Aluminum phenoxide

The most important appHcation of metal alkoxides in reactions of the Friedel-Crafts type is that of aluminum phenoxide as a catalyst in phenol alkylation (205). Phenol is sufficientiy acidic to react with aluminum with the formation of (CgH O)2Al. Aluminum phenoxide, when dissolved in phenol, greatiy increases the acidic strength. It is beheved that, similar to alkoxoacids (206) an aluminum phenoxoacid is formed, which is a strong conjugate acid of the type HAl(OCgH )4. This acid is then the catalyticaHy active species (see Alkoxides, metal). 

Other Compounds. Primary and secondary amines add 1,4- to isoprene (75). For example, dimetbylamine in ben2ene reacts with isoprene in the presence of sodium or potassium to form dimetby1(3-metby1-2-buteny1)amine. Similar results are obtained with diethylamine, pyrroHdine, and piperidine. Under the same conditions, aniline and /V-metbylaniline do not react. Isoprene reacts with phenol in the presence of aluminum phenoxide (76) or concentrated phosphoric acid (77) to give complex products. 

The choice of catalyst is based primarily on economic effects and product purity requirements. More recentiy, the handling of waste associated with the choice of catalyst has become an important factor in the economic evaluation. Catalysts that produce less waste and more easily handled waste by-products are strongly preferred by alkylphenol producers. Some commonly used catalysts are sulfuric acid, boron trifluoride, aluminum phenoxide, methanesulfonic acid, toluene—xylene sulfonic acid, cationic-exchange resin, acidic clays, and modified zeoHtes. 

ButylatedPhenols and Cresols. Butylated phenols and cresols, used primarily as oxidation inhibitors and chain terrninators, are manufactured by direct alkylation of the phenol using a wide variety of conditions and acid catalysts, including sulfuric acid, -toluenesulfonic acid, and sulfonic acid ion-exchange resins (110,111). By use of a small amount of catalyst and short residence times, the first-formed, ortho-alkylated products can be made to predominate. Eor the preparation of the 2,6-substituted products, aluminum phenoxides generated in situ from the phenol being alkylated are used as catalyst. Reaction conditions are controlled to minimise formation of the thermodynamically favored 4-substituted products (see Alkylphenols). The most commonly used is -/ fZ-butylphenol [98-54-4] for manufacture of phenoHc resins. The tert-huty group leaves only two rather than three active sites for condensation with formaldehyde and thus modifies the characteristics of the resin. 

Commercially available aluminum isopropoxide, aluminum butoxide and aluminum phenoxide are generally of sufficient purity for use in Oppenauer oxidations provided that these reagents are obtained from a freshly opened container and are freely soluble in the reaction solvent. The reagents may be conveniently stored as 20-40 per cent solutions in anhydrous benzene or toluene. 

Phenol-, phenol, phenol-, phenolic (in com-bination with the name of a metal) phenoxide (or phenolate) of, as Phenolaluminium, aluminum phenoxide, aluminum phenolate, phenolartig, a. of the nature of or like a phenol, phenoloid. 

Yasuda, T., Aida, T., and Inoue, S., Reactivity of (por-phinato)aluminum phenoxide and alkoxide as active initiators for polymerization of epoxide and lactone. Bull. Chem. Soc. Jap.. 9, 3931-3934, 1986. 

To vessel with flushed nitrogen at an elevated temperature to 165°C 490 parts of phenol was placed, then 4.5 parts of aluminum turnings were added in small increments.The reaction mixture was accompanied by evolution of hydrogen for 15 min, then the mixture was allowed to cool to about 60°C and agitation discontinued. Aluminum phenoxide catalyst mixture was ready. 

The opposite sense of diastereoselectivity has been observed frequently, giving, for example, alcohol 29 or 30 exclusively in the MAD/MeM (M = Li, MgX) system (Equations (57) and (58)).232,233 For the deprotonation events of the ct-proton of ketones, a monomer pathway was proposed (Figure 39),234 but the open dimer mechanism cannot be ruled out entirely. The relatively bulky aluminum phenoxide may be involved in the monomer pathway due to its... 

Among metal alkoxides, aluminum phenoxide is one of the most important Friedel-Crafts catalysts in the alkylation of phenol. ... 

Modifications of these resins are also known. For example, aluminum phenoxide bonded to an acidic E)owex resin has been used as a heterogeneous catalyst for alkylation and transalkylation of phenols and polysubstituted phenols, respectively. ... 

Alkylation of phenols with isobutene has also been accomplished using a heterogeneous catalyst system comprising an aluminum phenoxide bonded to a solid polymeric resin having acidic functional... 

Whereas a lower temperature is essential to mediate deprotonation with DATMP, diisobutyl aluminum phenoxide requires quite a high temperature (THF, reflux) to generate the aluminum enolates, with the aid of a shght excess of pyridine (Scheme 6.24) [44], Self aldol condensation of ketone 47 proceeded with acceptable yield under these conditions. An efficient synfhesis of tfl-muscone was achieved by way of an intramolecular aldol reaction by use of these reagents. 

Tsuji and coworkers have developed diisobutylaluminum phenoxide-pyridine as an effective aldol condensation catalyst and applied it to the macrocyclization of 2,15-hexadecanedione (equation 132). Addition of the diketone at high dilution to a solution of the catalyst in hexane provides a mixture of cis and trans isomers of the and A enones. Catalytic hydrogenation of the mixture affords ( )-muscone. The authors explain the regioselectivity of the process by assuming that the aluminum phenoxide functions as a Lewis acid, coordinating to the carbonyl group. Pyridine functions as a base to remove a proton from the less hindered methyl group. 

Aluminum halides have preparative importance, particularly for removal of methyl and ethyl groups it does not attack diaryl ethers. The ether-cleaving action of aluminum chloride was discovered with fission of anisole.23 A crystalline double compound is formed in the reaction and decomposes to alkyl halide and aluminum phenoxide when warmed. 

Isomerization of trisubstituted epoxides. A reversal of relative migratory aptitudes is revealed in the rearrangement induced by SbFj and by the bulky aluminum phenoxide. 

The p-block metal alkoxides construct the second group. Chukicheva et al. have effectively used aluminum phenoxide and isopropoxide for the alkylation of phenol by borneol, 85 and its stereoisomer, iso-borneol, 86 [60]. It was not seen any special chemo- or enantioselectivity with this catalytic systems. 

Aluminum chloride, 60, 61 Diels-Alder catalyst, 144 Friedel-Crafts acylation catalyst, 91-100 MA complex, 212 Aluminum, diethyl chloride, 345 Aluminum oxide, dehydrating catalyst, 87 Aluminum phenoxides, MA polymerization reactant, 273... 

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