REACTIVITY OF 2-METHYLENE-1,3-DICARBONYL COMPOUNDS - STEREOSELECTIVE AND ASYMMETRIC DIELS-ALDER REACTIONS

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.