V. A. Shagun

Superbase-Assisted Addition of Phosphine to 1-Methoxy-4-vinylbenzene: Toward a Rare Family of Organic Phosphines

Abstract Phosphine reacts with 1-methoxy-4-vinylbenzene in the superbase suspension KOH-dimethylsulfoxide (70–100 °C, atmospheric pressure) to form regiospecifically anti-Markovnikov adducts, bis[2-(4-methoxyphenyl)ethyl]phosphine (1) and tris[2-(4-methoxyphenyl)ethyl]phosphine (2), representatives of rare arylalkylphosphines. The conditions for the selective preparation of phosphines 1 or 2 in 67% and 80% yields, respectively, have been elaborated. The phosphines have been oxidized with aqueous solution of H2O2, elemental sulfur, or selenium to afford the corresponding phosphine chalcogenides in good yields (95–99%). GRAPHICAL ABSTRACT

Reactions of heterocumulenes with organometallic reagents: XI. Quantum-chemical study on the mechanism of noncatalytic cyclization of methyl 2-methoxy-N-methylbuta-2,3-dienimidothioate (1-aza-1,3,4-triene) into substituted pyrrole

Rotational isomerism of methyl 2-methoxy-N-methylbuta-2,3-dienimidothioate (1-aza-1,3,4-triene), which is readily available from 1-lithio-1-methoxyallene, methyl isothiocyanate, and methyl iodide, was studied by quantum-chemical methods. Four most stable rotamers with the energies of activation of their mutual transformations exceeding 35 kJ/mol were identified. The potential energy surfaces for the formation of pyrrole structure from 1-aza-1,3,4-triene via different ring closure channels were analyzed. According to the results of calculations, the most probable is direct [1,5]-cyclization of 1-aza-1,3,4-triene through a cyclic carbene species.

Reactions of heterocumulenes with organometallic reagents: XIX. Quantum-chemical study on S-alkylation and intramolecular cyclization of lithiated methoxyallene adducts with methyl, phenyl, and 3-(methylsulfanyl)phenyl isothiocyanates. Concurrent formation of pyrrole and/or thiophene rings

Concurrent reaction paths leading to the formation of thiophene and/or pyrrole rings from adducts of lithiated methoxyallene with methyl, phenyl, and 3-(methylsulfanyl)phenyl isothiocyanates were simulated by quantum-chemical methods. According to the calculations, pyrrole ring closure is kinetically more favorable for the adduct of 1-lithio-1-methoxyallene with methyl isothiocyanate, both reaction channels are equally probable for the adduct with phenyl isothiocyanate, and thiophene ring closure is the main reaction path for the adduct with 3-(methylsulfanyl)phenyl isothiocyanate.

Heterocumulenes reactions with organometallic reagents: XX. Quantum-chemical study of concurrent processes of structural reorganization of N-Methyl-2-methoxy- and 2-(methylsulfanyl)buta-2,3-dienimidothioates into pyrroles and/or 2,3-dihydropyridines

Utilizing the MP2/6-31G(d,p) method a quantum-chemical investigation was performed of thermally induced formation of pyrrole and/or 2,3-dihydropyridine structures from methyl N-methyl-2-methoxy- and 2-(methylsulfanyl)buta-2,3-dienimidothioates (1-aza-1,3,4-trienes). According to calculations the pyrrole and dihydropyridine cyclization of a methoxy-substituted 1-aza-1,3,4-triene is both kinetically and thermodynamically virtually equally probable with a little prevalence of the first pathway. The main direction of the structural reorganization of methylsulfanyl-substituted 1-aza-1,3,4-triene is the kinetically controlled formation of the dihydropyridine ring.

Heterocumulenes reactions with organometallic reagents: XXI. Quantum-chemical study of structural transformations of 2-methoxy- and 2-(methylsulfanyl)-N-methylbuta-2,3-dienimidothioates in the Presence of cubr: Pyrrole or methyl-3-(methylsulfanyl)but-2-enimidothioate?

Utilizing the MP2/6-31G(d,p) method a quantum-chemical investigation was performed of processes catalyzed by CuBr leading to the formation of pyrrole structures from methyl-2 methoxy- and methyl 2-(methylsulfanyl)-N-methylbuta-2,3-dienimidothioates (1-aza-1,3,4-trienes). According to calculations 1-aza-1,3,4-trienes may form highly stable adducts with CuBr owing to the coordination bonding of the copper atom with the π-system (C=C=C) and/or heteroatoms (N, S, O). The main channel of the structural reorganization of the CuBr adduct with methoxy-substituted 1-aza-1,3,4-triene is the thermodynamically controlled formation of the pyrrole ring. In the 3-(methylsulfanyl)-1-aza-1,3,4-triene CuBr initiates the cleavage of the C-S bond in the imidothioate fragment (MeS-C=N-Me) and the kinetically controlled formation of methyl N-methyl-2,3-bis(methylsulfanyl) but-2-enimidothioate.

