Synthese und Zerfall von Azoinitiatoren,I

Azoesters of the typePhR ¹R²CN=NCR ²R¹Ph(R ¹=alkyl,R ²=rest of carboxylic acids) were synthesized; their 10h-half-life-temperatures and energies of activation of the decomposition were determined. The decomposition of the azo compounds follows a law of first order. The variation of the substituentsR ¹ andR ² gives information about the effect on the decomposition of the azo compounds. The azoesters of acetic acid are outstanding by low temperatures of decomposition and are situated in the range of azoisobutyronitrile.

     

Empirical relations between σI, σoR and taft σ* values of alkyl,acyl, benzoyl and substituted phenyl groups

The X(X) values¹ of the halogens (which resemble the Pauling electronegativities) and of some oxa substituents can be interpreted in terms of the inductive and resonance parameters σ_I and σ^o_R according to the regression equation

and η*_R=η(X)?η(R) it is found that for some substituted methyl, phenyl and benzoyl groups [σ*]^X_R=αη^X_R where α equals ?10.6 and ?10.9 for R = Me and R = Ph, CHO and PhCO respectively. Thus [σ*]^X_Rand η^x_r represent Taft σ* and [σ_I(X)?σ_oR(X)] values relative to that of the parent R group. The hydroxyl frequencies of phenol, and benzoic, acrylic, acetic and formic acids measured in dilute carbon tetrachloride solutions correlate with σ_I(X) and σ^o_R(X) according to the equations v(OH) = ?423.0 σ_I(X) + 3654.7 v(OH) = ?270.0 σ⁰_R(X) + 3586.7 where X = Ph, PhCO, CH₂=CHCO, MeCO and HCO. From these results, it is inferred that the σ* values of substituents having an α sp² hybridized carbon atom are proportional to σ⁰_R according to the equation σ*(X) = 3.97 σ⁰_R(X) + 1 New σ_I σ^o_R and σ* values of some acyi, benzoyl and substituted phenyl groups are presented.     

New one-pot, efficient, and regioselective method for the synthesis of 3-Trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs

An efficient and regioselective procedure for the synthesis of a series of alkyl(aryl/heteroaryl) substituted 3-trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs, from the cyclocondensation reactions of 4-alkoxy-1,1,1-trihaloalk-3-en-2-ones [CX₃C(O)CR²=CR¹(OMe/OEt), where R¹ = H, Me, Ph, 2-Furyl; R² = H; R¹-R² = -C₄H₈- and X = F, Cl] and 1-phenylsemicarbazide in an acidified alcoholic medium (R³OH/H₂SO₄), where R³ = Me, Et, Prⁱ was successfully applied and is described here in detail.     

Alkali-metal ion formation constants of fluorine-substituted β-diketones

Chelating tendencies of β-diketones of the type RCOCR′COR″ toward alkali-metal ions in 75% (v/v) dioxane-water have been evaluated. Fluorine substituted compounds (R = CF₃, C₂F₅, C₃F₅; R′ = H; R″ = t-butyl) had poor lithium-ion chelating tendencies, relative to the unsubstituted compound dipivaloylmethane. Specificity for lithium, relative to sodium-ion chelation, was evaluated as the difference, log K₁^Li-log K₂^Na, and the greatest specificity observed was for di-isobutyrylmethane and dipivaloylethane.     

Behaviour of α-functional organotransition metals. Synthesis,characterisation and some reactions of 1-acetoxyalkyl derivatives of iron(II) and molybdenum(II)

Acetoxyalkyl metal derivatives M(C₅H₅)(CO)_n[CHROC(O)Me] [M = Fe, n = 2; M = Mo, n = 3; R = H, Me] are readily prepared by reaction of bromoalkylacetates with the appropriate cyclopentadienylcarbonylmetallate anion. The complexes are characterised by their NMR (¹H and ¹³C) and IR parameters and by mass spectrometry. The acetoxyethyl species are thermally labile via β-hydrogen transfer. Treatment of acetoxymethyl complexes with protic acids leads to carbon-oxygen cleavage and release of acetic acid; HCl affords chloromethyl complexes, carboxylic acids yield new carboxylatomethyl derivatives, HBF₄ leads to decomposition. The metalloesters are resistant to hydrolysis, transesterification and carboxylate displacement by nucleophiles (HO^?, MeO^?, H₂N^? Et₂N^?). Migratory insertion of CO could not be induced.     

