M. O. Lozinskii

2-Phenacylbenzothiazole in the Biginelli Reaction

The cyclocondensation of 2-phenacylbenzothiazole with aromatic aldehydes and urea or thiourea in the Biginelli reaction gave previously unreported 4-aryl-5-(2-benzothiazolyl)-2-oxo-6-phenyl-1,2,3,4-tetrahydropyrimidines and their 2-thioxo analogs. An efficient procedure was developed for carrying out the three-component reaction at low temperatures. The structure peculiarities of the products were analyzed using IR, 1H NMR, and X-ray diffraction data.

Synthesis of 2-Aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones and 7-Aryl-2,3,6,7-tetrahydro-5H-imidazo[2,1-b]-1,3-thiazin-5-ones

The reaction of 2-mercaptobenzimidazole, 5-ethoxy-2-mercaptobenzimidazole, and 2-mercaptoimidazoline with cinnamoyl chloride, its derivatives, and heteroanalogs was studied. Convenient methods were found for the synthesis of 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones and 7-aryl-2,3,6,7-tetrahydro-5H-imidazo[2,1-b]-1,3-thiazin-5-ones.

2-Acylmethyl-1H-benzimidazoles in the Biginelli Reaction

By cyclocondensation of 2-acylmethyl-1H-benzimidazoles with aromatic aldehydes and urea according to the Biginelli reaction, we have obtained previously unknown 6-substituted 4-aryl-5-(2-benzimidazolyl)-2-oxo-1,2,3,4-tetrahydropyrimidines. We have developed an efficient procedure for conducting the three-component reaction at fairly low temperatures. We have analyzed the structural features of the synthesized compounds based on 1H NMR spectra and IR spectroscopy.

6-Arylamino-3-methyl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines: Novel N-Arylamidine Structures

We propose a method for obtaining derivatives of 7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine by alkylation of 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol by substituted α-chloroacetanilides, followed by cyclization of the intermediate by phosphorus oxychloride.

Synthesis and Transformations of 3-Ethoxycarbonyl-2-(N-R-thioureido)thiophenes

Abstract3-Ethoxycarbonyl-2-(N-R-thioureido)-4,5,6,7-tetrahydrobenzo[b]thiophenes were obtained by the reaction of 2-amino-3-ethoxycarbonyl-4,5,6,7-tetrahydrobenzo[b]thiophene with isothiocyanates and of 3-ethoxycarbonyl-2-isothiocyanato-4,5,6,7-tetrahydrobenzo[b]thiophene with primary and secondary amines. The cyclization paths of the products leading to derivatives of thieno[2,3-d]pyrimidine and thieno[2,3-d]-1,3-thiazine were studied. The corresponding S-substituted derivatives were obtained by the alkylation of 3-R-2-thioxo-3,4,5,6,7,8-hexahydrobenzo[b]thieno[2,3-d]pyrimidin-4-ones.

Hydrazinolytic Recyclization of (Z)-3-Acetyl-2-methyl-2,3-dihydro-1,4-benzodioxin-2-ol

A convenient preparative method has been developed for obtaining previously unknown 4-(o-hydroxyphenoxy)-substituted pyrazoles by the reaction of (Z)-3-acetyl-2-methyl-2,3-dihydro-1,4-benzodioxin-2-ol with hydrazine.

Hydrazinolytic recyclization of 2-phenacylbenzothiazole

Hydrazinolytic recyclization of 2-phenacylbenzothiazole proceeds via cleavage of the C—S bond in the ring and is accompanied by oxidation of resulting 2-[(5-phenylpyrazole-3-yl)amino]thiophenol into the corresponding disulfide. The subsequent intramolecular cyclocondensation gives selectively pyrazolo[4,3-b][1,4]benzothiazines.

Synthesis of 2-(3-Indolyl)-1H-benzimidazoles from 2-Acylmethyl-1H-benzimidazoles

The interaction of 2-acetyl(aroyl)methyl-1H-benzimidazoles with phenylhydrazine on heating in trifluoroacetic acid proceeds by a type of Fischer reaction with the formation of 2-[2-methyl(aryl)-3-indolyl]-1H-benzimidazoles.

Isomerization of 2-Phenacyl-1H-benzimidazole Arylhydrazones to 1-Aryl-5-(o-aminoanilino)-3-phenylpyrazoles by Trifluoroacetylation and Hydrazinolysis

A convenient preparative two-stage method was developed for the isomerization of 2-phenacyl-1H-benzimidazole arylhydrazones to previously unknown 5-(o-aminoanilino)-1-aryl-3-phenylpyrazoles. The transformation scheme includes recyclization during acylation with trifluoroacetic anhydride leading to the formation of 1-aryl-3-phenyl-5-(o-trifluoroacetylaminoanilino)pyrazoles, which then undergo hydrazinolysis.

Isomerization in the Oxidative Cyclocondensation of 2-Aroylmethyl-1H-benzimidazoles with o-Aminothiophenol

Oxidative cyclocondensation of 2-aroylmethyl-1H-benzimidazoles with o-aminothiophenol gave the previously unknown 3-aryl-2-(2-benzimidazolyl)-4H-1,4-benzothiazines and (or) the isomeric 2H-1,4-benzothiazines. 2-(4-Nitrophenacyl)-1H-benzimidazole and 2-phenacylbenzothiazole gave 4H-1,4-benzothiazines which are not liable to isomerize but the reaction of the first compound is complicated by a hydrolytic fission which yields 2-[2-(4-nitrobenzoylamino)phenylthiomethyl]benzimidazole. A mixture of dimethylsulfoxide, acetic acid, and water was used as oxidant and solvent. The effect of the substituent and of the solvent on the tendency of the products to undergo prototropic isomerization in the benzothiazine ring have been studied.