Sigma complexes in the pyrimidine series. 12.* acylation and ethoxycarbonylation of acetonyl anionic sigma complexes of 5-nitropyrimidine

As a result of acylation and ethoxycarbonylation of acetonyl anionic sigma complexes of 5-nitropyrinddine containing a geminal unit in the 6 and 2 positions, we have obtained N₍₁₎-substituted 5-nitro-1,6-dihydropyrimidines and C₍₅₎-substituted pyrimidines respectively.For Communication 11, see [1]     

The Reactions of Hexafluorocyclotriphosphazene with Sodium Phenoxide

The reaction of N₃P₃F₆ ( 2 ) with NaOPh led to the phenoxyfluorocyclotriphosphazenes N₃P₃(OPh)_nF_6‐n (n = 1( 3 ), 2( 4 ), 3( 5 )). Structures were assigned using ³¹P decoupled ¹⁹F NMR spectroscopy. The reaction followed a non‐geminal pathway with a 50.7:49.3 cis:trans ratio for 4 and a 28.6:71.4 cis:trans ratio for 5 . Comparisons to the analogous reaction of N₃P₃Cl₆ ( 1 ) were facilitated by DFT calculations on N₃P₃(OPh)X₅ (X = F, Cl) which show that the NBO charges on the phenyl group are invariant with respect to the identity of the phosphazene. These observations have been correlated to mechanistic models for cyclophosphazene substitution reactions.     

Substitutionsprodukte eines spirocyclischen anorganischen λ5PN-Systems aus Cyclotriphosphazen und Cyclodi(phosphadiazan)

Substitution Products of 4,4,6,6-Tetrachloro-6′-phenoxy-6′ -thioxo-cyclotriphosphazene-2-spiro-3′-cyclodi(phosphadiazane) Reactions of the spiro compound 4,4,6,6-Tetrachloro-6′-phenoxy-6′-thioxo-cyclotriphosphazene-2-spiro-3′-cyclodi(phosphadiazene) Cl₄N₃P₃(NH? NH)₂P(S)OC₆ H₅ with an excess of ammonia, cyclopropylamine, aziridine, and sodium phenolate were investigated. Fully or partially substitution of the chlorine atoms occurs. The reaction with two equivalents of the aziridine yields a mixture of isomers which consists of two geminal and two vicinal disubstituted products. The constitutions of the substituted compounds were confirmed by IR, NMR, MS and elemental analyses.     

NMR-spektroskopische Untersuchungen an Mercaptophosphazenen. I. Verlauf der Reaktion von Natriumethylmercaptid mit Hexachlorocyclotriphosphazatrien bzw. Octachlorocyclotetraphosphazatetraen

N.M.R. Spectroscopic Investigations of Thiophosphazenes. I. Reactions of Sodium Ethylthiolate with Hexachlorocyclotriphosphazatriene and Octachlorocyclotetraphosphazatetraene By reactions of hexachlorocyclotriphosphazatriene with an excess of sodium ethylthiolate as a suspension in ether all of the possible geminal derivatives N₃P₃Cl_6?n(SEt)_n; n = 1–6, are formed in different quantities. Products from reactions of octachlorocyclotetraphosphazatetraene with sodium ethylthiolate, N₄P₄Cl_8?n(SEt)_n, likewise contain all of the geminally substituted derivatives up to n = 8 with the exception of the derivatives with n = 1 and n = 7. Compounds with n = 3, 4, or 5 exist in two geminal isomers respectively. Nongeminal ethylthiochlorophosphazenes were not found by any reaction. The formed compounds were isolated by chromatographic methods and studied by ³¹P n.m.r. spectroscopy.     

Conformational studies on pyranoid sugar derivatives by NMR spectroscopy. Correlations of observed proton—proton coupling constants with the generalized Karplus equation

Proton spin-spin coupling values measured for a wide range of tetrasubstituted tetrahydropyran ring-systems obtained from aldopentopyranose sugars have been correlated with values calculated from a generalized version of the Karplus equation which takes into account the electronegativities of the various atoms in the molecule and the configurations of these substituents. Minor discrepancies between observed and calculated values can be attributed to slight flattening of the tetrahydropyran ring as a result of steric interactions of the substituents. The magnitude of the geminal coupling J_5e,5a of these aldopentopyranose derivatives provides a rough measure of the conformational population; when H-4 is axial [Cl(D) or 1C(L ) conformation] J_5e,5a is ～10.9 Hz, and is ～13.4 Hz when H-4 is equatorial [1C(D ) or Cl(L ) conformation].     

