Abstract: Macrocyclic polyester oligomer compositions comprising alkylene isophthalate or terephthalate units or the like are prepared by the reaction of a diol with a diacid chloride in the presence of at least one amine characterized by substantially no steric hindrance around the basic nitrogen atom. The reaction is conducted under substantially anhydrous conditions and at a temperature from about -25.degree. to about +25.degree. C. The resulting macrocyclic oligomers may be converted to linear polyesters by contact with catalysts including basic reagents, stannous alkoxides, organotin compounds, titanate esters and metal acetylacetonates.

Abstract: Process for isolating macrocyclic polyester oligomers from impurities comprising the step of subjecting solutions of macrocyclic polyester oligomers to protonated molecular sieves.

Abstract: Macrocyclic polyester oligomer compositions comprising alkylene isophthalate or terephthalate units or the like are prepared by the reaction of a diol with a diacid chloride in the presence of a catalytic amount of at least one amine characterized by substantially no steric hindrance around the basic nitrogen atom, and an acid accepting amount of at least one other tertiary amine such as triethylamine. The reaction is conducted under substantially anhydrous conditions.

Abstract: Macrocyclic polyester oligomer compositions comprising alkylene isophthalate or terephthalate units or the like are prepared by the reaction of a diol with a diacid chloride in the presence of at least one amine characterized by substantially no steric hindrance around the basic nitrogen atom. The reaction is conducted under substantially anhydrous conditions and at a temperature form about -25.degree. to about +25.degree. C. The resulting macrocyclic oligomers may be converted to linear polyesters by contact with catalysts including alkali metal salicylates, stannous alkoxides and organotin compounds.