A bifunctional H-bond donor–Lewis basic anion (HBD–anion) organocatalyst manifold was proposed for ring-opening polymerizations (ROPs) of cyclic esters. A series of squaramide–phenolates (Sq–PhO) as representative HBD–anion catalysts were designed, in which the Lewis basic phenolate anion, in place of neutral bases of the Takemoto-type catalyst, activated the initiator/chain-end, while the squaramide activated the monomer by H-bonding, cooperatively. The squaramide–phenolate was generated in situ by deprotonating the phenolic hydroxyl of the counterpart squaramide–phenol with (super) strong bases. An optimal N-benzyl-N′-p-hydroxylbenzyl squaramide (Sq3-p) and the DBU base co-catalyst transformed lactides, lactones, and cyclic carbonates into the corresponding polyesters in a short time, with high conversion and a narrow dispersity (Đ = 1.06–1.19). The bifunctional activation mechanism was proposed and validated. Both the H-bond donors and basic anions are various and tunable, which is hopefully accessible to extend this catalytic tool in wider scope of bifunctional organocatalysis.

中文翻译：

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用于开环聚合的氢键供体-路易斯碱性阴离子双功能有机催化剂的开发

提出了一种双功能氢键供体-路易斯碱性阴离子（HBD-阴离子）有机催化剂歧管用于环酯的开环聚合（ROP）。设计了一系列作为代表性HBD阴离子催化剂的方酰胺酚盐(Sq-PhO)，其中路易斯碱性酚盐阴离子代替竹本型催化剂的中性碱，活化引发剂/链端，而方酰胺通过氢键合作激活单体。方酰胺苯酚盐是通过用（超）强碱使对应的方酰胺苯酚的酚羟基去质子化而原位生成的。最佳的N-苄基-N′-对羟基苄基方酰胺(Sq3- p )和DBU基助催化剂可以在短时间内将丙交酯、内酯和环状碳酸酯转化为相应的聚酯，转化率高，分散度窄( Đ = 1.06–1.19）。提出并验证了双功能激活机制。氢键供体和碱性阴离子都是多种多样且可调的，这有望将这种催化工具扩展到更广泛的双功能有机催化领域。