Aluminum chloride promoted

Fries rearrangement (Section 24.9) Aluminum chloride-promoted rearrangement of an aryl ester to a ring-acylated derivative of phenol. 

Ethylbenzene was the first petrochemical to be produced by petroleum refiners in large quantities. It is made by the alkylation of benzene by ethylene. Aluminum chloride promoted with ethyl chloride was originally the predominant catalyst used for the reaction, but solid phosphoric acid has been used more recently and is becoming more popular. Some of the newer fluoride-type catalysts are expected to become quite popular. 

In 196146 the initial work on ( —)-(/t)-dimenthyl fumarate (l)47 was revised and a diastereomeric ratio of 78.5 21.5 (15,25) for the aluminum chloride promoted addition to 1,3-butadiene (2) was reported. The absolute configuration was established by degradation of the major cycloadduct 3 to threo-2>,4-dimethyl adipic acid (5). Absence of Lewis acids reverses the sense of chiral induction [d.r. 51.2 48.8 (l/ ,27 )]. These observations are rationalized by means of a modified Prelog model. 

The aluminum chloride-promoted Friedel-Crafts acylation can also be successfully performed in ionic media. An easy-to-handle ionic liquid is that prepared from a mixture of one to two equivalents of aluminum chloride and l-ethyl-3-methylimidazolium chloride or iodide (EtMeimCl-AlCl3 and EtMeiml-AlCls, respectively). These solvent-catalysfs can be utilized in the easy and efficient acylation of unprotected indoles with a variety of acyl chlorides to give C-selective acylation at the 3-position in 38%-87% yield. ... 

Intermediate 35 can be alternatively produced by aluminum-chloride-promoted reaction of the cyclic dichloride 34 that can be in turn produced by the same ring-chain isomerization of phthalic dichloride 32. This hypofhesis has been sfrongly supported by NMR studies showing that cyclic dichloride 34 is produced by treatment of phfhalic dichloride 32 with... 

Indane-l,3-diones 44 can be synthesized by a three-component sequential aluminum-chloride-promoted cross condensation-cycloacylation of various acyl chlorides (Scheme 2.20). Thus, the poorly stable acetoacetyl chloride 41, produced in situ by aluminum chloride-promoted self-condensation of acetyl chloride, reacts at the methylene active carbon with aromatic acyl chlorides 42, giving the reactive complexes 43 that... 

Results of the Fries rearrangement of 1-naphthyl esters promoted by scandium triflate (5% mol) are reported in Table 5.6. The reaction proceeds smoothly in toluene at 100°C for 6 h to produce l-hydroxy-2-naphthyl ketones in high selectivity. The yields obtained are much higher than those achieved in the stoichiometric aluminum-chloride-promoted reactions. ... 

Table 5.8 Aluminum-chloride-promoted Fries rearrangement of 6-acyl-2(3H)-benzoxazolones and 6-acyl-2(3H)-benzothiazolones...

Aromatic fractions can be alkylated with olefins to produce products which are used as synthetic lubricants.An aromatic fraction boiling between 160 and 210°C is generally alkylated with Cm to Cw olefins in a ratio of about 2 1. A higher-boiling aromatic fraction (boiling between 210 and 260°C) is reacted with Cs to Cw olefins in a ratio of 1 3. Aluminum chloride promoted with hydrogen chloride is the catalyst normally used. When the alkylated aromatics are blended with thickeners such as polyisobutylene, the mixture obtained is an excellent lubricant with a good viscosity index, stability, and pour point. 

Before the war, using one of the earliest samples of tritium from the Radiation Laboratory c.t Berkeley, he found the rate of isomerization of n-butane to isobutane, over aluminum chloride promoted with water, was proportional to the rate of exchange of hydrogens between the hydrocarbon and a catalyst promoted with tritiated water. This observation may have been part of the stimulus for the more detailed studies with isotopic tracers of acid catalysis after the war. 

This reaction was first reported by Nenitzescu in 1931. It is the formation of an a,p-unsaturated ketone directly by aluminum chloride-promoted acylation of alkenes with acyl halides. Therefore, it is known as the Darzens-Nenitzescu reaction (or Nenitzescu reductive acylation), or Nenitzescu acylation. Under such reaction conditions, Nenitzescu prepared 2-butenyl methyl ketone from acetyl chloride and 1-butene and dimethylacetylcyclohex-ene from acetyl chloride and cyclooctene. However, in the presence of benzene or hexane, the saturated ketones are often resolved, as supported by the preparation of 4-phenyl cyclohexyl methyl ketone from the reaction of cyclohexene and acetyl chloride in benzene, and the synthesis of 3- or 4-methylcyclohexyl methyl ketone by refluxing the mixture of cycloheptene and acetyl chloride in cyclohexane or isopentane. This is probably caused by the intermolecular hydrogen transfer from the solvent. In addition, owing to its intrinsic strain, cyclopropyl group reacts in a manner similar to an oleflnic functionality so that it can be readily acylated. It should be pointed out that under various reaction conditions, the Darzens-Nenitzescu reaction is often complicated by the formation of -halo ketones, 3,)/-enones, or /3-acyloxy ketones. This complication can be overcome by an aluminum chloride-promoted acylation with vinyl mercuric chloride, resulting in a high purity of stereochemistry. ... 

The regiochemical course of Pechmaim condensations of poly-functionalized phenolic substrates generally appears to be controlled by the nature of the coupling partners. However, the choice of acidic promoter has been demonstrated to have some influence on product regiochemistry, particularly in the case of aluminum chloride-promoted condensations of resorcinols, as discussed above. ... 

Molecular rearrangements involving hydride, H , and alkyl, R, shifts become possible when a carbocation or a polarized cation-like complex is an intermediate in a reaction. Thus, the aluminum chloride-promoted reaction of 1-bromopropane with benzene gives w-propylbenzene (1) and isopropylbenzene (2) in a ratio of about 1 2 (Eq. 15.10). As shown in Scheme 15.1, the formation of 2 is explained by a 1,2-hydride rearrangement of the primary carbocation-like complex 3 to produce the secondary carbocation 4. The formation of comparable amounts of 1 and 2 in the reaction means that the rate of addition of 3 to benzene followed by deprotonation to give 1 must be competitive with that for isomerization of 3 to the secondary ion 4, which is the precursor of 2. In mathematical terms, fc2[ ][C6H6] must be similar to since these expressions measure the rates of formation of 1 and 2, respectively. 

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