Cocatalyst Binding Effects in Organocatalytic Ring-Opening Polymerization of l-Lactide

Abstract

Thiourea/alkylamine cocatalysts have previously been shown to be effective systems for the ring-opening polymerization (ROP) of lactide, but an experimental explanation for the varied activity and selectivity of these structurally similar alkylamine cocatalysts combined with thiourea is elusive. In this work, several alkylamine bases are shown to be weakly associated with a thiourea cocatalyst in solution, and the nature of cocatalyst interactions vary with the identity of the alkylamine. Kinetic analyses of the organocatalytic ROP reactions reveal noninhibitory behavior in [alkylamine] and a new mode of activity for thiourea. Reactivity patterns are proposed based on computed cocatalyst geometries, and a new cocatalyst pair for the ROP of lactide is disclosed.

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

“…Here, a synergistic catalytic mechanism was proposed, in which the bisurea activated the carbonyl group of monomer and MTBD facilitated the nucleophilic attack of the initiating/propagating alcohol by hydrogen bonding (Scheme ) . Kiesewetter expounded that (thio)urea/MTBD mediated ROP of VL proceeded through one of two mechanisms, (thio)‐imidate mechanism and classic H‐bond mediated mechanism.…”

Controlled Organocatalytic Ring-Opening Polymerization of ε-Thionocaprolactone

“…An NMR titration study 20–22 was conducted in C 6 D 6 to determine the binding constant between 1 and tnCL, K eq = 1.6 ± 0.2 (in eq 1). The comparable binding between CL and TU was measured to be K eq = 42 ± 5, 7 and a similarly dramatic perturbation from this latter strong binding value was previously measured for tCL, K eq = 2.7 ± 0.5.…”

From Zn(C6F5)2 to ZnEt2‐based Lewis Pairs: Significantly Improved Catalytic Activity and Monomer Adaptability for the Ring‐opening Polymerization of Lactones

“…However, the most of organocatalysts exhibited lower activity than metal complexes, and in some cases, extra introduction of H-bonding interaction was necessary in order to promote the ROP effectively. [23][24][25][26][27][28][29] Recently, cooperative catalytic systems, especially involving a combination of metal-based Lewis acid with nucleophilic organic base (Lewis base), were widely used in the polymerization of lactones and polar olefins. [30][31][32][33][34][35][36][37][38][39] In this strategy, ROP rate will be accelerated significantly, because the coordination of metal-center to lactone increase the reactivity of the carbonyl group and thus facilitate the ring-opening reaction.…”