Aluminum phenolate

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. 

The metalloporphyrin-initiated polymerizations are accelerated by the presence of steri-cally hindered Lewis acids [Inoue, 2000 Sugimoto and Inoue, 1999]. The Lewis acid coordinates with the oxygen of monomer to weaken the C— O bond and facilitate nucleophilic attack. The Lewis acid must be sterically hindered to prevent its reaction with the propagating center attached to the prophyrin structure. Thus, aluminm ortho-substituted phenolates such as methylaluminum bis(2,6-di-/-butyl-4-methylphenolate) accelerate the polymerization by factors of 102-103 or higher. Less sterically hindered Lewis acids, including the aluminum phenolates without ortho substituents, are much less effective. 

Ballard et al. [64] found that bulky dialkyl aluminum phenolate additives would improve the anionic polymerization of acrylic monomers. They called their method Screened Anionic Polymerization (Scheme 28). 

Selective alkylation of the y position of a,/3-unsaturated esters, aldehydes, or ketones can be achieved if a sterically demanding Lewis acid is used to coordinate to the carbonyl group and inhibit a-alkylation by steric shielding [123, 125, 126] (Scheme 5.11). This method not only results in high regioselectivity but also enables highly stereoselective aldol-type additions to be performed in good yields, even with sensitive substrates, such as a,/3-unsaturated aldehydes [126]. Thus, when two dia-stereotopic y positions are available, the addition of a bulky aluminum phenolate leads to the clean formation of the Z-alkene (second and third examples, Scheme 5.11). 

Controlled ortho alkylation of phenol by 1-hexene to produce the mono- or di-alkylated product has been achieved by using aluminum phenolate as the catsJyst under carefully optimiz reaction conditions. Sterically hindered phenols such as (15) are of particular interest as antioxidants (Scheme 4). 

Among the tertiary-butyl phenols, the o- and p-derivatives and 2,6-di-tert-butylphenol are commerically important. They are used in the production of antioxidants. o-tert-Butylphenol and 2,6-di-tert-butylphenol are produced by alkylation of phenol with isobutene at a reaction temperature of 100 °C in the presence of aluminum phenolate as catalyst. 

The aluminum phenolate complexes 75-86 were prepared by reacting the corresponding phenolate ligand with one equivalent of AlMe in toluene at -20°C (Scheme 6.16). Single crystals of compounds 75 were... 

It is also proposed that analogous compounds be produced by acylation of aluminum phenolates with acid chlorides in the presence of AICI3 [55, 56] ... 

That this concept can work in principle was shown with a few unsaturated ketones in the presence of the bulky aluminum phenolate 337 [123]. 

Very high selectivities were reported for aluminum phenolates of type 215 (R = CH3, C2H5) [68] and with the five-membered acetals 217 even trimethylalu-minum worked with excellent regioselectivity. 

It is known that reaction of metal phenolates with aldehydes or ketones proceeds in regioselective manner to afford ortho-substituted hydroxyalkylation products. Bigi and coworkers reported the chiral examples of this reaction using chiral aluminum Lewis acid prepared in situ from a chiral alcohol and 1 equivalent diethylaluminum chloride. Thus, after treating phenol with the chiral Lewis acid, the resulting aluminum phenolate is reacted with chloral in toluene as shown in Scheme 6.15... 

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