Organocatalysis has shown special potency for simplifying the construction of complex polymer structures. We are reporting here a one-pot synthetic pathway using amine as a selectivity-switching agent in the two-component catalytic system consisting of triethylborane (Et 3 B) and a phosphazene base. We first modelled the interactions of a variety of amines with Et 3 B by density functional theory calculations. The results indicate that the aliphatic diamines comprising both primary and tertiary amino groups, capable of forming stable intramolecular hydrogen bonds, undergo the strongest complexation with Et 3 B. Accordingly, experimental results demonstrate that the addition of such amines promptly actuates the in situ selectivity switch from Lewis pair-catalyzed ring-opening polymerization (ROP) of epoxide (propylene oxide, n -butylglycidyl ether, or glycidyl phenyl ether) to organobase-catalyzed ROP of δ -valerolactone, allowing one-pot continuous synthesis of ether-ester type block copolymers. We thus exploited the noncovalent interaction between amine and Et 3 B to refine the catalyst switch strategy by exempting it from loading of extra catalyst.
The need for sustainable alternatives to petroleum-based polymers has driven the development of advanced catalysts for polyester synthesis. Here we present a series of covalently tethered borane–oxyanion organocatalysts for the ring-opening copolymerization of epoxides and cyclic anhydrides. These catalysts achieve outstanding efficiency, with turnover frequencies up to 13,500 h −1 and high molecular weights ( M n ) up to 174.0 kDa of the resultant polymers. Mechanistic studies reveal that intramolecular cooperation between borane and propagating species accelerates the rate-limiting epoxide ring-opening step, resulting in nearly equivalent energy barriers for epoxide and anhydride ring opening. Notably, the covalent tethering strategy not only enhances performance but also imparts remarkable air stability, addressing key limitations of conventional borane-based catalysts. Furthermore, our catalysts exhibit broad substrate scope and high thermal stability, facilitating the production of metal-free polyesters with tailored characteristics. This work establishes a sustainable and robust platform for polyester synthesis, with promising applications in biomaterials and packaging.
危险品化学品经营许可证（带存储）