Researches on 2, 1, 3-thia- and selenadiazole

4-Hydroxy-, 4-hydroxy-5-methyl-, 4-hydroxy-7-methylbenzo-2,1,3-thiadiazoles are polymorphous.4-Hydroxybenzo-2,1,3-thiadiazole (I), 4-hydroxy-5-methyl- and 4-hydroxy-7-methylbenzo-2, 1, 3-thiadiazoles (II and III) melt at 114–115°, 110–112°, 100–102° C, respectively, after recrystallization from water [2–4], but after recrystallization from petrol ether [5] they melt at 128–129°, 124–125°, and 119–120° C [5]. In this connection we recrystallized these phenols repeatedly from petrol ether after recrystallizing them from water, and their melting points rose as expected [5]. On the other hand, the compounds with melting points 128–129°, 124–125°, 119–120° C (ex petrol ether), after repeated crystallization from water melted at 114–115°, 110–112°, 100–102° C, respectively.For Part XXXVIII see [1].     

Researches on 2, l, 3-thia- and selenadiazole

4-(,-Dicarboethoxy--acetylamino) ethyl-7-aminobenzo-2,1, 3-thiadiazole (IV) and ethylene oxide form mainly the 7-(-hydroxyethyl) amino derivative (V); the 7- di (-hydroxyethyl) amino derivative VII was isolated in low yield. Action of POCl₃ on compound VII gave the 7-di (-chloroethyl) amino derivative VIII, which was converted into 4-(-amino--carboxy)-ethyl-7 -di (-chloroethyl) aminobenzo-2, 1, 3-thiadiazole (IX). 5-(, -dicarboethoxy--acetylamino) ethyl-4-nitrobenzo-2, 1, 3-thiadiazole (XI) was converted to 5-(-carboxy--amino) ethyl-4-nitrobenzo-2, 1, 3-thiadiazole hydrochloride (XII), from which was prepared, by known routes, and in satisfactory yield, 5-(-carboxy--amino) ethyl-4-di (-chloroethyl)-aminobenzo-2, l, 3-thiadiazole hydrochloride (XVII).For Part XXXIX see [8].     

Research on 2, 1, 3-thia- and selenadiazole

The stability of the thiadiazole ring in chloro-substituted benzo-2, 1, 3-thiadiazoles to reductive fission increases with increasing chlorine substitution.For part LIII, see [1].     

Research on 2, 1, 3-thia-and selenadiazole

Reductive decomposition followed by hydrolysis of 5-(,-dicarethoxy--acetylamino) ethylbenz-2, 1, 3-selenadiazole gives -(3, 4-diaminophenyl)alanine.For Part XLVII see [1].     

Investigations of 2,1,3-thia- and selenadiazole s

All of the possible isomeric monoaminobenzo-2,1,3-selenadiazoles are formed in the reaction of benzo-2,1,3-selenadizaole 4- or 5-irethyl-, or 5,6-dimethylbenzo 2,1,3-selenadiazoles with hydroxylaminesulfate in concentrated sulfuric acid.See [1] for communication LXV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 328–330, March, 1972.     

Researches on 2,1,3-thia- and selenadiazole XLV. Nitration of 4-hydroxy- and 4-ethoxybenzo-2,1,3-thiadiazoIe

Nitration of 4-hydroxybenzo-2,1,3-thiadiazole under conditions generally used for phenols, gave a high yield of 4-hydroxy-5-nitrobenzo-2,1,3-thiadiazole. The latter is readily reduced to 4-hydroxy-S-aminobenzo-2,1,3-thiadiazole which on treatment with orthoformic ester gives oxazolo [5,4-e]benzo-2,1,3-thiadiazole. 4-Ethoxybenzo-2,1,3-thiadiazole is nitrated under similar conditions, giving a high yield of a mixture of equal quantities of 4-ethoxy-S-nitro- and 4-ethoxy-7-nitrobenzo-2,1,3-thiadiazole.For Part XLIV see [1].     

