V. M. Prokopenko

Reaction of 2-Aryl-4-Cyano-1,3-Oxazole-5-Sulfonyl Chlorides With 5-Amino-1H-Pyrazoles and 5-Amino-1H-1,2,4-Triazole

The reaction of 2-aryl-4-cyano-1,3-oxazole-5-sulfonyl chlorides with 5-amino-3-R-1H-pyrazoles and 5-amino-1H-1,2,4-triazole gave 5-[(3-R-5-amino-1H-pyrazol-1-yl)sulfonyl]-2-aryl-1,3-oxazole-4-carbo- nitriles and 5-[(5-amino-1H-1,2,4-triazol-1-yl)sulfonyl]-2-aryl-1,3-oxazole-4-carbonitriles. The action of sodium hydride on these carbonitriles leads to the elimination of sulfur dioxide and cyclocondensation to give new heterocyclic systems, namely, [1,3]oxazolo[5,4-d]pyrazolo[1,5-a]-pyrimidine and [1,3]oxazolo[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine.

Interaction of 2-aryl-4-cyano-1,3-oxazole-5-sulfonyl chlorides with amidines

Reaction of 4-cyano-1,3-oxazole-5-sulfonyl chlorides with amidines results in new 7-amino-1,3-oxazolo[5,4-d]pyrimidines. Their structure was confirmed by spectral methods and X-ray diffraction analysis.

Synthesis of 2-aryl-4-cyano-1,3-oxazole-5-sulfonyl chlorides and N-substituted sulfonamides

Oxidative chlorination of 2-aryl-5-benzylsulfanyl-1,3-oxazole-4-carbonitrile results in the previously unknown 4-cyano-1,3-oxazole-5-sulfonyl chlorides and N-substituted sulfonamides.

Reaction of 2-aryl-4-dichloromethylidene-1,3-oxazol-5(4H)-ones with 2-aminopyridine

Reactions of multicenter electrophilic substrates, 2-aryl-4-dichloromethylidene-1,3-oxazol-5(4H)-ones, with 2-aminopyridine, involved cleavage of the dihydrooxazole ring by the primary amino group of nucleophilic reagent and subsequent cyclization to imidazopyridine derivatives. The latter reacted with morpholine and its analogs via recyclization with formation of 5-amino-2-aryl-N-(pyridin-2-yl)-1,3-oxazole-4-carboxamides.

Synthesis and transformations of derivatives of 2-aryl-5-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3-oxazole-4-carboxylic acid

On the basis of methyl esters of 2-aryl-5-hydrazino-1,3-oxazole-4-carboxylic acids the earlier unknown methyl esters of 2-aryl-5-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3-oxazole-4-carboxylic acids as well as their functional derivatives were synthesized. The latter were used for further transformations, in particular, for introducing the residues of highly basic aliphatic amines into the 5 position of oxazole, and the oxazol-2-yl moiety into the 4 position of the oxazole ring.

Synthesis of methyl 2-aryl-5-chlorosulfonyl-1,3-oxazole-4-carboxylates and their reactions with amines and amidines

Previously unknown methyl 2-aryl-5-chlorosulfonyl-1,3-oxazole-4-carboxylates have been synthesized. Their reactions with amines and amidines have yielded the corresponding sulfonamides and 6H,7H-[1,3]oxazolo-[5,4-d]pyrimidin-7-ones.

Synthesis of 4-hetaryl-substituted 5-amino- and 5-sulfanyl-1,3-oxazole derivatives

Previously unknown 5-amino- and 5-sulfanyl-1,3-oxazole derivatives containing a 1,3,4-oxadiazole, 1,3,4-thiadiazole, or 1,2,4-triazole fragment at C4 were synthesized from accessible 1,3-oxazole-4-carboxylic acid hydrazides.

2-aryl-5-arylsulfanyl-1,3-oxazole-4-carboxylic acids and their derivatives

A convenient preparative procedure has been developed for the synthesis of previously unknown 2-aryl-5-arylsulfanyl-1,3-oxazole-4-carboxylic acids and their functional derivatives from accessible multicenter substrates of the general formula Cl2C=C(NHCOR)C(O)OMe. The products turned out to be suitable for various subsequent transformations. Some oxazole-4-carboxylic acid hydrazide derivatives containing a substituted oxazol-5-yl fragment at the N2 atom in the hydrazine moiety underwent recyclization on heating in acetic acid; as a result, one oxazole ring was converted into 1,3,4-oxadiazole.

Synthesis and Properties of 2-Substituted 5-Chloro-1,3-oxazole-4-carboxamides

Chlorination of 2-aryl-5-benzylsulfanyl-1,3-oxazole-4-carbonitrile in aqueous acetic acid at 50–60°C afforded new 2-aryl-5-chloro-1,3-oxazole-4-carboxamides. The reactivity of the chlorine atom with respect to the N-, O-, and S-nucleophiles was investigated.

A convenient approach to synthesis of benzoxazol-2-ylglycine and benzothiazol-2-ylglycicne derivatives

Introduction of pharmacophore heterocyclic moieties into the peptide chain is of particular interest because it results in a promising new bioregulators [1] with a significant anticonvulsant, neuropathic and analgesic activity [2–6], and also oxytocin antagonists [7]. However, the functionalization of α-amino acids with electron-acceptor heterocycles is a challenging task, due to their ease of decarboxylation. This substantially limits the use of such amino acids in peptide synthesis. In this work, we developed a convenient approach to the synthesis of glycine derivatives, which were modified at the α-position with benzoxazol-2-yl and benzothiazol-2-yl moieties. For the first time we used for this purpose available 2-phenyl-4-dichloromethylene-5(4H)-oxazolone [8], which was involved into the reactions sequence: I → III → V or VII. The reaction I → III has been previously described by an example of 2-aminothiophenol [9], and all the other reaction were investigated by us for the first time. The DOI: 10.1134/S1070363213060364