Aluminium diamine complex

The first organoaluminium complex that catalysed a Diels Alder reaction was formed from menthol and ethylaluminium dichloride. This finding was complemented by work of Corey who showed that the aluminium diamine complex (49) was effective for controlling the stereochemistry of Diels-Alder reactions involving cyclopentadiene and acryloyl and crotonyl amides (e.g. 

Several new chiral modifications of lithium aluminium hydride have been reported, including those formed by reaction with chiral secondary benzylamines (14), with diols such as (15) derived from D-mannitol, or with terpenic glycols such as (16). These complexes reduce phenyl alkyl ketones to optically active phenyl carbinols, and enantiomeric excesses of up to 50% have been observed in the case of reagents derived from (14). However, in the diol complexes, believed to have structures of the type shown in (17), lower chiral selectivity is observed, e.g. up to ca. 12% in the case of (15), or up to an optical yield of 30% with an ethanol-modified complex of (16). Better results have been reported with the chiral diamine complex (18), derived originally from L-proline, which reduces acetophenone in 92% optical yield. Asymmetric induction with reagents in this class (i.e. derivatives of lithium aluminium hydride) is usually low in the reduction of aliphatic ketones, but a complex of UAIH4 and the amino-alcohol (19) has been shown to reduce... 

Vickery and Vickery [9] have investigated the interference by aluminium and iron in the ion-selective electrode method for the determination of fluoride in plant extracts. They demonstrated that plant ashes may contain sufficient of these two elements to seriously interfere in the determination of fluoride when using the fluoride-selective electrode. In the presence of these metals, the known additions method gives erroneous results, as did that involving the attempted formation of complexes with ethylene diamine tetraacetic acid (disodium salt) or 1,2-cyclohexylenedinitrilotetraacetic acid. 

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. 

The most effective chiral ligands out of the dozens tried are bidentate, i.e. those which can form a cyclic complex around the aluminium atom. The proline-based diamine (85) of Mukaiyama is a good example. 

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