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 (PPh 3) 3 Cl afforded 3, 3, 4-cis-trisubstituted ...
[Jackson, Anthony H.; Supphayen, Damrus Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1987 , p. 277 - 286]