Application of Rh-catalyzed cyclization to the formation of a chiral quaternary carbon.
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.
Takahashi
M
M
Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Tanaka
M
M
Sakamoto
E
E
Imai
M
M
Funakoshi
K
K
Sakai
K
K
Suemune
H
H
D002384:Catalysis; D003500:Cyclization; D003517:Cyclopentanes / Q000138:chemical synthesis* / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D013237:Stereoisomerism
D003517:Cyclopentanes; C007201:cyclopentanone; D012238:Rhodium