(Salen)Ti(IV) complex catalyzed asymmetric ring-opening of epoxides using dithiophosphorus acid as the nucleophile

A series of chiral bis-Schiff bases were synthesized starting from (1R,2R)-(+)-diaminocyclohexane, (+)-cis-1,2,2-trimethyl-1,3-diaminocyclopentane, (R)-2,2^′-diamino-1,1^′-binaphthalene, and (1S,2S)-diphenyl-1,2-ethanediamine. The enantioselective ring-opening of meso epoxides with dithiophosphorus acids catalyzed by a (salen)Ti(IV) complex formed in situ upon the treatment of Ti(OPr-i)₄ and the aforementioned chiral Schiff base was realized. The resulting products were obtained with low to good enantioselectivities (up to 73% ee). The (salen)Ti(IV) complex containing the backbone of 1,2-diaminocyclohexane exhibited the best enantioselectivity. The substituents in dithiophosphorus acids and those on the salen aromatic ring have a significant influence on the reaction. Moderate enantioselectivity were obtained for the (salen)Ti(IV) complex catalyzed ring-opening of racemic monosubstituted epoxides. High regioselectivity was observed for the alkyl substituted epoxides, whereas poor regioselectivity was obtained for the aryl substituted ones.     

Free-radical decarboxylation of carboxylic acids as a concerted abstraction and fragmentation reaction

Two variants of the reaction of radicals with the carboxyl group of carboxylic acids, namely, RO ₂ ^? + R _i COOH → ROOH + R _i CO ₂ ^? and RO _i ^? + R _j COOH → ROOH + R _i ^? + CO₂ are theoretically analyzed. It is demonstrated by the intersecting-parabolas method that if the reaction proceeded via the formation of an intermediate carboxyl radical, it would be much slower than is actually observed. Quantum-chemical calculations carried out by the density functional method using the nonempirical functional PBE have shown that the reactions of the methyl radical with the carboxyl group of acetic, butyric and vinylacetic acids include concerted H atom abstraction and C-C bond breaking. In the framework of the intersecting-parabolas model, an algorithm has been developed to calculate the activation energy and rate constant for X^? + R _i COOH → XH + CO₂ + R _i ^? reactions, where X = R^?, RO^?, HO^?, ArO^?, Ar₂N^? or H^?     

Biaryl-bridged Schiff base complexes of zirconium alkyls: synthesis structure and stability

Three substituted salicylaldimine derivatives H₂L^1-3 of 2,2′-diamino-6,6′-dimethylbiphenyl give, under appropriate conditions, isolable alkyls of zirconium [ZrL^1-3R₂] (R=CH₂Ph, CH₂Bu^t). Two molecular structures confirm their cis-α geometry (C₂-symmetric with cis alkyl ligands). They decompose via 1,2-migratory insertion of an alkyl group to imine, followed in some instances by a second similar reaction. The dimeric molecular structure of one such doubly-inserted product is presented. The kinetics of decomposition by this process are studied briefly, and it is noted that the rate increases with increased steric demand of the salicylaldimine unit.     

