Friedel-Crafts alkylation polymers

As catalysts Lewis acids such as AICI3, TiCU, SbFs, BF3, ZnCh or FeCl3 are used. Protic acids such as FI2SO4 or FIF are also used, especially for reaction with alkenes or alcohols. Recent developments include the use of acidic polymer resins, e.g. Nafion-Fl, as catalysts for Friedel-Crafts alkylations and the use of asymmetric catalysts. ... 

Mohanty et al. were the first to introduce pendent r-butyl groups in die polymer backbones. The resulting material was quite soluble in aprotic dipolar solvents.83 The PEEK precursors were prepared under a mild reaction condition at 170°C. The polymer precursor can be converted to PEEK in die presence of Lewis acid catalyst A1C13 via a retro Friedel-Crafts alkylation. Approximately 50% of die rerr-butyl substitutes were removed due to die insolubility of the product in die solvent used. Later, Risse et al. showed diat complete cleavage of f< rf-butyl substitutes could be achieved using a strong Lewis acid CF3SO3H as both die catalyst and the reaction medium (Scheme 6.15).84... 

Aromatic compounds, 13 108-109 13 680. See also Aromatics acylation of, 12 173-181 amination of, 12 184 arylation of, 12 170-171 Cycloalkylation of, 12 169 in diesel fuel, 12 425 formylation of, 12 178 Friedel-Crafts acylation of, 12 174 Friedel-Crafts alkylation of, 12 164 nitration of, 12 182-183 oxidative coupling of, 19 654 sulfonation of, 12 181 sulfonation reagents for, 23 521-524 Aromatic-containing polymers, sulfonation of, 23 535-536... 

The topics analysed here include reversible termination and the formation of p-tolyl end-groups on polystyrenes made in toluene. For unknown reasons, most authors have very largely ignored this Friedel-Crafts alkylation, which in a polymer context is a transfer reaction. It was unfortunately termed molecular termination by Overberger and was explored by his and Smets groups. 

Beside borosilicate and fused silica capillaries, PS/DVB monoliths have been fabricated within the confines of steel and PEEK tubings [52]. In order to increase the hydrophobic character of the supports, a Friedel-Crafts alkylation reaction was used for the attachment of Cig-moieties to the polymer surface. The derivatized material was demonstrated to be more retentive and to provide more efficient peptide separations compared with the original, nonderivatized monolith. 

Friedel-Crafts alkylation of benzo[6]thiophene has received little attention. The published results, which deserve reexamination, indicate that exclusive 3-substitution occurs in some cases, whereas in others, 2-substitution predominates. Benzo[6]thiophene is alkylated with isopropyl chloride, isopropanol, or propene in the presence of various acid catalysts under a variety of reaction conditions to give a mixture of 2- and 3-isopropylbenzo[6]thiophene in which the 2-isomer predominates (78-92%).358 410 In contrast, alkylation with isobutene in the presence of either 80% sulfuric acid415 or 100% phosphoric acid416 is said to afford exclusively 3-/er<-butylbenzo[6]thiophene in yields of 100 and 75%, respectively. In neither case was the structure of the product rigorously confirmed. Likewise, 3-Jeri-amylbenzo [63-thiophene is the exclusive product of alkylation with tert-amyl alcohol in the presence of stannic chloride414 alkylation with pent-l-ene, hex-l-ene, and a Ci8 propylene polymer is also claimed to give... 

Bakelite, the first synthetic polymer, is an example of a thermoset polymer. It is prepared by the polymerization of phenol and formaldehyde in the presence of ail acid. Carbocations produced by protonation of formaldehyde bond to the ortho and para positions of the highly reactive phenol molecules in a Friedel-Crafts alkylation reaction. The benzylic alcohols that are produced in this step react to produce carbocations that then alkylate additional phenol molecules. A mechanism for the first few steps of this polymerization process is shown in Figure 24.4. 

Ortho-substitution is also used to prepare branched liquid crystalline polyethers of 3,4-(di-n-alkoxy)benzyI derivatives in which the cyclotetraver-atrylene disc-like mesogen is formed in situ during the polymer-forming Friedel-Crafts alkylation, [30-32],... 

We have omitted from the above brief survQ tho studies dealing with the cationic grafting of a polymer onto another since these Friedel-Crafts alkylation reactions, although proceeding via carbenium ion intermediates, do not initiate any polymerisation and fall therefore outside the realm of the present review. Kennedy has recently summarised this type of work ° ... 

Shape selectivity has also been demonstrated within FAU zeolites. For example, meta selectivity was observed for the NaY-mediated Friedel Crafts alkylation of benzyl chloride (BnCl) with itself. In addition to polymer inhibition, the FAU zeolite favored the formation of the banana-shaped l-(chloromethyl)-3-(phenyl-methyljbenzene (m-3) regioisomer (Equation (4)) 53... 

The Second polymeric substrate with a longer chain length was prepared by the Friedel-Crafts alkylation of Bio-Bead SXl and AICI3 with 4-chlorobutyric acid in nitrobenzene for 5 hours at 80 C. The resin was washed with AcOH, 61 HCl-dioxane (1 1), HaOrdioxane (1 1), dioxane and CH2CI2. Titration was effected as stated earlier 0.9 mequiv of carboxyl per gram of polymer was determined. 

Other o-nitrophenol-containing resins have been prepared with the aim of increasing the distance between the reactive center and the macromolecular backbone, which should accelerate the active ester formation by achieving an easier approach of the reagents. Thus, the Friedel-Crafts alkylation of styrene-divinyl-benzene copolymer with 4-hydroxy-3-nitrobenzyl chloride promoted by aluminium trichloride gave 4-hydroxy-3-nitrobenzylated polystyrene (70) (approximately 30% of the aromatic rings of the polymer were substituted according to elemental... 

Friedel-Crafts alkylation of lib with 1,3-di-isopropenylbenzene was used to prepare an oligomeric stabilizer for diene based polymers. SBR may serve as a co-reactant in the alkylation of the pendant phenyl group with DHQ and yields... 

Alone or complexed to MeN02 or Ph2CO as Friedel-Crafts alkylation catalyst to functionalize polystyrene resin with iV-chloromethylphthalimide to produce aminomethylated polymer (for solid phase peptide synthesis), FeCls performs well."... 

A new technique was developed recently, by introducing cationic to anionic transformation. A living carbocationic polymerization of isobutylene is carried out first. After it is complete, the ends of the chains are transformed quantitatively to polymerization-active anions. The additional blocks are then built by an anionic polymerization. A triblock polymer of poly(methyl methacrylate)-polyisobutylene-poly(methyl methacrylate) can thus be formed. The transformation involves several steps. In the first, a compound like toluene is Friedel-Craft alkylated by a,6t>"di-rerr-chloro-polyisobutylene. The ditolylpolyisobutylene which forms is lithiated in step two to form a,cu-dibenzyllithium polyisobutylene. It is then reacted with 1,1-diphenylethylene to give the corresponding dianion. After cooling to -78 °C and dilution, methyl methacrylate monomer is introduced for the second polymerization in step three. 

Friedel-Crafts alkylation of aromatics with CMF to give rise to benzyl derivatives 34a and 34b was first demonstrated in 1909 [139] and reprised by Rauchfuss and co-worker in 2013 to provide feedstock 34c for hydrodeoxygenation to diesel-range hydrocarlxMis [140]. Similar reactions have been used to produce a range of novel monomers and polymers. Thus, Szmant et al. reported as far back as 1981 the application of CMF to the synthesis of polymeric building blocks 35 and 36, among others (Fig. 1) [141]. 

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