Stereocontrol in radical cyclization: change in rate-determining step.
Intramolecular cyclization of an alpha-carbon radical of ester carrying a chiral 2,4-pentanediol tether shows low stereoselectivity when the radical carbon has an alkyl substituent, while the selectivity becomes high to give a single stereoisomer (>99% pure) when the substituent is an aryl group. The difference in the selectivity is attributable to the change in the rate-determining step from the conformational process to the cyclization.
Hakim
Siddiki S M A
SS
Graduate School of Material Science, University of Hyogo, 3-2-1, Kohto, Kamigori, Ako-gun, Hyogo 678-1297, Japan.
Sugimura
Takashi
T