gures/ol8002282n00001.gif" ALIGN="left" HSPACE=5> |
An efficient catalytic asymmetric hetero-Diels-Alder reaction of Brassard's diene with aliphatic aldehydes was reported. The catalyst, whichwas generated from (
R)-BINOL, Ti(
i-PrO)
4, and 4-picolyl chloride hydrochloride, promoted the reaction smoothly to afford the corresponding
,
-unsaturated
-lactone derivatives in moderate-to-good yields (46-79%) with high enantioselectivities (up to 88% ee). Natural products(
R)-(+)-kavain (70% ee, >99% ee after single recrystallization) and (
S)-(+)-dihydrokavain (84% ee) were also prepared in one step by using thismethodology.