Photoinitiated cationic oligomerization of terminal and internal epoxides

The iodonium salt-catalyzed, photoinduced cationic oligomerization of termi nal and internal monoepoxides from oleochemical as well as the petrochemica l origin was studied. The ring-opening of terminal epoxides (1,2-octene oxi de, phenyl glycidyl ether, 9,10-epoxy decanoic acid methyl ester and 10,11- epoxy undecanoic acid methyl ester) predominantly led to macrocyclic oligoe thers (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) wer e achieved by the conversion of internal epoxides (7,8-tetradecene oxide an d cis-9,10-epoxy octadecanoic acid methyl ester) in yields of 80-95%. Macro cyclization was completely suppressed by addition of 20 mol-% water or ethy lene glycol receiving diol-oligoethers for potential application as soft se gments for polyurethanes with molecular weights of approximately 1,300 g/mo l.