title: Concurrent induction of two chiral centers from symmetrical 3, 4-disubstituted and 3,3,4-trisubstituted 4-pentenals using Rh-catalyzed asymmetric cyclizations
abstract: Asymmetric cyclization of symmetrical 3,4-disubstituted and 3,3, 4-trisubstituted 4-pentenals was studied using Rh-complexes with chiral ligands. The cyclization of symmetrical 4-pentenals 4a,b by a neutral Rh[(R)-BINAP]Cl afforded cis-3,4-disubstituted (4R)-cyclopentanones 9a,b of >95% ee in 25-31% yields; on the other hand, the cyclization of 4a-c by a cationic Rh[(R)-BINAP]ClO(4) afforded trans-3,4-disubstituted (4S)-cyclopentanones 10a-c of >95% ee in 70-81% yields. All stereoisomers could be stereoselectively made by the selection of a neutral or cationic Rh-complex, and (R)- or (S)-BINAP ligand. The Rh-catalyzed cyclization could be applied to the construction of cyclopentanones 17 and 18 bearing a chiral quaternary carbon. The cyclization by the cationic Rh[(R)-BINAP]ClO(4) afforded the optically active trans-3,3, 4-trisubstituted cyclopentanones 18a-c of 92-95% ee in 75-83% yields. The catalytic cycle was also studied by using deuterium aldehyde, and the tentative mechanisms of the enantio- and diastereoselection were proposed.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.initials: M
authors.lastname: Tanaka
authors.initials: M
authors.lastname: Imai
authors.initials: M
authors.lastname: Fujio
authors.initials: E
authors.lastname: Sakamoto
authors.initials: M
authors.lastname: Takahashi
authors.initials: Y
authors.lastname: Eto-Kato
authors.initials: XM
authors.lastname: Wu
authors.initials: K
authors.lastname: Funakoshi
authors.initials: K
authors.lastname: Sakai
authors.initials: H
authors.lastname: Suemune