Vanadocene complexes with asymmetric alkyne ligands, [Cp2V(1-2η-R1C=CR2)]

A number of vanadocene complexes with asymmetrically substituted acetylenes, [Cp₂V-(1-2η-R¹C=CR²)] (R¹ = Ph and SiMe₂Ph; R² = 4-biphenyl, 1-naphthyl, and Ge(CF₃)₃), were obtained and examined by ESR spectroscopy. The isotropic and anisotropic ESR spectra of the complexes containing the phenyl, biphenyl, naphthyl, or dimethyl(phenyl)silyl substituent in the alkyne ligand are typical of d¹ complexes of vanadocene with alkynes. This is not the case of the complex containing the electron-withdrawing tris(trifluoromethyl)germyl group, whose isotropic and anisotropic ESR spectra show anomalous values of g factor and hyperfine coupling constant.     

σ-Complexes of transition metals in organic synthesis. 9. Reactions of allyl organomanganese compounds with γ-bromine derivatives of esters of α, Β-unsaturated carboxylic acids

The allyl Mn(II) organic compounds R¹CH=C(R²)CH₂MnCl (R¹=H, Me; R²=H, Me, Bu), obtained in situ from Grignard reagents and Li₂MnCl₄, react with esters of 4-bromocrotonic, (2-bromobutylidene)-, (4-bromo-2-butenylidene)-, (2-bromoisobutylidene) malonic, and (2-bromoheptylidene)cyanoacetic acids in THF at –78 to +20C to give derivatives of substituted cyclopropanecarboxylic or cyclopropane-1, 1-dicarboxylic acids. These derivatives contain a fragment of the allyl type. When ethers of 2-(bromomethyl)acrylic, 4-bromo-2-methyl-, and 4-bromo-3-methyl-2-butenoic acids are used, cross-combination products result.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 656–663, March, 1991.     

Thermal decomposition of C3-substituted peroxyacyl nitrates

The gas phase thermal decomposition rates of C₃-substituted peroxyacyl nitrates, RC(O)OONO₂ have been measured at ambient temperature (287–298 K) and 1 atm. of air. Two saturated compounds (PnBN, R = n-C₃H₇- and PiBN, R = i-C₃H₇-) and two unsaturated compounds (MPAN, R = CH₂=C(CH₃)- and CPAN, R = CH₃CH=CH-) have been studied. In the narrow temperature range studied, thermal decomposition rates for PiBN, PnBN and MPAN exhibited linear Arrhenius behavior with, in units of 10^-4 s^-1, and at 298 K, k = 2.2 for PiBN, 2.3 for MPAN, and 2.7 for PnBN. The thermal decomposition rate of CPAN was 1.6 x 10^-4 s^-1 at 291.6 K and 1.73 x 10^-4 s^-1 at 293.2 K. These thermal decomposition rates are of the same magnitude as that for PAN, R = CH₃. Implications for the atmospheric persistence of C₃- substituted peroxyacyl nitrates are briefly discussed.     

Membrane Transport of Inorganic Acids with α- Aminophosphoryl Compounds

Transport of some inorganic acids (HCl, HBr, HClO₄, HNO₃, H₂SO₄, and H₂PO₄) through hydrophobic impregnated membranes with aminophosphoryl compounds of the general formula R ₂ ¹ P(O)CH₂ ⋅ NR²R³ [R¹ = C₄H₉(C₂H₅)CHCH₂O, R² = C₄H₉, R³ = C₈H₁₇; R¹ = R³ = C₈H₁₇, R² = H; R¹ = C₁₀H₂, R² = R³ = C₂H₅; R¹ = C₁₀H₂₁, R² + R³ = (CH₂)₂O(CH₂)₂; R¹ = C₈H₁₇, R² = H, R³ = 2-quinolyl] and dodecylamine as carriers was studied. The membrane phases were solutions of the carriers in phenylcyclohexane and tridecane. General regularities that correlate the structure of an aminophosphoryl compounds to its transport properties toward inorganic acids were established. The largest flows are characteristic of perchloric, nitric, and hydrobromic acids.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 575–578.Original Russian Text Copyright © 2005 by Garifzyanov, Shirshova, Cherkasov.     

