固定化ホモサレン配位子の合成とラセミラクチドの立体選択的重合反応への応用

摘要

再利用可能かつポリマーが着色しないラセミラクチドのイソタクチック選択的重合触媒配位子として，ホモサレン配位子を市販のMerrifield樹脂に固定化した.まず適当な保護基を有する1,3-ジァミノプロパン-2-オール誘導体を用い，樹脂とカップリング反応を行った後，脱保護後して置換基を有するサリチルアルデヒドと脱水縮合により，固定化ホモサレン配位子を合成した.%Three polymer-supported homosalen ligands for the stereoselective polymerization of racemic lactide were synthesized: the Ph-substituted and tBu-substituted ligand on the Merrifield resin and the tBu-substituted ligand on the Wang resin. The corresponding aluminum catalyst was prepared by mixing with Et_3Al in toluene at 70℃. Excess Et_3Al was efficiently removed together with the solvent from the catalyst mixture. All of the catalysts stereoselectively polymerized racemic lactide to afford isotactic poly(racemic lactide)s， which were partially crystalline. Among the three examined catalysts, the tBu-substituted homosalen-Al catalyst on the Merrifield resin gave the most crystalline poly(racemic lactide), which showed a melting peak in the DSC measurement in the second run. Because of the immobilization of the catalyst on the resin, the obtained poly(racemic lactide) was colorless and never included the ligand-derived organic compounds in the polymer. The ligand resin was collected by filtration and was reusable.