开发了一种新的钠/钾冠醚配合物体系,该体系以一系列的螯合磺酰胺为配体,用于外消旋丙交酯的开环聚合(ROP)。在该系统中,由于由BnOH和磺酰胺阴离子引发的ROP速率非常不同,因此可以很好地抑制环状聚合的副反应。成功合成了分子量高达107 kg / mol的高分子量线性聚丙交酯。最佳的等选择性也可以达到较高的P m = 0.84。外消旋丙交酯与配合物3的反应混合物的NMR分析连同动力学研究表明,在不存在酒精的情况下ROP的机制是配位插入机制。加入BnOH后,由于醇与配合物3的协同作用,ROP速率可以显着提高。
Suppressing Cyclic Polymerization for Isoselective Synthesis of High-Molecular-Weight Linear Polylactide Catalyzed by Sodium/Potassium Sulfonamidate Complexes
A new sodium/potassium crown ether complex system with a series of bichelating sulfonamides as ligands was developed for the ring-openingpolymerization (ROP) of rac-lactide. In this system, the side reaction of cyclicpolymerization can be suppressed very well because of very different ROP rates initiated by BnOH and sulfonamide anion. The synthesis of high molecular weight linear polylactide with
开发了一种新的钠/钾冠醚配合物体系,该体系以一系列的螯合磺酰胺为配体,用于外消旋丙交酯的开环聚合(ROP)。在该系统中,由于由BnOH和磺酰胺阴离子引发的ROP速率非常不同,因此可以很好地抑制环状聚合的副反应。成功合成了分子量高达107 kg / mol的高分子量线性聚丙交酯。最佳的等选择性也可以达到较高的P m = 0.84。外消旋丙交酯与配合物3的反应混合物的NMR分析连同动力学研究表明,在不存在酒精的情况下ROP的机制是配位插入机制。加入BnOH后,由于醇与配合物3的协同作用,ROP速率可以显着提高。
Benzylic Oxidation and Functionalizations of Xanthenes by Ligand Trasfer Reactions of Hypervalent Iodine Reagents
on the xanthenes, and the yield of 2-nitroxanthone 2c was only 44% after the reaction for 24 h. Unfortunately, the yield was not improved at an elevated reaction temperature due to the over-oxidation of the product and partial ring-bromination of the xanthene aromatic ring. For the methyl-substituted xanthene 1d, the reaction was highly chemoselective at the xanthene benzylic position and the methyl