S. V. Baranin

Pyrazol-5-one diaminomethylidene derivatives as reagents for the synthesis of heterocyclic compounds and as new chelating ligands

Abstract1-Arylpyrazol-5-ones added to the C≡N bond of benzoylcyanamide in the presence of Ni(OAc)2, giving the corresponding pyrazol-5-one diaminomethylidene derivatives, which were used as reagents for the synthesis of heterocyclic compounds and as chelating ligands.

Synthesis of 6-hydrazino-3,4-dimethyl-1H-pyrazolo[3,4-d]pyrimidine and its application for the construction of a pyrazolo[4,3-e][1,2,4]triazolo[4,3-a]pyrimidine system

A new representative of heterocyclic hydrazines, viz., 6-hydrazino-3,4-dimethyl-1H-pyrazolo[3,4-d]pyrimidine (3) was synthesized from diacetyl ketene N,S-acetal. A condensation of hydrazine 3 with amide acetals or aldehydes and subsequent cyclization furnished pyrazolo[4,3-e][1,2,4]triazolo[4,3-a]pyrimidines, whose structure was confirmed by 1H, 13C, and 1H/15N HMBC NMR spectroscopy. Reactions of hydrazine 3 with acetylacetone, ethyl acetoacetate, diethyl malonate, and acetic anhydride were studied.

Trifluoromethyl-substituted 1,6-naphthyridines and pyrido[4,3-d]pyrimidines

A convenient method for the synthesis of 1-alkyl-5-trifluoromethyl-1,6-naphthyridin-4(1H)-ones was elaborated based on the reaction of 4-alkylamino-3-trifluoroacetimidoyl-3-penten-2-one diphenylboron chelates with dimethylformamide dimethyl acetal. 3-Acetyl-4-amino-2-trifluoromethylpyridine was used to obtain 5-trifluoromethyl-1,6-naphthyridin-4(1H)-one and its 2-methoxycarbonyl derivative, as well as 4-methyl-5-trifluoromethylpyrido-[4,3-d]pyrimidine.

Synthesis of pyrazolo[1,5-c]pyrimidines from difluoroboron chelates of aroylacetones

A convenient method was developed for the synthesis of derivatives of 6H-pyrazolo[1,5-c]pyrimidine-7-thione and 7-aminopyrazolo[1,5-c]pyrimidine from difluoroboron chelate complexes of aroylacetones, amide acetals, and thiosemicarbazide or aminoguanidine.

Synthesis of 3-arylazo-1H-pyridazin-4-ones from difluoroboron chelates of 1,3-diketones

A convenient method for the synthesis of 6-R-3-arylazo-1H-pyridazin-4-ones from difluoroboron chelates of acetylacetone and aroylacetones was developed. The method is based on the ability of the methyl group of the chelates to react with two equivalents of a diazonium salt.

Reactions of alkyl 3-amino-5-aryl-2-benzoyl-5-oxopent-2-enoates with hydrazine

Reactions of alkyl 3-amino-5-aryl-2-benzoyl-2-oxopent-2-enoates with hydrazine were accompanied by debenzoylation and isomerization to give 3-amino-5-aryl-5-oxopent-3-enohydrazides, which underwent cyclization in the presence of an excess of hydrazine into 5(3)-arylpyrazol-3(5)-ylacetohydrazides.

Four-coordinate six-membered ketiminate and diketiminate boron complexes. Synthesis, structure, reactivity, and application in the design of nitrogen heterocycles

The data on ketiminate and diketiminate boron complexes are first reviewed. The present review is focused on the synthesis and chemical transformations of these chelates. The special attention is paid to the application of these boron chelates in the synthesis of nitrogen heterocycles including CF3-substituted derivatives.

A new approach to the synthesis of 3-amino- and 3-benzoylamino-5-aminoalkyl-1,2,4-triazoles

Nickel(II) acetylacetonate for the first time was shown to efficiently catalyze the addition of Boc-protected amino acid hydrazides to the nitrile group of benzoylcyanamide with the formation of the corresponding 3-benzoylamino-substituted 1,2,4-triazoles with the Boc-aminoalkyl group at position 5. A further modification of the latter led, depending on the conditions, to mono- or dihydrochlorides of 1,2,4-triazole-derived amines.

Synthesis of 5-aroylmethylpyrazoles and their hydrazones from dif luoroboron chelates of aroylacetones

A convenient method for the synthesis of 5-aroylmethylpyrazoles and their hydrazones from difluoroboron complexes of aroylacetones, acetals of amides, and hydrazines was developed.

Methyl (5-oxopyrazol-3-yl)acetate N , S -ketene acetal as a new building block for the construction of pyrazolo[4,3- c ]pyridines

Methyl (5-oxopyrazol-3-yl)acetate is added to methylthiocyanate C≡N bond in the presence of Ni(OAc)2 giving a corresponding heterocyclic N,S-ketene acetal. The latter compound was used as a convenient synthon in the synthesis of new pyrazolo[4,3-c]pyridin-3-ones and pyrazolo[4,3-c]pyridine-3,6-diones.