Aluminum alkoxides, and

Aluminum Alkoxides and the Meerwein-Ponndorf-Verley (MPV) Reduction... 

HI. CHIRAL TRICOORDINATE ALUMINUM REAGENTS A. Aluminum Alkoxides and Derivatives... 

Contrary to the statements of Schulman etal. (81) and Taft et al. (77), there is very little similarity between thermal decomposition of aluminum alkoxides and dehydration of alcohols over aluminas. The thermal decomposition mechanism would not explain the skeletal isomerization occurring during the dehydration of 2-methyl-1-propanol (82). 

It is worth noting that 6,7-dihydro-2(3//)-oxepinone is an unusual lactone because it can be polymerized by two distinct mechanisms ROP of the cyclic esters by aluminum alkoxides, and the ring-opening metathesis polymerization (ROMP) of endocyclic olefins by the Schrock s catalyst (Fig. 28) [121]. 

Polymerizations of six- and four-membered lactones initiated with aluminum porphyrins [(TPP)AlX, 1] proceed via (porphinato)aluminum alkoxide and car-boxylate as the growing species, respectively (Schemes 9 and 10) [74,75] to give polyesters with narrow MWD, although it is well known that the polymerization... 

As indicated in Scheme 27, indoles may be alkylated by their acid-catalyzed reaction with alcohols. Similarly, r-butylation of pyrroles has been effected by the acid-catalyzed reaction with t- butyl acetate (B-77MI30502), and the diarylmethylation of 1-methylpyrrole from the acid-catalyzed reaction with the chromium trichloride complex of the diarylcarbinol has been described (78JA4124). The alkylation of indoles by alcohols in the presence of the aluminum alkoxide and Raney nickel appears to be efficient for the synthesis of 3-substituted indoles, but is less successful in the alkylation of 2-methylindole (79JHC501). The corresponding isopropylation of pyrrole produces 2,5-diisopropylpyrrole and 1-isopropylpyrrolidine, as the major products (79JHC501). 

The two aluminum alkoxide primers on mild steel showed improved adhesion and better resistance to crack propagation with both the thermoplastic polyether-sulfone (PES) and the FM 300U thermoset epoxy adhesive. The titanium alkoxide exhibited the poorest resistance to crack growth, while tetrabutyl orthosilicate showed intermediate behavior between the two aluminum alkoxides and the titanium alkoxide. 

The reaction between an aluminum alkoxide and a ketone can be reversed. This is the basis of the Oppenauer oxidation of a secondary alcohol to the ketone.44 8 The aluminum derivative of the alcohol is prepared by mOans of aluminum t-butoxide and is oxidized with a large excess of acetone or cyclohexanone. 

Besides acid-base chemistry, combining two elements that have similar properties sometimes gives mixed oxides. An example is formation of -Al203-Ga203 by the reaction of aluminum alkoxide and gallium acetylacetonate. A linear relationship between the lattice parameter of the solid solution and the composition of the two starting materials is observed. Since the products have particle sizes in nano scale with quite large surface areas, reaction mechanisms are not yet fully elucidated, but statistical decomposition of the intermediates seems to be most plausible. 

Greco, C. C. and Triplett, K. B., Stabilized liquid aluminum alkoxides and process. US Patent 4,596, 881, June 24,1986. 

Dihydroxyaluminum Sodium Carbonate. [Carbon-aloil — )-G dihydroxyalvminum monosodium salt,-aluminum sodium carbonate hydroxide Kompensan Minicid. CHjAl-NaOs mol wt 144.00. C 8,34%, H 1.40%, Al 18.74%, Na 15.97%, O 55.55%. (H0)2AJ0C02Na. Prepd by the reac. tion between an aluminum alkoxide and NaHCOj in water Grote, U.S. pat. 2,783,179 (1957 to Chattanooga Medicine). 

F.H. Oppenauer Oxidation. In oxidation reactions involving both Cr(VI) and DMSO reagents, the alcohol is converted to a complex in which the a-hydrogen of an alcohol can be removed as an acid. A classical and alternative method for the oxidation of alcohols focuses on the reversible reaction between ketones and metal alkoxides, which is especially effective when the metal is aluminuml34 xhe reversibility of the aluminum alkoxide reaction was first demonstrated by Verley 35 Ponndorf 36 for the reaction of a ketone with an aluminum alkoxide, which led to formation of a new aluminum alkoxide and a new ketone. In... 

Due u> possibility of hydrt>lysis of the halides w ith moisture and relatively slow reactions, synthesis is conducted in an inert atmosphere at elevated temperature (60-1 KfX ). AI-O-AI bonds arc established through decay of the interinediate complex, obtained by reacting aluminum alkoxide and aluminum halide. There are two possible pathways for this reaction a) nucleophilic attack of X on the electrophilic aluminum atom and b) nucleophilic attack of... 

The formation of equilibrium between carbonyl compounds and alcohols is general for this reaction, except for the reduction of trifluoromethyl phenyl ketone. The Meerwein-Ponndorf-Verley reduction has advantages of chemoselectivity, mild reaction conditions, operational simplicity, low cost, and scalability." " In addition, this reaction does not affect other double bonds or triple bonds as well as other enolizable carbonyl compounds (e.g., j8-keto ester, j8-diketone). The catalysts suitable for this reaction include aluminum alkoxide and some transition-metal alkoxides (e.g., zirconium," " iron, ... 

In this work the formation of nickel, cobalt or zinc aluminum hydrotalcite-type coprecipitates upon impregnation of y-alumina at near neutral pH and ambient temperature was confirmed by EXAFS and X-ray dif action. The role of the metal ion concentration in solution on the composition of the supported coprecipitate was studied as well as the influence of the specific surface area of the Y-alumina. The deposition of Co(II), Ni(II) and Zn(II) ions onto a commercial almnina was first investigated. Since the coprecipitation mechanism is likely to be affected both by the impurity level and the thermal pretreatment of the carriers before impregnation, supports of high purity were prepared by hydrolysis of aluminum alkoxides and were submitted to identical pretratments immediately before impregnation. The deposition of Ni(ll) onto these supports was then examined. 

Although aluminum alkoxide- and aluminoxane-based catalysts have shown promise for the isospecific polymerization of epoxides, the poorly defined nature of these species has significantly hampered their use in such polymerizations. Some examples of discrete aluminum complexes have been reported, however. 

As a result, random and/or block copolymers were obtained. Aluminum alkoxides and/or Sn(Oct)2 were usually applied as initiators. In some cases, polymerization of cyclic phosphates was initiated by hydroxy-terminated compounds dodecanol, MPEG, poly-L-lactide (PLLA), and poly(8-caprolactone) (PCL) with Sn(Oct)2 as the catalyst. 

Buzas, A.J. and Schenck Remsen, T.E. (1965) Process for making aluminum alkoxides and separation of impurities therefrom. US Patent 3446828A, filed Feb. 9, 1965 and issued May 27,1969. 

Wengrovius, J.H., Garbauskas, M.F., Williams, EA., Going, R.C., Donahue, P.E., and Smith, J.F. (1986) Aluminum alkoxide chemistry revisited synthesis, structures, and characterization of several aluminum alkoxide and siloxide complexes. /. Am. Chem. Soc., 108, 982-989. 

Heinrich, T., Raether, F., and Marsmarm, H. (1994) Growth and structure of singlephase muUite gels from chelated aluminum alkoxides and alkoxysilanes. /. Non-Cryst. Solids, 168,14-22. 

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