ASYMMETRIC MICHAEL ADDITION OF 2-TRIMETHYLSILYLOXYFURAN TO CHIRAL NAPHTHOQUINONES

Asymmetric Michael reactions of 1,4-naphthoquinones bearing a chiral a uxiliary at C-2 1-4 with 2-trimethylsilyloxyfuran using various Lewis acids afforded the corresponding furofuran adducts 5-12. Moderate leve ls of diastereomeric excess were obtained using (R)-pantolactone, (S)- N-methyl-2-hydroxysuccinimide and (R)-(+)-4-benzyl-2-oxazolidinone as chiral auxiliaries. Low asymmetric induction was achieved using a camp horsultam auxiliary. X-Ray crystallographic analysis of the pantolacto ne adduct enabled determination of the absolute stereochemistry of all adducts obtained. Evidence that the TMS-furan addition occurs via a M ichael reaction rather than a Diels-Alder cycloaddition is provided. ( C) 1998 Elsevier Science Ltd. All rights reserved.