Small carbon‐carbon couplings in monosubstituted benzenes – their signs and magnitudes determined by HCSE method

Signed values of all intra‐ring ^2,3,4J(C,C) couplings in nine monosubstituted benzenes (C₆H₅‐X where X = F, Cl, Br, CH₃, OCH₃, Si(CH₃)₃, C ≡ N, NO, NO₂) are experimentally determined as well as nine couplings to substituent carbons. It is confirmed that while all the vicinal intra‐ring ³J(C,C) are positive and all geminal ²J(C2,C4) are negative, both signs are found for geminal ²J(C1,C3) couplings. All the determined signs agree with those already predicted by theoretical calculations. Copyright © 2013 John Wiley & Sons, Ltd.     

Equilibrium and <Superscript>1</Superscript>H NMR Kinetic Study of the Reactions of Dichlorido [S-Methyl-L-Cysteine(N,S)]Platinum(II) Complex with Some Relevant Biomolecules

The formation equilibria of the [Pt(SMC)(H₂O)₂]⁺ complex with some biologically relevant ligands such as L-methionine (L-met) and glutathione (GSH) were studied. The stoichiometry and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. The reaction between [PtCl₂(SMC)] and guanosine-5′-monophosphate (5′-GMP) was studied by ¹H NMR spectroscopy. The NMR spectra indicated that first step is the hydrolysis of the [PtCl₂(SMC)] complex and second step is the substitution of an aqua ligand, either in the cis or trans position with guanosine-5′-monophosphate in molar ratio 1:1. The values of rate constant showed faster substitution of coordinated H₂O in the trans position to the S donor atom of S-methyl-L-cysteine, whereas the slower reaction was assigned to the displacement of the cis coordinated aqua molecule. This is due to the strong trans labilization effect of coordinated sulfur. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Molecular Properties of Additive Poly(bis(trimethylsilyl)tricyclonones) with Vicinal and Geminal Side Substituents

The molecular properties of the additive poly(bis(trimethylsilyl)tricyclononene) with the vicinal position of two side groups Si(CH₃)₃ in the monomer unit are studied for the first time, and its conformational and kinetic properties are compared with those of the isomer with the geminal position of the same groups. Using the methods of static/dynamic light scattering and viscometry for the samples of the vicinal isomer, the hydrodynamic parameters of molecules are determined and their molecular mass dependences in toluene are ascertained. In addition, the Kuhn segment length of this isomer is estimated. The kinetic rigidity of vicinal and geminal isomers is evaluated by ¹H NMR relaxation from the mobility of protons in Si(CH₃)₃ groups. The reasons behind different gas permeabilities of the films based on the polymers with the vicinal and geminal positions of Si(CH3)3 side groups in the monomer unit are discussed.     

AN INVESTIGATION OF THE REACTION PRODUCTS OF N3P3CL4(NH2)2 WITH NUCLEOPHILIC REAGENTS. EXAMPLES OF GEMINAL → NON-GEMINAL REARRANGEMENTS

Abstract

Based on its reactions with various nucleophiles both geminal and non-geminal structures have been earlier proposed for N₃P₃Cl₄(NH₂)₂, although its geminal structure is now considered established. The reactions of this compound with alcohols have been investigated and the products examined by NMR spectroscopy and X-ray crystallography. Evidence for both unrearranged as well as geminal → non-geminal rearranged alcoholysis products is presented.     

Condensed pyridine bases. Electrophilic substitution in 1,7-dimethyl-3(2H)-benzo[b]furo[2,3-c]pyridone

Nitration, bromination, thiocyanation, and acylation of 1, 7-dimethyl-3(2H)-benzo[b]furo[2, 3-c]pyridone were investigated. It was shown that either the 4-nitro- or the 4,6-dinitro derivative is formed as a function of the nitration conditions. Bromination with bromine and thiocyanation with dithiocyanogen yields a bromo derivative at position 4. The product of substitution at the C₍₆₎, atom is obtained in acylation with acetyl chloride, and the product of substitution at atoms C₍₄₎ and C₍₆₎ is obtained with benzoyl chloride. The results of the calculations were generalized in the MNDO approximation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 534–541, April, 1996     

Synthesis of anthra[9,1-cd]isothiazolium derivatives and their reactions with nucleophiles

The methylation of 9-methyl-4-methylamino-5H-anthra[1,9,8-bcde]-1,10⁴-dithia-9-azapentalen-5-one takes place at the S₍₁₎, atom and leads to a 2-methyl-7-methylamino-10-methylthio-6-oxo-6H-anthra[9,1-cd]isothiazolium salt, while protonation is directed to the N₍₉₎ atom to give a 5,10-bis(methylamino)-6-oxo-6H-anthra [1,9-cd]dithiolium salt. Depending on their nature, substitution of the hydrogen atom in the 5 or 3 position, reversible addition of a hydroxide ion in the 10b position, demethylation, or opening of the heteroring occurs in the reaction of the anthraisothiazolium cation with nucleophilic reagents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 256–263, February, 1992.     

