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

Article abstract of DOI:10.1016/S0040-4020(01)88235-1

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.