Zukhra I. Niazimbetova

Cross-condensation of derivatives of cyanoacetic acid and carbonyl compounds. Part 1: Single-stage synthesis of 1′-substituted 6-amino-spiro-4-(piperidine-4′)-2H,4H-pyrano[2,3-c]pyrazole-5-carbonitriles

Abstract To develop a method of synthesis of the potentially physiologically active compounds, 1′-substituted 6-amino-spiro-4-(piperidine-4′)-2 H ,4 H -pyrano[2,3- c ]pyrazoles, we studied the three-component condensation of substituted piperidin-4-ones, malononitrile and pyrazolin-5-ones. It was found that the electrochemical method of synthesis is more regioselective, the products of the reaction are analytically pure and do not require further recrystallization.

Synthesis and electrochemical investigation of oligo-(arylenevinylenes) intended for the preparation of two-dimensional polymer networks

Four phenylenevinylene oligomers (1/4 )h ave been synthesized and characterized by cyclic voltammetry, absorption spectroscopy and photoluminescence (PL). Two of the oligomers contain a tri-substituted central benzene ring, while one contains a tetrasubstituted central ring. These oligomers were prepared in an effort to increase hole and electron mobility in organic materials via extension of conjugation to two dimensions. Optical and electrochemical evidence is given for significant interactions of the alkoxysubstituted styryl units of 3 that are attached to the central benzene ring in meta positions. The tetra-substituted oligomer (4) also exhibits strong interactions between the pair of para substituted arms. The photoluminescence (PL) quantum yield for the tetrasubstituted oligomer is high, indicating that it is an excellent candidate for the active layer in organic light-emitting diodes. # 2002 Elsevier Science B.V. All rights reserved.

Cathodically Promoted Addition of Nitromethane to Aldehydes and Exploratory Studies of the Mechanism of the Electrochemical Reduction of the Nitroolefins so Produced

Addition of nitromethane to aromatic and heteroaromatic aldehydes has been carried out in nitromethane. The reaction is catalyzed by superoxide produced by cathodic reduction of dioxygen, which serves as an electrogenerated base. The initially formed products are nitroalcohols which undergo dehydration, either in situ or in a subsequent chemical dehydration, to give 1-nitroalkenes. The addition of nitroethane to benzaldehyde, thiophene-2-carboxaldehyde, and furan-2-carboxaldehyde was also investigated, and good yields of diastereomeric mixtures of the nitroalcohols were obtained. The electrochemical reduction of seven of the 1-nitroalkenes prepared in this and earlier work was studied by cyclic voltammetry and controlled potential coulometry. The reduction is thought to proceed by initial formation of the radical anion which subsequently dimerizes. However, in many cases, the reduction is accompanied by oligomerization of the starting material, leading to coulometric n-values that are much less than one.

Electrochemical Synthesis of Aliphatic 1,3-Dinitro Compounds

A one-step electrochemical synthesis of 1,3-dinitro compounds from aromatic and heteroaromatic aldehydes and nitromethane has been developed. In the procedure, an electrogenerated base is prepared by cathodic reduction of air-saturated nitromethane solutions. Then the aldehyde is added and allowed to react. The reaction presumably proceeds in three base-catalyzed steps: addition of nitromethane to the aldehyde to form a nitroalcohol, dehydration of the nitroalcohol to produce nitroolefin, and Michael addition of nitromethane to the nitroolefin. The synthesis produces the 1,3-dinitro products in very good yields when the aryl group is electron-donating in character. For less strongly electron-donating groups, only moderate yields are obtained and with electron-withdrawing groups the reaction tends to stop at the stage of the nitroalcohol. For purposes of comparison, four of the products were prepared in a multistep synthesis with the last step being the cathodically promoted Michael addition of nitromethane to the nitroolefin. It was found that this last procedure was also successful in forming the 1,3-dinitro derivative from 2-thiophenecarboxaldehyde and nitroethane in good yield and all three isomers of the product were separated and characterized. The stereochemical identity of one isomer was proved by X-ray crystallography whereas that of the other two was established by comparison of nuclear magnetic resonance spectra with those of the isomers of an analogous compound of known stereochemistry.

Cathodically Promoted Addition of Nitroalkanes to Ferrocenecarboxaldehyde

The addition of ferrocenecarboxaldehyde, 5, to nitromethane and nitroethane has been studied through the use of cathodically generated superoxide as an electrogenerated base to catalyze the reaction. The electrolyses were conducted in the pure nitroalkane as solvent. The nitroalcohol obtained from nitromethane, (1 -hydroxy-2-nitroethyl)ferrocene, (6), was produced in higher yield than obtained in earlier work. Approximately equal amounts of the two diastereomers of (1-hydroxy-2-nitropropyl)ferrocene (8) were produced from reaction with nitroethane. The threo isomer was separated and crystallized, and its stereochemical identity was proven by X-ray crystallography. Conditions were found for which reaction of 5 with nitromethane produced the double addition product, [2-nitro- 1 -(nitromethyl)ethyl]ferrocene, 7, in almost quantitative yield. Reversible potentials for oxidation of the ferrocene moiety of 5-8 and other ferrocene derivatives were measured by means of cyclic voltammetry in acetonitrile. The nitroalcohols (6 and 8) are only slightly more difficult to oxidize than ferrocene (75 and 65 mV, respectively) whereas the potential for 1,3-dinitro compound 7 is 140 mV positive of that of ferrocene. Irreversible reduction peak potentials are also reported.

Cathodically Promoted Stereoselective Addition of 1,3‐Dinitro Compounds to Levoglucosenone

This paper reports new applications of the cathodically promoted addition of nitro compounds to the biomass-derived enone, levoglucosenone. A series of 2-substituted 1,3-dinitropropanes were found to undergo addition to levoglucosenone with generation of a tricyclic product containing a fused cyclohexane system. The reaction yields are good to excellent and are catalyzed by base (superoxide) generated electrochemically. Derivatives were prepared from 1,3-dinitropropanes with the following 2-substituents: 2-thienyl, 2-furyl, N-methyl-2-pyrryl, phenyl, 9-anthryl, and ferrocenyl. The structure of the derivative from 2-ferrocenyl-1,3-dinitropropane was established by X-ray crystallography, thus confirming the NMR-based stereochemical assignments of all of the other products.

Studies of Cathodically-Promoted Addition Reactions of Nitromethane with Various Aldehydes

Addition of nitromethane to five heterocyclic aldehydes, anthracene-9-carboxaldehyde and ferrocenecarboxaldehyde has been studied. In all cases, the corresponding nitroalcohols are formed initially and, for the less basic aldehydes, this product can be isolated in good to excellent yield. For the more basic heterocyclic aldehydes, the initially formed nitroalcohol dehydrates under the reaction conditions forming the nitroolefin. This is particularly evident for the reaction of N-methylpyrrole-2-carboxaldehyde where the nitroolefin was found to add a second molecule of nitromethane forming 2-(N-methyl-2-pyrrolyl)-1,3-dinitropropane. Similar results were obtained with ferrocenecarboxaldehyde where it was possible to obtain the 1,3-dinitro compound as the sole product.