Menthoxyaluminum complexes

The reaction of methacrolein with cyclopentadiene catalyzed by a chiral menthoxyaluminum complex gives adducts with ee s of up to 72%, but with other dienophiles little, if any, induction was noted.9495 A chiral cyclic amido aluminum complex 2 catalyzes the cycloaddition of cyclopentadiene with the fran.v-crotyl derivative 3 in good yield and enantioselectivity (Scheme 26.2).47 This chiral catalyst can also be easily recovered. 

Recently, Diels-Alder reactions between cyclopentadiene and menthoxyaluminum dichloride-acrolein complexes were investigated by means of combined AM1/AM3 calculations and the results were compared to full AMI results211. 

In 1979, Koga and coworkers disclosed the first practical example of a catalytic enantioselective Diels-Alder reaction [44] promoted by a Lewis acidic complex, presumed to be menthoxyaluminum dichloride (1), derived from menthol and ethylaluminum di chloride, whose structure remains undefined [45]. This complex catalyzed the cycloaddition of cyclopentadiene with acrolein, methyl acrylate, and methacrolein with enantioselectivities as high as 72% ee. Oxidation of 2 (predominantly exo) followed by recrystallization actually lowered the ee ... 

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