Base-Promoted Ring Contractionof Eight-Membered Cyclic Acyloins and their Ethers to<i>C</i>
<sub>s</sub>-Symmetric α-Ketols
作者:Leo A. Paquette、Ivan Vilotijevic、Jiong Yang、David Hilmey
DOI:10.1055/s-2003-41003
日期:——
In the presence of potassium hexamethyldisilazide and 18-crown-6in THF at room temperature, 2-benzyloxycyclooctanone andits Î5-unsaturated congener undergo a two-stagerearrangement to give symmetrical seven-membered ringproducts. The pathway consists of the sequential operation of anO → C 1,2-shift and an α-ketol rearrangement.The greater thermodynamic stability of the cycloheptane or cycloheptenegenerated in this fashion is substantiated by MM3 calculations.