Lewis acids room-temperature ionic liquids

Tsuda T, Hussey CL (2008) Electrodeposition of photocatalytic AllnSb semiconductor alloys in the lewis acidic aluminum chloride-l-ethyl-3-methylimidazolium chloride room-temperature ionic liquid. Thin Solid Eifrns 516(18) 6220-6225. doi 10.1016/J.tsf.2007.11.114... 

Room-temperature ionic liquids have recently attracted a great deal of industrial interest (Carmichael, 2000 Guterman, 1999 see also the brief overview by Earle et al. (2003) and the extensive and detailed review by Olivier-Bourbigou et al. (2010). They are versatile as solvents or nonsolvents for organic substances, and some exhibit strongly temperature-dependent water solubility. They are nonvolatile. Some, notably those containing haloaluminate anions, have widely variable Lewis and Brpnsted acidity (into the superacid range). Others, such as those with tetrafluoroborate or hexafluorophosphate... 

Tsuda, T., Hussey, C. L. Stafford, G. R. (2007). Progress in Surface Finishing with Lewis Acidic Room-Temperature Chloroaluminate Ionic Liquids, ECS Trans., 3(35) 217-231. 

It is not surprising that electrophilic aromatic substitutions were the first organic reactions investigated using acidic room-temperature chloro-almninate(III) ionic liquids. Indeed, chloroaluminate(ni) species combine their properties of good solvents for simple arenes to their role as Lewis acid catalysts. In Friedel-Craft alkylations, polyalkylation is common as well as the isomerisation of primary halides to secondary carbonium ions. 

Few aHyl monomers have been polymerized to useful, weH-characterized products of high molecular weight by ionic methods, eg, by Lewis acid or base catalysts. Polymerization of the 1-alkenes by Ziegler catalysts is an exception. However, addition of acidic substances, at room temperature or upon heating, often gives viscous liquid low mol wt polymers, frequently along with by-products of uncertain stmcture. 

Chloroaluminate ionic liquids (typically a mixture of a quaternary ammonium salt with aluminum chloride see Table 6.9) exhibit at room temperature variable Lewis acidity and have been successfully used as solvent/catalyst for Diels-Alder reactions [57]. The composition of chloroaluminate ionic liquids can vary from basic ([FMIM]C1 or [BP]C1 in excess) to acidic (AICI3 in excess) and this fact can be used to affect the reactivity and selectivity of the reaction. The reaction of cyclopentadiene with methyl acrylate is an example (Scheme 6.31). 

Then the potential for asymmetric induction of some of these chiral ionic liquids was investigated. The aza Diels-Alder cycloaddition between the enantiomericaUy pure (/ )-imine 31 and the Danishefsky s diene 32 was chosen as model asymmetric reaction (Scheme 8). The reaction was performed at room temperature for 5 h using 0.5 equiv. of ionic liquid and 1.5 equiv. of diene. In the absence of chiral ILs, the same coupling required a Lewis acid catalyst (0.1 equiv. of ZnC ) and afforded the main product 33 in 60% yield and low diastereoselectivity (32% de). 

A simple ionic liquid, octylmethylimidazolium (with PI >> counterion), promotes TMSCN addition to aldehydes in yields up to quantitative, in 1 day at room temperature. Environmentally friendly and recyclable, the solvent requires no Lewis acid or other activation.268 The long-chain substituent and the nature of the counterion are important contributors to the high yield. Deprotection to give the product as cyanohydrin just requires an HC1-THF workup. 

Abbott et al. [98-103] reported the synthesis and characterization of new moisture-stable, Lewis acidic ionic liquids made from metal chlorides and commercially available quaternary ammonium salts (see Chapter 2.3). They showed that mixtures of choline chloride (2-hydroxyethyltrimethylammonium chloride, [Me3NC2H40H]Cl and MCU (M=Zn, Sn) give conducting and viscous liquids at or around room temperature. These deep eutectic solvents/ionic liquids are easy to prepare, are water-and air-stable, and their low cost enables their use in large-scale applications. Furthermore, they reported [104] that a dark green, viscous liquid can be formed by mixing choline chloride with chromium(III) chloride hexahydrate and that the... 

In this protocol we describe an electroplating procedure for mild steel with an adhesive aluminum layer in Lewis acidic ionic liquid l-ethyl-3-methylimidazolium chloride [EMIMJC1 containing AICI3. We aim to electroplate mild steel with dense, adherent and uniform aluminum layers in the employed ionic liquids at room temperature. 

Ionic liquids containing chloroaluminate anions are strong Lewis acids. This characteristic, coupled with the fact that they are relatively easy to handle, makes them attractive alternatives to standard Lewis and Bronsted acids such as HF. The IL can function both as a catalyst and a solvent for acid-catalyzed processes. Some of the first reactions studied in ILs were Friedel-Crafts alkylations and arylations. The [emim][Al2Cl7] affords complete conversion of benzene and acetyl chloride to acetophenone in less than 5 minutes at room temperature. 

The electrochemistry of titanium (fV) has been exanuned in acidic l-ethyl-3-methyUmidazolium chloride/AlClj ([EmimJCl/AlClj) in 1990 by Carlin et al. [180]. It was shown that titaifium is reduced to Ti(lll) and Ti(n) in two one-electron steps, both of which exhibit slow electron-transfer kinetics. Ten years later, Mukhopadhyay et al. smdied the deposition of Ti nanowires at room temperature from 0.24 M TiCl in the ionic liquid l-butyl-3-methylimidazohumbis((trifluoromethyl)sulfonyl)amide [181]. They found that up to six wires grow at constant potential over a period of about 20 min wires exhibit a narrow width distribution of 10 2 nm and have a length of more than 100 nm. The chemical and electrochemical behavior of titanium was examined in the Lewis acidic [EmimlCl/AlClj molten salt at 353.2 K. The electrodeposition of Al-Ti alloys at Cu rotating disk and wire electrodes was investigated by Tsuda et al. [55]. It was found that Al-Ti alloys which contain up to 19% (atomic fraction) titanium, could be electrodeposited from saturated solutions of Ti(II) in the... 

The formation of ionic liquids by the reaction of halide salts with Lewis acids (most notably AICI3) dominated the early years of this area of chemistry. The great breakthrough came in 1951 with the report by Hurley and Weir on the formation of a salt that was liquid at room temperature based on the combination of 1-butylpyridinium with AICI3 in the relative molar proportions 1 2 (X = 0.66) [26]. ... 

Asymmetric aza-Diels-Alder reaction of chiral imines with Danishefsky s diene in chiral ionic liquids have been reported [89]. These reactions occur at room temperature under green chemistry conditions without using Lewis acid catalyst and organic solvent. For example, the reaction of Danishefsky s diene 76 with imine 104 in the presence of chiral ionic liquid (EL) 105, gives pyridone derivative in moderate diastereoselectivity [89]. In the TS, the chiral liquid 105 binds the diene... 

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