Arylation with aryllead triacetates produced in situ by mercury-lead exchange

Reaction of a diarylmercury with lead tetraacetate to give an aryllead triacetate has been found to be a rapid reaction. The in situ generation of aryllead triacetates is thus an attractive alternative to the use of the purified reagents in the various electrophilic arylation reactions of these compounds.     

Cascade synthesis of polyoxygenated 6H,11H-[2]benzopyrano-[4,3-c][1]benzopyran-11-ones

2-(methoxymethoxymethyl)aryllead triacetates, obtained in situ from the corresponding arylboronic acids, reacted with 4-hydroxycoumarins, leading to 3-(2-methoxymethoxymethyl)aryl-4-hydroxycoumarin derivatives in good to high yields. These compounds underwent a cascade sequence of reactions, deprotection-halogenation-annulation, to afford polyoxygenated tetracyclic 6H,11H-[2]benzopyrano-[4,3-c] [1]benzopyran-11-ones in good yields. Some compounds showed a moderate cytotoxicity against human epithelial mammary HBL100 cells.     

The α-arylation of derivatives of malonic acid with aryllead triacetates. New syntheses of ibuprofen and phenobarbital.

Derivatives of Meldrum's acid and the sodium salts of substituted malonic esters undergo rapid arylation in high yield when treated with aryllead triacetates. These reactions have been applied to the synthesis of ibuprofen, an analgesic, and in a closely related reaction 5-ethylbarbituric acid has been reacted with phenyllead triacetate to give phenobarbital.     

Reductive coupling of polyfunctionalized organobismuth and organolead arylating reagents in the synthesis of benzopyran derivatives

Benzopyran derivatives were synthesized in good yields by the reactions of tris[2-(chloromethyl)phenyl]bismuth diacetate and 2-(halomethyl)aryllead triacetates with phenols and naturally occurring 4-hydroxycoumarins in the presence of bases according to a three-step one-pot procedure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2520–2529, November, 2005.     

Use of the electrophilic c-arylation by aryllead triacetates in the construction of synthons for aizoaceae and amaryllidaceae alkaloid synthesis

The vinylogous β-keto esters, ethyl 2-methyl-4-oxocyclohex-2-ene-carboxylate (Hagemann's Ester) (4), ethyl 4-oxocyclohex-1-ene-carboxylate (7a) and its double bond isomer (7b), undergo regiospecific arylation with aryllead triacetates at C1; reaction of the mixture of isomers (7a) and (7b) with aryllead compounds (5a), (5c) and (5d) provides intermediates for the synthesis of (±)-o-methyl-joubertiamine (1), (±)-mesembrine (2) and (±)?lycoramine (3) respectively.     

Source of Selectivity in Oxidative Cross‐Coupling of Aryls by Solvent Effect of 1,1,1,3,3,3‐Hexafluoropropan‐2‐ol

Solvents such as 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) with a high capacity for donating hydrogen bonds generate solvates that enter into selective cross‐coupling reactions of aryls upon oxidation. When electric current is employed for oxidation, reagent effects can be excluded and a decoupling of nucleophilicity from oxidation potential can be achieved. The addition of water or methanol to the electrolyte allows a shift of oxidation potentials in a specific range, creating suitable systems for selective anodic cross‐coupling reactions. The shift in the redox potentials depends on the substitution pattern of the substrate employed. The concept has been expanded from arene–phenol to phenol–phenol as well as phenol–aniline cross‐coupling. This driving force for selectivity in oxidative coupling might also explain previous findings using HFIP and hypervalent iodine reagents.     

Modeling synergistic adsorption of phenol/aniline mixtures in the aqueous phase onto porous polymer adsorbents

The adsorption equilibria of phenol and aniline on nonpolar polymer adsorbents (NDA-100, XAD-4, NDA-16 and NDA-1800) were investigated in single- and binary-solute adsorption systems at 313 K. The results showed that all the adsorption isotherms of phenol and aniline on these adsorbents can be well fitted by Freundlich and Langmuir equations, and the experimental uptake of phenol and aniline in all binary-component systems is obviously higher than predicted by the extended Langmuir model, arising presumably from the synergistic effect caused by the laterally acid-base interaction between the adsorbed phenol and aniline molecules. A new model (MELM) was developed to quantitatively describe the synergistic adsorption behavior of phenol/aniline equimolar mixtures in the binary-solute systems and showed a marked improvement in correlating the binary-solute adsorption of phenol and aniline by comparison with the widely used extended Langmuir model. The newly developed model confirms that the synergistic coefficient of one adsorbate is linearly correlated with the adsorbed amount of the other, and the larger average pore size of adsorbent results in the greater synergistic effect of phenol/aniline equimolar mixtures adsorption.     

