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  • Title: Application of Rh-catalyzed cyclization to the formation of a chiral quaternary carbon.
    Author: Takahashi M, Tanaka M, Sakamoto E, Imai M, Funakoshi K, Sakai K, Suemune H.
    Journal: Chem Pharm Bull (Tokyo); 2000 Nov; 48(11):1822-5. PubMed ID: 11086927.
    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.
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