Bypassing the lack of reactivity of endo -substituted norbornenes with the catalytic rectification-insertion mechanism

• Published in: Chemical science (Cambridge) Vol. 6; no. 4; pp. 2172 - 2181
• Main Authors: Commarieu, Basile, Claverie, Jerome P
• Format: Journal Article
• Language: English
• Published: England 01.04.2015
• Subjects: Bearing; Bypasses; Catalysts; Esters; Insertion; Monomers; Niobium; Polymerization
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c4sc03575e

The catalytic 1,2-insertion polymerization of polar norbornenes (NBEs) leads to the formation of functional rigid macromolecules with exceptional thermal, optical and mechanical properties. However, this remarkable reaction is plagued by the low reactivity of the polar monomers, and most notably of those bearing a functional group in position. We have examined the polymerization mechanism of NBEs bearing one or two CO Me groups either in or position catalyzed by the so-called naked allyl Pd SbF catalyst ( ). Although dimethyl ester of 5-norbornene-2,3-dicarboxylic acid (NBE(CO Me) ) is polymerized by , two units are never inserted consecutively along the polymer chain. Indeed, is a tandem catalyst which not only catalyzes the insertion of the monomer but also the isomerization of and isomers. Thus, the polymerization of monomers proceeds a novel mechanism, coined rectification-insertion mechanism, whereby half of the monomers are rectified into ones prior insertion, leading to the formation of an alternating - copolymer using an only feedstock. With this mechanism, the lack of reactivity of norbornenes is bypassed, and the polymerization of predominantly polar NBEs bearing a variety of functionalities such as esters, imides, acids, aldehydes, alcohols, anhydrides, or alkyl bromides proceeds with catalyst loadings as low as 0.002 mol%.