Organocatalyzed polymerization has advanced rapidly since the early 2000s, with polyesters emerging as one of the most important target material classes. Although numerous organocatalysts have been reported for the controlled synthesis of polyesters, achieving broad monomer compatibility and enabling multiple polymerization modes with a single organocatalyst while maintaining a balanced combination of reactivity, stability, and ease of handling remains a significant challenge. In this study, we demonstrate that (methylsulfonyl)2-(4-(pyrrolidinium-1-ylidene)pyridinyl-1(4H))-cyclohexylamide (MPPA), a bench-stable amide–iminium zwitterionic bifunctional catalyst originally developed for transesterification in organic chemistry, functions as a highly versatile organocatalyst for controlled polyester synthesis. In the ring-opening polymerization (ROP) of cyclic esters, MPPA exhibits sufficiently high activity toward a broad range of monomers and, notably, enables well-controlled polymerizations of both lactide (LA) and ε-caprolactone (ε-CL), as well as their block copolymerization in a one-pot fashion. MPPA also efficiently catalyzes the ring-opening alternating copolymerization (ROAC) of cyclic anhydrides with epoxides. Furthermore, it allows the integration of ROP and ROAC within a one-pot, one-step procedure, often referred to as “self-switchable polymerization,” to produce structurally controlled copolyesters. Collectively, these results establish MPPA as a highly promising organocatalyst for polyester synthesis, enabling not only well-defined homopolymers but also complex copolymers derived from different monomers and polymerization mechanisms.
Matsuda et al. (Mon,) studied this question.