Photoinitiated cationic oligomerization of terminal and internal epoxides

The iodonium salt-catalyzed, photoinduced cationic oligomerization of terminal and internal monoepoxides from oleochemical as well as the petrochemical origin was studied. The ring-opening of terminal epoxides (1,2-octene oxide, phenyl glycidyl ether, 9,10-epoxy decanoic acid methyl ester and 10,11-epoxy undecanoic acid methyl ester) predominantly led to macrocyclic oligoethers (M-n=650-1,100g/mol) via backbiting in quantitative yields. Mixtures of cyclic and bishydroxy-terminated oligoethers (M-n= 1,050-1,500g/mol) were achieved by the conversion of internal epoxides (7,8-tetradecene oxide and cis-9,10-epoxy octadecanoic acid methyl ester) in yields of 80-95%. Macrocyclization was completely suppressed by addition of 20 mol-% water or ethylene glycol receiving diol-oligoethers for potential application as soft segments for polyurethanes with molecular weights of approximately 1,300 g/mol.