Abstract:
Diels-Alder reactions of 1,4-naphthoquinones bearing a chiral auxiliary at C-2, with cyclopentadiene under Lewis acid conditions afforded the corresponding Diels-Alder. adducts. High levels of diastereomeric excess were obtained using (R)-pantolactone, (S)-N-methyl-2-hydroxysuccinimide and trans-2-phenylcyclohexanol as auxiliaries. Moderate asymmetric induction was achieved using Oppolzer's camphorsultam and (R)-(+)-4-benzyl-2-oxazolidinone as auxiliaries. X-Ray crystallographic analysis of the pantolactone adduct enabled determination of the stereochemistry of all adducts obtained.