Isomerization aluminium chloride

Ionic ring-expansions of 2-substituted thietanes in many cases probably proceed via the ion 106, which can open to a five-membered cyclic cation. The ring-expansion of 74 by such a mechanism has already been discussed in Section The conversion of 2-methylthietane to thiophene and di- and tetrahydro-thiophenes with triphenylmethyl cations, chloranil, and aluminum oxide also may occur via similar ions. 2-Methylthietane also yields 3-butenethiol when heated with alumina. ° The isomerization of hydroxy-benzodihydrothiophenes by aluminium chloride is believed to involve common thietane intermediates that subsequently undergo ring expansion. ... 

A somewhat similar problem is revealed by the acid-catalyzed ring opening of oxetans (104). These are formed by photochemical [2 + 2] additions, and with boron fluoride or aluminium chloride they supply 3-furylcarbinols (105) mixed, however, with the isomeric 2-furylcarbinols (106). With toluene-sulfonic acid only the expected 3-furylcarbinol results, but this is changed into the 2-isomer when treated with one of the Lewis acids. The rearrangement is believed to be effected by dissociation into furan and a carbenium ion... 

Acid catalyzed Cracking alkylation isomerization polymerization Synthetic silica-aluminas, acid-treated montmoril-lonite and other clays aluminium chloride, phosphoric acid... 

Cumene (isopropylbenzene) is presently produced fix>m benzene and propylene using either solid phosphoric acid or anhydrous aluminium chloride or zeolite as catalyst. Large amounts of m- and p- diisopropylbenzenes (DIPB) were produced as by-products from the above processes. Therefore, in order to study the activity of trifluoromediane-sulphonic acid (triflic acid) as catalyst to produce higher yield of cumene from DIPB isomers a series of isomerization and transalkylation reactions, of m- and p-isomers in benzene with different molar ratios 1 1 1, 1 3 1 and 1 6 1 of isomer to benzene to catalyst respectively with each isomer using triflic acid as catalyst, were carried out in liquid phase at room temperature and imder nitrogen atmospheric pressure. 

The cationic cyclization of polyisoprene with acid catalysts is well documented. The same reaction in polybutadienes requires much more severe conditions, higher temperatures and more acidic catalysts, and until recently has received much less attention. A cyclized polymer with a reduction of 35—40% of the initial unsaturation, can be prepared by treating cis-l,4-polybutadiene with an alkyl aluminium chloride-organic halide catalyst in xylene solution at >100 C."- Such polymers, containing polycyclic sequences apparently at random within the chains, have better skid resistance and tensile properties than the parent polymer. Cyclization has been reported to accompany other reactions in polydienes, for example the radiation-induced addition of carbon tetrachloride to 1,2-polybutadiene, and the direct addition of a o j unsaturated carboxylic acids (acrylic and cinnamic) to polydienes and polypentenamers. It is reported that the thermal isomerization of cis-transoidal poly(phenylacetylene) is accompanied by cyclization, and additionally chain scission and aromatization at temperatures >120°C. ... 

The presence of by-products such as 1-chloro-ethyl acetate 3 and a small amoimt of ethyl acetate, suggests that the initial step is an intermolecular hydride ion transfer from cyclohexane or methylcyclopentane towards acetyl chloride-aluminium chloride complex to give 1-methylcyclopentene. From cyclohexane, the cyclohexyl cation isomerizes to 1-methyl-l-cyclopentyl carbenium ion which loses a proton. Then, the 1-chloro-ethylate-aluminium chloride... 

A superacid polymer catalyst was obtained by binding aluminium chloride to sulfonated, macroporous co(polystyrene-DVB) (Magnotta et u/., 1976 Magnotta and Gates, 1977a,b). The catalyst was active in bringing about cracking and isomerization of -hexane at 357 C at atmospheric pressure. 

Also obtained by isomerization of 4-hydroxy-2-methylbenzophenone with aluminium chloride at ISO-IW for 20 min (92%) [132]. 

Also obtained by isomerization of 2-hydroxy-4,6-dimethylbenzophenone in the presence of aluminium chloride between 140° and 180° for several hours (quantitative yield) [724]. There is a methyl group migration. 

Also obtained by isomerization of 2-hydroxy-3,4,6-trimethylacetophenone by heating with aluminium chloride [2965]. 

Also obtained by isomerization of 3-chloro-4-hydroxypropiophenone with aluminium chloride at 180-200° for 1 h (24%) [64, 6468]. 

With isomeric chlorosulfonylbenzoyl chlorides, the reaction with an aromatic substrate and aluminium chloride yields the products of benzoylation and not sulfonylation indicative of the comparatively powerful electrophilic character of the acyl chloride (COCl) group as compared with the chlorosulfonyl (SO2CI) moiety. ... 

The same method has been applied to the spherically symmetrical chloro-substituent through equilibration of (16) and (17) in chloroform in the presence of aluminium chloride at temperatures between 210 and 334 K- Chloride ratios were estimated by g.l.c. after hydrolysis to the alcohols. The derived thermodynamic parameters are AH° = 0.68 0.03 kcal mol and A5° = 2.2 + 0.1 cal deg" mol" and the value of AS may be associated with the value indicated by symmetry considerations (see above) and suggests that for the isomerization (16) (17) AS° should approximate to zero. The present value for AH bears comparison with earlier studies with cyclohexyl chloride thus Reisse obtained —AH equal to 0.52kcalmol" with AS ss 0, and Jensen found — A.ff = 0.53 kcalmol" at — 80°C, both by the reliable peak area method. Calculations indicate —AH° to be 0.56 kcal mol for cyclohexyl chloride. 

Certain refining and petrochemical processes, such as butane isomerization, ethylbenzene production and polybutene production, use aluminium chloride as a catalyst. It is not corrosive if it is kept absolutely dry, otherwise it hydrolyzes to hydrochloric acid. 

The ionic liquid process has a number of advantages over traditional cationic polymerization processes such as the Cosden process, which employs a liquid-phase aluminium(III) chloride catalyst to polymerize butene feedstocks [30]. The separation and removal of the product from the ionic liquid phase as the reaction proceeds allows the polymer to be obtained simply and in a highly pure state. Indeed, the polymer contains so little of the ionic liquid that an aqueous wash step can be dispensed with. This separation also means that further reaction (e.g., isomerization) of the polymer s unsaturated ot-terminus is minimized. In addition to the ease of isolation of the desired product, the ionic liquid is not destroyed by any aqueous washing procedure and so can be reused in subsequent polymerization reactions, resulting in a reduction of operating costs. The ionic liquid technology does not require massive capital investment and is reported to be easily retrofitted to existing Cosden process plants. 

The enantiomerically pure indolizidine (—)-422 has been synthesized starting from L-malic acid diethyl ester 407. The hydroxyl function of L-malic acid diethyl ester 407 has been protected as dihydropyranyl ether 408 with 2/7-dihydropyran and Amberlyst 15 in pentane at room temperature. The diethyl ester 408 was then reduced with lithium aluminium hydride in diethyl ether under reflux and the newly generated hydroxyl functions then protected with mesyl chloride in the presence of triethylamine in dichloromethane at 0°C. This was converted into newly protected pyrroline nitrone 409 in 44% overall yield through a well-established method (Scheme 90). The regio-isomeric 5-pyrroline-iV-oxide 410 formed in 4% overall yield was easily separated by column chromatography <20000L2475>. 

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