Insight into the Rh-catalyzed cyclization of dissymmetrically racemic(+-)-3,4-disubstituted 4-pentenal:regio-,diastereo-,enantioselectivity,and kinetic resolution

摘要

Rh-Catalyzed cyclization was applied for the kinetic resolution of dissymmetrical(+-)-3-(1-methylvinyl)-4-phenylpent-4-enal.The cyclization by a chiral neutral Rh[(S)-BINAP]Cl afforded a mixture of 3,4-cis-4-emthylcyclopentanone(>95%ee,19% yield),3,4-trans-4-methylcyclopentanone,and 3,4-cis-4-phenylcyclopentanone(>95%ee,21% yield).The cyclizatio by a cationic Rh[(R)-BINAP]-ClO_4 afforded a mixture of 3,4-trans-4-methylcyclopentanone(>95% ee,36% yield),3,4-cis-4-emthyl-,and 3,4-trans-4-phenylcyclopentanone,accompanied with recovery of the starting meterial (-)-4-pentenal (54% ee,34%yield),and by a cationic Rh[(S)-BINAP]ClO_4 afforded the corresponding enantiomers.The course of the cyclization and the stereochemistry of products are discussed based on the plausible acyl-hydride rhodium intermediates.