Titanium<i>cis</i>-1,2-Diaminocyclohexane Salalen Catalysts of Outstanding Activity and Enantioselectivity for the Asymmetric Epoxidation of Nonconjugated Terminal Olefins with Hydrogen Peroxide
作者:Markus Lansing、Hauke Engler、Tobias M. Leuther、Jörg-M. Neudörfl、Albrecht Berkessel
DOI:10.1002/cctc.201601154
日期:2016.12.19
oxidant, these complexes catalyze the epoxidation of terminal, nonconjugated olefins in high yields with high enantioselectivities. We furthermore discovered that the addition of certain acidic or basic co‐catalysts significantly accelerated the epoxidation. For example, in the presence of 1 mol % Ti catalyst and 1 mol % pentafluorobenzoic acid, 1‐octene epoxidation (95 % ee) was completed at room temperature
我们报告了一种新的且易于获取的钛盐酸盐复合物,该盐来源于顺式1,2-二氨基环己烷(cis - DACH)和氟化的水杨醛衍生物。用过氧化氢水溶液作为氧化剂,这些络合物以高收率和高对映选择性催化末端非共轭烯烃的环氧化。我们进一步发现,某些酸性或碱性助催化剂的加入可显着加速环氧化。例如,在1 mol%的Ti催化剂和1 mol%的五氟苯甲酸的存在下,1-辛烯环氧化(95% ee)在室温下8小时内完成。催化过程与许多官能团(例如醚,酯,卤化物,腈和硝基)相容,而游离羟基似乎在一定程度上减慢了反应速度。催化剂回收是可能的。