SEARCH Articles Figures Tables 2- azetidine, ring enlargement Azetidine Azetidine ring compounds Azetidine ring opening Azetidine ring synthesis Azetidines ring synthesis Azetidines, ring opening Cationic ring-opening polymerization azetidines Four-membered ring heterocycles azetidine-2-ones Four-membered ring heterocycles azetidines Ring expansion azetidines