectra of a number of fused 1,2,4-triazin-5-ones have been studied and the relevance of the results to triazinone tautomerism is discussed.     

Aroylation of 5-amino-2H-1,2,4-thiadiazolin-3-ones

2-Aroyl-5-aroylamino-1,2,4-thiadiazolin-3-ones ( 2 ) have been synthesized through aroylation of 5-arruno-2H-1,2,4-thiadiazolin-3-one ( 1 ) as an analog of cytosine. The aroylation was carried out with a substituted aroyl chloride in pyridine at 56～58°C. It has been established that the intermediates of the reactions are 2-aroyl-5-amino-1,2,4-thiadiazolin-3-ones ( 3 ) on the basis of the spectral data, additional experimental information and ab initio molecular orbital calculations.     

Synthesis of 4-hydroxy-4,5-dihydro-1,2,4-triazol-5-ones

Summary A series of hydroxamic acid ethoxycarbonylhydrazides was obtained by reactions of ester ethoxycarbonylhydrazones with hydroxylamine. The corresponding 3-substituted 4-hydroxy-4,5-dihydro-1,2,4-triazol-5-ones were synthesized by cyclization of these hydroxamic acid derivatives in basic medium.

---

Synthesen von 4-Hydroxy-4,5-dihydro-1,2,4-triazol-5-onen

Zusammenfassung Durch Reaktion von Esterethoxycarbonylhydrazonen und Hydroxylamin wurde eine Reihe von Hydroxamsäureethoxycarbonylhydraziden gewonnen; Cyclisierung dieser Verbindungen durch Base gab die entsprechenden 3-substituierten 4-Hydroxy-4,5-dihydro-1,2,4-triazol-5-one.

     

Base-induced fragmentations of 1,2,4-oxadiazolin-5-ones and their N-alkyl salts

Titration with triethylamine suffices to cleave the previously unknown title compounds ($\text{2}$ and $\text{3}$) to cyanamides and carbodiimides, respectively.     

Cycloaddition-elimination reactions of 5-imino-1,2,4-dithiazolidin-3-ones with heterocumulenes

5-Benzylimino-1,2,4-dithiazolidin-3-one ( 2a ) reacts with heterocumulenes (isocyanates, isothiocyanates, ketenes) with elimination of carbonyl sulfide, yielding the heterocycles 6–8 . The thiadiazolidine 6a , obtained from 2a and phenyl isocyanate, underwent similar reactions but under milder conditions, indicating that phenyl isocyanate is a better leaving group than carbonyl sulfide.     

Synthesis and properties of 5-aroylamino-2H-1,2,4-thiadiazol-3-ones

5 -Aroylamino-2H-1,2,4-thiadiazol-3-ones 3 were obtained from the corresponding 1-aroyl-2-thiobiurets 2 by oxidative cyclization with bromine. 5 -Aroylamino-2H-1,2,4-thiadiazol-3-ones 3 can exist in two tautomeric forms a lactam form and a lactim form. On the basis of the ¹³C nmr spectra and additional experimental information, it has been established that the stable form, in which these compounds exist, is the lactam form.     

Adamantylazoles: VIII. Acid-catalyzed adamantylation of 1,2,4-triazol-5-ones

3-R-1,2,4-Triazol-5-ones are adamantylated in sulfuric acid. The reaction involves the N¹ atom of the ring. 4-Adamantyl-1-methyl-, 1-adamantyl-4-methyl-, and 1,4-diadamantyl-1,2,4-triazol-5-ones were also prepared. Therewith, it was found that N¹ exhibits a higher reactivity than N⁴.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1377–1382.Original Russian Text Copyright © 2004 by Amandurdyeva, Saraev, Kuzmina, Golod.For communication VII, see [1].This revised version was published online in April 2005 with a corrected cover date.     

1,2,4-Triazines. 8. Reduction of 4-methyl-1,2,4-triazin-5(4H)-ones with sodium borohydride. Regioselective preparation of dihydro-1,2,4-triazin-5(4H)-ones

Reduction of 3-methylthio-1,2,4-triazin-5(4H)-one ( 1a ) with sodium borohydride afforded 3-methylthio-1,6-dihydrotriazin-5(4H)-one ( 2b ) selectively. 3-Methylthio-6-t-butyl-1,2,4-triazin-5(4H)-one ( 1d ) reacted with sodium borohydride to give mainly 6-t-butyl-2,3-dihydro-1,2,4-triazin-5(4H)-one ( 3d ). The reaction of various 4-methyl-1,2,4-triazin-5(4H)-ones with sodium borohydride and the influence of bulkiness and electronic effect of the substituents at the 3- and 6-positions upon the product ratio, are also discussed.     

Synthetic and spectroscopic study of 5-amino-2-acyl-1,2,4-thiadiazolin-3-ones

5-Amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 can be synthesized from 5-amino-2H-1,2,4-thiadiazolin-3-one ( 1–1 ) via a selective acylation with an acid anhydride in pyridine. The ¹H nmr spectral characteristics of 5-amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 is in particular, compared with 5-amino-2H-1,2,4-thiadiazolin-3-one ( 1–1 ) and 5-amino-2-alkyl-1,2,4-thiadiazolin-3-ones 1–2, 1–3 . The 5-amino group of 2–1 appeared as two peaks in its ¹H nmr spectrum, which merged to a single peak at a higher temperature, while those of compound 1–1, 1–2 and 1–3 appear only as a single peak. The restricted rotation of the C(5)-N(5) (at amino) bond of 5-amino-2-acetyl-1,2,4-thiadiazolin-3-one (2a-1) is about 14.5 Kcal/mol.     

Chlorination of isothiocyanates. V . 5-imino-1,2,4-thiadiazolidin-3-ones

S-[N'- (Chlorocarbonyl)amino]isothiocarbamoyl chlorides (II), obtained from S-chloroisothiocarbamoyl chlorides (I) and isocyanates, react with primary aliphatic and aromatic amines to form the unknown class of 5-imino-1,2,4-thiadiazolidin-3-ones. The structures were confirmed by chemical means and by spectroscopic methods.