Researches on 2,1,3-thia- and selenadiazole XLV. Nitration of 4-hydroxy- and 4-ethoxybenzo-2,1,3-thiadiazoIe

Nitration of 4-hydroxybenzo-2,1,3-thiadiazole under conditions generally used for phenols, gave a high yield of 4-hydroxy-5-nitrobenzo-2,1,3-thiadiazole. The latter is readily reduced to 4-hydroxy-S-aminobenzo-2,1,3-thiadiazole which on treatment with orthoformic ester gives oxazolo [5,4-e]benzo-2,1,3-thiadiazole. 4-Ethoxybenzo-2,1,3-thiadiazole is nitrated under similar conditions, giving a high yield of a mixture of equal quantities of 4-ethoxy-S-nitro- and 4-ethoxy-7-nitrobenzo-2,1,3-thiadiazole.     

Investigations on 2, 1, 3-thia- and selenadiazoles

Nitration and nitrosation of 4-hydroxy-5-methyl-benzo-2, 1, 3-thiadiazole gives 4-hydroxy-5-methyl-7-nitro-and 4-hydroxy-5-methyl-7-nitrosobenzo-2, 1, 3-thiadiazoles. Oxidation of the latter, or of 4,7-diamino-5-methylbenzo-2,1,3-thiadiazole gives 5-methyl-4,7-dihydroxy-2, 1, 3-thiadiazole, forming derivatives with sodium bisulfite or hydroxylamine, and reduced by sodium dithionite to 5-methyl-4, 7-dihydroxybenzo-2, 1, 3-thiadiazole. The latter is also obtained by diazotizing 5-methyl-4-hydroxy-7-aminobenzo-2, 1, 3-thiadiazole, and decomposing the diazonium salt. Nitration of 4-ethoxybenzo-2, 1, 3-thiadiazole with sodium ethoxide gives 4-ethoxy-7-aminobenzo-2, 1, 3-thiadiazole, acetylated to 4-ethoxy-7-acetaminobenzo-2, 1, 3-thiadiazole.For Part XXXVII see [1].     

Researches on 2,1,3-thia-and selenadiazole

Chlorination of benzo-2,1,3-thiadiazole (I) in the presence of iron and paraform gives only 4-chlorobenzo-2,1,3-thiazole. Chlorination of 5,6-dimethylbenzo-2,1,3-thiadiazole (II) under exactly the same conditions gives only 5,6-dimethyl-4,7-dichlorobenzo-2,1,2-thiadiazole. Similarly chloromethylation of II in the presence of paraform gives only 5,6-dimethly-4,7-di(chloromethyl)benzo-2,1,3-thiadiazole. Chlorination and chloromethylation of I proceed through the intermediate formation of monosubstituted compounds which change into disubstimted ones.It is known [2,3] that Chlorination of benzo-2,1,3-thiadiazole (I) and its 5,6-dimethyl derivative (II) with chlorine in the presence of iron gives mainly the 4,7-dichloro substitution products III and IV respectively.It was previously shown [4] that chloromethylation of I with dichlorodimethyl ether in the presence of anhydrous aluminum chloride also gives mainly 4,7-di(chloromethyl)benzo-2,1,3-thiadiazole (V). Bases and pseudo-bases (paraform, urotropine. dimethylformamide) have a retarding effect on chloromethylation. When the reaction is run in the presence of these latter the products comprise besides V, 4-chloromethyl-2,1,3-thiadiazole (VI), or else, if enough base is added, there is no reaction.For Part XLII see [1].     

Investigation of 2, 1, 3-thia- and 2, 1, 3 selenadiazoles

The nitration of naphtho[1,2-d][2,1,3]thiadiazole under the conditions that are normally used for aromatic compounds gives a mixture of 6- and 9-nitronaphthothiadiazoles, which can be reduced to 6- and 9-amino derivatives, respectively. 6-Hydroxynaphthothiadiazole is obtained from 6-aminonaphthothiadiazole by the Sandmeyer reaction, while 8-hydroxynaphthothiadiazole is converted to the 8-amino derivative under the conditions of the Bucherer reaction. 4-Carboxy-5-(o-carboxyphenyl)-2,1,3-thiadiazole was obtained by the oxidation of naphtho[1,2-d][2,1,3]-thiadiazole with a potassium dichromate-dilute sulfuric acid mixture.See [1] for communication LXVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1496–1502, November, 1972.     

