ESR Studies on a Friedel‐Crafts Alkylation Reaction in [bmim]Cl‐AlCl3 Ionic Liquid

The paramagnetic complexes formed in Friedel‐Crafts alkylation reaction systems are invistigated by electron spin resonance (ESR) spectroscopy, in room temperature ionic liquids system 1‐butyl‐3‐methyl‐limidazolium chloride‐aluminium chloride ([bmim]Cl‐AlCl₃). The results indicate that ESR spectra observed are due to polycyclic aromatic radical cations formed from their parent hydrocarbons. ESR spectrum of spin adduct is obtained in an ionic liquid system composed of [bmim]Cl‐AlCl₃. In acidic solution the ¹⁴N hyperfine coupling constant of 4‐oxo‐TEMPO, 2.15 mT, is appreciably larger due to an adduct formed with AlCl₃.     

Effect of Different Ionic Liquids on 5-Hydroxymethylfurfural Preparation from Glucose in DMA over AlCl3: Experimental and Theoretical Study

In this work, effect of different ionic liquids (ILs) on 5‐hydroxymethylfurfural (HMF) preparation from glucose in N,N‐dimethylacetamide (DMA) over AlCl₃ was revealed by a combined experimental and computational study. ILs used as cocatalysts in this work included N‐methyl‐2‐pyrrolidone hydrogen sulfate ([NMP]HSO₄), N‐methyl‐2‐pyrrolidone methyl sulfate ([NMP]CH₃SO₃), N‐methyl‐2‐pyrrolidone chlorine ([NMP]Cl) and N‐methyl‐2‐pyrrolidone bromide ([NMP]Br) which were endowed with the same cation but different anions. According to the conclusion that fructose was intermediate product from glucose to HMF, we found fructose was transformed to more by‐products by [NMP]HSO₄, making HMF yield decline significantly when glucose was treated as substrate. Neither glucose nor fructose could be converted by [NMP]CH₃SO₃ efficiently, leading to its no influence on glucose conversion to HMF. [NMP]Br had a higher selectivity for HMF from fructose than [NMP]Cl and AlCl₃. Besides, Al³⁺ preferred to combine with Br^?, slightly decreasing both the overall free energy barrier for glucose isomerization and activation barrier for H‐shift at 393.15 K. So a high HMF yield of 57% was obtained from glucose catalyzed by AlCl₃ together with [NMP]Br under mild conditions.     

Polymerization of phenylacetylene catalysed by RhTp(cod) and RhBp(cod) in ionic liquids: effect of alcohols and of tetraammonium halides

RhTp(cod) ( 1 ) and RhBp(cod) ( 2 ), almost inactive in CH₂Cl₂, became good catalysts of phenylacetylene polymerization in ionic liquids ([bmim]Cl, [bmim]BF₄: bmim = 1‐butyl‐3‐methylimidazolium, [mokt]BF₄: mokt = 1‐methyl‐3‐oktylimidazolium, [bumepy]BF₄: 1‐butyl‐4‐methylpyridinium) and in CH₂Cl₂ in the presence of tetraammonium halides ([R₄N]X, R = Bu, Et; X = Cl, Br). The highest yields of polyphenylacetylene with catalyst 1 were obtained in [bmim]Cl at 65°C (64% after 2 h) and in [mokt]BF₄ at 20°C (56% after 24 h). In alcohols (CH₃OH, (CH₃)₂CHOH, (CH₃)₃COH) as solvents, up to 100% of the polymer was produced. When a mixture of an ionic liquid and CH₃OH was used as the reaction medium, the polymer yield was similar to the yield achieved in an ionic liquid only, but the molecular weight increased remarkably. Tetraammonium salts, [R₄N]X, are co‐catalysts for 1 , and the yield of the polymer increased in the order [Et₄N]Br < [Bu₄N]Br < [Et₄N]Cl < [Bu₄N]Cl. Polymers with molecular weights from 6900 to 38 800 Da were obtained with catalyst 2 in [R₄N]Br or [R₄N]Cl, whereas in ionic liquids ([bmim]Cl, [bmim]BF₄) the corresponding molecular weights were higher, from 51 300 to 60 300 Da. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of imidazolium salts on the catalytic reaction of 1,3-dioxolanes with methyl diazoacetate

Effect of imidazolium salts, [bmim]⁺Cl^?, [bmim]⁺BF₄ ^?, and [bmim]⁺PF₆ ^?, on the reaction of 1,3-dioxolanes with methyl diazoacetate in the presence of copper-containing catalysts was studied. The product composition was found to depend on the reaction conditions and the nature and ratio of components of the catalytic system.     

