A new synthesis of 3-alkyl-6-alkylthio-1,2,4-triazolo[3,4-b]1,3,4-thiadiazoles

4-Amino-5-R-1,2,4-triazole-3-thiones react with alkyl(alkylaryl)thiocyanates in polyphosphoric acid to give the title compounds.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 230–231, January, 1993.     

Reaction of ethyl cyanoacetate with 4-amino-3 mercapto-5R-1,2,4-triazole

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 137–138, January, 1994.     

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.     

Composition of the essential oil of Origanum tyttanthum from Tajikistan

Origanum tyttanthum Gontsch. was collected from two different sites in south-central Tajikistan. The essential oils were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. A total of 52 compounds were identified representing 99.0-100% of total oil compositions. The major components of Origanum tyttanthum Gontsch. oil were carvacrol (34.3-59.2%), thymol (10.8-46.4%), p-cymene (0.7-7.3%), beta-thujone (1.9-4.1%), piperitenone oxide (0.1-3.8%), gamma-terpinene (0.3-3.5%), cis-piperitone epoxide (0.8-3.3%), carvacrol acetate (0.4-2.4%), menthone (0.6-2.1%) and borneol (1.0-2.3%).     

Preparation of 2‐amino‐5‐methyl‐7H‐1,3,4‐thiadiazolo[3,2‐α]pyrimidin‐7‐ones

2‐Amino substituted 7H‐1,3,4‐thiadiazolo[3,2‐α]pyrimidin‐7‐ones 11a‐e were prepared by the reaction of 2‐bromo‐5‐amino‐1,3,4‐thiadiazole ( 1b ) and diketene ( 8 ), subsequent cyclocondensation ( 9b → 3b ) and displacement of the bromo substituents by the reaction with primary or secondary amines ( 3b → 11a‐e ). The hydrogen atom 6‐H in the heterobicycle 3b is replaced by a Cl or Br atom in the transformation of 3b → 14a,b. The 2‐bromo‐6‐chloro compound 14a reacts chemoselectively in the 2‐position with dimethylamine ( 14a → 15 ). The structure elucidations are based on one‐ and two‐dimensional NMR techniques including a heteronuclear NOE measurement.     

Syntheses based on 2-ethoxycarbonylmethyl-7-methyl-1,3,4-thiadiazolo[3,2-a]pyrimidin-5(5H)-one

2-Ethoxycarbonylmethyl-7-methyl-1,3,4-thiadiazolo[3,2-a]pyrimidin-5(5H)-one containing the active methylene group reacts easily with carbon disulfide and phenyl isothiocyanate in the presence of sodium hydride. Further alkylation of the reaction product by alkyl halides results in the formation of the corresponding 1,3,4-thiadiazolo[3,2-a]pyrimidine derivatives containing a ketene dithioacetal fragment. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2371–2373, November, 1998.     

Polyfunctional nitriles in the synthesis of derivatives of 1,3,4-thiadiazolo-[3,2-<Emphasis Type="Italic">a</Emphasis>]pyrimidines

A one-pot method has been developed for the synthesis of 2-R-7-methyl-5-oxo-5H-1,3,4-thia-diazolo[3,2-a]pyrimidine by condensation of β-alkylthio(alkoxy)propionitrile, thiosemicarbazide, and ethyl acetoacetate in PPA, and also (7-methyl-5-oxo-5H-1,3,4-thidiazolo[3,2-a]pyrimidin-2-yl)-acetamide from cyanoacetamide, thiosemicarbazide, and ethyl acetoacetate. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, 1096–1100, July, 2008.