The Reaction of H2PtCl6 with aromatic compounds in CF3COOH/H2O affording the anionic σ-aryl complexes of platinum(IV) : IV. The synthesis of platinum(IV) complexes of fluorinated benzenes and the electronic influence of the platinum moiety

The reaction of H₂PtCl₆ with fluorobenzene, σ-chlorofluorobenzene and m-chlorofluorobenzene in CF₃COOH/H₂O affords anionic σ-aryl complexes of platinum(IV). The first two compounds give rise to mixtures of two isomers (meta and para), the latter forms only one isomer (1,3,5-substituted). The ¹⁹F NMR spectrum shows that [PtCl₄NH₃]^? group, when bound to fluorobenzene, is an electron donor in both the inductive and resonance senses.     

Prediction of ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous acetonitrile

The second-order rate constants k for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C₆H₄CO₂C₆H₅, in aqueous 50.9% acetonitrile have been measured spectrophotometrically at 25°C. The log k values for meta and para derivatives correlated well with the Hammett σ_m,p substituent constants. The log k values for ortho-substituted phenyl benzoates showed good correlations with the Charton equation, containing the inductive, σ_I, resonance, σ^○ _R, and steric, E _s ^B, and Charton υ substituent constants. For ortho derivatives the predicted (log k _X)_calc values were calculated with equation (log k _ortho)_calc = (log k ^H _AN)_exp + 0.059 + 2.19σ_I + 0.304σ^○ _R + 2.79E _s ^B ? 0.0164ΔEσ_I — 0.0854ΔEσ^○ _R, where DE is the solvent electrophilicity, ΔE = E _AN — E _H20 = ?5.84 for aqueous 50.9% acetonitrile. The predicted (log k _X)_calc values for phenyl ortho-, meta- and para-substituted benzoates in aqueous 50.9% acetonitrile at 25°C precisely coincided with the experimental log k values determined in the present work. The substituent effects from the benzoyl moiety and aryl moiety were compared by correlating the log k values for the alkaline hydrolysis of phenyl esters of substituted benzoic acids, X-C₆H₄CO₂C₆H₅, in various media with the corresponding log k values for substituted phenyl benzoates, C₆H₅CO₂C₆H₄-X.     

Experimental and theoretical study of the structure of N,N-dimethyl-4-nitroaniline derivatives as model compounds for non-linear optical organic materials

Molecular and crystal structure of a series of derivatives of N,N-dimethyl-4-nitroaniline has been studied by both X-ray diffraction method and high-level ab initio calculations. According to these data, the dimethylamino groups were found to have a trigonal-pyramidal configuration and are considerably turned with respect to the ring plane in all molecules having a substituent in the ortho-position; on the contrary, this group is planar in the meta-substituted molecules. Topological analysis of the electron density function for all molecules studied within the framework of Bader's ‘atoms in molecules’ (AIM) theory revealed that introduction of a substituent into the ortho- or meta-position of the ring results in increasing of the contribution of the resonance forms different from the quinoid one. Contribution of the latter form is predominant for the structure of N,N-dimethyl-4-nitroaniline (1). Topological analysis of the electron density distribution was used to explain a decreasing of the molecular hyperpolarisabilites of the ortho- and meta-substituted compounds as compared with those for 1.     

In vitro microbial studies of new pyrazolyl quinazolin-4(3H) ones

A series of new 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-[(5-substituted phenyl)-1,5-dihydro-1H-pyrazol-3-yl-amino]-6-iodoquinazolin-4(3H) ones (6a–m) have been synthesized by the reaction of 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-substituted phenyl acryl amido-6-iodoquinazolin-4(3H) ones with hydrazine hydrate in the presence of glacial acetic acid. The chalcone (5a–m) have been prepared by the condensation of 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-acetamido-6-iodoquinazolin-4(3H) one with different substituted aromatic aldehyde. The compound 1 on treatment with 5-iodoanthranilic acid in pyridine undergoes cyclisation gave 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-6-iodo-3,1-benzoxazin-4(3H) one (2). Treatment on benzoxazine with hydrazine hydrate gave 3-amino-2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-6,8-dibromo quinazolin-4(3H) one (3) followed by acetylation synthesized 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-acetamido-6,8-dibromoquinazolin-4(3H)-one (4). The structure of synthesized compounds has been elucidated by IR, ¹H NMR, ¹³C NMR and elemental analysis. The products were screened for antibacterial and antifungal activity. Among the series containing some of the compounds showed promising results against standard drugs.     