A question concerning the pk range within which an organic free radical exhibits normal radical behaviour. The case of galvinoxyl

Galvinoxyl (G^*) reacts with a series of substituted acetic acids and forms hydrogalvinoxyl (GH) as the sole product. The kinetic data conform with a Bronsted type analysis. Hydrogalvinoxyl may dissociate to the relevant cation G⁺, in a process which appears to be a thermal hydride ejection. In addition GH exhibits thermochromism with the following parameters: ΔH = -17.0 ±0.8 kcal mol^-1 and at 298 K, K_e = 1.16 (±0.28) × 10^-5 M^-1, ΔS = -79.0±8.0 cal Kcal mol^-1. The behaviour of G^* at various acidities is described.     

Synthesis and study of new rod-like mesogens containing 2-aminothiophene unit

We present a synthesis and mesomorphic properties of a new series of rod-like mesogens. All the compounds possess a substituted 2-aminothiophene unit as a main element in the structure attached to a stilbene moiety with a terminal alkyloxy chain (OR¹, OR² where R¹=C_nH_2n+1, R²=C_mH_2m+1; n, m ranging from 6 to 12). The synthesis of alkyloxybiphenyl substituted 2-aminothiophenes was carried out by the Gewald reaction and the appropriate reaction conditions were investigated. The liquid–crystalline properties were studied via polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. These materials exhibit nematic and/or smectic A phases. The influence of structural changes (variation in alkyloxy chain length and symmetry of the molecule) on mesogenic behaviour is discussed. Evaluation of UV–vis, fluorescent and electrochemical properties are also included.     

Dissociation constants of 2‐azidoethanamines in aqueous solution

Aqueous‐phase dissociation constants (K_a) for the conjugate acids of a series of 2‐azidoethanamine bases: R¹N(R²)CH₂CH₂N₃ ( 1 , R¹ = CH₃, R² = H; 2 , R¹ = CH₃, R² = CH₃; 3 , R¹ = CH₂CH₃, R² = CH₂CH₃; 4 , R¹/R² =  CH₂CH₂CH₂CH₂ ; 5 , R¹/R² =  CH₂CH₂OCH₂CH₂ ; 6 , R¹ = CH₂CH₃, R² = CH₂CH₂N₃) were measured and found to fall between those for analogous unfunctionalized and cyano‐functionalized ethanamines. To explore the possibility of a relationship existing between the constants and molecular geometry, a theoretically based study was conducted. In it, the Gibbs free energies of aqueous‐phase (equilibrium) conformers of the bases and their conjugate acids were determined via a density functional theory/polarizable continuum model method. The results indicate that an attractive interaction between the amine and azide groups that underlies the lowest‐energy gas‐phase conformer of 2 is negated in an aqueous environment by solvent–solute interactions. The magnitudes of the free energy changes of solvation and −TS (entropic) energies of the conformers of the 2‐azidoethanamines and their conjugate acids are observed to correlate with the magnitude of the separation between the conformers' amine and azide groups. However, those correlations are not by themselves sufficient to predict the relative free energies of a molecule's conformers in an aqueous environment. That insufficiency is due to the influence of the correlations being mitigated by three other parameters that arise within the thermodynamic framework employed to compute the observable. The nature of those parameters is discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

A New Synthesis of 3-Aryl-5-Arylmethylene-2(5H)-Furanones

A recent report about the synthesis of di and tri-substituted 2 (5H)-furanones starting from bromoaldehydes and potassium phenyl-acetate¹ prompts us to report our own studies on the preparation of 3-aryl-5-arylmethylene-2 (5H)-furanones (or butenolides) 1. We have earlier reported² a general method for the synthesis of 1 from phenylpropargyl aldehyde, 2 and arylacetic acids. Although several methods have been reported for the synthesis of the parent compound 1 (R = R₁ = Ph)^3–6, these methods have not been extended to other substituted furanones. Saikachi and Taniguchi⁷ prepared 1 (R = 5-nitro-2-thenyl, R₁ = 2-thenyl and 2-furyl) in 16–17% yields.     