Determination of aromatic amines in FD&C yellow no. 5 by diazotization and coupling followed by reversed-phase HPLC

Benzidine, aniline, 4-aminobiphenyl (4-ABP) and 4-aminoazobenzene are determined at trace levels in the colour additive FD&C Yellow No. 5 by diazotization and coupling with disodium 3-hydroxy-2,7-naphthalenedisulphonate (R-salt). The products are separated and determined by reversed-phase HPLC. All four amines were found in a survey of commercial colours. 4-ABP is determined with 4,5-dihydro-5-oxo-1-(4-sulphophenyl)-1H-pyrazole-3-carboxylic acid as the coupling agent. Calibration is done by spiking a reference commercial colour at several levels.     

General but discriminating fluorescent chemosensor for aliphatic amines

Aliphatic amines are sensitively and discriminatively detected through binding with demethylated naphthol AS-BI (7-bromo-3-hydroxy-2-naphth-o-hydroxyanilide, 2) and fluorescence of the resulting complex. Recognition of the amine by the chemosensor 2 occurs via proton transfer of the naphtholic proton to the amine and is facilitated by the presence of the phenol group. Amine basicity is the primary controller of detection. Poorly basic aromatic and conjugated amines such as pyridine and aniline are not detected. Hydrogen bonding within the complex allows further differentiation of aliphatic amines. Doubly primary, conformationally flexible diamines are the most sensitive to detection, followed by secondary amines.     

A comparative study of amide-bond forming reagents in aqueous media – Substrate scope and reagent compatibility

A survey of amidation reagents demonstrating DIC-HOPO, DMT-MM, COMU-collidine, TPTU-NMI, EEDQ, CDI and EDC-Oxyma to be effective for the coupling of carboxylic acids with amines in the presence of water and the absence of problematic dipolar aprotic solvents is reported. DMT-MM was shown to provide the best yields for the coupling of a secondary amine, TPTU-NMI and COMU-collidine for aniline, whilst the combination of DIC with HOPO afforded the broadest substrate scope and the highest yields for a sterically demanding carboxylic acid.     

聚苯乙烯基偶氮聚合物的合成研究

改进了聚苯乙烯的硝化、还原、重氮化和偶合反应路线 (NRDC) ,使每步反应都得到很高的产率 ,并利用大分子重氮盐 (MDS)分别与苯胺、N 烃基苯胺和酚等三类化合物偶合 ,得到相应的聚苯乙烯基偶氮聚合物 .核磁共振分析结果证明了产物的高偶联率 .通过对大分子重氮盐热稳定性的研究 ,发现偶合反应之后需要一步加热反应以消除残余重氮基团 .还研究了这些聚合物的紫外 可见吸收光谱性质 ,氨 (胺 )基偶氮产物的水溶液表现出了明显的pH敏感性     

苯酚和苯胺在超高交联吸附树脂上的共吸附行为

研究了水溶液中苯酚和苯胺在超高交联吸附树脂NDA103、NDA101、NDA100上的竞争吸附和协同吸附行为.实验结果表明,单组分苯酚或苯胺水溶液和双组分共存水溶液中吸附质分子在超高交联吸附树脂上的吸附等温线均符合Langmuir模型.当双组分摩尔比为1∶1时,在较低平衡浓度范围内苯酚和苯胺在树脂上呈现竞争吸附行为,其主导机制是两种吸附质分子对树脂内外表面上π-π作用吸附位点的直接竞争;而在较高平衡浓度范围内呈现协同吸附行为,其主导机制是两种吸附质分子之间的氢键作用.吸附温度由293K升至313K时,苯酚和苯胺在NDA103上的协同吸附作用加强,而在NDA101和NDA100上的协同吸附作用变化不明显.     

