G. A. Golubeva

Structure and properties of 1-acylpyrazolines

Proton magnetic resonance spectroscopy and the method of dipole moments demonstrated that 1-acylpyrazolines exist primarily in the s-trans form, which is stabilized by the repulsion of like-charged nitrogen and oxygen atoms. Simultaneous reduction of the C =O and C =N bonds was observed during the action of lithium aluminum hydride on 1-formyl-and 1-trifluoroacetylpyrazolines, which is explained by the relatively high polarity of the C=N bond.

Electrophilic substitution in the 1-phenyl-2-acylpyrazolidine series

Bromination, nitration, and sulfonation reactions in the acylphenylpyrazolidine series were investigated. 1-(p-Bromophenyl)-2-acylpyrazolidines are formed in good yields in the bromination of these compounds over a wide range of temperatures in various solvents. Removal of the acyl group takes place simultaneously with sulfonation in the para position of the phenyl ring in the sulfonation of phenylacylpyrazolidines with concentrated sulfuric acid at room temperature; the p-sulfophenylpyrazolidines formed in this case exist in the form of betain structures. The nitration of acylphenylpyrazolidines with concentrated nitric acid (sp. gr. 1.52) leads to 1-(2,4-dinitrophenyl)-2-acylpyrazolidines. However, the nitration of these compounds with dilute nitric acid (sp. gr. 1.35) is accompanied by pronounced resinification; both 2,4-dinitrophenyl and p-nitrophenyl-2-acylpyrazolidines, as well as dimers of the latter, were detected among the reaction products.

Three-dimensional structures of 1-acyl-5-hydroxypyrazolidines

It was shown by x-ray diffraction analysis and PMR spectroscopy that 1-acyl-5-hydroxy- and -5-hydrazinopyrazolidines have a conformation with an axial orientation of the functional group attached to the C(5) atom. The 1-salicylyl derivatives constitute an exception: in methanol solutions they exist in a conformation with an equatorial hydroxy group, whereas in dimethylformamide (DMF) the ring undergoes partial opening to give the corresponding β-hydrazido aldehydes.

Preparation and properties of azinium salts of the 2-pyrazoline series

Azinium salts containing pyrazoline fragments have been obtained by the reaction of 2-pyrazolines with aromatic and heteroaromatic aldehydes, acetylacetone, and acetoacetic ester in the presence of H2SnCl5 and HBF4. Reactions of nucleophilic addition to the multiple bonds and also some cycloaddition reactions among the arylidene derivative have been studied. From the azinium salts of a series of β-dicarbonyl compounds have been obtained previously unknown enamino carbonyl compounds of the 2-pyrazoline series.

Reaction of 10-formyl-3-methyl-1,2,3,4-tetrahydropyrimido [1,2-a]indole and its dimethyliminium salt with nucleophilic agents

The reaction of 10-dimethyliminium-3-methyl-1,2,3,4-tetrahydropyrimido[1,2-a] indole chloride and the protonated form of 10-formyl-3-methyl-1,2,3,4-tetrahydropyrimido[1,2-a]indole with some N- and C-nucleophiles leads to the formation of products of condensation at the carbonyl carbon atom. Condensation with the potassium enolate of cyanoacetic ester is accompanied by subsequent cyclization to give compounds of the α-carboline series. Acidic hydrolysis of the aldehyde gives 3-methyl-1,2,3,4-tetrahydropyrimido[1,2]indole hydrochloride.

Reaction of 1-acyl-2-phenylpyrazolidines with imminium salts

The reaction of 1-acetyl-2-phenyl-4-methylpyrazolidine with imminium salts leads to the formation of 3-methyl-1,2,3,4-tetrahydropyrimido[1,2-a]-10-methylenedimethylimininium chloride, the alkaline hydrolysis of which gives 3-methyl-1,2,3,4-tetrahydropyrimido[1,2-a]-10-aldehyde. Similar reactions with 1-propionyl and 1-phenylacetyl derivatives leads to nonformylated indolization products. The relative reactivities of the imminium were studied.

Cyclization of arylthiohydrazides of carboxylic acids under the influence of phosphorus halides

It is shown that arylthiohydrazides of carboxylic acids undergo cyclization to give both bis (1-methyl-2-indolyl) disulfides and salts of the corresponding 1-methyl-2-aminoindole under the influence of phosphorus halides (POCl3 or PCl3).

Condensation of 1-acylpyrazolines

Under the influence of phosphorus oxychloride, 1-acylpyrazolines condense to give 3-pyrazolinylpyrazoles; cleavage of the pyrazoline molecule occurs at the C3-N2 bond.

Reaction of l-aryl-?2-pyrazoline salts with lithium aluminum hydride

The corresponding pyrazolidines were obtained by reduction of 1-aryl(1-hetaryl)pyrazoline salts. The structure of the products and the reaction mechanism are discussed.

Synthesis of 2,3,4,5-tetrahydropyrimido[2,1-b]-benzothiazoles

Abstract1-Thiocarbamoyl-2-phenylpyrazolidines are cyclized to give 2,3,4,5-tetrahydropyrimido[2,-1-b]benzothiazoles, the structure of which was proved by mass spectrometry.