Allylic Oxidation of Unsaturated Spiroketals.

Abstract Allylic bromination of the bicyclic spiroketals ( 4a–c ) gave predominantly the axial bromides ( 6 ), ( 9 ) and ( 12 ) which underwent S N 2 displacement to the equatorial alcohols ( 7 ), ( 11 ) and ( 14 ) respectively using KO 2 /18-crown-6 in THF/DMSO (10:1).