S. S. Gitis

3-Methyl-1,5-dinitro-3-azabicyclo[3.3.1]non-7-ene

The 3-azabicyclo[3.3.1]non-7-ene skeleton of the title compound, C 9 H 13 N 3 O 4 , has a sofa-chair conformation. There are two molecules in the asymmetric unit with different orientations of their nitro groups.

Regioselectivity in the reactions of the acetonate ion with electron-deficient arenes

The reactions of the acetonate ion with 1,3-dinitro-5-X-, 1,3-X2-5-nitro- (X = NO2, CN, COOCH3, CONH2, COO–, and H), and 1,3,5-tricyanobenzenes were studied by 1H NMR and electronic absorption spectroscopy and by quantum-chemical methods. The kinetic factor is decisive for the initial attack of the carbanion on the C(2) atom of unsymmetrical arenes. However, σ-adducts in which a nucleophile is added to the C(4) atom are more stable thermodynamically. In the case of 1,3-X2-5-nitrobenzenes (X = CN, COOCH3, or CONH2), the σ-adducts with the acetonate group in para-position to the X group unexpectedly proved to be very stable. The structures of the σ-adducts based on trinitro- and 1,3-dinitro-5-cyanobenzenes were determined by X-ray diffraction analysis. Quantum-chemical calculations (the AM1 and PM3 semiempirical methods and the density functional method) were used to interpret the reaction regioselectivity and the molecular and electronic structures of the σ-adducts.

Molecular and electronic structures and conformational analysis of derivatives of 9-nitroanthracene, anionic σ-complexes

Potassium 10-methoxy-9-nitroanthracenide was studied by X-ray diffraction analysis. The central ring of the anthracene fragment adopts an asymmetrically flattened boat conformation. The bond lengths in the C(Ar)−C(NO2)−C(Ar) fragment are indicative of the presence of conjugation between the π-systems of the benzene rings and the nitro group owing to a substantial contribution of theaci form to the structure of the nitro group. Quantum-chemical calculations of anionic σ-complexes of 9-nitroanthracene derivatives were performed. In all cases, the central ring adopts two conformations with the pseudoaxial and pseudoequatorial orientations of the substituents at the saturated C(10) atom, respectively. The relative stability of the conformers and the factors determining the stability were considered. The minima on the potential energy surface have a flattened shape in spite of relatively high barriers to the conformational transition (2–4 kcal mol−1). The deviation of the C(Ar)−C(Ar)−C(sp3)−C(Ar) torsion angle from the equilibrium value by ±20° causes an increase in the energy of the anion by less than 1 kcal mol−1. The effect of the substituents on the charge distribution was considered.

Structure features of ions and ion pairs of nitroarene anionic σ-complexes in aprotic solvents

Abstract The structure of ions and ion pairs of Meisenheimer and Janovsky σ-complexes of 1,3,5-trinitrobenzene has been studied by derivative spectroscopy and semiempirical quantum chemical PM3 and CNDO/S methods. On the base of comparison of theoretical and experimental electronic absorption spectra the three types of co-ordination of anion and cation have been defined. It was established that the structure of ion pairs is determined by the nature of the substituents of the pyramidal unit.

3-Azabicyclo[3.3.1]nonane Derivatives: III. Synthesis of 3-Substituted 9-Acetonyl-1,5-dinitro-3-azabicyclo[3.3.1]-non-6-en-8-ones by Mannich Condensation of the Janovsky σ-Adduct of 2,4-Dinitrophenol with Acetonide Ion

A number of 9-acetonyl-1,5-dinitro-3-azabicyclo[3.3.1]non-6-en-8-one derivatives were synthesized by Mannich condensation of 3-acetonyl-2,4-bis(aci-nitro)cyclohex-5-en-1-one disodium salt with formaldehyde and primary amines.

Synthesis and conformation of 6,8,10-trinitro-1,4-dioxaspiro[4.5]decane

Abstractcis, trans-6,8,10-Trinitro-1,4-dioxaspiro[4.5]decane was synthesized by reduction of the corresponding spirocyclic anionic δ-complex with potassium tetrahydroborate. The molecular structure and the conformation of the title compound were established by X-ray diffraction analysis and1H NMR spectroscopy.

Synthesis and IR spectra of 2-phenylbenzimidazole and its amino derivatives

Abstract2-Phenylbenzimidazole and its mono and diamino derivatives were synthesized in yields up to 85% by cyclodehydration of o-aminobenzanilides in hydrochloric or sulfuric acid. The IR spectra of the compounds obtained were studied, the principal bands of the stretching and deformation vibrations of the NH and NH2 groups were assigned, and the presence of associates with a hydrogen bond was established.

Role of Association of Yanovskii Anionic σ Adducts in Their Oxidation with Quinones

In oxidation of 1,3-dinitro- and 1,3,5-trinitrobenzene acetonate σ adducts (Yanovskii complexes) with sodium, potassium, and tetrabutylammonium cations in acetonitrile and tetrahydrofuran (290-313 K), ion pairs are less reactive than free ions, which is explained by charge redistribution in the ring of the σ adducts, decreasing the electron-donor power of the associated anion. Separation of the apparent rate constants into ionic and ion-pair contributions showed that the reactivity of the ion pairs depends on the radius of their cation. The revealed kinetic regularities are interpreted on the basis of AM1 semiempirical quantum-chemical calculations of the ions and ion pairs with lithium cation.

Kinetic Effects of Electrolytes in Oxidation of Sodium, Potassium, and Tetrabutylammonium 1-Acetonyl-2,4-dinitrocyclohexa-2,5-dienides with 1,4-Benzoquinone

The kinetics of oxidation of sodium, potassium, and tetrabutylammonium 1-acetonyl-2,4-dinitro- cyclohexa-2,5-dienides with 1,4-benzoquinone in acetonitrile and tetrahydrofuran was studied spectrophotometrically. The reaction is of the first order with respect to the substrate and quinone and of the total second order. In the course of the process, a charge-transfer complex with an absorption maximum at about 716 nm is formed, accelerating the reaction. The rates of its accumulation and consumption increase with increasing concentrations of reactants and decrease on addition of sodium or tetrabutylammonium perchlorate. The factors facilitating association of σ adducts in solution (increase of the concentration in THF, addition of NaClO4 or [N(C4H9)4]ClO4), decelerate oxidation owing to decrease of the negative charge in the cyclohexadienide ring of the contact ion pair of the σ adduct as compared to the free ion.

Reactions of Aromatic Nitro Compounds: LXXIV. Azo Coupling of Anionic Nitroarene σ-Complexes with Aromatic Diazo Compounds. Effect of Reaction Conditions on the Yield of Nitroazobenzenes

Effect of a number of factors on the yield of nitroazobenzenes in the reaction of 4-nitro- and 4-dimethylaminobenzenediazonium tetrafluoroborates with anionic σ adducts derived from 1,3-dinitrobenzene was studied. Conditions were found which allow nitroazobenzenes to be prepared in 80-90% yield.