New synthesis of poly(phenothiazine-3,7-diyl)

Development of the chemistry of phenothiazine is stimulated by therapeutic effect of some its derivatives in the treatment of nervous system disorders [1]. At present, researchers’ interest is focused on the synthesis and properties of macromolecular systems based on phenothiazine. It is known that polyphenothiazine derivatives exhibit unique electrical and photoelectric properties [2]. Poly(phenothiazine-3,7-diyl) compounds are commonly prepared by the Grignard and Heck reactions in the presence of nickel and palladium catalysts [3, 4]. Unsubstituted poly(phenothiazine-3,7-diyl) was synthesized by phase-transfer oxidative polymerization using ammonium peroxosulfate as oxidant [5]. We were the first to reveal that photolysis of fused (130°C) 2-iodo-1-(10H-phenothiazin-10-yl)ethanone (I) in the absence of a catalyst yields 66% of iodinedoped poly(phenothiazine-3,7-diyl) (II). The reaction involves cleavage of the N–C, C–C, and C–I bonds and is accompanied by liberation of carbon(II) oxide and ethylene. The IR spectrum of the gas mixture contained absorption bands at 1640 and 3100 cm typical of stretching vibrations of the C=C and C–H bonds in ethylene molecule and a band at 2100 cm belonging to carbon(II) oxide. Presumably, migration of the radical center in the initially formed nitrogencentered phenothiazine radical to the 3(7)-position is followed by combination with formation of dimeric structures, which promotes 1,5-prototropic shifts. Further growth of the polymer chain is favored by abstraction of hydrogen atoms from C (C) by iodine radical.

Heterocumulenes reactions with organometallic reagents: XV. Quantum-chemical investigatiom of skeleton rearrangements of 2-methyl-6-methoxy-3H-azepine originating from valence tautomerism

In the framework of quantum-chemical simulation (DFT) the structure was explored of six potentially probable tautomeric forms of 2-methyl-6-methoxy-3H-azepine and their relative thermodynamic stability was evaluated. In the tautomers obtained the preferred gradient channels are localized of [1,n]-H shifts capable of initiating their tautomerism. The most probable typical concerted reactions were analyzed of the formation of valence isomers, fused three-/six- and four-/five-membered carbo- and heterocycles, azabicyclo[4.1.0]hepta-2,4-dienes (azanorcaradienes) and azabicyclo[3.2.0]hepta-3,6-dienes respectively.

Quantum-chemical study on the mechanism of formation of geminal hydroxy thiols by reaction of 1,3-dihalopropan-2-ones with hydrogen sulfide

The reaction mechanism of 1,3-dihalopropan-2-ones with hydrogen sulfide in the presence of hydrogen chloride was studied in terms of the density functional theory. Unlike 1-halopropan-2-ones which give rise to 1-halo-2-sulfanylpropan-2-ols via preliminary enolization, 1,3-dihalopropan-2-ones preferentially undergo direct nucleophilic attack on the carbonyl group by hydrogen sulfide. The potential energy surface for rotational isomerism of 1,3-dihalopropane-2-thiones and 1,3-dihalo-2-sulfanylpropan-2-ols was analyzed, and their most stable rotamers were identified.

Impurity Luminescence in

This paper presents both investigations of high-energy luminescence with maximum at 7.5 eV in BaF2:Y3+ and BaF2:Yb3+ crystals and theoretical calculations of cross-luminescence spectrum in crystals of barium fluoride with interstitial ions of fluorine. The dependencies of the 7.5 eV emission intensity as function of different impurities mol. concentration are presented. The intensity of this emission increases with concentration of rare-earth impurity, but in the case of doping by Yb3+ and Y3+ this intensity is less than that in the case of La3+ doping. This feature (as well as the nonlinear dependence) can be due to the creation of clusters, i.e., aggregation of impurity ions and F--interstitials. The intensity of the 7.5 eV luminescence in a BaF2:Y3+ crystal after annealing at 1000 K increased by three times but it remained less than in the case of La3+ doping. Theoretical calculations of the core hole electronic and spatial structure and cross-luminescence spectrum were performed in the [Ba6F12] cluster. This cluster contains interstitial ion of fluorine, which is surrounded by six ions of Ba2+. In the case of using Hartree-Fock method the calculated luminescence spectrum of BaF2 crystal with interstitial fluorine shows cross-luminescence band with main maximum at 5.2 eV and high-energy band at 11.7 eV. In the case of using TD DFT method the energies of both cross-luminescence transitions and of transition between interstitial ion and core levels are in satisfactory agreement with experimental data, being all overestimated by approximately the average value of 0.8 eV.

{\rm BaF} _{2}

Mechanisms of syn-(Z)/anti-(E) isomerization of methyl 2-methoxy-N-methylbuta-2,3-dienimidothioate, including rotational, inversion, promoted by N-protonation, and nucleophile-catalyzed, were studied by quantum-chemical methods, and the corresponding thermodynamic and kinetic parameters were calculated. The most probable mechanisms of isomerization of buta-2,3-dienimidothioates were found to be inversion (Ea = 74.4 kJ/mol) and nucleophile-catalyzed (Ea = 61.6 kJ/mol).