Furan derivatives. Part 8 On substituent effects in the synthesis of 4,5-dihydro-3H-naphtho[1,8-bc]furans

4,5-Dihydro-3H-naphtho[1,8-bc]furans 4 and 6 which have various substituents (R¹ and R²) have been synthesized from 8-oxo-5,6,7,8-tetrahydro-1-naphthyloxyacetic acids 1 and 3 or their ethyl esters 2 . The reaction of acids 1 and 3 with sodium acetate in acetic anhydride gave a mixture of furans 4 and 6 and lactones 5 and 7 . The ratios of the products were varied according to the types of substituents (R¹ and R²) in acids 1 and 3 . As the substituent R¹ (R² = hydrogen) in acids 1 was changed from hydrogen to a methyl, ethyl or isopropyl group, production of furans 4 became more difficult. However, when a phenyl group was used as the substituent, furan 4 was obtained in good yield. Similarly, as the substituent R² (R¹ = hydrogen) in acids 1 was changed from hydrogen to a methyl, ethyl or isopropyl group, furan formation was more difficult. In contrast, acids 3 which had electron-withdrawing substituents such as chlorine, bromine or a nitro group at the 4-position afforded furans 6 in good yield. 4,5-Dihydro-3H-naphtho[1,8-bc]furans 4 and 4,5-dihydro-3H-naphtho[1,8-bc]furan-2-carbocylic acids 8 were synthesized from the reaction of esters 2 and potassium hydroxide in dioxane. When the substituents R¹ or R² in esters 2 were varied from hydrogen to a methyl, ethyl or isopropyl group the total yields of furans 4 and furancarboxylic acids 8 were reduced.     

Features of thermal decomposition of acrylates and methacrylates based on tert-butylperoxy-α-chloroalkoxyethanes

The kinetics of thermal decomposition of acrylic and methacrylic peroxides of general formula (CH₃)₃COOCH₂CH₂OCH(R¹)OC(O(R², where R¹ = H, Me, Et and R² = CH=CH₂, (CH₃)c=CH₂, Et, in the absence of solvent was studied.     

Synthesis, structure, and antimicrobial activity of copper(II) chelates containing imidazole and condensation products of α-amino acids with salicylaldehyde and its derivatives

Salicylaldehyde, 5-bromo- and 5-nitrosalicylaldehydes, 2-hydroxynaphthalene-1-carbaldehyde, and 2,3-, 2,4-, and 2,5-dihydroxybenzaldehydes reacted with glycine, alanine, and phenylalanine in ethanol in the presence of imidazole (Im) and copper(II) acetate hydrate to give copper(II) chelates with the composition Cu(Im)(L) · nH₂O (H₂L is the condensation product of the above aldehydes with α-amino acids; n = 0–2). The structure of the complex Cu(Im)(L¹) [H₂L¹ = 2-(2-hydroxybenzylideneamino)acetic acid] was determined by X-ray analysis. The crystalline structure of [2-(2-hydroxybenzylideneamino)acetato](imidazole)copper is formed by polymeric chains of the Cu(Im)(L¹) molecules linked through bridging oxygen atoms in the carboxy groups of the Schiff base ligand. The coordination unit has a distorted tetragonal pyramid configuration, where the pyramid base is composed of the phenol and carboxy oxygen atoms, CH=N nitrogen atom in the ligand H₂L¹ and imidazole nitrogen atom. The oxygen atom in the carboxy group in the neighboring molecule occupies the apical position of the coordination pyramid. The other coordination compounds also have polynuclear structure with the Schiff base H₂L acting as doubly deprotonated tridentate O,N,O-ligand and bridging carboxy groups. Thermal decomposition of the complexes includes their dehydration (70–95°C), while complete thermal decomposition occurs at 360–530°C. The synthesized complexes showed selective antimicrobial activity in the concentration range from 75 to 300 μg/ml against a number of standard strains of Staphylococcus aureus and Escherichia coli.