Cyclizations of N-alkyl-substituted azinium cations with bifunctional nucleophiles. 28. Orientation of the nucleophile in the reaction of quinoxalinium salts with indan-1,3-dione

In reactions with quinoxalinium salts in alcoholic-base media indan-1,3-dione acts as a C nucleophile, adding at the 2 or 3 position of the heterocycle to give the corresponding ylidene derivatives; attack by the nucleophile at the C₍₃₎ atom (the position relative to the quaternary nitrogen atom) is preceded by addition of alcohol at the a position. Dissociative substitution at the C₍₂₎ atom in 2-alkoxy-3-(1,3-dioxoindan-2-ylidene)-1,2,3,4-tetrahydroquinoxalines by another nucleophile makes it possible to regard lyate complexes as probable intermediates in cyclizations of 1,4-diazinium salts with dinucleophiles.See [1] for Communication 27.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 667–674, May, 1990.     

Modeling of Substituent Effects: Self-Parametrization, a Case of Interdependence of the Coefficients, Illustrated on the Linear Plus Cross-Term Models

The effect of one or several substituents X _i on a molecular property f (reaction rate, spectroscopic property, etc.) is often described in terms of substituent parameters _i (X) depending on the nature X of the substituent, and the position i of substitution. We call self-parametrization the case when the substituents are parameterized by the value _i (X)=f _i (X) of f itself in the molecule monosubstituted by X in position i. On the example of the linear plus cross-term models, we show that self-parametrization implies that the coefficients of the model are interdependent. The theoretical relations between them are given, for equivalent or nonequivalent positions of substitution, and tested on measured acid–base equilibrium constants, and NMR coupling constants.     

Sigma-complexes in the pyrimidine series. 11. 5-arylazo-5-nitro-2,5- and -4,5-dihydro-pyrimidines from anionic sigma complexes of 5-nitropyrimidine

We have studied the reaction of acetonyl anionic sigma complexes of 5-nitropyrimidines with aryldiazonium salts. We have established that, independently of the position of the geminal unit in the sigma complex, electrophilic attack by the diazonium ion occurs at the C₍₅₎ atom with formation of 5-arylazo-5-nitro-2,5- and 4,5-dihydropyrimidines. The latter are unstable and upon isolation are converted to N-methoxycarbonyl-N-(1-acetonyl-2-nitro-2-arylhydrazono)ethyl-O-methylisourea. The structure of one of these compounds has been proven by x-ray diffraction. Under alkaline conditions, aromatization of 2,5-dihydropyrimidines to 5-arylazo-2-acetonylpyrimidines occurs.For Communication 10, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 215–223, February, 1993.     

Substitution effects on the molecular structures and the longitudinal molecular polarizabilities of all‐trans polyacetylene oligomers of increasing size

AM1 calculations have been performed on all‐trans polyacetylene (PA) oligomers with an increasing number of unit cells to study the effect of donor or acceptor groups capped at opposite ends of PA chains, substituents included in the monomers, substituents' number and position in the monomers, on the molecular structures, and the static longitudinal polarizabilities (α_L) and second‐order hyperpolarizabilities (γ_L). Substitution of CH₃, Cl, or F group at opposite ends of an oligomer results in an increase of α_L and γ_L, but the substitution effects on Δα_L(N) and Δγ_L(N) are very small. The asymptotic limit values are unaffected by the substitution. F substituent included in the monomer of an oligomer enhances the Δα_L(N) and Δγ_L(N) values, especially at large N, but including monomers with CH₃ or Cl substituents substantially reduces the Δα_L(N) and Δγ_L(N) values. We alter the number of F substituents included in the monomers of oligomers and find that including two F substituents in the monomer leads to the larger enhancement of Δγ_L(N). The effect of F substituents' position in the monomers of oligomers on Δα_L and Δγ_L is obvious. The results may be helpful for the design of new materials for applications in nonlinear optics, particularly in the area of poled polymer films. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Hydrosilanes are not always a reducing reagent: a ruthenium-catalyzed introduction of primary alkyl groups to electron-rich aromatic rings using esters as a source of the alkyl groups

A triruthenium cluster, (μ₃, η², η³, η⁵-acenaphthylene)Ru₃(CO)₇ effectively catalyzes primary-alkylation reaction of electron-rich aromatic rings using a combination of hydrosilane and ester as a source of the primary-alkyl group. The reaction involves electrophilic substitution of arenes by carbocationic species stabilized by a neighboring alkoxy or siloxy group generated during the reduction of esters giving alkylated arenes after reductive removal of the alkoxy or siloxy group at the benzylic position.     