Stereoselective cycloadditions of (1Z,4R,5R)-1-arylmethylidene-4-benzoylamino-5-phenylpyrazolidin-3-on-1-azomethine imines to maleimides

A library of 15 1,6,7,9-tetrasubstituted 6,7,9,9a-tetrahydro-5H-pyrazolo[1,2-a]pyrrolo[3,4-c]pyrazole-1,3,5(2H,3aH)-triones was prepared by combinatorial stereoselective cycloadditions of (1Z,4R^∗,5R^∗)-1-arylmethylidene-4-benzoylamino-5-phenylpyrazolidin-3-on-1-azomethine imines to N-substituted maleimides. Stereochemistry was controlled by the stereodirecting phenyl group at position-3 and by the ortho-substituents at the aromatic ring at position-1′ in azomethine imines. Consequently, two sets of diastereomeric cycloadducts were obtained, one set from the ortho-unsubstituted dipoles and the other set from the ortho-disubstituted dipoles.     

Steric effect of ortho-substituents of 1-phenyl-3-methyl-4-aroyl-5-pyrazolones on the synergic extraction of lutetium with trioctylphosphine oxide

The substituent effect of ortho-substituted 4-aroyl derivatives of 1-phenyl-3-methyl-5-pyrazolones (HA) on the adduct formation reaction between their lutetium chelates and a neutral ligand, trioctylphosphine oxide (TOPO, L), in benzene was studied using a liquid-liquid extraction system. The lutetium 4-aroyl-5-pyrazolonates react with TOPO to form LuA₃L and LuA₃L₂ types of adducts. An obvious steric hindrance of the terminal group on the adduct formation reaction was observed. Linear relationships between the acid dissociation constant of the ortho-substituted 4-aroyl-5-pyrazolone derivatives and those of the corresponding benzoic acids, between the extraction constants of lutetium and the acid dissociation constants of pyrazolones and between the adduct formation constants of TOPO and the acid dissociation constants of pyrazolones could be obtained.     

Gas phase 1,3-deoxystannylation reactions of γ-substituted organotin alcohols utilizing chemical ionization mass spectrometry

The gas phase 1,3-deoxystannylation reactions of γ-substituted organotin alcohols have been studied by methane and isobutane chemical ionization mass spectrometry. It was found that γ-hydroxybutyltributyltin and γ-hydroxybutyldibutyltin chloride undergo the 1,3-deoxystannylation reaction to a greater extent than the corresponding 1,4-deoxystannylation using the δ-substituted analogues of the above named compounds. This result substantiates the unusual reactivity of γ-substituted organotin alcohols under gas phase protonolysis conditions.The electronic factors affecting the stabilization of the transition state were ascertained with γ-phenyl-γ-hydroxypropyltrimethyltin derivatives, in which the γ-phenyl group was substituted with groups such as H, p-OMe, p-Me, p-Cl, p-F, m-OMe, m-Me, m-Cl and m-CF₃. We observed a reasonably linear Hammett relationship when plotting the log [P ? 17]_x⁺/[P ? 17]_H⁺ vs. σ⁺ with rho (ρ) equal to ?1.0.Thus electron-donating groups stabilize the [P ? 17]⁺ ion and carbon—tin sigma (σ) electrons can either, by a neighbouring group effect, attack the nucleofugic center, or the carbonium ion can attack the carbon—tin σ electrons to form the trimethyltin cation and a cyclopropane derivative. Consequently, we propose that a two-step mechanism for the 1,3-deoxystannylation reaction is operating in the gas-phase with this type of compound. The factors contributing to this gas phase reaction will be discussed.     

