Allylsamarium Bromide-Mediated Cascade Cyclization of Homoallylic Esters. Synthesis of 2‑(2-Hydroxyalkyl)cyclopropanols and 2‑(2-Hydroxyethyl)bicyclo[2.1.1]hexan-1-ols

In continuation of our previous study
on the intramolecular reductive
coupling of simple homoallylic esters promoted by allylSmBr/HMPA/H2O, which afforded a facile synthesis of 2-(2-hydroxyalkyl)­cyclopropanols,
here we report the reductive cascade cyclization of but-3-enyl but-3-enoates
mediated by allylSmBr/HMPA/CuCl2·2H2O,
in which the two CC bonds were successively coupled to allow
the construction of the structurally interesting bridged bicyclic
tertiary alcohols. Thus, the 2-(2-hydroxyethyl)­bicyclo[2.1.1]­hexan-1-ols
were prepared in moderate to good yields with excellent diastereoselectivity.