CuOTf/NNN三齿钳形配体催化不对称Henry反应

以(R)-BINOL为原料合成NNN三齿钳形手性配体,研究了其与各种金属盐形成金属络合物在室温下原位催化芳香醛与硝基甲烷的不对称Henry反应.考察了不同金属盐、溶剂、碱对反应的影响,优化得到最佳反应条件为:CuOTf/NNN三齿配体(1∶1)催化体系,催化剂用量为10 mol%,甲醇作溶剂,室温反应5 d,收率57%,对映选择性80%ee;加入10 mol%有机碱(Me3Si)2MeN后反应速度加快,对映选择性略有降低,室温反应17 h,收率37%,ee值67%.此催化体系适用于大部分的芳香醛,收率中等,对映选择性可达75%ee.

Asymmetric Henry Reaction Catalyzed by CuOTf/NNN Tridentate Pincer Ligand

The NNN tridentate pincer chiral ligand was synthesized from(R)-BINOL to combine with a series of metal salts to catalyze asymmetric Henry reaction in situ at room temperature.The system of CuOTf/NNN ligand(1∶1) was proved to be potential catalyst in Henry reaction of 4-nitrobenzaldehyde with nitromethane.Various solvents and bases were surveyed for the reaction subsequently.When the loading of catalyst was 10 mol%,it showed catalytic efficiency for the reaction in metha-nol with 80% enantiomeric excess.With the assistance of(Me3Si)2NMe,the reaction was accelerated although enantiomeric excess was decreased to 67% ee.In addition,the catalyst showed moderate catalytic efficiency for Henry reaction between a variety of benzaldehydes and nitromethane to afford the expected products in moderate yields with good enantioselectivities(up to 75% ee).