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].     

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

All three possible isomeric amines are obtained by the reaction of 4- or 5-methylbenzo-2,1,3-thiadiazoles with hydroxylamine sulfate in concentrated sulfuric acid. Under similar conditions, 5,6-dimethyl-4-aminobenzo-2,1,3-thiadiazole is obtained from 5,6-dimethylbenzo-2,1,3-thiadiazole.See [1] for communication LXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 601–602, May, 1971.     

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

The reaction of benzo-2,1,3-thiadiazole with hydroxylamine sulfate in concentrated sulfuric acid at 150° C for 1–10 hr has been studied. It has been shown that under these conditions mixtures of different amounts of 4- and 5-aminobenzo-2,1,3-thiadiazoles are formed.For part LII, see [1].     

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

The reaction of benzo-2,1,3-thiadiazole with hydroxylamine sulfate in concentrated sulfuric acid at 150° C for 1–10 hr has been studied. It has been shown that under these conditions mixtures of different amounts of 4- and 5-aminobenzo-2,1,3-thiadiazoles are formed.     

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, 1, 3-thia- and selenadiazole

Depending on the reaction conditions, benzo-2, 1, 3-selenadiazole (I), dichlorodimethyl ether and aluminum chloride react to give a complex IV, or else 4-chloromethyl-(V) or 4, 7-di(chloromethyl) benzo-2, 1, 3-selenadiazole (VI). 5-(II) and 4-methylbenzo-2,l,3-selenadiazole(III) are chloromethylated by dichlorodimethyl ether in the presence of chlorosulfonic acid. Compound II is converted mainly into 5-methyl-4-chloromethylbenzo-2, 1, 3-selenadiazole(VII) or a mixture of three possible isomers VII, VIII, and IX, depending on the amount of base or pseudo-base in the reaction mixture. Ill gives mainly 4-methyl-7-chlorornethylbenzo-2, 1, 3-selenadiazole(X), independent of the presence of base. The structures of the chloromethylation products are shown by reductive splitting to o-diamides, and chromatography of the latter in the presence of reference spots. The high reactivity of the chlorine in the chloromethyl group made it possible to obtain new derivatives by replacing it with a hydroxyl, cyano, or thiocyano group.For Part XL see [1].     

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].     

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],     

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.     

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].     

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 .     

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.     

Investigation of Isomerization of 2—Seleno—1,3,2—diazaphospholidine Derivatives

For the first time the isomerization of 1,3,2-diazaphospholidine-2-sclenide dervatives in refluxing benzene in the presence of trace water was observed. The structures of isomerized products were determined by IR, ^1H NMR,^31P NMR, elemental analysis and X-ray crystallography. The mechanism of isomerization was also proposed.     

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.     

Synthesis,structure, and chemistry of a 1-thia-4-azanaphthalene

From a crystal structure determination and thermal rearrangement studies, it is evident that 1-methyl-2-carbethoxy-3-phenyl-1-thia-4-azanaphthalene is an $\text{alias}$ for a molecule more properly represented by a name emphasizing its zwitterionic character.     

Metallomesogens: enaminoketone derivatives of the 3-oxa, 3-thia- and 3-selena-butyric amides

Liquid crystalline Ni(II) and Cu(II) complexes of tetradentate ligands, enaminoketones and 3-oxa; 3-thia- and 3-selena-butyramides were synthesized and examined. The compounds show very low C ₁ symmetry resulting from the chiral donor atoms — oxygen, sulphur and selenium — incorporated in the butyric amide moiety. This chirality can be observed in NMR studies. The complexes exhibit enantiotropic as well as monotropic calamitic SmA and N phases.     

Metallomesogens: enaminoketone derivatives of the 3-oxa, 3-thia- and 3-selena-butyric amides

Liquid crystalline Ni(II) and Cu(II) complexes of tetradentate ligands, enaminoketones and 3-oxa; 3-thia- and 3-selena-butyramides were synthesized and examined. The compounds show very low C₁ symmetry resulting from the chiral donor atoms — oxygen, sulphur and selenium — incorporated in the butyric amide moiety. This chirality can be observed in NMR studies. The complexes exhibit enantiotropic as well as monotropic calamitic SmA and N phases.