Bw. Gung et al., STERIC AND ELECTRONIC EFFECTS IN CONFORMATIONAL PREFERENCES OF C1-OXYGENATED CHIRAL ALKENES, Journal of organic chemistry, 60(7), 1995, pp. 1947-1951
A variable temperature NMR study shows that the benzyl protective grou
p on the hydroxy function of a chiral allylic alcohol enhances the CH
eclipsed form (I). On the other hand, various silyl ethers enhance the
preference for the CO eclipsed conformer. However, when both the ally
lic R group and the hydroxy protective group are bulky (R tert-butyl,
P = TIPS), the staggered conformation of the chiral alkene becomes pre
ferred. An acetate group does not have an apparent effect on the confo
rmational preference of the protected allylic alcohol. These facts are
explained in terms of steric and electronic interactions.