仿生催化空气氧化1-丁烯制备1,2-环氧丁烷：亚胺催化性能及机理

Biomimetic catalytic air oxidation of n-butene to prepare 1,2-epoxybutane: catalytic performance and mechanism of imine

摘要:

氧化1-丁烯制备1,2-环氧丁烷（BO）是化学工业高附加值利用C4烃类化合物的重要方法之一。然而，直接使用分子氧作为氧化剂，因其三线态难以活化而面临较大的挑战。本工作结合仿生催化氧气活化的反应思路，以1-丁烯为原料，邻苯二甲酰亚胺为催化剂，正丁醛为递氢体，空气为氧化剂，高效绿色合成BO的方法。1-丁烯转化率可达50%，产物1,2-环氧丁烷的选择性超过96%。该合成方法条件温和，绿色低碳，催化剂经济且易于获得，且该体系可针对不同的底物，适用范围广，具有较大的工业应用潜力。机理研究表明，在邻苯二甲酰亚胺催化作用下，递氢体正丁醛脱氢原位产生高活性酰基自由基，其与空气中的O2结合形成高活性的过氧自由基物种。顺式/反式异构对照实验表明，过氧自由基辅助过氧酸是促进烯烃环氧化的途径。

Abstract:

The preparation of 1,2-epoxybutane (BO) through the oxidation of n-butene is one of the important methods for high-value utilization of C4 hydrocarbons in the chemical industry. However, the direct use of molecular oxygen as an oxidant still faces significant challenges due to the difficulty in activating its triplet state. This work combines the idea of biomimetic catalytic oxidation and reports a highly efficient and green synthesis method of BO using n-butene as raw material, phthalimide as catalyst, n-butanal as hydrogen donor, and air as oxidant. The conversion rate of n-butene can reach 45%, and the selectivity of product 1,2-epoxybutane exceeds 95%. This method has the characteristics of mild reaction conditions, green and low-carbon, and the catalyst is economical and easy to obtain. And this catalytic system is suitable for different substrates, with a wide range of applications and great industrial potential. Mechanistic studies show that under the catalysis of phthalimide, the dehydrogenation of n-butanal generates highly active acyl free radicals in-situ, which combine with oxygen molecules in the air to form highly active peroxide radical species. The cis/trans-stilbene isomerization experiment shows that the peroxide free radical assisted peroxide acid was the way to promote olefin epoxidation.