Allylic functionalization of the 1,7-dioxaspiro[5.5]-undec-4-ene and d1,6,8-trioxadispiro[4.1.5.3]-pentadec-13-ene ring systems.

Abstract Allylic bromination of the bicyclic spiroacetals 5, 6 and 7 gave predominantly the axial bromides 15, 21 and 23 which underwent S N 2 displacement to the equatorial alcohols 17, 22 and 25 respectively, using potassium superoxide and 18-crown-6 in THF/DMSO (10:1). Allylic bromination of the cis -bis-spiroacetal 26 gave predominantly the rearranged allylic bromide 29 which afforded alcohols 30 and 31 resulting from both S N 2′ and S N 2 displacement upon treatment with potassium superoxide. Bromination of the trans -bis-spiroacetal 27 afforded a complex mixture from which only the non-rearranged bromide 34 could be isolated. This bromide 34 afforded the axial alcohol 37 upon treatment with potassium superoxide.