Lewis aluminium chloride

BenZotrichloride Method. The central carbon atom of the dye is supphed by the trichloromethyl group from iJ-chlorobenzotrichloride. Both symmetrical and unsymmetrical triphenyhnethane dyes suitable for acryhc fibers are prepared by this method. 4-Chlorobenzotrichloride is condensed with excess chlorobenzene in the presence of a Lewis acid such as aluminium chloride to produce the intermediate aluminium chloride complex of 4,4, 4"-trichlorotriphenylmethyl chloride (18). Stepwise nucleophihc substitution of the chlorine atoms of this intermediate is achieved by successive reactions with different arylamines to give both symmetrical (51) and unsymmetrical dyes (52), eg, N-(2-chlorophenyl)-4-[(4-chlorophenyl) [4-[(3-methylphenyl)imino]-2,5-cyclohexadien-l-yhdene]methyl]benzenaminemonohydrochloride [85356-86-1J (19) from. w-toluidine and o-chloroaniline. 

Azaferrocene reacts with aromatic hydrocarbons in the presence of aluminium chloride, giving rise to the cationic complexes of the type (Ti -arene)(Ti -cyclopenta-dienyl)iron(l+) isolated as BF4 salts [87JOM(333)71]. The complex 28 is obtained by reaction of the sulfane compound [Cp(SMc2)3Fe]BF4 with pentamethyl-pyrrole [88AG(E)579 88AG(E)1468 90ICA(170)155]. The metallic site in this center reveals expressed Lewis acidity (89CB1891). 

A similar catalytic dimerization system has been investigated [40] in a continuous flow loop reactor in order to study the stability of the ionic liquid solution. The catalyst used is the organometallic nickel(II) complex (Hcod)Ni(hfacac) (Hcod = cyclooct-4-ene-l-yl and hfacac = l,l,l,5,5,5-hexafluoro-2,4-pentanedionato-0,0 ), and the ionic liquid is an acidic chloroaluminate based on the acidic mixture of 1-butyl-4-methylpyridinium chloride and aluminium chloride. No alkylaluminium is added, but an organic Lewis base is added to buffer the acidity of the medium. The ionic catalyst solution is introduced into the reactor loop at the beginning of the reaction and the loop is filled with the reactants (total volume 160 mL). The feed enters continuously into the loop and the products are continuously separated in a settler. The overall activity is 18,000 (TON). The selectivity to dimers is in the 98 % range and the selectivity to linear octenes is 52 %. 

As mentioned several times Lewis acids are highly valuable catalysts but the most commonly used ones such as aluminium chloride and boron trifluoride are highly water sensitive and are not usually recovered at the end of a reaction, leading to a significant source of waste. In recent years there has been much research interest in lanthanide triflates (trifluoro-methanesulfonates) as water stable, recyclable Lewis acid catalysts. This unusual water stability opens up the possibility for either carrying out reactions in water or using water to extract and recover the catalyst from the reaction medium. 

Many standard reactions that are widely applied in the production of fine chemicals employ. strong mineral or Lewis acids, such as sulphuric acid and aluminium chloride, often in stoichiometric quantities. This generates waste streams containing large amounts of spent acid, which cannot easily be recovered and recycled. Replacement of these soluble mineral and Lewis acids by recyclable. solid acids, such as zeolites, acid clays, and related materials, would represent a major breakthrough, especially if they functioned in truly catalytic quantities. Consequently, the application of solid acids in fine chemicals synthesis is currently the focus of much attention (Downing et al., 1997). 

All acids but especially Lewis acids (particularly aluminium chloride), give rise to dangerous interactions with nitrated derivatives and nitrates (there is not much information about nitrates). Aluminium chloride causes a large number of accidents due to nitrobenzene and sometimes nitromethane when used as a solvent in Friedel-Crafts reactions for which aluminium chloride is the common catalyst. 

Mixtures of C4 alkene isomers (largely isobutene) are polymerised commercially in contact with low levels of aluminium chloride (or other Lewis acid) catalysts. The highly exothermic runaway reactions occasionally experienced in practice are caused by events leading to the production of high local levels of catalyst. Rapid increases in temperature and pressure of 160°C and 18 bar, respectively, have been observed experimentally when alkenes are brought into contact with excess solid aluminium chloride. The runaway reaction appears to be more severe in the vapour phase, and a considerable amount of catalytic degradation contributes to the overall large exotherm. 

Yoshino reports a novel and general method for the C-3 acylation of indoles with acyl chlorides in the presence of dialkylaluminium chloride which obviates the need for prior N-protection . Interestingly, as described in this preliminary communication, the unprotected indoles 147 are first treated with the Lewis acids prior to addition of the acid chlorides, yielding the desired 3-acyl derivatives 148. In reactions more typical of indoles under acidic conditions, Nakatsuka determined the structures of the dimers and trimers of 1-trimethylacetylindole produced in the presence of aluminium chloride . 

Bound reagents are an excellent alternative in cases where the reagent is used in excess and can be difficult to remove. Purification is now a simple process of filtration and evaporation. For example, silica-supported aluminium chloride is a Lewis acid and an effective catalyst for Friedel-Crafts alkylations (Figure 3.15). 

