Catalysis aluminium complex

Vincens, V., Le Borgne, A. and Spassky, N., Oligomerization of Oxiranes with Aluminium Complexes as Initiators , in Catalysis in Polymer Synthesis, ACS Symp. Ser. 496, Washington, DC, 1992, pp. 205-214. 

The best results before organic catalysis were with amides 125 and Lewis acid catalysts based on Al, Ti, and Cu(II) with C2-symmetric ligands. Corey s aluminium complex 127 derived from the diamine whose resolution was described in chapter 22 works well with substituted cyclo-pentadienes 124 and the product 126 was used in prostaglandin synthesis.28 There are three aspects of stereoselectivity in this reaction which diastereotopic face of 124 is attacked (that anti to the CH2OBn group), is the product exo or endo (endo) and which endo product is formed, 126 or its enantiomer Only for the last question is asymmetric catalysis necessary, though Lewis acid catalysis of any kind enhances endo/exo selectivity. 

In the catalytic enantioselective Strecker reaction, chiral aluminium complexes, especially aluminium-salen-based catalysts and aluminium-binaphthol-based catalysts have been widely used, and great achievements have been obtained. In 2010, the Li group reported a highly enantioselective Strecker reaction of achiral IV-phosphonyl imines by using primary free L-phenglycine 42 as the catalyst and diethylaluminium cyanide as the nucleophile. This work also presented the novel use of nonvolatile and inexpensive diethylaluminium cyanide in asymmetric catalysis (Scheme 19.51). ... 

The detail of the structure of the polymerisation centre present in suppported Ziegler-Natta catalysts for a-olefin polymerisation has been the subject of much research effort (e.g./-/2) The catalyst consists of a solid catalyst MgC /TiC /electron donor and a co-catalyst, an aluminium alkyl complexed with an electron donor. Proposed mechanisms for the polymerisation involve a titanium species attached to magnesium chloride with the olefin coordinated to titanium. The detail of the site at which the titanium species is attached is an important area of study in understanding the mechanism of catalysis and several recent papers 10-12) have investigated the surface structure of magnesium chloride and the attachment of TiCl4, in particular the interaction of titanium species with the 100 and 110 planes of a and (3- magnesium chloride. 

In addition to the prolonged lifetime of the complex catalysts, such enhanced yields are also made possible by improved catalyst-hydrocarbon contact. Aluminium chloride is insoluble in hydrocarbons catalysis occurs in this case by surface contact with the solid. While the complex catalysts are also insoluble in hydrocarbons, they are liquids the ease of mixing is therefore greatly facilitated. 

Both anhydrous and hydrated sodium or potassium sulfide in ethanol have been used in the synthesis of thietanes. A common procedure is to use a solution of sodium or potassium hydroxide saturated with hydrogen sulfide. Liquid ammonia has been used as a solvent for the preparation of thietane (32%) from sodium sulfide and 1,3-dibromopropane. Phase-transfer catalysis has been used to good effect.A variation in which l,3-dichloro-3-methylbutane 3 is treated with aluminium chloride and hydrogen sulfide followed by aqueous sodium hydroxide gave 2,2-dimethylthietane 4 in 90% yield. An intermediate aluminium chloride-alkene complex, 5 or 6, was proposed. 

Other fates are possible for the enolate formed in the initial conjugate addition and an obvious possibility is an aldol reaction. With an asymmetric catalyst, the combination of three simple molecules leads to one enantiomer of one diastereoisomer of the tandem Michael-aldol product14 83. The catalyst 84 is based on a BINOL A1 complex (see chapters 25, 26). It can be drawn either as a lithium salt with an aluminium cation or, better, as a lithium aryloxide with a Lewis-acidic aluminium atom. This is better because both basic ArCT and Lewis acidity are necessary for catalysis. 

Hydrolysis of complexes of the type MFe is catalysed not only by acid but also by a series of metal ions. Kinetic data have been obtained for catalysis of hydrolysis of PFe, AsFg", AsFgCOH)- and also of BF4-, by beryllium(ii), aluminium(iii), zirconium(iv), and thorium(rv). Again this may be seen as an extension of studies on cation catalysis of hydrolysis of transition-metal complexes, e.g. the numerous studies of mercury(ii)-catalysed aquations of cobalt(iii)-ammine-halide complexes, or the recent study of metal ion catalysis of chloro(ethylenediaminetriacetato)-cobaltate(m). ... 

The manganese(iii) oxidation of methanoP has been reported. The reaction, which takes place via an inner-sphere mechanism, is first order in both oxidant and substrate. The effects of other cations have been examined, catalysis by cobalt(n) and aluminium(iii) being exhibited with retardation of the reaction specific to manganese(n). Inner-sphere complexes have also been detected in the corresponding reaction with pinacol in acidic perchlorate media. The oxidation of a-hydroxyisobutyric acid, however,... 

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