Guest-induced supramolecular isomerism in inclusion complexes of T-shaped host 4,4-bis(4'-hydroxyphenyl)cyclohexanone

The T-shaped host molecule 4,4-bis(4'-hydroxyphenyl)cyclohexanone (1) has an equatorial phenol group and a cyclohexanone group along the arms and an axial phenol ring as the stem. The equatorial phenyl ring adopts a "shut" or "open" conformation, like a windowpane, depending on the size of the guest (phenol or o/m-cresol), for the rectangular voids of the hydrogen-bonded ladder host framework. The adaptable cavity of host 1 expands to 11x15-18 A through the inclusion of water with the larger cresol and halophenol guests (o-cresol, m-cresol, o-chlorophenol, and m-bromophenol) compared with a size of 10x13 A for phenol and aniline inclusion. The ladder host framework of 1 is chiral (P2(1)) with phenol, whereas the inclusion of isosteric o- and m-fluorophenol results in a novel polar brick-wall assembly (7x11 A voids) as a result of auxiliary C-H...F interactions. The conformational flexibility of strong O-H...O hydrogen-bonding groups (host 1, phenol guest), the role of guest size (phenol versus cresol), and weak but specific intermolecular interactions (herringbone T-motif, C-H...F interactions) drive the crystallization of T-host 1 towards 1D ladder and 2D brick-wall structures, that is, supramolecular isomerism. Host 1 exhibits selectivity for the inclusion of aniline in preference to phenol as confirmed by X-ray diffraction, 1H NMR spectroscopy, and thermogravimetry-infrared (TG-IR) analysis. The T(onset) value (140 degrees C) of aniline in the TGA is higher than those of phenol and the higher-boiling cresol guests (T(onset)=90-110 degrees C) because the former structure has more O-H...N/N-H...O hydrogen bonds than the clathrate of 1 with phenol which has O-H...O hydrogen bonds. Guest-binding selectivity for same-sized phenol/aniline molecules as a result of differences in hydrogen-bonding motifs is a notable property of host 1. Host-guest clathrates of 1 provide an example of spontaneous chirality evolution during crystallization and a two-in-one host-guest crystal (phenol and aniline), and show how weak C-H...F interactions (o- and m-fluorophenol) can change the molecular arrangement in strongly hydrogen-bonded crystal structures.     

用于碱性物质分离的高效液相色谱键合相的制备及评价

采用２,４－戊二酮与正辛烷基二甲基氯硅烷反应制成活泼的中间体——硅醚型硅烷中间体,然后再与硅胶进行键合。经元素分析、漫反射红外光谱和高效液相色谱法对键合相进行了鉴定和评价。结果表明,键合反应按预定路线进行,硅胶表面被键合相基团覆盖的较均匀、完全。键合相具有较好的色谱性能,可有效地用于碱性化合物的分离分析中。     

Absorption,fluorescence, and photoinitiating properties of the aromatic ethers and aromatic amines complexes of cyclopentadienyliron

The aromatic ethers complexes of cyclopentadienyliron (O-CpFe) and aromatic amines complexes of cyclopentadienyliron (N-CpFe) were prepared by coupling several aniline derivatives and phenol derivatives with (η6-chlorobenzene) (η5-cyclopentadienyl) iron hexafluorophosphate through nucleophilic aromatic substitution reaction. The UV/vis absorption, fluorescence, and excitation spectra of the compounds were measured. The abilities of the photoinitiator in photopolymerizing the diglycidyl ether of the bisphenol-A epoxy oligomer under a halogen lamp were evaluated by near-infrared spectroscopy. The results show that the absorption of N-CpFe is higher than that of O-CpFe in the visible region. However, the photoinitiation ability of N-CpFe is lower than that of O-CpFe.     

Supramolecular binding of amines with functional magnesium tetraphenylporphyrin for CO2 capture

In this work,magnesium tetraphenylporphyrin (MgTPP) was used as a new supramolecular amine-fixing agent. Once introduced, CO2 easily competes with MgTPP for amines, leading to the release of MgTPP. The processes can be explained by the fact that the association constant (Kassoc) values of MgTPP with amines were in the range of 0.6 (ethanolamine) to 3.9 (ethylenediamine), which are lower than the Kassoc values of CO2 with these amines. MgTPP interacted with aniline, ethanolamine, pyrrolidine, or ethylenediamine to form 1:1 adducts. Ethylenediamine presents a stronger Kassoc value for MgTPP, so it was considered an optimal agent for CO2 capture.     