Anthraquinone itself is traditionally available from the anthracene of coal tar by oxidation, often with chromic acid or nitric acid a more modern alternative method is that of air oxidation using vanadium(V) oxide as catalyst. Anthraquinone is also produced in the reaction of benzene with benzene-1,2-dicarboxylic anhydride (6.4 phthalic anhydride) using a Lewis acid catalyst, typically aluminium chloride. This Friedel-Crafts acylation gives o-benzoylbenzoic acid (6.5) which undergoes cyclodehydration when heated in concentrated sulphuric acid (Scheme 6.2). Phthalic anhydride is readily available from naphthalene or from 1,2-dimethylbenzene (o-xylene) by catalytic air oxidation. 

Many ene reactions can be catalysed by lewis acids, particularly A1C13 and ethyl aluminium chloride. 

The transitory existence of alkylcarbonium ions in alkyl halide-Lewis acid halide systems has been inferred from a variety of observations, sueh as vapour-pressure depressions of OHsCl and C2H5CI in the presence of gallium chloride (Brown et al., 1950), the electric conductivities of aluminium chloride in ethyl chloride (Wertyporoch and Firla, 1933) and of alkyl fluorides in boron trifluoride (Olah et al., 1957), as well as the... 

Aniline does not undergo Frledel-Crafts reaction (alkylation and acetylation) due to salt formation with aluminium chloride, the Lewis acid, which Is used as a catalyst. Due to this, nitrogen of aniline acquires positive charge and hence acts as a strong deactivating group for further reaction. 

The weak nucleophilic nature of polynitroaliphatic alcohols means that reactions often need to be catalyzed by Brpnsted acids or Lewis acids. The following methods are commonly used for the esterification of polynitroaliphatic alcohols (1) heating a solution of the alcohol and acid in the presence of sulfuric acid with Dean-Stark removal of water ° (2) using the acid chloride or anhydride in the presence of aluminium chloride " (3) reacting the acid and alcohol... 

Abstract The term Lewis acid catalysts generally refers to metal salts like aluminium chloride, titanium chloride and zinc chloride. Their application in asymmetric catalysis can be achieved by the addition of enantiopure ligands to these salts. However, not only metal centers can function as Lewis acids. Compounds containing carbenium, silyl or phosphonium cations display Lewis acid catalytic activity. In addition, hypervalent compounds based on phosphorus and silicon, inherit Lewis acidity. Furthermore, ionic liquids, organic salts with a melting point below 100 °C, have revealed the ability to catalyze a range of reactions either in substoichiometric amount or, if used as the reaction medium, in stoichiometric or even larger quantities. The ionic liquids can often be efficiently recovered. The catalytic activity of the ionic liquid is explained by the Lewis acidic nature of then-cations. This review covers the survey of known classes of metal-free Lewis acids and their application in catalysis. 

The Beckmann rearrangement of oxime esters is catalysed by Brpnsted or Lewis acids and these conversions are usually non-stereospecific, as demonstrated by the studies of Beckmann rearrangement of 1-indanone oximes derivatives 240a with aluminium chloride as a catalyst " (equation 88). 

Acetylcarbazole has been prepared in yields up to 90% by the aluminium chloride catalyzed Fries rearrangement of 9-acetylcarbazole. Photo-Fries rearrangement of this substrate gave an equimolar mixture of 1- and 3-acetylcarbazoles in cyclohexane it has been used to prepare the 1-isomer by reaction in isopropanol. The Lewis acid-catalyzed Fries process was used to prepare 3-phenacetylcarbazole. ... 

With bromine and excess aluminium chloride, 2-acetylfuran was converted into a mixture of 2-acetyl-4,5-dibromofuran (major product) and about equal quantities of the 4- and 5-bromo derivatives. The swamping catalyst effect is operating here. Coordination of the catalyst with the carbonyl function makes the substituent more electronegative, and in the presence of a large excess of Lewis acid catalyst, positions ortho and para to the substituent are deactivated more than the me/a-position [68AG(E)519 82AHC(30)167]. In terms of a 2-acylfuran, this means that... 

Almost all ethylbenzene is produced commercially by alkylating benzene with ethylene, either in the liquid phase with aluminium chloride catalyst or in the vapour phase with a synthetic zeolite or Lewis acid catalyst (Coty et al., 1987 Cannella, 1998). 

FC acylation and alkylation As pyrroles and furans are not stable in the presence of Lewis acids, which are necessary for FC alkylations and acylations, only thiophene, which is stable in Lewis acids, can undergo these reactions. Thiophene reacts with benzoyl chloride in the presence of aluminium chloride to produce phenyl 2-thienyl ketone. 

IMMOBILISED LEWIS ACIDS 3.1 Supported aluminium chloride... 

Aluminium chloride is often used as a Lewis acid catalyst (equations 68 and 69), although there are many other suitable catalysts (equations 70 and 71). Strong electrophiles such as chlorosulphonyl isocyanate or an aluminium salt do not require catalysis (equations 72 and 73). 

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