Aluminium alkyl substrates

Changing the aluminium alkyl substrate to [AIBU3] allows isolation of the mono-aryloxide derivative. ... 

Low substrate selectivity accompanying high positional selectivity was also found in isopropylation of a range of alkyl and halogenobenzenes by /-propyl bromide or propene in nitromethane, tetramethylene sulphone, sulphur dioxide, or carbon disulphide, as indicated by the relative rates in Table 86. The toluene benzene reactivity ratio was measured under a wide range of conditions, and varied with /-propyl bromide (at 25 °C) from 1.41 (aluminium chloride-sulphur... 

Ligands are not always innocent spectator groups. Cationic j -diiminate alkyl complexes of aluminium, rather than undergoing insertion in the Al-alkyl bond, show attack of the unsaturated substrate (ethene or acetylene) at the ligand (Scheme 1). Surprisingly, the C-C coupling reaction observed with ethene is reversible [42]. 

The evidence for single-electron transfer (SET) in the reactions of lithium aluminium hydride (LAH) with hindered primary alkyl iodides is overwhelming. A study has now shown for the first tune that SET may also be involved in reactions of LAH with unhindered, unsubstituted primary alkyl iodides, the particular substrate studied being 1-iodoctane.98 A theory of the rates of, k 2 reactions and then relation to those of outer-sphere bond-rapture electron transfers has been presented in detail.99 A unified approach is introduced in which there can be a flux density for crossing the transition state, which is either bimodal, one part leading to, k 2 and the other to ET products, or... 

A new method of kinetically controlled generation of the more substituted enolate from an unsymmetrical ketone involves precomplexation of the ketone with aluminium tris(2,6-diphenylphenoxide) (ATPH) at —78°C in toluene, followed by deprotonation with diisopropylamide (LDA) highly regioselective alkylations can then be performed.22 ATPH has also been used, through complexation, as a carbonyl protector of y./)-unsaturated carbonyl substrates during regioselective Michael addition of lithium enolates (including dianions of /i-di carbonyl compounds).23... 

The Barbier reaction is an organic reaction between an alkyl halide and a caiboityl group as an electrophihc substrate in the presence of magnesium, aluminium, zinc, indium, tin or its salts. The reaction product is a primary, secondary or tertiary alcohol. Cf. Grignard reactioa... 

The main limitations of the methodology are the low reactivity observed with ortho-substituted aryl(dimethyl)aluminium reagents and the competing methyl transfer-derived by-product which can be detected. Conversely, the addition of alkyl aluminium reagents to bulky substrates and non-aromatic enones proceeds with very high enantioselectivity, as exemplified in Fig. 6. 

Cerfontain and co-workers suggested that the last step of the reaction, namely proton removal from the complex, was not rate-contributory, but this argument may not be valid since a more recent publication reported a higher value of the kinetic isotope effect (kn kxi) of 1.9-2.5. In sulfonylation using alkylsulfonyl chlorides, there is competing alkylation the latter is enhanced by increasing stability of the alkyl cation. Thus reaction of isopropyl, tertiary butyl and benzylsulfonyl chlorides caused facile alkylation of aromatic substrates in the presence of aluminium chloride in nitromethane at 25 °C. ... 

Extending this reaction to anisole as substrate, no aldehyde product was observed, while extensive de-alkylation of anisole to phenol occurred (Run 3). The important role of an added Bronsted acid (hydrogen fluoride) was confirmed as some aldehyde product was obtained from anisole in the presence of aluminium trichloride together with HF (Run 4). 

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