功能化纤维表层特定微环境中的绿色有机化学连续转化

Much attention has been given to the supported organocatalysts. They are widely utilized to catalyze organic reaction continuously with the advantage of isolating from the reaction mixture conveniently. Up till now, a wide range of supporting materials such as silica, resin and nano-particles were used. Our group chose fiber as a new supporter, and many fiber-supported organocatalysts have been firstly prepared to catalyze varieties of organic reactions efficiently. Along with the development of investigations, we found that the modified fibers are essentially different from those other traditional supporting materials, in which not only the sole surface was modified but also a three-dimensional high density modification with depth of hundred nanometers was obtained. A “quasi-liquid microenvironment” was built beneath the surface with organic small molecules and polymeric segments in which many reactions proceed efficiently. In this project, the fiber surface microenvironment will be further investigated by modified with amino, hydroxyl, pyridyl, carcoxyl and amide groups and further tuned with the aid of assistant molecules. Effect of polarity, types of functional groups and modification extent on catalytic activity will be extensively studied. And transformations on nucleophilic substitution, reduction of aldehydes and ketones and Diels-Alder reaction in aqueous phase with the special functionalized fiber surface microenvironment will be carried out. Furthermore, the tubular reactor will be equipped with our special functionalized fiber, which will be tested for continuous organic transformations.

固载有机小分子催化是当今有机化学研究的热点，通过催化剂的固载，可使催化剂与反应混合物便捷分离，也可实现化学反应过程的连续化。目前常用载体材料有硅胶、树脂、纳米颗粒等。本课题组率先以纤维为载体，制备出固载有机小分子的纤维催化剂，实现了多种有机反应的高效催化。随着研究的深入，我们意识到纤维功能化与传统载体有着本质不同，即修饰发生在表面下数百纳米，是一种深层次、高密度修饰。这样在纤维表层营造了由有机小分子和聚合物链段构成的特定“准液相微环境”，使反应在该微环境中高效进行。本项目将进一步构建富含氨基、羟基、羧基、吡啶基、酰胺基等特性官能团的微环境，采用辅助分子对微环境极性进行调谐；研究功能基类型、修饰度以及微环境极性对催化活性的影响；探索水介质中进行的亲核取代、醛酮的还原、Diels-Alder等反应在纤维表层特定微环境中的规律；将功能纤维填充在管状反应器中，测试其连续催化有机反应的效果。

本项目对腈纶纤维进行了高密度深层次的修饰，引入带有催化活性的功能基和调节极性的辅助基，聚合物上残余基团、功能基、辅助基构成柔韧性和可塑性的催化微环境，既有利于底物分子的富集，还象酶那样，通过多官能团的缔合协调作用，使反应的活化能降低，反应速度加快。所营造的特定催化微环境可以高效催化多种缩合反应，如：Michael加成反应、Knoevenagel缩合反应、Michael-Henry串联反应、多组分Biginelli缩合反应、Gewald反应、1,3-偶极环加成反应、Friedlander反应、杂环化合物构建反应等。多数反应都是条件温和、收率高，且纤维催化剂便于分离，可以反复使用数次甚至几十次。实验发现多数反应可以在绿色的水中高效进行，在常见反应介质如醇、卤代烃、芳烃中反而不能顺利进行，这一反常特性也表明我们所合成的多种纤维催化剂既不同于传统的均相催化剂，也不同于其他非均相催化剂，后者往往在载体表面进行，而本文构建的纤维催化剂，反应可以在纤维表层更深处进行。实现了连续催化有机反应，为多种有机化合物的连续化生产提供了重要依据和应用前景。项目执行过程中本课题组在高水平学术期刊发表第一标注论文15篇，一名教师晋升教授，4名和6名学生分别获得博士和硕士学位。