Conformational change in a urea catalyst induced by sodium cation and its effect on enantioselectivity of a Friedel-Crafts reaction
作者:Arjun K. Chittoory、Gayatri Kumari、Sudip Mohapatra、Partha P. Kundu、Tapas K. Maji、Chandrabhas Narayana、Sridhar Rajaram
DOI:10.1016/j.tet.2014.03.068
日期:2014.5
indeed in an unfavorable conformation. Infrared and Raman spectroscopic studies show that sodium binds the catalyst through the carbonyl and sulfonyl groups. Simulated IR and Raman spectra match well with the experimentally recorded spectra, thereby corroborating the proposed conformational change. This result shows that weak Lewis acids can be used to tune the conformation of hydrogen-bonding catalysts
在开发双樟脑磺酰脲作为氢键合催化剂时,我们发现该催化剂的天然构象不适合诱导对映选择性。通过使催化剂与弱路易斯酸性钠阳离子络合,我们能够改变催化剂的构象并显着提高选择性。我们提供了来自X射线晶体学的结构信息,以表明未络合的催化剂确实处于不利的构型。红外和拉曼光谱研究表明,钠通过羰基和磺酰基与催化剂结合。模拟的IR和拉曼光谱与实验记录的光谱非常匹配,从而证实了所提出的构象变化。