Synergistic asymmetric activation of α,β-unsaturated carboxylic acids and its synthetic application

虽然已经研究了使用α，β-不饱和羧酸作为底物的催化不对称反应，但是不能开发有用的反应。主要原因是羧酸的高酸性导致催化剂分解。然而，新的光学活性配体容易地从天然存在的氨基酸脯氨酸制备的合成和其钛配合物被发现是一个有效的催化剂，烯烃的不对称环氧化在过氧化氢水溶液作为化学计量的氧化剂的存在下。在苯乙烯衍生物的反应中，实现了96 - 98%ee的高对映选择性。

While catalytic asymmetric reactions using α,β-unsaturated carboxylic acids as substrate have been examined, useful reactions could not be developed. The main reason is the catalyst decomposition due to the high acidity of carboxylic acids. However, novel optically active ligands readily prepared from naturally occurring amino acid proline were synthesized and its titanium complexes were found to be an efficient catalyst for asymmetric epoxidation of olefins in the presence of aqueous hydrogen peroxide as the stoichiometric oxidant. In the reaction of styrene derivatives, high enantioselectivity ranging from 96 to 98% ee was achieved.