Reactions of some arenes and pyrazoles in MeCN under conditions of undivided-cell electrolysis

As exemplified for the first time by pyrazole and its 4-nitro and 3,5-dimethyl derivatives, N-arylation of pyrazoles can be performed under conditions of undivided-cell amperostatic electrolysis (Pt electrodes, MeCN) of systems containing the pyrazolate anion and (or) pyrazole, arene (benzene, 1,4-dimethoxybenzene, or xylene), and a supporting electrolyte. In the case of electrolysis involving 1,4-dimethoxybenzene as arene, N-arylation followed simultaneously three routes to form an ortho-substitution product (1,4-dimethoxy-2-(pyrazol-1-yl)benzene), an ipso-substitution product (4-methoxy-1-(pyrazol-1-yl)benzene), and an ipso-bisaddition product (1,4-dimethoxy-1,4-di(pyrazol-1-yl)cyclohexa-2,5-diene) in a total current yield of up to 50%. The acid-base properties of the pyrazoles under study affect the ratio of the N-arylation products and govern the required composition of the starting reaction mixture. In the case of a stronger base, such as 3,5-dimethylpyrazole, N-arylation with 1,4-dimethoxybenzene occurred even in the pyrazole—arene—tetraalkylammonium perchlorate system, whereas N-arylation of 4-nitropyrazole (a weaker base) proceeded only in the presence of the pyrazolate anion or another base, viz., sym-collidine. Oxidation of arene to the radical cation is the key anodic reaction. Not only the pyrazolate anion, but also highly basic pyrazole or a solvate complex of weakly basic pyrazole with collidine can serve as a nucleophilic partner in subsequent transformations of these radical cations.     

Chemistry of 2-methylene-2,3-dihydro-3-furanones

2-p-Chlorobenzoylmethylene-5-phenyl-2,3-dihydro-3-furanone reacts with arylamines orN-arylideneamines to form the products of ring opening, 1,6-diaryl-1-arylamino-4-hydroxy-1,4-hexadiene-3,6-diones. The reaction of 5-aryl-2-p-chlorobenzoylmethylene-2,3-dihydro-3-furanones witho-aminophenol afforded 3-p-chlorobenzoylmethylene-3,4-dihydro-2H-benzo[b]-1,4-oxazin-2-one. Nucleophilic attack of amines is directed either to electrophilic centers at the C(5) and C(2) atoms or to the carbonyl group of the 2-phenacylidene substituent of the 3-oxofuran ring. For communication 15, see Ref. 1. Translated fromIzestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1340–1345, July, 1997.     

Degradation processes in the cellulose/<Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide system studied by HPLC and ESR. Radical formation/recombination kinetics under UV photolysis at 77 K

Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC) and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature, radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide type radicals ∼CH₂–NO^•–CH₂∼ and/or ∼CH₂–NO^•–CH₃∼ at the first and methyl ^•CH₃ and formyl ^•CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g., Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO.     

Electrosynthesis of N-Arylazoles by Electrolyzing a Mixture of Azole and 1,4-Dimethoxybenzene in a Diaphragmless Cell

An analysis is performed and data are compared on the electrosynthesis of N-arylazoles and regularities of this process in conditions of a diaphragmless galvanostatic electrolysis (Pt, MeCN, Bu₄NClO₄) of a mixture of 1,4-dimethoxybenzene (DMB) with azoles (pyrazole, triazole, their derivatives, tetrazole). Electrolysis of an azole/DMB mixture leads to the formation of products of an ortho-substitution—1,4-dimethoxy-2-(azolyl-1)benzenes—and, simultaneously, hydrolytically unstable products of an ipso-bis-attachment—1,4-dimethoxy-1,4-di-(azolyl-1)cyclohexa-2,5-dienes. The overall yield of these compounds increases upon adding a base (collidine) or an acid (AcOH) into the initial mixture, and the basicity of initial azoles substantially affects the electrosynthesis results. New notions on the nature of nucleophilic species interacting with radical cation of DMB are considered. The species in question are complexes of azoles with one another or with collidine generated at the expense of the hydrogen bond, rather than azolate ions. Furthermore, the cathodic process is largely connected not with the generation of azolate ions (as a result of the reduction of initial azoles) but with the deprotonation of onium compounds (BH⁺)—products of the interaction of azoles or collidine with protons. The mechanism of electrosynthesis of N-arylazoles is discussed. The key stages of the synthesis are the attack of a nucleophile on the ipso- and, possibly, ortho-positions of the benzene ring of radical cation of DMB, as well as the rearrangement of the intermediate cation of 1,4-dimethoxy-1-(azolyl-1)arenonium into the cation of 1-(azolyl-1)-2,5-dimethoxyarenonium, which affects both the yield and ratio of final products of the reaction mixture.     

Electrochemical oxidation of 2H-imidazole N-oxides

Electrochemical oxidation of 2H-imidazole N-oxides was studied using cyclic voltammetry and ESR spectroscopy. The formation of the 2,2-dimethyl-4,5-diphenyl-2H-imidazole 1,3-dioxide radical cation was noticed for the first time. The possibility of reaction between the 2H-imidazole N,N-dioxide radical cation and methanol including the detachment of a hydrogen atom from the MeOH methyl group was demonstrated.     

