Organoaluminum complexes

Araki,T, Oguni,N, Aoyagi.T. A new series of organoaluminum complexes and their use as highly stereospecific catalysts for the polymerization of acetaldehyde. J. Polymer Sd. B4, 97 (1966). 

Yamamoto reported an aluminum complex-catalyzed asymmetric hetero Diels-Alder reaction (Scheme 9.19) [36]. Chiral ketone d-3-bromocamphor discriminates (R)-organoaluminum complex 34 from (S)-complex 34 by diastereoselective complexation, whereas the remaining (S)-isomer 34 catalyzes the enantioselective cycloaddition of an activated diene to benzaldehyde. 

Asymmetric ene reactions.1 The reaction of alkenes with prochiral, electron-deficient aldehydes can furnish optically active homoallylic alcohols when catalyzed by ( + )- or (-)-l and in the presence of activated 4-A molecular sieves. In the absence of the sieves, a stoichiometric amount of the organoaluminum complex is essential for high chemical and optical yields. 

A number of coupling reactions are possible with the organoaluminum complexes, as shown in equations (III) , (IV), and (V). ... 

Direct and selective conversion of esters into ketones, a fundamental reaction but difficult to achieve, has been accomplished by Ahn and co-workers [59] by use of organoaluminum-diamine complexes. The reaction of methyl benzoate with MesAl (3.1 equiv.) and A V -dimethylethylenediamine (DMEDA) (1.1 equiv.) in toluene under reflux followed by an aqueous work-up produced only acetophenone in almost quantitative yield (98 %). Notably, ketones and even aldehydes survive under the reaction conditions. A mechanistic investigation established that the conversion proceeds through transamidation and subsequent intramolecular nucleophilic attack mediated by organoaluminum complexes this provides an explanation of the need for 3 equiv. MesAl for the fast reaction (Sch. 35). 

A highly effective catalytic method for alkynylation of epoxides has recently been reported this involves the chelation-controlled alkylation of hetero-substituted epoxides with Mc3A1 and alkynyllithiums via pentacoordinate organoaluminum complexes [82]. For instance, reaction of epoxy ether, (l-benzyloxy)-3-butene oxide (75) in toluene with PhC = CLi under the influence of catalytic MesAl (10 mol%) proceeded smoothly at 0 °C for 5 h to furnish the alkynylation product l-(benzyloxy)-6-phenylhex-5-yn-3-ol (76) in 76 % yield. The yield of the product was very low (3 %) without MeaAl as catalyst under similar conditions. This is the first catalytic procedure for amphiphilic alkylation of epoxides. The participation of pentacoordinate MesAl complexes of epoxy ethers of type 75 is emphasized by comparing the reactivity with the corresponding simple epoxide, 5-phenyl-l-pentene oxide (77), which was not susceptible to nucleophilic attack of PhC s CLi with catalytic Me3Al under similar conditions (Sch. 50). 

This catalytic system was successfully applied to the alkynylation of tosyl aziridine with adjacent ether functionality this should provide a promising method for the synthesis of amino alcohols. Treatment of tosyl aziridine 81 with PhC CLi in the presence of catalytic Mc3Al in toluene at 0 °C for 5 h gave rise to the corresponding alkynylation product 82 in 66 % yield (Sch. 53), whereas reaction in the absence of Me3Al proceeded sluggishly under similar reaction conditions (7 % yield). The control experiment with simple aziridine 83, in which addition of catalytic McaAl had almost no influence on the reaction rate, supports the proposed catalytic cycle its efficacy is based on the formation of the pentacoordinate organoaluminum complex. 

The first production plant in the world for electrolytic aluminum coating from organoaluminum complexes was put into operation by SEDEC (Berlin) in 1983. In order to shorten the processing time required by the HGA plant, this unit was designed as a rectangular cell. The production cell has an electrolyte volume of 15,000 L. The capacity of this automatic aluminum plating unit amounts to 32 m /h, with a layer thickness of 10 pm. Articles mounted on 32 frames, each 500 X 1000 mm in size, can be simultaneously coated. Fig. 19 shows the electrolysis... 

B.B. Snider and FI. Yamamoto respectively developed formaldehyde-organoaluminum complex as formaldehyde source in several reactions, (a) Snider, B.B. Rodini, D.J. Kirk, T.C. Cordova. R. 

Snider BB and Yamamoto K respectively developed formaldehyde-organoaluminum complex as formaldehyde source in several reactions (a) Snider BB, Rodini DJ, Kirk TC, Cordova R (1982) J Am Chem Soc 104 555 (b) Snider BB (1989) In Schinzer D (ed) Selectivities in Lewis acid promoted reactions. Kluwer Academic Publishers, London, pp 147-167 (c) Maruoka K, Conception AB, Hirayama N, Yamamoto H (1990) J Am Chem Soc 112 7422 (d) Maruoka K, Concepcion AB, Murase N, Oishi M, Yamamoto H (1993) J Am Chem Soc 115 3943... 

Recently, numerous methods for the preparation of organoaluminum complexes have been published in which interconversion of the complex... 

Exchange Reactions Involving Various Saltlike Organoaluminum Complex Compounds... 

The [24-2]cycloaddition of ketene with j tion by chiral organoaluminum complexes, sulfonamides (3). ... 

Organoaluminum compounds are sufficiently Lewis acidic to interact with weak Lewis bases such as alkyl halides, although stable and thoroughly characterized examples are few. Instead, many trialkylaluminum compounds react violently with halogenated solvents. The adduct MeaSiF-AlEta, with weak F- -Al donation, has been characterized by NMR spectroscopy and this adduct is thermally stable to 30 °C. Structurally characterized examples of aryl halides forming dative bonds to aluminum have been reported for cationic organoaluminum complexes as will be discussed later. 

Figure 5. Optimized structures of the organoaluminum complexes Ca/hsxatriene (left) and Ca/benzene (right). Ali distances in (A. ...

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