Facile preparation of aromatic esters from aromatic bromides with ethyl formate or DMF and molecular iodine via aryllithium

Various aromatic bromides were treated with n-BuLi and subsequently with ethyl formate, followed by the reaction with ethanol and molecular iodine in the presence of K₂CO₃ to provide the corresponding aromatic ethyl esters in good yields. Moreover, aromatic bromides could be transformed into the corresponding aromatic methyl esters in good yields by the treatment with n-BuLi and subsequently with DMF, followed by the reaction with methanol, molecular iodine, and K₂CO₃. Some aromatics could be also converted into the corresponding aromatic esters in good yields by the treatment with n-BuLi, and subsequently with ethyl formate or DMF, followed by the reaction with molecular iodine and K₂CO₃. The present reactions offer a novel route for the transition-metal-free, carbon-monoxide-free, and therefore environmentally benign one-pot conversion of aromatic bromides and aromatics into aromatic esters.     

Transformation of aromatic bromides into aromatic nitriles via formations of grignard reagents and their DMF adducts

Various aromatic bromides were efficiently transformed into the corresponding aromatic nitriles in good yields via the formations of Grignard reagents and subsequently N,N-dimethyl formamide (DMF) adducts, followed by treatment with molecular iodine (I₂) in aq NH₃ at room temperature. The present reaction is an easy and practical method for the preparation of aromatic nitriles from aromatic bromides with less toxic reagents, such as Mg, DMF, I₂, and aq NH₃.     

Facile preparation of aromatic ketones from aromatic bromides and arenes with aldehydes

Aromatic ketones were efficiently prepared in good yields by the reactions of aryl bromides with n-BuLi, followed by the reactions with aromatic aldehydes or aliphatic aldehydes and the subsequent treatment with molecular iodine and K₂CO₃, in a one-pot method. The same treatment of arenes, instead of aromatic bromides, also provided the corresponding aromatic ketones in good yields. Using these methods, various diaryl ketones and alkyl aryl ketones bearing electron-rich aromatics and electron-deficient aromatics could be prepared efficiently by a simple, transition-metal-free, and therefore environmentally benign experimental procedure.     

One-pot conversion of aromatic bromides and aromatics into aromatic nitriles via aryllithiums and their DMF adduct

Various aromatic bromides and iodides were smoothly converted into the corresponding aromatic nitriles in good to moderate yields by the treatment with n-butyllithium and subsequently DMF, followed by treatment with molecular iodine in aq NH₃. The same treatment of typical aromatics and heteroaromatics with n-butyllithium and subsequently DMF, followed by treatment with molecular iodine in aq NH₃ also provided the corresponding aromatic nitriles in good yields. Moreover, the same treatment of aromatic bromides and aromatics with half amount of DIH (1,3-diiodo-5,5-dimethylhydantoin) instead of molecular iodine worked effectively to give the corresponding aromatic nitriles, respectively, in good yields. These reactions are novel and environmentally benign one-pot methods for the preparation of aromatic nitriles from aromatic bromides and aromatics, respectively, through the formation of aryllithiums and their DMF adducts.     

N-methyl-substituted aromatic polyamides

A series of N-methyl-substituted aromatic polyamides derived from the secondary aromatic diamines 4,4′-bis(methylamino)diphenylmethane, 3,3′-bis(methylamino)diphenylmethane, 4,4′-bis(methylamino)benzophenone or 3,3′-bis(methylamino)benzophenone and isophthaloyl dichloride, and terephthaloyl dichloride or 3,3′-diphenylmethane dicarboxylic acid dichloride was prepared by high-temperature solution polymerization in s-tetrachloroethane. Compared with analogous unsubstituted and partly N-methylated aromatic polyamides, the full N-methylated polyamides exhibited significantly lower glass transition temperatures (T_g), reduced crystallinity, improved thermal stability, and good solubility in chlorinated solvents.     

The interaction of alkali metal cations with aromatic molecules in complexes of the type M[AlMe3X]·aromatic,M[Al2Me6X]·aromatic,and related

The crystal structures of 13 compounds of the form M[Al₂Me₆X]·aromatic and related have been examined in order to learn about the M⁺...aromatic approach. Four types of interactions have been discerned: (1) metal...aromatic, (2) metal...aromatic...metal, (3) aromatic...metal...aromatic, and (4) no metal...aromatic contact. It was found that the closest K⁺...C(aromatic) and Cs⁺...C(aromatic) separations are essentially equal after a correction for the difference in metal radii. The strength of the K⁺...aromatic attraction was found to be sufficient to move the K⁺ ion 0.3 Å out of the plane of the crown ether in two complexes of dibenzo-18-crown-6.     

