Sn(OTf)(2) and Sc(OTf)(3): Efficient and versatile catalysts for the controlled polymerization of lactones

A general and novel method for the controlled synthesis of aliphatic polyes ters is presented. The evaluation of stannous (II) trifluoromethane sulfona te [Sn(OTf)(2)] and scandium (III) trifluoromethane sulfonate [Sc(OTf)(3)] as catalysts for the ring-opening polymerization (ROP) of various lactones is described as a route to polyesters under mild and highly selective polym erization conditions. Size exclusion chromatograms of poly(epsilon-caprolac tone) initiated from ethanol in the presence of either Sn(OTf)(2) or Sc(OTf )(3) demonstrate the facile synthesis of narrowly dispersed products. Predi ctable molecular weights, typical of a living or controlled polymerization, were obtained with high yields. These catalysts are versatile and applicab le toward the ROP of other cyclic (di)esters, including beta-butyrolactone, which produces the synthetic analogue of the biopolymer poly(beta-hydroxyb utyrate). (C) 2000 John Wiley & Sons, Inc.