One-pot synthesis of 2-amino- 5-aryl -5H-thiazolo[4,3-b]-1,3,4-thiadiazoles

Equimolar mixtures of aromatic aldehydes with thioglycolic acid and thiosemicarbazide in H₂SO₄ transform into 2-amino-5-aryl-5H-thiazolo[4,3-b]-1,3,4-thiadiazoles.Translated fromIzvestiya Akademioi Nauk. Seriya Khimicheskaya, No. 3, pp. 763–764, March, 1996.     

Interaction of 2-bromo-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-α]pyrimidine with methylene-active compounds and acid hydrolysis of its products

Reactions of 2-bromo-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidine with sodium derivatives of pentane-2,4-dione, malonodinitrile, Meldrum acid, acetoacetic, cyanoacetic and malonic esters have been shown to give the respective substituted derivatives. Azinyl-ylidene tautomerism has been found to be characteristic of these compounds, the latter existing mainly in the ylidene form. The acid hydrolysis of pentane-2, 5-dione and cyanoacetic and malonic esters derivatives has been investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1961, November, 1993     

Synthesis of 3-methyl-6-r-6h-thiazolo-[4,3-<Emphasis Type="Italic">b</Emphasis>]-1,2,4-triazolo[4,3-<Emphasis Type="Italic">d</Emphasis>]-1,3,4-thiadiazoles

A one-reactor method has been developed for the synthesis of 3-methyl-6-R-6H-thiazolo[4,3-b]-1,2,4-triazolo[4,3-d]-1,3,4-thiadiazoles by the condensation of aromatic aldehydes, thioglycolic acid, and 4-amino-5-methyl-1,2,4-triazole-3(2H)-thione in a sulfuric acid medium.     

New synthesis of 2-R-thio-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidines

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, p. 1148, August, 1992.     

New reaction of thionohydrazides with semithioacetals of thioglycolic acid. One-step synthesis of 2-R-thio-5-R-5H-thiazolo[4,3-b]-1,3,4-thiadiazoles

It was found that aromatic aldehydes, thioglycolic acid and thionohydrazides (methyldithiocarbazate) in equimolar proportions at room temperature in concentrated sulfuric acid are converted into 2-methylthio-5-R-5H-thiazolo[4, 3-bJ-1, 3, 4-thiadiazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 271–273, February. 1996.     

A 2D kernel determination problem in a visco-elastic porous medium with a weakly horizontally inhomogeneity

We consider a system of hyperbolic integro-differential equations of SH waves in a visco-elastic porous medium. In this work, it is assumed that the visco-elastic porous medium has weakly horizontally inhomogeneity. The direct problem is the initial-boundary problem: the initial data is equal to zero, and the Neumann-type boundary condition is specified at the half-plane boundary and is an impulse function. As additional information, the oscillation mode of the half-plane line is given. It is assumed that the unknown kernel has the form K(x,t)=K₀(t)+ϵxK₁(t)+…, where ϵ is a small parameter. In this work, we construct a method for finding K₀,K₁ up to a correction of the order of O(ϵ²).     

Preparation of 5‐methyl‐2‐sulfanyl‐7h‐1,3,4‐thiadiazolo[3,2‐a]‐pyrimidin‐7‐ones

7H‐1,3,4‐Thiadiazolo[3,2‐a]pyrimidin‐7‐ones can be prepared by the acylation of 5‐amino‐1,3,4‐thiadiazoles with diketene and subsequent ring closure (dehydration). Whereas arylthio substituents (SC₆H₅) can be introduced in 2‐position by the replacement of Br, alkylthio groups (SC₂H₅) have to be already presentin the starting 5‐amino‐1,3,4‐thiadiazole. The ambident nucleophile 2‐thiazolidinethione reacts in the Br substitution reaction on the N atom.     

Synthesis of 2-amino-5-aryl-1,3,4-thiadiazoles and their condensed analogs with the use of aromatic nitrites

Aromatic nitrites are found to readily react with thiosemicarbazide and 4-amino-3-methyl-1,2,4-triazol-5-thione in a solution of polyphosphoric acid to give corresponding 2-amino-5-aryl-1,3,4-thiadiazoles.