Ricinin — einfach synthetisiert

Cyclization of 1,1-dicyano-4-(N,N-dimethylamino)-2-methoxy-1,3-butadiene leads to 4-methoxy-2(1H)-pyridone-3-carbonitrile and 2,4-dimethoxy-pyridine-3-carbonitrile. Methylation of both products yields ricinine.

     

Selective hydrogenation of nitrobenzene top-Aminophenol by the polymer-supported palladium-based mono- and bimetallic catalyst

In acidic reaction medium, polymer-supported monometallic palladium catalyst, PVP-PdCl₂ [(PVP=poly(N-vinyl-pyrrolidone)], is used to catalyze the hydrogenation of nitrobenzene top-aminophenol and aniline. The addition of a second transition metal compound or a very small amount of 2-mercaptopyrimidine gives rise to an increase in the selectivity forp-aminophenol.     

An Efficient Method for the Synthesis of N-Acylsulfonamides: One-pot Sulfonylation and Acylation of Primary Arylamines under Solvent-Free Conditions

Summary. The preparation of N-acylsulfonamides is described using primary amines, arylsulfonyl chlorides and acyl chlorides. Reaction of primary aryl amines with arylsulfonyl chlorides in the presence of NaHCO₃ produced N-arylsulfonamides, which reacted in situ with benzoyl chloride furnishing the corresponding N-benzoyl-N-arylsulfonamides in 72–96% yields. Accordingly, 4-nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were used as acylating agents. All the reactions were carried out under solvent-free conditions at room temperature and the products were isolated after simple work-up in high yields and purity.     

Synthesis of potassium salts ofO-substitutedN-nitrohydroxylamines

Potassium salts of O-substitutedN-nitrohydroxylamines were synthesized by nitration of O-substituted.N-acetylhydroxylamines followed by treatment of the reaction products with potassium methoxide.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 178–179, January, 1994.     

DFT Study on Intermolecular Cleavage Reaction of N-（2-Hydroxyphenyl）-phthalamic Acid

The reaction mechanisms of intermolecular cleavage reaction of N-（2-hydroxyphenyl）-phthalamic acid were studied via the density functional theory（DFT）. All geometries of the reactant, transition states, and products were optimized at the B3LYP/6-31G（d, p） level. Vibration analysis was carried out to confirm its identity as transitions＇ structure, and the intrinsic reaction coordinate method（IRC） was used to search the minimum energy path. Two possible reaction channels are reported in this article. The calculated results indicate that O-cyclization reaction channel has the lower activation barrier, and therefore, it occurs more easier than the other.     

Synthesis of N-nitrooxazolidines and N-nitrotetrahydro-1,3-oxazines from N-(2-hydroxyalkyl)- and N-(3-hydroxyalkyl)sulfamates

A method was developed for the preparation of functionally substituted N-nitrooxazolidines and N-nitrotetrahydro-1,3-oxazines by nitration of the products obtained in the reactions of N-(2-hydroxyalkyl)- and N-(3-hydroxyalkyl)sulfamates with formaldehyde.     

Reactions of N"-acyl- and N"-tosyl-substituted hydrazides of 2-aminobenzoic acid with carbonyl compounds

The reactions of N"-acyl and N"-tosyl-substituted hydrazides of 2-aminobenzoic acid with aliphatic, aromatic, and heterocyclic aldehydes or aliphatic ketones afforded 3-acyl- and 3-tosylamido-1,2-dihydroquinazolin-4-one derivatives, respectively. The structures of the reaction products were established by NMR spectroscopy and X-ray diffraction analysis.     

RuO<Subscript>4</Subscript>-mediated oxidation of<Emphasis Type="Italic">N</Emphasis>-benzylated tertiary amines. Are amine<Emphasis Type="Italic">N</Emphasis>-oxides and iminium cations reaction intermediates?

N-Benzylmorpholine,-piperidine, and-pyrrolidine (1A-C, resp.) are oxidised by RuO₄ (generated in situ) at both endocyclic and exocyclic (benzylic) N—α-methylene positions to afford lactams (and dioxo-derivatives) and benzaldehyde (and benzoyl derivatives), respectively. The N-oxides of 1A-C, formed by a minor side reaction, are not involved as intermediates. Control experiments showed the transient formation of endo- and exocyclic iminium cations trapped with NaCN as the corresponding nitriles. The proposed course of the RuO₄-mediated oxidation of 1A-C involves the consecutive steps 1⇒iminium cations+cyclic enamine⇒oxidation products. The endocyclic/exocyclic regioselectivity of the oxidation reaction lies between 0.8 (for 1A) and 2.1 (for 1B). The amine cation radical and the N-α-C· carbon-centered radical seem not to be involved.     

