Asymmetric Kinetic Resolution Polymerization of Racemic Lactide Mediated by Axial-Chiral Thiourea/Phosphazene Binary Organocatalyst.
Chemistry
; 30(53): e202402201, 2024 Sep 19.
Article
in En
| MEDLINE
| ID: mdl-39008613
ABSTRACT
Asymmetric kinetic resolution polymerization (AKRP) provides an ideal way to obtain highly isotactic polylactide (PLA) with superior thermal-mechanical properties from racemic lactide (rac-LA). However, the development of a new catalytic system with concurrent high activity and selectivity at ambient temperature remains a great callenge. Here, a series of simple and effective binary organocatalytic pairs containing axial-chiral thioureas and commercially available phosphazene bases were designed. These chiral binary organocatalytic pairs allow for both high polymerization activity and moderate enantioselectivity for AKRP of rac-LA at room temperature, yielding semi-crystalline and metal-free stereoblock PLA with a melting temperature as high as 186 °C. The highest kinetic resolution coefficient (krel) of 8.5 at 47 % conversion was obtained, and D-LA was preferentially polymerized via kinetic resolution with a maximum selectivity factor (kD/kL) of 18.1, indicating that an enantiomorphic site control mechanism (ESC) was involved.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Chemistry
Journal subject:
QUIMICA
Year:
2024
Document type:
Article
Affiliation country:
China
Country of publication:
Germany