title: Application of Rh-catalyzed cyclization to the formation of a chiral quaternary carbon.
abstract: Rh-Catalyzed cyclization was applied to the formation of a chiral quaternary carbon. It has become clear that the Rh-complex can discriminate between isopropenyl and 2-isopentenyl (or isopentyl) substituents, and the cyclization afforded 3,3,4-trisubstituted cyclopentanones with a chiral quaternary carbon in a stereoselective manner. The cyclization of 4-pentenals 6a, b by an achiral neutral Rh(PPh3)3Cl afforded 3,3,4-cis-trisubstituted cyclopentanones (+/-)-7a,b in 86-96%, and the cyclization by a cationic Rh[(R)-BINAP]CIO4 afforded 3,3,4-trans-trisubstituted cyclopentanones (-)-8a, b of 82-86% ee in 88-98% yields. The mechanism of stereoselection by Rh-complexes is also discussed.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: E
authors.initials: E
authors.lastname: Sakamoto
authors.forename: M
authors.initials: M
authors.lastname: Imai
authors.forename: K
authors.initials: K
authors.lastname: Funakoshi
authors.forename: K
authors.initials: K
authors.lastname: Sakai
authors.forename: H
authors.initials: H
authors.lastname: Suemune
mesh_terms: D002384:Catalysis; D003500:Cyclization; D003517:Cyclopentanes / Q000138:chemical synthesis* / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D003517:Cyclopentanes; C007201:cyclopentanone; D012238:Rhodium