One‐Pot Synthesis of Hydroxy Pyrazolo[1,2‐a][1,2,4]triazoles and Their Dehydration Using Recyclable Ionic Liquids as Reaction Media

An eco‐friendly, simple, and efficient one‐pot new procedure has been developed for the synthesis of hydroxy phenylhexahydropyrazolo[1,2‐a][1,2,4]triazoles by condensation of 4‐phenylurazole, aldehydes, and ethyl/methyl acetoacetate using ionic liquid [bmim]BF₄ in presence of l ‐proline at 80°C. The hydroxy pyrazolo[1,2‐a][1,2,4]triazoles could be dehydrated in presence of [bmim]HSO₄ to give corresponding phenyltetrahydropyrazolo[1,2‐a][1,2,4]triazoles in high yields. High yields, less reaction time, operational simplicity, and recyclability of reaction media are the advantages of this protocol.     

Facile and Stereospecific Synthesis of Various Dienones Using Task‐specific Ionic Liquid/Borohydride as Stable and Promoted Hydrogen Release Reagent

In this work, for the first time, task‐specific ionic liquid, 1‐n ‐butyl‐3‐methylimidazolium borohydride ([bmim]BH₄), was used as the medium as well as reagent for the regiospecific reduction of triarylpyrylium perchlorates to provide aromatic dienones as only product. The [bmim]BH₄ having a reactive anion also could promote the desired reaction thereby reducing the reaction times and improving the yields substantially. The products could be easily isolated from the reaction mixture by simple extraction.     

Oxidation of Thiols Using K 2 S 2 O 8 in Ionic Liquid

A green, straightforward, and novel method for oxidation of thiols to the corresponding disulfides is reported using K ₂ S ₂ O₈ in the ionic liquid 1-butyl-3-methylimidazolium bromide [(bmim)Br] at 65–70°C. The corresponding disulfides were obtained in excellent yield and short reaction time.     

Synthesis of Dichlorophenylphosphine via a Friedel-Crafts Reaction in [Et4N]Br-XAlCl3 Ionic Liquids

The Friedel-Crafts reaction of phosphorus trichloride and benzene in [Et ₄ N]Br-XAlCl ₃ ([Et ₄ N]Br = tetraethylammonium bromide) ionic liquids (ILs) was investigated for the clean synthesis of dichlorophenylphosphine (DCPP). A simple product isolation procedure was achieved, and the effects of IL's composition, reaction time, and quantity on this reaction were studied. The [Et ₄ N]Br-XAlCl ₃ ILs gave this reaction a green character. From the isolation experiments, it was found that (a) because of the formation of the complex of DCPP and AlCl ₃ , the catalytic activity of the [Et ₃ NH]Cl-XAlCl ₃ ([Et ₃ NH]Cl = triethylhydrogenamonium chloride) was reduced; (b) with the addition of quaternary ammonium to the IL's residue, additional DCPP could be recovered.     

Three-Component,One-Pot Synthesis of Benzo[b][1,4]oxazines in Ionic Liquid 1-Butyl-3-methylimidazolium Bromide

Benzo[b][1,4]oxazines have been synthesized in good to excellent yields in the presence of the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]Br under relatively mild conditions without any added catalyst, The method offers the advantages of good yields and short reaction times, and the ionic liquid can be easily separated from the product and reused.     

