V. I. Sorokin

Pyrazolopyrimidines Based on 5-Aminopyrazoles Unsubstituted at the Position 1

By condensation of various symmetric β-diketones with a series of 5-aminopyrazoles that are unsubstituted at the position 1, we have obtained a series of pyrazolo[1,5-a]pyrimidines that are of interest as physiologically active compounds. Hexafluoroacetylacetone reacts in another direction, forming pyrazolo[4,5-b]pyridine.

Condensation of 1-Substituted 5-Aminopyrazoles with β-Dicarbonyl Compounds

Condensation of N-substituted 5-aminopyrazoles with β-diketones occurs with the formation of pyrazolo[4,5-b]pyridines. Depending on the conditions, their reaction with β-keto acids can give either 6-oxo- or 4-oxopyrazolo[4,5-b]pyridines.

Synthesis of N(1)-substituted 5-amino-3-methylpyrazoles

With the aim of preparing new biologically active compounds a series of N(1)-substituted 5-amino-3-methylpyrazoles has been obtained from β-aminocrotononitrile and mono-substituted hydrazines.

New method for the sulfonation of pyrazoles

It has been found that pyrazoles are readily sulfonated in position 4 by concentrated sulfuric acid in acetic anhydride.

C-acylation of pyrazole and its derivatives byo-chlorobenzenesulfonylisocyanate

N-Substituted pyrazoles with a free 4-position on the ring and not containing electron-acceptor substituents easily react with o-chlorobenzenesulfonylisocyanate according to an electrophilic substitution scheme, forming 4-o-chlorobenzenesulfonylcarbamoyl derivatives.

Steric Effects in the Nucleophilic Addition of Pyrazoles Unsubstituted at a Nitrogen Atom to the Double Bond of Maleic Anhydride

Only one isomer, 5-methyl-3-phenyl-1-pyrazolylsuccinic acid, is formed on addition of 3(5)-methyl-5(3)-phenylpyrazole to the double bond of maleic anhydride.

Synthesis of tryptamines containing a sulfo group in the benzene ring

It has been shown that sulfophenylhydrazines can be used successfully in a single stage synthesis of tryptamines from arylhydrazines and γ-chlorocarbonyl compounds.

Once again the question of cyclization of pyrazolones-5 unsubstituted at the nitrogen into tripyrazolynenes

The experimental data were refined and the yields were improved significantly in cyclization of pyrazolones-5 into tripyrazolylenes-1,5 with phosphorus oxychloride.

N-o-chlorophenylsulfonylcarbamoyl derivatives of pyrazoles, pyrazolines, and imidazole

In the reaction of o-chlorosulfonyl isocyanate with imidazole, pyrazoles, and pyrazolines with a free NH group of the nucleus under mild conditions, N-acylation takes place with the formation of a heterocyclic containing, at the nitrogen atom of the nucleus, an o-Cl-C6H4SO2NHCO- group which hydrolyzes very easily in the case of pyrzoles.

C-acylation of π-rich heterocycles byo-chlorobenzenesulfonylisocyanate

Nitrogen-containing π-rich heterocycles under mild conditions are acylated by o-chlorobenzene-sulfonylisocyanate, forming C-arylsulfonylcarbamoyl derivatives; O- and S-containing heterocycles do not react under these conditions.