Synthesis of high-molecular-weight polyamine by radical polymerization ofN,N-diallyl-N-methylamine

The first synthesis of high-molecular-weight poly(N,N-diallyl-N-methylamine) by thermal (at 30 and 50°C) and photoinduced (at 21 °C) radical polymerization ofN,N-diallyl-N-methylamine (DAMA) in aqueous solution in the presence of an equimolar amount of trifluoroacetic acid (TFA) and by polymerization of the newly synthesized equimolar DAMA·TFA salt is reported. Data of¹H NMR spectroscopy indicate that the molecules of the monomer under chosen conditions are in the protonated form. This leads to a decrease in the contribution of the reaction of degradative chain transfer to the monomer and its transformation into effective chain transfer to the monomer. A bimolecular chain termination mechanism was estabilished and the possibility of controlling the polymerization rate and the molecular weight of the polymer was demonstrated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 430–436, March. 2000.     

Effect of solvent on the kinetics of arylsulfonylation of N-alkylated anilines in a water-propan-2-ol system

The effect of the composition of a water-propan-2-ol solvent on the kinetics of arylsulfonylation of N-ethyl-, N-isopropyl-, and N-butylanilines with 3-nitrobenzenesulfonyl chloride at 298 K was studied. The reaction rate constant increases monotonically with an increase in the water fraction in the solvent from 5 to 30 wt.%. The apparent activation parameters of the reaction of N-butylaniline with 3-nitrobenzenesulfonyl chloride were calculated. No considerable changes in the activation parameters of the reaction were observed on going from pure propan-2-ol to a 10% aqueous solution, which indicates that the mechanism remains unchanged upon solvent change. Propan-2-ol with a water content of 5–30 wt.% can be used in the synthesis of arylsulfonylation products of the amines under study in 98–99% yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 937–939, June, 2006.     

Syntheses based on anabasine. Preparation and transformations of N-oxides

The oxidation of N-acetyl-and N-benzoylanabasine with the tert-butyl hydroperoxide (TBHP)— MoCl₅ system or MCPBA proceeds selectively at the nitrogen atom of the pyridine ring. The oxidation of N-methylanabasine under similar conditions gives a mixture of stereo-isomeric N-oxides at the piperidine nitrogen atom, their ratio depending on the reagent used. The oxidation of anabasine by TBHP— MoCl₅ or MCPBA is accompanied by dehydrogenation and results in anabaseine N-oxide. The reactions of anabasine and anabaseine pyridine N-oxides with acetic anhydride were investigated. The substituted 1H-3-pyridin-2-ones were prepared. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 322—328, February, 2006.     

N-Arylation of azoles with low basicity by 1,4-dimethoxybenzene during undivided electrolysis

The reactions of 1,4-dimethoxybenzene with 4-nitropyrazole, 3,4-dinitro-5-methylpyrazole, 1,2,4-triazole, 3-nitro-1,2,4-triazole, and tetrazole were studied during undivided amperostatic electrolysis on a Pt electrode in MeCN, CH₂Cl₂, and MeOH. The main reaction products were 2-azolyl-1,4-dimethoxybenzenes and (or) 1,4-diazolyl-1,4-dimethoxycyclohexa-2,5-dienes. In all cases except 1,2,4-triazole, N-arylation occurs only in the presence of the Alk₄N⁺ salts of azoles or 2,4,6-trimethylpyridine as a base. The mechanism of the reactions is discussed.     

Convenient synthesis of dodeca-1,3-diynyl ketones by the “diacetylene zipper” reaction

Dodeca-1,3-diynyl ketones were synthesized by isomerization of dodeca-5,7-diyne with H₂N(CH₂)₂NHLi and treatment of the in situ prepared lithium derivative of dodeca-1,3-diyne with N-methoxy-N-methylcarboxamides. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1017–1019, April, 2005.     

New β-amino-α-trifluoromethyl alcohols and their exploration in the synthesis of trifluoromethylated imidazole derivatives

Racemic and enantiomerically pure β-amino-α-trifluoromethyl alcohols were obtained via sequential nucleophilic trifluoromethylation of selected α-imino ketones, derived from arylglyoxals, and subsequent removal of the MeO or Ph(Me)CH substituent, respectively, located at the N-atom. The obtained products, containing a primary amino group, were used for the synthesis of imidazole N-oxides bearing a trifluoromethyl group as a part of the N(1)-alkyl chain. Imidazole N-oxides with an electron-withdrawing ester group at C(4) underwent spontaneous isomerization under the reaction conditions, and the corresponding imidazol-2-ones derivatives were isolated as final products.     

Synthesis and study of some properties of 1-aryl-2-oxo-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole 4-oxides

A number of 1-aryl-2-oxo-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole 4-oxides were synthesized based on 3-[N-aryl-N-(chloroacetyl)amino]-2-formylindoles. The nature of the substituent in the 1-aryl fragment has a pronounced influence on the course of reactions throughout the whole sequence of transformations during the synthesis of diazepinoindoles. The reduction of 4-oxides by formamidinosulfinic acid, hydrogen in the presence of Pd/C, and sodium bisulfite was studied. The structures of the reaction products were confirmed using IR and ¹H NMR spectroscopy and mass spectrometry.