Iridium-catalyzed regiospecific allylation of dimethyl malonate in ionic liquids

Allylation of dimethyl malonate with 1-(4-chlorophenyl)prop-2-enyl methyl carbonate in the presence of [Pd(All)Cl]₂, [Rh(COD)Cl]₂, [Ir(COD)Cl]₂ (COD is cycloocta-1,5-diene), and a chiral ferrocenyl-containing phosphite ligand based on (R)-BINOL (BINOL is 2,2′-dihydroxy-1,1′-binaphthyl) in CH₂Cl₂ gave a mixture of linear and branched cross-coupling products, the latter having a moderate optical purity (below 51%). The rhodium-and iridium-catalyzed reactions were very highly regioselective (regiospecific in the case of Ir), giving a branched product. In ionic liquids ([bmim][BF₄] and [bdmim][BF₄]) (bmim is 1-butyl-3-methylimidazolium and bdmim is 1-butyl-2,3-dimethylimidazolium), the Ir-catalyzed reaction regiospecifically afforded a branched product as a racemate. The same result was obtained with [Ir(COD)Cl]₂ as a catalyst; this reaction easily occurred in ionic liquids even without a base. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 519–521, March, 2007.     

Ultrasonic and Lewis acid ionic liquid catalytic system for Kabachnik-Fields reaction

A combination of ultrasonic (US) and [bmim]AlCl₄ ionic liquid is used as an alternative to conventional acid catalysts in the Kabachnik-Fields reaction of an amine and aryl aldehyde with phosphite leading to the formation of aminophosphonates. The reaction time was significantly reduced and the reaction progressed very smoothly.     

Photochromic dihetarylethenes. 14. Synthesis of symmetrical and unsymmetrical dihetarylcyclobutene-1,2-diones

A procedure was developed for the synthesis of symmetrical and unsymmetrical cyclobutene-1,2-dione derivatives bearing thiophene and thieno[3,2-b]thiophene substituents by the Friedel—Crafts reaction of the corresponding heterocyclic compounds with squaric acid dichloride in the presence of AlCl₃. In addition to the target dihetarylcyclobutenediones, monoacylation products of methyl (2,5-dimethylthiophen-3-yl)acetate and methyl 5-methylthieno[3,2-b]thiophene-2-carboxylate with squaric acid dichloride were isolated and characterized.     

One‐Pot,Three‐Component Synthesis of Novel Spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones in an Ionic Liquid as a Reusable Reaction Media

A facile one‐pot, three‐component protocol for the synthesis of novel spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones by condensing 1H‐indole‐2,3‐diones, 4H‐1,2,4‐triazol‐4‐amine and 2‐sulfanylpropanoic acid in [bmim]PF₆ (1‐butyl‐3‐methyl‐1H‐imidazolium hexafluorophosphate) as a recyclable ionic‐liquid solvent gave good to excellent yields in the absence of any catalyst (Scheme 1 and Table 2). The advantages of this protocol over conventional methods are the mild reaction conditions, the high product yields, a shorter reaction time, as well as the eco‐friendly conditions.     

Ionic liquid promoted synthesis of 3-(2′-benzothiazolo)-2,3-dihydroquinazolin-4(1H)-ones

3-(2′-Benzothiazolo)-2,3-dihydroquinazolin-4(1H)-ones have been synthesized in high yields in the presence of 1-butyl-3-methylimidazolium bromide [bmim]Br as an ionic liquid; the reaction work-up is simple and the ionic liquid can be easily separated from the product and reused.     

3-exo-tet Cyclization of 2,2-disubstituted 1,3-dihalopropanes with indium in aqueous and ionic liquid solvent system

The 3-exo-tet cyclization of 2,2-disubstituted 1,3-dihalopropanes with In powder in THF solution of 20% H₂O, dioxane solution of 20% H₂O, and ionic liquids, such as [bmim]Br, [bmim]Cl, and [bmin]BF₄, respectively, was efficiently carried out to form the corresponding 1,1-disubstituted cyclopropanes in good yields. The cyclopropanation of 2,2-disubstituted 1,3-dihalopropanes with In powder in ionic liquids, such as [bmim]Br, [bmim]Cl, and [bmin]BF₄, was markedly accelerated compared with that in a THF solution of 20% H₂O and a dioxane solution of 20% H₂O. The mechanism was proposed to involve the radical 3-exo-tet cyclization of the formed 3-halopropyl radical.     

