Synthesis of functionalized cycloolefins and their polymerization by late transition metals

Abstract

PART I. Optically active exo-isomers of norbornene-2-carboxylic acid esters (methyl, benzyl, and menthyl) were prepared via Diels-Alder reaction, efficient epimerization, and separation by column chromatography. These monomers were polymerized by Pd(II)-based catalysts. The polymer of methyl ester exhibited large optical rotation values while other polymers exhibited rather low rotation values. The large rotation value of methyl ester polymer is interpreted to be attributable to that the polymer possesses isotactic stereoregularity. The optically active polymer exhibited significantly different peaks of C1 and C4 around 39 ppm in the $^{13}C$ NMR spectrum, being in contrast with racemic polymer. PART II. Novel highly branched α,β-unsaturated polyesters were synthesized via ring-opening metathesis polymerization (ROMP) catalyzed by Ru catalyst. The monomer, 5-acryloyl-1-cyclooctene (ACO) was prepared through esterification of 5-hydroxy-1-cyclooctene with acryloyl chloride. ACO was polymerized by ROMP at first and then the pendant group of linear poly(ACO) was reacted with active chain end group through cross metathesis (CM) reaction. This procedure was repeated. Finally the highly branched aliphatic polyesters was obtained. Copolymerization of ACO with cyclooctene (CO) was also conducted to complete the branch of acryloyl pendant group. The structure of resulting polymers was confirmed by $^1H$ NMR and Differential Scanning Calorimeter (DSC). DSC data showed that glass transition temperature of highly branched polyester was higher than that of linear polymer.