Reaction of 4-thioxo-1,3-benzothiazines with thiocarbohydrazine: Synthesis and reactivity of 1,3,4-triazolo[3,2-c]quinazoline derivatives

2-Aryl-4-thioxo-1,3-benzothiazines react with thiocarbohydrazide to give the new mesoionic compounds an-hydro 1-amino-5-aryl-2-mercapto-1,3,4-triazolo[3,2-c]quinazolin-4-ium hydroxides. These compounds react with methyl iodide, aldehydes and phenacyl bromides to give 1-amino-5-aryl-2-methylthio-1,3,4-triazolo-[3,2-c]quinazolin-4-ium iodides, 4-arylidenamino-3-(o-aroylamino)phenyl-1H-1,2,4-triazolin-5-thiones and 3-(o-aroylamino)phenyl-6-aryl-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines, respectively. These latter compounds by sequential treatment with methyl trifluoromethanesulphonate and triethylamine lead to 3-(o-aroylamino)-phenyl-6-aryl-1-methyl-7-mercapto-1H-pyrazolo[5,1-c]-1,2,4-triazoles.     

Synthesis and conversions of 6-nitro derivatives of 1,3,4-thiadiazolo[3,2-a]pyrimidines

Convenient procedures were developed for the preparation of new 2-R-thio and 2-amino derivatives of 7-methyl-6-nitro-5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidines and products of their condensation with aldehydes.     

具有生物活性的1,3,4-噻二唑并[3,2-a]-1,3,5-三嗪衍生物的合成方法

由1，3，4-噻二唑和1，3，5-三嗪稠合而成的1，3，4-噻二唑并[3，2．a]-1，3，5-三嗪衍生物具有广泛的生物活性，是一类重要的药用物质。本文对其在近二十年的合成方法进行了综述，重点介绍通过1，3，4-噻二唑衍生物为母体的合成方法。参考文献45篇。     

Synthesis of derivatives of a new heterocyclic system, 9-oxo-1,3,4-thiadiazolo[3,2-a]pyrido[3,2-e]pyrimidine

Reaction of 2-substituted 5-imino-7-oxo-1,3,4-thiadiazolo[3,2-a]pyrimidines with pentane-2,4-dione in polyphosphoric acid yields 9-oxo-1,3,4-thiadiazolo[3,2-a]pyrido[3,2-e]pyrimidines.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2037–2038, October, 1995.The authors are grateful to V. A. Dorokhov for the skilled preparation of the paper for publication.     

On the preparation of substituted 4H- 1,3,4-thiadiazolo[2,3-c]-1,2,4-triazin-4-ones and 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles

The reaction of benzoyl isothiocyanates and methoxycarbonyl isothiocyanate with 4-amino-4,5-dihydro-3-(methylthio)-1,2,4-triazin-5-ones in acetonitrile gave several substituted 4H-1,3,4-thiadiazolo[2,3-c]-1,2,4-triazin-4-ones VIa-h instead of the expected thioureas. In addition, benzoyl isothiocyanate reacted with 4-amino-3-(methylthio)-5-(trifluoromethyl)-4H-1,2,4-triazole to give the benzoyl thiourea IX and with 4-amino-3-mercapto-5-(trifluoromethyl)-4H-1,2,4-triazole to give the bicyclic compound N-[3-(trifluoromethyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazol-6-yl]benzamide IX .     

Electron impact mass spectra of 1,3,4-thiadiazolo[3,2-a]pyrimidin-7-one and isomeric-5-one derivatives

The 70 eV electron impact mass spectra of some 1,3,4-thiadiazolo[3,2-a]pyrimidin-7-one and isomeric-5-one derivatives are discussed with the aid of defocused metastable spectra and exact mass measurements. The compounds are shown to be very stable to electron impact and ring contraction reactions are in most cases the characterstic fragmentations. Most importantly, the 7-one derivatives fragment by a retro-Diels–Alder process which does not occur in the 5-one isomers. This provides a diagnostic tool for differentiation between the isomers and for the unequivocal assignment of the structure.     

Synthesis of 1,3,4-thiadiazolo[3,2-α]pyrimidin-5-one and isomeric 7-one derivatives

Continuing preceeding studies, designed to obtain derivatives of 1,3,4-thiadiazolo[3,2-α]pyrimidin-5-one and of the isomeric 7-one of pharmacological interest, some of the above mentioned compounds were prepared. Their structural identification was obtained by mass spectra.     

Single-reactor synthesis of 2R-thio-5,7-dimethyl-1,3,4-thiadiazolo[3,2-a]pyrimidinium perchlorates

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1146–1147, August, 1993.     

Syntheses and reactions of [1,3,4]thiadiazolo[3,2-a]pyrimidinone derivatives

5-Imino-6H-7-one, 7-amino-5-one and 5-isocyano-7-one derivatives of [1,3,4]thiadiazolo- and -[1,3]thiazolo-[3,2-a]pyrimidines were synthesized. 5-Isocyano-7-one derivatives were obtained by the reaction of the corresponding 5-imino-6H-7-ones with the Vilsmeier reagent in one step.     

