T. Morikawa et al., STEREOSELECTIVE RADICAL ADDITIONS OF GAMMA-OXY-ALPHA,BETA-UNSATURATEDESTER DERIVATIVES - 1,2-ASYMMETRIC INDUCTION IN ACYCLIC AND CYCLIZATION SYSTEMS, Journal of the Chemical Society. Perkin transactions. I, (3), 1995, pp. 271-281
Examination was made of 1,2-asymmetric induction in the addition of al
kyl radicals to gamma-oxy-alpha,beta-unsaturated ester derivatives 1 a
nd 2 prepared from ethyl lactate and (R)-2,3-0-isopropylideneglycerald
ehyde 3, respectively. The addition reactions of hexyl, cyclohexyl and
3-phenylpropyl radicals to (Z)-2 derived from aldehyde 3 gave beta-ad
dition products with syn-stereoselectivity (syn:anti = 8.6:1-syn only)
. The reactions of (E)-2 were non-stereoselective. Based on allylic st
rain, a transition-state model for the syn-stereoselectivity is propos
ed. 1,2-Asymmetric induction was carried out in radical cyclisation to
synthesize optically active cyclohexane derivatives.