Synthese,Strukturuntersuchung und Reaktionen Phosphansubstituierter Derivate von Fe3(CO)9(μ3-CF)2

Syntheses, Structure Determination and Reactions of Phosphine Substituted Derivatives of Fe₃(CO)₉(μ₃-CF)₂ Photolysis of Fe₃(CO)₉(μ₃-CF)₂ 1 in the presence of acetonitrile 2a or benzoenitrile 2b results in the substitution of a single carbonyl ligand by a nitrile ligand yielding Fe₃(CO)₈(CH₃CN)(μ₃-CF)₂ 3a and Fe₃(CO)₈(C₆H₅CN)(μ₃-CF)₂ 3b, respectively. The acetonitrile ligand in 3a can be easily replaced by trimethyl-phosphine 4a or triphenylphosphine 4b . The monosubstituted compounds Fe₃(CO)₈(PR₃)(μ₃-CF)₂5, R = CH₃ a, R = C₆H₅, b are obtained as major products besides a small amount of the disubsituted products Fe₃(CO)₇(PR₃)₂(μ₃-CF)₂ 6. The structure of 5a has been elucidated by a single crystal X-ray structure determination. Thermal ligand substitution in 1, however, results in the formation of a mixture of mono-, disubstituted, and trisubstituted products, in which 6b is the major product for diphenylphosphine. 5a reacts with ethyne 7 forming a phosphine substituted diferra-allyl-cluster Fe₃(CO)₇(PR₃)(μ₃-CF)(μ₃? CF? CH? CH) 8. The structure of one isomere of 8 has been determinated by X-ray crystallography.     

Isolation and single crystal study of [Nb2(μ-OMe)2(OiPr)8]. Can alcohol interchange provide the homoleptic niobium isopropoxide?

Niobium isopropoxide, Nb(OⁱPr)₅, is an attractive precursor of simple and complex niobium oxides in sol-gel technology. This compound cannot, unfortunately, be obtained by alcohol interchange starting from linear chain homologues such as Nb(OMe)₅ or Nb(OEt)₅. The equilibrium in the latter reaction favours formation of mixed-ligand complexes, [Nb₂(OR)₂(OⁱPr)₈], R = Me, Et. In particular, [Nb₂(OMe)₂(OPrⁱ)₈] (1) has been isolated in high yield from repeated treatment of Nb₂(OMe)₁₀ with excess of isopropanol. The X-ray single crystal study reveals a dinuclear structure containing a pair of edge-sharing octahedra with methoxide ligands in the bridging position. Infrared (IR) and mass spectroscopy (MS) studies confirmed the incomplete ligand substitution. The ¹H-NMR spectra suggest equilibrium between different molecular forms in solution. Solvothermal interaction of 1 with La chips in toluene/isopropanol media results in formation of a mixture of LaNb₂(OⁱPr)₁₃ and La₂Nb₄(μ₄−O)₄(OH)₂(μ−OⁱPr)₈(OⁱPr)₈ (2). Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorised users.     

Syntheses,Molecular Structures,and Complex Formation of Geminal Di(2-pyridylmethylamino)-substituted Cyclotriphosphazenes

N₃P₃Cl₆ reacts with 2-(aminomethyl)pyridine under formation of the stable geminal difunctionalized compound gem-N₃P₃Cl₄(NHCH₂(C₅H₄N)-2)₂ 1 . The chlorine atoms can be substituted by reacting 1 with sodium phenoxide to yield gem-N₃P₃(OC₆H₅)₄(NHCH₂(C₅H₄N)-2)₂ 2 . A vicinal di(pyridylmethylamino)-substituted compound, vic-N₃P₃(OC₆H₅)₄(NHCH₂(C₅H₄N)-2)₂ 3 can be obtained from the reaction of vic-N₃P₃(OC₆H₅)₄Cl₂ with 2-(aminomethyl)pyridine. Decomposition to [Cu(NH₂CH₂(C₅H₄N)-2)₂(NO₃)₂] 4 occurs when 1 is exposed to copper(II) nitrate · H₂O. By contrast, 2 forms the stable copper complex [Cu(NO₃)₂ · ( 2 )] 2 a in which the copper atom is bonded to three nitrogen atoms of the new chelating ligand and three oxygen atoms of the unsymmetrically coordinated nitrate groups. The structures of 1 , 2 , and 2 a were determined by X-ray crystallography.     

Bimolecular substitution and oxidation reactions of 17-electron pentacoordinate metal carbonyl radicals

Summary Quantitative and semiquantitative data for reactions of M₂(CO)_10-2nL_2n (M=Mn or Re; L=P-donor ligand; n=0, 1) are analyzed to provide information regarding the mechanisms and relative rates of substitution and oxidation reactions of the [M(CO)_5-nL_n] radicals. Both associative and dissociative paths for substitution can be inferred, but the dissociative paths are generally much slower and occur only at high temperatures and/or when associative substitution is sterically disfavoured. Quantitative comparison of the reactivities of various radicals is made.