Synthesis and solution properties of sulfate-type hybrid surfactants with a benzene ring

Nine novel sulfate-type hybrid surfactants, C_mF_2m+1C₆H₄CH(OSO₃Na)C_nH_2n+1 (FmPHnOS: m=4, 6, 8; n=3, 5, 7; C₆H₄: p-phenylene), with a benzene ring in their molecules were synthesized. Alkanoyl chlorides were allowed to react with iodobenzene in the presence of aluminum chloride to give the corresponding aromatic ketones. The reaction of the ketones with perfluoroalkyl iodides yielded 1-[4-(perfluoroalkyl)phenyl]-1-alkanones as intermediates. The intermediates were allowed to react with methanol in tetrahydrofuran in the presence of sodium borohydride to yield 1-[4-(perfluoroalkyl)phenyl]-1-alkanols. The desired hybrid surfactants were obtained by the reaction of 1-[4-(perfluoroalkyl)phenyl-1-alkanols with sulfur trioxide/pyridine complex in pyridine and by the subsequent neutralization of the products with sodium hydroxide solution. When compared with the conventional hybrid surfactants, C_mF_2m+1C₆H₄COCH(SO₃Na)C_nH_2n+1 (FmHnS: m=4, 6; n=2, 4, 6; C₆H₄: p-phenylene), the new hybrid surfactants thus synthesized were found to have a comparable ability to lower the surface tension of water and a high hydrophilicity. The cmc of FmPHnOS obeyed Kleven’s rule and their occupied areas per molecule increased with increasing m and n with the values between 0.66 and 1.05 nm². The aggregation number for FmPHnOS micelles ranged from 6 to 45 and the hydrodynamic radius of the micelles was in the range of 1.4-3.1 nm.     

Direct alkenylation of arylamines at the ortho-position with magnesium alkylidene carbenoids and some theoretical studies of the reactions

1-Chlorovinyl p-tolyl sulfoxides were synthesized from ketones and chloromethyl p-tolyl sulfoxide in high yields. Treatment of the sulfoxides with isopropylmagnesium chloride at −78 °C in toluene gave magnesium alkylidene carbenoids (α-chloro alkenylmagnesium chlorides), which were treated with N-lithio arylamines to afford ortho-alkenylated arylamines in moderate yields. The reaction, in some cases, proceeded in a highly stereospecific manner at the carbon bearing the chlorine and the sulfinyl group. The structures of the α-chloro alkenylmagnesium chlorides and the reactivity of the N-lithio meta-substituted anilines were studied at the B3LYP and MP2 levels of theory with the 6-31(+)G* basis set. This reaction offers a quite novel and direct alkenylation of arylamines at the ortho-position of the aromatic ring.     

Structure-activity relationship in the case of intramolecular ortho-cyclization of aromatic nitroso oxides: Inverted steric effect of substituent in the 2-R-C6H4NOO transformation

A systematic theoretical study at the M06L/6-311+G(d, p) level of theory was carried out to calculate the activation barriers ΔH^≠ for the intramolecular ortho-cyclization of aromatic nitroso oxides 2-R-C₆H₄NOO and to reveal the effect of substituent nature and position in the benzene ring on the nitroso oxides reactivity. A set of 24 substituents with widely differing spatial and electronic properties (inductive, resonant, steric effects of R) was studied. The para-substituent was shown to have little effect on the ΔH^≠ value. The full set of effects of the R substituent contributes to the reactivity of ArNOO for 3-substituted aromatic nitroso oxides. In the case of 5-substituted ArNOO the Hammett-type relationship was obtain to describe inductive and resonant effects of R on the ortho-cyclization reactivity. The ortho-cyclization for 2-substituted nitroso oxides is a nontrivial example of the existence of an “inverted” steric effect, when an increase in substituent size accelerates intramolecular transformation. The substituent in position 6 also exhibits an “inverted” steric effect, but it is noticeably weaker than that for 2-R-C₆H₄NOO.     

