Asymmetric Henry reaction of trifluoromethyl ketone and aldehyde using Cu(II)-complex: computational study offers the origin of enantioselectivity with varied size of catalysts
作者:Anjan Das、Manoj K. Choudhary、Rukhsana I. Kureshy、Kalyanashis Jana、Shailesh Verma、Noor-ul H. Khan、Sayed H.R. Abdi、Hari C. Bajaj、Bishwajit Ganguly
DOI:10.1016/j.tet.2015.06.033
日期:2015.8
Chiral ligand 3 was synthesised from inexpensive and readily available (1R,2R)-(+)-1,2-diphenyl-1,2-diaminoethane and tert-butylbromoacetate. In situ generated complex obtained by the reaction of ligand 3 with copper triflate was used as catalyst for asymmetric Henry reaction of trifluoromethyl ketone having different substituents in the aromatic ring with nitromethane at 0 °C in presence of N,N-DIPEA
由廉价且容易获得的(1 R,2 R)-(+)-1,2-二苯基-1,2-二氨基乙烷和叔丁基溴乙酸酯合成手性配体3。在N,N -DIPEA作为添加剂存在下,通过配体3与三氟甲磺酸铜反应获得的原位生成的配合物,用作芳香环中具有不同取代基的三氟甲基酮与硝基甲烷在0°C下与硝基甲烷的不对称亨利反应的催化剂,得到硝基醛产品具有出色的对映选择性(ee高达99%)和良好的收率(高达80%)。配体3在-5°C下,用乙酸铜原位生成的配合物也被发现是醛与EE的不对称硝基醛醛缩醛反应(ee可达80-92%,产率高达85%)的良好催化剂。用B3LYP和M06-2X官能团进行的DFT计算揭示了非共价相互作用(例如π-π相互作用和氢键)的作用,并且催化剂中的空间因素对增强对映选择性具有重要作用。