Application of Rh-catalyzed cyclization to the formation of a chiral quaternary carbon

Rh-Catalyzed cyclization was applied to the formation of a chiral quaternar y carbon. It has become clear that the Rh-complex can discriminate between isopropenyl and 2-isopentenyl (or isopentyl) substituents, and the cyclizat ion 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)(3)Cl afforded 3,3,4-cis-trisubstituted cyclopen tanones (+/-)-7a,b in 86-96%, and the cyclization by a cationic Rh[(R)-BINA P]ClO4 afforded 3,3,4-cis-trisubstituted cyclopentanones (-)-8a, b of 82-86 % ee in 88-98% yields, The mechanism of stereoselection bg Rh-complexes is also discussed.