Synthesis and characterization of wholly aromatic polyesters derived from 1-phenyl-2,6-naphthalene-dicarboxylic acid and aromatic diols

A series of new wholly aromatic polyesters was synthesized by melt polycondensation of 1-phenyl-2,6-naphthalenedicarboxylic acid (PNDA) and diacetates of various aromatic diols. The aromatic diols studied are hydroquinone (HQ), methylhydroquinone (MHQ), phenylhydroquinone (PHQ), (α-phenylisopropyl)hydroquinone (PIHQ), 2,6-naphthalenediol (2,6-ND), 1,4-naphthalenediol (1,4-ND), and 4,4′-biphenol (BP). These polyesters were characterized for their crystallinity, glass transition temperature (T_g), melting temperature (T_m), liquid crystallinity, and thermal stability. In general, crystallinity of the polyesters are very low and the T_g values of the polyesters range from 150 to 172°C depending on the structure of aromatic diols. All of the polymers formed nematic phases above their T_m or T_g. The polyesters derived from PHQ and PIHQ are soluble in chlorinated hydrocarbon solvents. The initial decomposition temperatures of the polyesters are above 400°C under N₂ atmosphere. © 1996 John Wiley & Sons, Inc.     

Iron-mediated aromatic allylation

Electron rich aromatic and heteroaromatic compounds react with (n³-allyl)Fe(CO)₄BF₄ to produce allylated aromatics in moderate to good yields. Unsymmetrically substituted allyl complexes afford the corresponding butenyl-, 1,1-dimethylallyl-, cinnamyl-, and geranyl-derivatives with moderate to excellent regioselectivity and complete stereoselectivity.     

Aromatic polyamides. V. A general synthesis of polyamides from aromatic diacids and aromatic diamines in sulfur trioxide

The reaction of terephthalic acid (TA) and para-phenylenediamine sulfate (PPD-S) in sulfur trioxide to form anisotropic, sulfonated poly(p-phenyleneterephthalamide) (SPT) dopes was reported in Part IV of this series. We have found now that the TA/PPD-S polymerization is only one example of a more general polyamide condensation reaction of aromatic diamines and aromatic diacids. Sulfonation of the aromatic diamine ring during TA/PPD-S polymerization in SO₃ was a major side reaction. Sulfonation was reduced or eliminated by aromatic diamine ring substitution with unreactive substituents, particularly chlorine and fluorine. Polymerization of 2,3,5,6-tetrafluoro-phenylenediamine with TA in SO₃ at 80°C (18% concentration) produced unsulfonated poly(tetrafluoro-para-phenyleneterephthalamide) (F-PPT) with an inherent viscosity of 2.2. The halogenated, all-para aromatic polymers formed highly anisotropic (liquid crystalline) dopes. Monomers that formed polymers in which the chain bond angle deviated from 180° (e.g., meta-oriented monomers) yielded only isotropic polymer solutions. The mechanism and rate of diamine–diacid reactivity in SO₃ was related to diamine basicity. Whereas the less basic aromatic diamines (as sulfates) polymerized with aromatic diacids in SO₃, the more basic aliphatic diamines (as sulfates) would not. Aliphatic, cycloaliphatic, and aryl-aliphatic diacids were degraded by or reacted with the solvent (SO₃). Thermogravimetric analyses of F-PPT and monosulfonated poly(chloro-para-phenyleneterephthalamide) at 20°C/min showed weight loss only above 380 and 370°C, respectively.     

Bis-perfluoroalkylation of aromatic compounds with sodium perfluoroalkanesulfinates

Bis-perfluoroalkylation of aromatic compounds such as dimethoxybenzenes (2,4,6), anisole (8), pyridine (10) and quinoiine (13) was accomplished by reaction with excess sodium perfluoroalkanesulfinates, RFSO2Na (1), in the presence of Mn(OAc)3·2H2O under mild conditions. The reaction provides a facile method for the synthesis of bis-perfluoroalkylated aromatic compounds.     

Preparation and properties of novel soluble aromatic polyimides from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides

New aromatic polyimides containing triphenylamine unit were prepared by two different methods, i.e., a conventional two-step method starting from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides and the one-step thioanhydride method starting from the aromatic diamine and aromatic tetracarboxylic dithioanhydrides. Both procedures yielded high-molecular-weight polyimides with inherent viscosities of 0.47–1.17 dL/g. Some of these polymers were soluble in organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, m-cresol, and pyridine. All the polyimides afforded transparent, flexible, and tough films, and the color varied from pale yellow to dark red, depending markedly on the tetracarboxylic acid components. The glass transition temperatures (T_gs) of these polyimides were in the range of 287–331°C and the 10% weight loss temperatures were above 520°C in air. The polyimides prepared by the one-step method exhibited better solubility in organic solvents and had somewhat lower T_gs than the polymers prepared by a conventional two-step method.     