Studies in the field of 2, 1, 3-thia- and -selenadiazoles

The thiadiazole ring activates a chlorine atom in the ortho or para positions with respect to the nitro group in the nucleophilic animation of chloronitrobenzo-2, 1, 3-thiadiazoles. The action of ammonia on a chlorobenzo-2, 1, 3-thiadiazole activated by a nitro group in ethylene glycol readily leads to the replacement of the chlorine by an amino group. The resulting aminonitrobenzo-2, 1, 3-thiadiazoles have been reduced to the corresponding diamines and these have been converted into pyrazine, quinoxaline, thiadiazole, and acetic acid derivatives.     

Studies in the field of 2, 1, 3-thia- and -selenadiazoles

The thiadiazole ring activates a chlorine atom in the ortho or para positions with respect to the nitro group in the nucleophilic animation of chloronitrobenzo-2, 1, 3-thiadiazoles. The action of ammonia on a chlorobenzo-2, 1, 3-thiadiazole activated by a nitro group in ethylene glycol readily leads to the replacement of the chlorine by an amino group. The resulting aminonitrobenzo-2, 1, 3-thiadiazoles have been reduced to the corresponding diamines and these have been converted into pyrazine, quinoxaline, thiadiazole, and acetic acid derivatives.For communication L, see [1],     

2-Amino-4-dimethylamino-1-thia-3-azabutadienes as Precursors of Thiazoles

The reaction of 2-amino-4-dimethylamino-1-thia-3-azabutadienes 1 with f -bromoketones gave rise to 2-aminothiazoles 2 together with 2-( N , N -dimethylaminomethylenamino)thiazoles 3 . Competitive mechanisms are described. Furthermore, reaction of diene 1a with methyl f -bromoacetate or hydroxylamine- O -sulfonic acid yielded respectively 2-( N , N -dimethylaminomethylenamino)thiazolin-4-one 4 and 5-amino-1,2,4-thiadiazole 5 .     

Researches on 1, 2, 4-triazoles

A new method of preparing 1, 2, 4-triazolinethione derivatives by directly sulfurating the corresponding triazoles is described. 4-(-Pyridyl)-1, 2, 4-triazoline-3-thione undergoes aminomethylation, cyanoethylation, and pyridylethylation at the nitrogen of the thioamide group. Replacement of the phenyl group in 4-phenyl-1, 2, 4-triazolinethione by -pyridyl, gives a compound closely resembling 1-phenyltetrazoline-5-thione in its properties.For Part VII see [1].     

Researches on 1, 2, 4-triazoles

Determination of the acidity constants of 1-aryltetrazolinethiones-5, 4-aryl-1, 2, 4-triazolinethiones-3, 1-aryltetrazolinones-5, 4-aryl-1, 2, 4-triazolinones-3 shows that carbonyl compounds are 10^–1–10^–2 times less acid than compounds with a thione group. Acidities are found to increase considerably, 10³–10⁴ times, on passing from triazole compounds to tetrazole ones. 4-Aryl-1, 2, 4-triazolinones-3 and 1-aryl-tetrazolinones-5 are aminomethylated and cyanoethylated and the reactions found to take place at the amide nitrogen atom.For Part VI see [1].     

New synthesis of 2-amino-1-thia-4-chromones

The reaction of arylacetonitriles with methyl thiasalicylate leads to 2-amino-3-aryl-1-thia-4-chromones. The spectral characteristics and the reactions at the amino group were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1047–1048, August, 1982.     

Stereostructure of condensed-skeleton cis- and trans-dihydro-1,3-thiazines and 1-thia-3-azaspiroalkenes

The stereostructures of some condensed-skeleton cis- and trans-dihydro-1,3-thiazines and 1-thia-2-phenyl-3-azaspiro[4n + 1]alk-2-enes (n = 3–6) were established by ¹H and ¹³C NMR spectroscopy. A comparative study indicated that the cis-thiazines have greater conformational mobility than the corresponding oxazines, although the preferred conformer of the two types of cis compounds is the same, with the sulphur axial and the 4-methylene group equatorial relative to the rings.