Crown ether complexes of sodium and potassium 2-(benzotriazol-2-yl)phenolates: Synthesis and catalysis towards the ring-opening polymerization of rac-lactide

Crown ether complexes of sodium and potassium 2-(benzotriazol-2-yl)phenolates were synthesized and characterized. In the presence of BnOH these complexes are highly active catalysts for the controlled ring-opening polymerization of rac-lactide. The polymerizations are iso-selective and the P_m of polylactide reached 0.77 when the polymerization was performed in toluene at −60°C; whereas heterorich-polylactide was obtained when the polymerization was carried out in CH₂Cl₂ or THF.