V. M. Vinogradov

Synthesis of 3-substituted 1-aryl-4,6-dinitro-1H-indazoles based on picrylacetaldehyde and their behavior in nucleophilic substitution reactions

A method for the synthesis of 1-aryl-3-formyl-4,6-dinitro-1H-indazoles by the reaction of picrylacetaldehyde with aryldiazonium salts followed by intramolecular cyclization of the resulting picrylglyoxal monoarylhydrazones was developed. Various 4,6-dinitro-1-phenyl-1H-indazoles substituted in position 3 were prepared via transformations involving the formyl group of 3-formyl-4,6-dinitro-1-phenyl-1H-indazole. 3-R-4,6-Dinitro-1-phenyl-1H-indazoles (R = CHO, CN, 1,3-dioxolan-2-yl) react regiospecifically with anionic O-, S-, and N-nucleophiles, in particular, with replacement of only the 4-NO2 group. Thus previously unknown 3-R-4-Nu-6-nitro-1-phenyl-1H-indazoles were synthesized (Nu is a nucleophile residue).

Synthesis of 4,6-dinitro-3-R-benzo[d]isoxazoles and their transformations under the action of nucleophiles

A new procedure was developed for the preparation of 4,6-dinitro-3-R-benzo[d]isoxazoles (R are derivatives of the aldehyde group) based on 2,4,6-trinitrophenylacetaldehyde. The resulting compounds are characterized by the regiospecific substitution of the nitro group at position 4 under the action of anionic nucleophiles RS–, RO–, F–, or N3–, which allowed the development of a new method for the preparation of previously unknown 4-Nu-6-nitro-3-R-benzo[d]isoxazoles (Nu is the residue of a nucleophile). At the same time, oxidative nucleophilic substitution under the action of anions of some β-dicarbonyl compounds leads to the replacement of the hydrogen atom at position 7 with the corresponding C-nucleophiles.

Methods of synthesis and technology of drug manufacture N-aminopyrazoles (review)

N-Aminopyrazoles have been known for about the past 30 years but their chemistry began to be developed fairly actively only in the early seventies when the first publications appeared on the oxidative conversion of N-aminopyrazoles into 1,2,3triazines. Interest in N-aminopyrazoles is also generated by their use as valuable intermediates in the synthesis of polycyclic heterocycles, which are biologically active substances and include analgesics and antidepressants. The accumulated data have not yet been systematized. Literature data up to 1992 and part of 1993 on pyrazoles having an NH 2 group on a ring nitrogen atom are summarized in the present review according to preparation, physicochemical properties, conversions, and applications.

Synthesis of mesoionic 3-aryl(hetaryl)-1,2,3,4-oxatriazol-5-ones b based on N-aryl-and N-hetarylhydrazones of bromonitroformaldehyde

Dehydrobromination of N-arylhydrazones of bromonitroformaldehyde (at 20°C) in the presence of alkali and ammonium salts of strong mineral acids, HNO3, silica gel, and Al2O3 forms mesoionic 3-aryl-1,2,3,4-oxatriazol-5-ones (3-arylazasydnones). The effect of the electronic properties of the aryl substituent on the course of the reaction is evaluated. This evaluation is used to develop a general method for preparing 3-arylazasydnones with various substituents including novel 3-hetarylazasydnone derivatives of pyrazole, 1,2,4-triazole and pyridine. Aromatic electronic effects (σI, σR, σm, σp) of the mesionic 1,2,3,4-oxatriazol-5-on-3-yl moiety are determined by19F NMR. A scheme is proposed for the dehydrobromination of the bromonitroformaldehyde N-arylhydrazones that includes the intermediate N-aryl-C-(nitro) nitrilimines, ArN−−N=C+NO2, with subsequent isomerization of the latter into 3-arylazasydnones.

Synthesis of peri-annelated heterocyclic systems based on 3-substituted 1-aryl-4,6-dinitro-1H-indazoles

A method for the synthesis of peri-annelated trinuclear heterocycles, including 14π-electron heteroaromatic systems, namely, 1H-thiopyrano[4,3,2-cd]indazoles and 1,5-dihydropyrazolo[3,4,5-de]cinnolines, from 3-R-1-aryl-4,6-dinitro-1H-indazoles was developed. The method is based on the high mobility of the NO2 group in position 4 and consists of either selective nucleophilic substitution of the 4-NO2 group on treatment with the HSCH2CO2Me—K2CO3 system followed by intramolecular cyclization of the resulting sulfide (R = CHO) or the corresponding sulfone (R = CN) formed upon its oxidation or direct intramolecular substitution of the 4-NO2 group (R = CH=NNHPh).

Reaction of NH-azoles with O-fluorosulfonyl-N,N-difluorohydroxylamine. Synthesis of N-fluorosulfonylazoles

O-Fluorosulfonyl-N,N-difluorohydroxylamine (FH) reacts with anions of NH-azoles (imidazoles, pyrazoles, and 1,2,3-triazoles) to give the corresponding N-fluorosulfonylazoles, which were used to obtain N,N′-sulfonylbisazoles. The N-fluorosulfonylation proceeds at the nitrogen atom furthest from the most electron-withdrawing substituent in the azole ring..Nonaromatic NH-acid anions (imides and primary N-nitroamines) are sometimes capable of giving N-flurosulfonyl derivatives although in yields less than 5%. These products are much less stable than N-fluorosulfonylazoles. The N-fluorosulfonylation presumably proceeds as nucleophilic substitution at the sulfur atom of FH.

Interphase analysis in the chemistry of aliphatic nitro compounds. 1. Alkylation of alkali metal salts of trinitromethane under interphase catalysis conditions in solid phase-liquid systems

Methylation of trinitromethane salts was studied under interphase catalysis conditions in a solid phase (a trinitromethane salt)-liquid (methyl iodide) system in the presence of interphase transfer catalysts — onium salts, cyclic and acyclic polyethers. The dependence of the yield of the methylation product-1,1,1-trinitroethane — on the nature of the catalyst was also investigated, and based on this, catalysts were found, in whose presence the methylation process is realized more effectively than under homogeneous conditions.

New rearrangement of benzo[d]isoxazoles: recyclization of 4-R-6-nitrobenzo[d]isoxazole-3-carbaldehyde arylhydrazones into 2-aryl-4-(2-hydroxy-4-nitro-6-R-phenyl)-1,2,3-triazoles

The previously unknown recyclization of nitrobenzo[d]isoxazoles into 1,2,3-triazoles was found. A general method for the synthesis of 2-aryl-4-(2-hydroxy-4-nitro-6-R-phenyl)-1,2,3-triazoles from 4-R-6-nitrobenzo[d]isoxazole-3-carbaldehyde arylhydrazones was developed.

Phase transfer catalysis in the chemistry of aliphatic nitrocompounds

The methylation of trinitromethane (TNM) Na-salt under phase transfer catalysis (PTC) conditions was studied in a two-phase system (aqueous solution of TNM Na-salt-CH3I). The obtained data revealed a relationship between the yield of the methylation product (1,1,1-trinitroethane) and the nature of the phase transfer catalyst and the degree of TNM anion transfer to the organic phase. The kinetic measurements showed that higher efficiency of methylation was achieved under PTC conditions than occurs in a homogeneous reaction due to the fact that the reaction proceeded in the CH3I medium.