Friedel-Crafts catalyst aliphatic

G-5 Aliphatic Petroleum Resins. Carbocationic polymerization of C-5 feedstreams has been accomptished with various Friedel-Crafts catalyst systems. Table 3 compares the efficiencies of selected Lewis acids ia the polymerization of a typical C-5 stream containing 43 wt % C-5—C-6 diolefias and 47 wt % C-5—C-6 olefins (20). Based on weight percent yield of resia at equimolar coaceatratioas of catalyst (5.62 mmol/100 g), efficieacy follows AICI3 AlBr3 > BF3etherate-H20 > TiCfy > SnCl. The most commonly used catalyst in petroleum resin synthesis is AlCl. ... 

Ai lepiesents an aiyl group. Diaiyl products are obtained after long reaction times. Other Friedel-Crafts catalysts, eg, ZnCl2, FeCl2, FIF, and BF, can also be used. In most cases, stoichiometric amounts of the catalyst ate requited. Flowever, strong complexation of the phosphine by the catalyst necessitates separation by vacuum distillation, hydrolysis, or addition of reagents such as POCl to form more stable aluminum chloride complexes. Whereas yields up to 70—80% are possible for some aryl derivatives, yields of aliphatic derivatives are generally much less (19). 

As films are used e.g. the polymerization product of ethylbenzene and divinylbenzene (33) the copolymer of styrene and butadiene (755) the copolymer of styrene and butadiene mixed with polyethylene (157) a vulcanized or cyclized copolymer of an aromatic vinylcompound and an aliphatic conjugated polyene (2). As a crack resisting matrix is mentioned the copolymer of styrene, divinylbenzene and butadiene with e.g. dioctylphthalate as a plasticizer (176). Other examples are the copolymers of unsaturated aromatic compounds and unsaturated aliphatic compounds (77) and the reaction products of polyolefines and partially polymerized styrene (174). Primary groups can be introduced also with the help of Friedel-Crafts catalyst. Ts. Kuwata and co-workers treated a film of a copolymer of styrene and butadiene with an aluminium-ether complex and ethylenedichloride (79). Afterwards they allowed the film to react with trimethylamine. Another technique is the grafting of e.g. a polyethylene film with styrene (28). 

The substitution of the hydrogen in the aliphatic side-chain by chlorine occurs in as a radical chain mechanism. In industrial chlorinations the formation of chlorine radicals is achieved either by irradiation (ultraviolet light, beta-radiation), or by the use of elevated temperature (100 - 200 °C). The reactants must be free of dissolved iron salts (build-up of Friedel-Crafts-catalysts), oxygen (radical scavenger), and water (build-up of hydrochloric acid). 

Acylation of both aromatic and aliphatic compounds can be carried out with relative ease using acyl halides, acid anhydrides, ketenes, nitriles, amides, acids and esters in the presence of Friedel-Craft catalysts to give ketones. Similar substitution reactions with formic acid derivatives are therefore expected to yield the appropriate aldehydes. However, since the anhydride and acyl halides of formic acid, with the exception of formyl fluoride, are either not known or are not sufficiently stable to be used in Friedel-Crafts type acylation reactions, this objective cannot be fully realized. Table 1.1 compares the main ketone syntheses (based on acylating reagents) with the corresponding aldehyde syntheses (based on formylating reagents). 

Aliphatic Aldehyde Syntheses. Friedel-Crafts-type aUphatic aldehyde syntheses are considerably rarer than those of aromatic aldehydes. However, the hydroformylation reaction of olefins (185) and the related oxo synthesis are effected by strong acid catalysts, eg, tetracarbonylhydrocobalt, HCo(CO)4 (see Oxo process). 

Alkenes can be acylated with an acyl halide and a Lewis acid catalyst in what is essentially a Friedel-Crafts reaction at an aliphatic carbon. ° The product can arise by two paths. The initial attack is by the acyl cation RCO (or by the acyl halide free or complexed see 11-14) at the double bond to give a carbocation ... 

A1C13 is the strongest and most frequently used Lewis acid catalyst in aliphatic Friedel-Crafts acylations usually applied with acid chlorides, whereas ZnCl2 is... 

Fries rearrangement—that is, the transformation of phenolic esters to isomeric hydroxyphenyl ketones—is related to Friedel-Crafts acylations.392,393 Olah et al.394 have found a convenient way to perform the Fries rearrangement of a variety of substituted phenolic esters in the presence of Nafion-H in nitrobenzene as solvent [Eq. (5.153)]. A catalytic amount of Nafion-H is satisfactory, and the catalyst can be recycled. In contrast, Nafion-silica nanocomposites, in general, exhibit low activities in the Fries rearrangement of phenyl acetate to yield isomeric hydroxyacetophe-nones.239,395 In a recent study, BF3-H20 was found to be highly efficient under mild conditions (80°C, 1 h) to transform phenolic esters of aliphatic and aromatic carboxylic acids to ketones (71-99% yields).396 In most cases the para-hydroxyphenyl isomers are formed with high (up to 94%) selectivity. 

Jorgensen and co-workers employed chiral bis-sulfonamide catalyst 27, a proven ligand for metal-based asymmetric catalysis, for the Friedel-Crafts alkylations of N-methylindoles (24) using -substituted nitroolefins [52]. Using optimized conditions, 2 mol% 27 gave the desired indole alkylation products of substituted aryl and heteroaryl nitroolefins in moderate to high yields (20-91%) and moderate enantiopurities (13-63% ee Scheme 6.3). Aliphatic -substitution... 

Friedel-Crafts acylation of 2-benzimidazolone and its 5-methyl derivative with aliphatic acid chlorides occurs at the 5(6)-positions. It is necessary to use a large excess of aluminum chloride catalyst because it binds at the oxygen function <84CHE658>. 

The corresponding ketones 76 can be made by aliphatic Friedel-Crafts reactions between an acid chloride and acetylene using A1C13 as catalyst. Under these conditions chloride adds to the acetylenic ketone to give the P-chloroenone 77 directly. These compounds are converted into the sulfides 78 by conjugate substitution13 and are used as vinyl cation equivalents in the next section. 

Aluminum chloride is the most fiequently used Lewis acid in aliphatic Friedel-Crafts acylations, and is one of the strongest. Its complexes with acyl halides are strong, producing very active acylating species. Titanium and tin tetrachlorides also find use as catalysts, and are powerful enough to induce reaction at low temperatures. 

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