Pteridines. Part LXXXVII. Synthesis and Properties of 8-Substituted 2-Thiolumazines

Various 8-substituted 2,8-dihydro-2-thioxopteridin-4(3H)-ones ( 14 – 21 ) and 2-(methylthio)pteridin-4(8H)-ones ( 27 – 32 ) have been synthesized by condensation of the appropriate 5-amino-6-(substituted amino)-1,2-dihydro-2-thioxopyrimidin-4(3H)-ones ( 22 – 34 ) and 5-amino-6-(substituted amino)-2-(methylthio)pyrimidin-4(3H)-ones ( 25 , 26 ), respectively, with glyoxal, biacetyl, and benzil. The presence of a quinonoid cross-conjugated π-electron system makes this type of compounds susceptible to nucleophilic additions in position 7, which leads to intramolecular ( 43 , 45 ) and intermolecular ( 44 ) covalent adducts. The newly synthesized compounds have been characterized by elemental analyses, pK_a determinations, ¹H-NMR and UV spectra. UV-Spectral changes in dependence of the pH are associated with the most appropriate molecular species including the monocations, neutral forms, covalent adducts, mono- and dianions.     

An effective procedure for the preparation of 3-substituted-4- or 6-azaindoles from ortho-methyl nitro pyridines

3-Substituted-4- and 6-azaindoles were prepared from ortho-methyl-nitropyridines in a practically convenient, one-pot process based on the Leimgruber-Batcho reaction. The procedure comprises a sequence of (a) condensation of an ortho-methyl-nitropyridine with N,N-dimethylformamide dimethyl acetal; (b) alkylation or acylation of the enamine intermediate; (c) reduction of the nitro group to an aniline with in situ cyclization and elimination of dimethylamine to generate the 3-substituted azaindole heterocycle.     

3,3′-Functionalized octahydro-BINOL: a facile synthesis and its high enantioselectivity in the alkyne addition to aldehydes

A facile synthesis of an enantiomerically pure 3,3′-bismorpholinylmethyl H₈-BINOL ligand has been developed. This compound in combination with Et₂Zn and Ti(OⁱPr)₄ is found to catalyze the highly enantioselective reaction of phenylacetylene with aromatic aldehydes. The enantioselectivity of this catalytic process for the reactions of ortho-substituted benzaldehydes is significantly higher than that based on H₈-BINOL.     

Synthesis of chiral,non-racemic ferrocene derivatives by ortho-metallation and partial reductive removal of ortho-directing amino groups

Chiral, non-racemic 1,2-disubstituted ferrocenes have been prepared from monosubstituted ferrocene derivatives by amine-mediated ortho-directed reactions and subsequent partial reductive removal of the stereogenic ortho-directing group. It was found that the ortho-directing amino group of 2-substituted derivatives of N,N-dimethylaminoethyl-ferrocene and similar compounds can, after quaternisation with methyl iodide, be reductively removed with sodium borohydride to give 2-substituted methyl- or ethylferrocenes. In most cases the substituents I, Br, COOEt, P(O)Ph₂ and CN tolerate the reaction conditions used. In addition, a few examples are reported that show how the use of LiTMP allows 2-bromo- and especially 2-cyano-substituted derivatives to be further ortho-lithiated and reacted to give 1,2,3-trisubstituted ferrocenes.     

Diels–Alder reactions of directly C3-dieneylated chlorophyll derivatives

The [4π?+?2π] cycloaddition of methyl 3-(1,3-butadien-1/2-yl)pyropheophorbides-a with tetracyanoethylene, dimethyl acetylenedicarboxylate, and naphthoquinone gave the corresponding Diels–Alder reaction adducts. The trans-1-substituted 1,3-butadiene was more reactive than its regioisomeric 2-substituent. The oxidation of some cycloadducts gave C3-arylated chlorophyll derivatives, whose ortho-substitution blue-shifted the corresponding Qy absorption maxima in dichloromethane because of the steric repulsion between the aryl and chlorin π-planes.     