Mild chlorination of aromatic compounds with tin(IV) chloride and lead tetraacetate

SnCl₄/Pb(OAc)₄ acts as a safe source of Cl₂ for the chlorination of aromatic compounds. A variety of aromatic compounds are effectively chlorinated with SnCl₄/Pb(OAc)₄ under mild conditions. The mixture is a selective chlorinating agent, particularly with polyalkylbenzenes, polycyclic aromatic compounds and anisoles.     

Organometallic chemistry at the edge of polycyclic aromatic hydrocarbons

Zirconocene and bisphosphine nickel chemistry developed in our labs and directed towards the derivatization and synthesis of polycyclic aromatic carbon compounds is reviewed. Complexes with the formula Cp₂ZrMe(η¹-PAC) (PAC=anionic polycyclic aromatic carbon ligand) eliminate methane to produce zirconacycles and yne complexes. Treatment of the zirconacycles with L₂NiX₂ (L=phosphine, X=Cl, Br) in the presence of alkynes results in metallacycle transfer to nickel and cycloaddition of the alkyne. The resulting polycyclic aromatic carbon compounds contain an additional ring. The nickelacycles may also be accessed by oxidative addition of Ni(0) to polycyclic aromatic dihalides followed by reduction. The application of this chemistry to the step-growth synthesis of single-walled carbon nanotubes is proposed.     

Nonoxidative methane conversion into aromatic hydrocarbons on tungsten-containing pentasils

The effects of the tungsten concentration and of the method of tungsten introduction into ZSM-5 pentails with different SiO₂/Al₂O₃ molar ratios on the acidity and the activity of the resulting catalysis in nonoxidative methane conversion into aromatic hydrocarbons are considered. The catalysts obtained from the SiO₂/Al₂O₃ = 40 pentasil and a nanosized tungsten powder are the most active and the most stable. The maximum methane conversion and the highest yield of aromatic hydrocarbons are achieved on the zeolite containing 8.0 wt % tungsten nanopowder.     

An efficient chemoselective etherification of phenols in polyfunctional aromatic compounds

A simple and efficient chemoselective alkylation of phenols in polyfunctional aromatic compounds with different alkyl halides in the presence of K₂CO₃/TBAB is reported. The method is successful with various hydroxy aromatic acids or oximes possessing other functional groups.     

Triflic acid promoted synthesis of polycyclic aromatic compounds

The triflic acid (CF₃SO₃H) promoted cyclizations of 2-styrylbiaryls are found to be useful for the synthesis of polycyclic aromatic compounds, including functionalized derivatives of polycyclic aromatic compounds and heterocyclic systems. The reaction involves cationic cyclization followed by an elimination of benzene from the intermediate product.     

Palladium-catalyzed sequential alkylation-alkenylation reactions: application towards the synthesis of polyfunctionalized fused aromatic rings

The synthesis of polyfunctionalized fused aromatic carbo- and heterocycles from aryl iodides and bromoenoates via a tandem palladium-catalyzed aromatic substitution intramolecular Heck sequence is reported. Using Pd(OAc)₂ and tri-2-furylphosphine (TFP) in the presence of norbornene and Cs₂CO₃ in CH₃CN at 85 °C gave a variety of functionalized bi- and tricyclic fused aromatic rings in good yield.     

Fluoroalkylation of aromatic compounds

Perfluoroalkylation of benzene, halobenzenes, pyridine, furan and thiophene has been accomplished through thermolysis of perfluoroalkyl iodides (CF₃I, n-C₁₀F₂₁I and R_fOR_fI) in the presence of the appropriate aromatic compound. Yields of alkylated products vary depending on temperature, presence of an HI acceptor and reactants ratio. Isomeric mixtures are obtained with halobenzenes, pyridine and thiophene. Furan however yields only the alpha substituted product.     

Ring-chain tautomerism of 2-mercaptobenzoylhydrazones of aromatic aldehydes

It has been shown by ¹H NMR spectroscopy that 2-mercaptobenzoylhydrazones of aromatic aldehydes 2-HSC₆H₄CONHN=CHC₆H₄X (X = 4-NO₂, 3-NO₂, 4-Br, H, 4-Me, 4-MeO, 4-Me₂N) exist in DMSO-d₆ solution as tautomeric mixtures of linear and cyclic benzo-1,3,4-thiadiazepine forms. The linear hydrazone form is represented by (E,Z′)-conformational isomers, differing in the disposition relative to the amide C–N bond. It was shown that the logarithm of the tautomeric equilibrium constant K _T correlates with the σ-constants of the substituents in the aromatic nucleus.     

Spin-forbidden electronic transitions in non-planar aromatic amines

Evidence is presented which indicates that the direct spin—orbit coupling between low-lying ππ^* states is largely responsible for the efficient S₁ → T₁ intersystem crossing and T₁ → S₀ radiative transition in non-planar aromatic amines.