Dynamic kinetic resolution via asymmetric conjugate reduction: enantio- and diastereoselective synthesis of 2,4-dialkyl cyclopentanones.
Herein, we report the kinetic and the dynamic kinetic resolutions of racemic 3,5-dialkyl-2-cyclopenten-1-ones. Kinetic resolution, with good selectivity factors (25-52), was achieved by conjugate reduction with catalytic CuCl/NaOt-Bu/(S)-p-tol-BINAP and stoichiometric quantities of poly(methylhydrosiloxane) (PMHS). When stoichiometric amounts of NaOt-Bu and t-BuOH were included in the reaction mixture, rapid racemization of the starting material occurred allowing for the dynamic kinetic resolution of the cyclopentenone substrates. In this process, chiral 2,4-dialkylcyclopentanones were isolated with high stereoselectivity (ee > or = 91%, dr > or = 90:10) and in high yield (> or =89%).
Jurkauskas
Valdas
V
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Buchwald
Stephen L
SL
D003517:Cyclopentanes / Q000138:chemical synthesis* / Q000302:isolation & purification; D007700:Kinetics; D013237:Stereoisomerism
D003517:Cyclopentanes; C007201:cyclopentanone