Carbanion stabilization by distal silyloxy groups. Origin of the high diastereoselectivity in the formation of quaternary centers with aryllead(IV) triacetate reagents.
Derivatives of methyl 5-hydroxy-2-oxo-1-cyclohexanecarboxylate react with aryllead(IV) reagents in high yield and with wide variation in diastereoselectivity. Ab initio calculations are consistent with a heretofore unrecognized attraction between the carbanionic center of the beta-ketoester intermediate and the distal OSiR(3) group. This attractive interaction stabilizes the silyl group in the axial conformation and leads to the excellent trans diastereoselection in the formation of quaternary centers. [reaction: see text]
Konopelski
Joseph P
JP
Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA. joek@chemistry.ucsc.edu
Lin
Jinzhen
J
Wenzel
Philip J
PJ
Deng
Hongbo
H
Elliott
Gregory I
GI
Gerstenberger
Brian S
BS