Organoaluminum reagents regioselectivity

Regioselective aldol reactions can be achieved with organoaluminum reagents, and a good example of this application is in the synthesis of muscone (131 Scheme 57). The key step involves macrocycli-... 

For further examples of regioselective rearrangements with organoaluminum reagents see refs 123 and 129. For organoaluminum-promoted rearrangements of allylphenyl ethers see ref 140. 

Schneider et al. reported that the reactivity of trialkylaluminum to epoxides was dramatically enhanced under the influence of catalytic amount of Lewis base additives such as triphenylphosphine (Scheme 7) [21, 22]. The authors explain that the coordination between organoaluminum reagents and Lewis base is important for the breakage of trialkylaluminum dimer and the formation of a monomeric aluminum-phosphine adduct from which the aUcyl substituent easily migrates. In addition, this procedure was found to improve not only chemical yields but also regioselectivity in the reactions of terminal epoxides (Scheme 8) [22]. 

Yamamoto and Maruoka found that organoaluminum amides are highly effective in the Fischer indole synthesis. In particular, DATMP is the reagent of choice for regioselective Fischer indole synthesis [120]. For instance, treatment of the E)-N-methyl-A-phenylhydrazone of 5-methyl-3-heptanone (123) with DATMP affords 3- ec-butyl-2-ethyl-l-methylindole (125) as the sole isolable product its (Z) isomer gives l,3-dimethyl-2-(2-methylbutyl)indole (124) with high regioselectivity under similar reaction conditions, as illustrated in Sch. 84. 

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