Synthesis of sugar-derived isoselenocyanates, selenoureas, and selenazoles

Aryl, alkyl, and sugar-derived isoselenocyanates were prepared by a one-pot procedure starting from the corresponding formamides, using triphosgene as a dehydrating agent, triethylamine, and black selenium powder. The preparation of sugar selenoureas by coupling of O-protected sugar-derived isoselenocyanates with different amines, and by coupling of unprotected glycopyranosyl amines with phenyl isoselenocyanate was also accomplished. The synthesis of a glucopyranos-2-yl-selenazole starting from O-protected 2-amino-2-deoxy-d-glucose by coupling with benzoyl isoselenocyanate, Se-alkylation with phenacyl bromide, and acid-catalyzed dehydration is also reported. Unprotected N-(β-d-glucopyranosyl)-N′-phenylselenourea was transformed into a 1,2-trans-fused bicyclic isourea upon treatment with aqueous hydrogen peroxide; the same isourea was prepared by a one-pot three-step procedure from β-d-glycopyranosylamine by thiophosgenation, coupling with aniline, and HgO-mediated desulfurization.     

(t-Bu)2PN=P(i-BuNCH2CH2)3N: new efficient ligand for palladium-catalyzed C-N couplings of aryl and heteroaryl bromides and chlorides and for vinyl bromides at room temperature

By employing Pd(OAc)2, Cs2CO3, or NaOH, and the new ligand (t-Bu)2PN=P(i-BuNCH2CH2)3N (3a), an electronically diverse array of aryl bromides and chlorides possessing base-sensitive substituents (nitro, ester, and keto) provide coupling products with bulky aryl amines in good to excellent yields. Aryl halides possessing other functional groups including cyano, amino, trifluoromethyl, and phenol, coupled with equal ease, producing highly functionalized amines in good to excellent yields. Moreover, an aryl chloro group can be preserved in the presence of a bromo substituent under our reaction conditions. BOC-protected amines also participated efficiently. Heterocyclic bromides and chlorides underwent clean couplings with amines in excellent yields. An important strength of our protocol is the use of lower palladium loadings than those reported earlier, without compromising yields. The air-stable palladium complex (eta3-cinnamyl)PdCl.(3a) (5) was also employed successfully in C-N coupling reactions while the crotyl analogue was less efficacious. The 3a/Pd(OAc)2 catalyst system promotes, for the first time, efficient coupling of vinyl bromides with a variety of amines to produce imines and enamines at room temperature.     

Study on products and reaction paths for synthesis of 3,4-dihydro-2H-3-phenyl-1,3-benzoxazine from phenol,aniline and formaldehyde

To study the synthesis of 3,4-dihydro-2H-3-phenyl-1,3-benzoxazine (benzoxazine), the reaction paths of phenol, aniline and formaldehyde were investigated by analyzing the synthesis crude products. With the aid of high-performance liquid chromatography (HPLC), chromatographic column and preparative HPLC, seven compounds originated from the crude products were obtained and their chemical structures were elucidated. Possible reaction paths are proposed based on these compounds. Results show that Nhydroxymethyl aniline (HMA) derived from the reaction of formaldehyde and aniline is probably the key intermediate during the reaction. HMA can react with itself or other reactants to form other intermediates, such as 1,3,5-triphenyl-1,3,5-triazinane and 2-((phenylamino)methyl)phenol, and further form benzoxazine and byproducts.     

Microwave-assisted oxidative coupling of amines to imines on solid acid catalysts

A K-10 montmorillonite catalyzed microwave-assisted oxidative coupling of amines is described. Substituted benzylamines readily undergo self-coupling reactions to produce benzylidene-benzylamines, while aliphatic amines and anilines cannot form self-coupled products. A mixture of a benzylamine and an aniline or aliphatic amine, respectively, effectively, and selectively produces mixed imines, such as benzylidene-anilines and benzylidene-alkylamines.