Synthesis of 1,2,4-triazolo[4,3-c]-, tetrazolo[1,5-c]-, and 1,2,4-triazino[5,6-c]pyrano[4'3':4,5]pyrrolo-[3,2-e]pyrimidine derivatives

4-Hydrazinopyrano[4',3':4,5]pyrrolo[2,3-d]pyrimidines served as precursors in the synthesis of new heterocyclic systems, namely, 1,2,4-triazolo[4,3-c]-, tetrazolo[1,5-c]-, and 1,2,4-triazino[5,6-c] pyrano[4',3':4,5]-pyrrolo[3,2-e]pyrimidines.A. L. Mndzhoyan Institute of Fine Organic Chemistry, National Academy of Sciences of the Republic of Armenia, 375014 Yerevan. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 700-703, May, 1995. Original article submitted January 10, 1995; revision submitted April 20, 1995.     

Stereoselective synthesis of piperidine derivatives [3,2-c]-fused with oxygen heterocycles

The reaction of tert-butyl 4-oxopiperidine-1-carboxylate dimethylhydrazone with BuLi and further with iodides of protected alcohols ICH₂(CH₂) _n OSiMe₂(t-Bu) (n = 1–4) led to the formation of the corresponding tert-butyl 3-{[tert-butyl(dimethyl)silyl]alkyl}-4-oxopiperidine-1-carboxylates that under the treatment with triethylsilane in the presence of anhydrous BiBr3 underwent cyclization with a high stereoselectivity into cis-isomers of N-Boc piperidine derivatives [3,2-c]-fused with oxygen heterocycles. The latter at the treatment with anhydrous HCl eliminate the Boc group affording hydrochlorides of stereochemically homogeneous N-unsubstituted fused bicyclic systems.     

Synthesis of tetra- and pentaazaheterocyclic systems and benzimidazo[1,2-c]quinazoline derivatives

Starting with 5-carboxy-4-hydroxy-2-phenylpyrimidine and 4-hydroxy-6-methyl(hydroxy)-2-phenylpyrimidinyl-5-propanoic acids derivatives of two heterocyclic systems, benzimidazopyrido- and pyrimidopyrimidine, were synthesized. Synthesis of new S-substituted benzimidazo[1,2-c]quinazolines was also carried out.     

Pyrrolo[3,2-c]piperidines

The heterocyclization reaction of oximes derived from aliphatic ketones with acetylene has been applied to piperidone oximes. Pyrrole[3,2-c]piperidines substituted on the six-membered ring have been prepared in this manner. Assumptions have been made concerning their conformational and configurational properties. These reactions have been demonstrated to lead to the formation of condensed systems containing a pyrrolenine fragment.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 973–977, July, 1987.     

Synthesis of imidazo[1,2-c] quinazoline and some of its methyl derivatives

The synthesis of imidazo [1,2-c] quinazoline was effected by manganese dioxide oxidation of the 5,6-dihydroimidazo [1,2-c] quinazoline which was prepared by treatment of 2-(o-nitro-phenyl)-1-hydroxyimidazole-3-oxide with zinc powder and formic acid. The synthesis of some methyl derivatives of this ring system are also described. Structural assignments for all of the products were made from spectral data.     

Synthesis of 1,2,4-triazole, 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole and 1,2,4-triazolo[3,4-b][1,3,4]thiadiazine derivatives of benzotriazole

A novel series of 1-(1-carbonylmethyl-1H-benzotriazole) thiosemicarbazides 3a-e was synthesized and then cyclized with sodium hydroxide to afford 1-(4-substituted-4H-1,2,4-triazole-3-thion-5-yl)methyl-1H-benzotriazoles 4a-e , which were alkylated with ethyl iodide to l-(3-ethylthio-4-substituted-4H-1,2,4-triazol-5-yl)-methyl-1H-benzotriazoles 5b-e . The reaction of 1H-benzotriazol-1-acetic acid hydrazide ( 2 ) with carbon disulphide and potassium hydroxide followed by hydrazine hydrate gave 1-(4-amino-4H-1,2,4-triazole-3-thion-5-yl)methyl-1H-benzotriazole ( 6 ). Its subsequent condensation with carboxylic acids in the presence of phosphorus oxychloride or with phenacyl bromides afforded two series of fused heterocycles namely; 6-substituted-3-[1-(1H-benzotriazole)methyl]-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles 7a-e and 6-substituted phenyl-3-[1-(1H-benzotriazole)methyl]-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazines 8a-e respectively. The structure of the newly synthesized compounds was elucidated by elemental analyses, ir and nmr spectra.     

Reaction of tetrachloropyrazine with active methylene compounds

When tetrachloropyrazine was allowed to react with the anions formed from diethyl malonate and malonitrile, the normal alkylation took place. When the anions from ethyl acetoacetate and N,N-diethylacetoacetamide were used, alkylation was followed by enolization and ring formation to give furo [2,3-b] pyrazines. The structure proof and reaction of the furo [2,3-b] pyrazines are discussed.