Microwave‐Assisted Functionalization of Carbon Nanostructures in Ionic Liquids

The effect of microwave (MW) irradiation and ionic liquids (IL) on the cycloaddition of azomethine ylides to [60]fullerene has been investigated by screening the reaction protocol with regard to the IL medium composition, the applied MW power, and the simultaneous cooling of the system. [60]Fullerene conversion up to 98 % is achieved in 2–10 min, by using a 1:3 mixture of the IL 1‐methyl‐3‐n‐octyl imidazolium tetrafluoroborate ([omim]BF₄) and o‐dichlorobenzene, and an applied power as low as 12 W. The mono‐ versus poly‐addition selectivity to [60]fullerene can be tuned as a function of fullerene concentration. The reaction scope includes aliphatic, aromatic, and fluorous‐tagged (FT) derivatives. MW irradiation of IL‐structured bucky gels is instrumental for the functionalization of single‐walled carbon nanotubes (SWNTs), yielding group coverages of up to one functional group per 60 carbon atoms of the SWNT network. An improved performance is obtained in low viscosity bucky gels, in the order [bmim]BF₄> [omim]BF₄> [hvim]TF₂N (bmim=1‐methyl‐3‐n‐butyl imidazolium; hvim=1‐vinyl‐3‐n‐hexadecyl imidazolium). With this protocol, the introduction of fluorous‐tagged pyrrolidine moieties onto the SWNT surface (1/108 functional coverage) yields novel FT‐CNS (carbon nanostructures) with high affinity for fluorinated phases.     

Electron‐pair‐donor reaction order in the cationic polymerization of isobutylene coinitiated by AlCl3

The cationic polymerizations of isobutylene (IB) initiated by an H₂O/AlCl₃ system were carried out in a mixture of n‐hexane/methylene dichloride of 60/40 v/v at ?50 °C in the presence of various external electron pair donors (EDs), including methyl benzoate (MB), ethyl benzoate (EB), and methyl acrylate (MA). The effects of the concentrations of EDs ([ED]) and polymerization time on monomer conversion and kinetics of IB polymerization were also investigated. The complexes between AlCl₃ and the esters were soluble in the polymerization system at ?50 °C. The polymers with high molecular weights and relatively narrow molecular weight distributions were obtained in the presence of the EDs. The rate of polymerization decreased with increasing [ED]. The kinetic orders of the EDs were remarkably dependent on their chemical structure, steric hindrance from moieties, and concentration in the polymerization system. The reaction order of MB was determined to be around ?1.3 when [MB] ≤ 0.40 mmol/L, whereas it was ?12.9 when [MB] ≥ 0.40 mmol/L. The reaction order of EB was determined to be ?1.36 when [EB] ≤ 0.41 mmol/L, whereas it was ?3.36 when [EB] ≥ 0.41 mmol/L. The reaction order of MA was determined to be ?1.85 when [MA] ≤ 0.48 mmol/L, whereas it was ?16.7 when [MA] ≥ 0.48 mmol/L. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3053–3061, 2007     

Combined dealkoxycarbonylation and lactonisation of unsaturated malonates in ionic liquids

Heating unsaturated malonates with LiCl and water in [bmim][Br] or [bmim][BF₄]/[bmim][Br] produces unsaturated esters or lactones, respectively.     

Ionothermal Synthesis of a NaCl‐type Topological Network Based on Trinuclear Cobalt(II) Clusters as Nodes

A new metal‐organic network [Co₃(tbip)₃(H₂O)₄] · 2H₂O ( 1 ) (H₂tbip = 5‐tert‐butyl‐isophthalic acid) was synthesized through the ionothermal reaction of H₂tbip, cobalt nitrate, and [bmim]Br ionic liquid ([bmim]Br = 1‐butyl‐3‐methylimidazolium bromide). It exhibits a three‐dimensional (3D) framework with NaCl topology based on trinuclear cobalt(II) clusters as nodes. The magnetic studies show that there exist antiferromagnetic interactions between the Co^II ions.     

Ionic‐Liquid‐Influenced Expeditious and Stereoselective Synthesis of Olefins

1‐Butyl‐3‐methylimidazolium chloroaluminate, [bmim]Cl·.AlCl₃ (molar fraction, N=0.67), ionic liquid has been used in combination with metallic Zn for the reductive coupling of carbonyl compounds to synthesize symmetrical olefins, with the Z‐isomer formed predominantly. The ionic liquid played a dual role of Lewis acid catalyst and solvent.