M. Yamauchi et al., REACTIVITY OF 2-METHYLENE-1,3-DICARBONYL COMPOUNDS - STEREOSELECTIVE AND ASYMMETRIC DIELS-ALDER REACTIONS, Journal of organic chemistry, 61(8), 1996, pp. 2719-2725
The Diels-Alder reaction of 1,1-dicarbonylethenes 1 with dienes was in
vestigated. The adduct of the reaction of 1, whose two carbonyl groups
were different, with cyclopentadiene showed moderate stereoselectivit
y and this was explained by FMO theory. However, in the Lewis acid-cat
alyzed addition, the reaction proceeded with high stereoselectivity to
give the exo adduct 3x. This might be due to steric hindrance because
the benzene ring cannot orient in the plane of the conjugated system
in the metal-chelated enedione 6. Applying this principle to 5'R)-5-me
thyl-2-(1-methyl-1-phenylethyl)cyclohexyl 2-benzoylacrylate (1d), we a
chieved a diastereomeric Diels-Alder reaction to afford 3x-R, whose st
ructure was confirmed by the X-ray crystal analysis.