Aluminum enolates via retroaldol reaction: catalytic tandem aldol-transfer—Tischtschenko reaction of aldehydes with aldol adducts of ketones to ketones

Bidentate aluminum chelates derived from biphenol, binaphthol and catechol were found to be efficient catalysts for aldol-transfer reactions of ketone to ketone aldol adducts with aliphatic or aromatic aldehydes giving rise to the formation of aldol adducts of ketones to the aldehydes. In the presence of an excess of an aliphatic aldehyde, a catalytic tandem aldol-transfer—Tischtschenko reaction is observed. The tandem reaction produces monoesters of 1,3-diols with high anti selectivity and with modest to good chemical yield. 1,2-Unsaturated aldehydes are less reactive in the aldol-transfer reaction and require 2-4 times higher load of the catalyst to be used than aliphatic and aromatic aldehydes. Poor diastereoselectivity was observed in the formation of α-substituted aldols and 2-substituted monoesters of anti-1,3-diols indicating that the aldol-transfer reaction is not diastereoselective with the catalysts studied. The utility of the highly 1,3-anti selective formation of diolmonoesters was found to be limited by acyl migration.     

Hammet correlations for the solvolysis of silylpyrroles

The siliconnitrogen bond in (XC₆H₄)Me₂SiNC₄H₄ (X = p-MeO, p-Me, m-Me, H, p-Cl) is cleaved in absolute ethanol containing sulphuric acid or amine buffers. The logarithms of the rate constants correlate with σ^o-constants, the p-values being -0.97 for the acid-catalysed reaction, and +1.8 and +2.6 for the reactions catalysed by amine and ethoxide anion, respectively. Mechanisms involving pentacoordinate silicon are suggested.     

C-C and C-H bond activation in the fragmentation of the [M + Ni]+ adducts of aliphatic amino acids

The major metal-containing species formed upon fast atom bombardment of amino acid/Ni⁺² mixtures is the [M + Ni]⁺ adduct, involving reduction of the Ni⁺² to the +1 oxidation state. By contrast, electrospray ionization of amino acid/Ni⁺² mixtures produces predominantly [Ni(M ? H)M]⁺; this species, on collisional activation, produces predominantly [M + Ni]⁺ by elimination of [M - H], presumably a carboxylate radical. The unimolecular fragmentation reactions occurring on the metastable ion time scale for the [M + Ni]⁺ adducts of a variety of α-amino acids have been recorded. The adducts with phenylalanine, α-aminoisobutyric acid and α-aminobutyric acid fragment by elimination of H₂O, H₂O + CO and, to a minor extent, by elimination of CO₂. These reactions are similar to those observed for the [M + Cu]⁺ adducts of α-amino acids. A reaction distinctive for the [M + Ni]⁺ adducts involves formation of the immonium ion RCH=NH ₂ ⁺ . By contrast, the [M + Ni]⁺ adducts with leucine, isoleucine, and norleucine show extensive metastable ion fragmentation by elimination of H₂, CH₄, C₂H₄, C₃H₆, and C₄H₈, with the relative importance of the different fragmentation channels depending on the configuration of the C₄H₉ side chain. These results are interpreted in terms of C-C and C-H bond activation of the C₄H₉ side chain by the Ni⁺. The adducts with valine and norvaline fragment in a fashion similar to the adduct with phenylalanine, except that minor elimination of C₃H₆ is observed.     

Oxidative nucleophilic substitution of hydrogen in nitroarenes by silyl enol ethers

Enolates generated by treatment of silyl ketene acetals and enol ethers with fluoride ion sources add to nitroarenes to produce σ^H adducts that oxidize either with KMnO₄ to give substituted nitroarenes or with dimethyldioxirane to give substituted phenols. In the latter case the oxidation results in replacement of the nitro group with a hydroxy group. It was shown that high effectiveness of these reactions is not due to stabilization of the σ^H adducts via O-silylation but due to the nature of the accompanying cation.     

不饱和半夹芯式16e化合物Cp*Ir(S2C2B10H10)与邻、间位取代苯基叠氮的反应性

考虑取代基的位置和电子效应对反应体系的影响, 本文系统地研究了16e化合物Cp^*Ir(S₂C₂B₁₀H₁₀) (1)与邻、间位取代苯基叠氮的反应。研究结果表明:与邻、间位取代苯基叠氮反应均生成苯环邻位碳发生C-H 活化形成C-S 键的金属配合物。这些配合物通过核磁(¹H、¹¹B、¹³C)、红外、质谱、元素分析和单晶结构解析进行了全面地表征。在光照反应结果的基础上, 提出了形成这类产物的自由基机理。