Imidazolium-based chiralionicliquid containing α,α-diaryl-(S)-prolinol trimethylsilyl ether acts as an efficient and reusable organocatalyst for the enantioselective Friedel-Crafts reaction between indoles and α, β-unsaturated aldehydes. 3-Alkylated indoles were obtained in 62–89 % yields with 47–88 % enantiomeric excesses using α,α-diphenyl-(S)-prolinol trimethylsilyl ether having hexafluorophosphate
含α,α-二芳基-( S )-脯氨醇三甲基甲硅烷基醚的咪唑基手性离子液体可作为一种高效且可重复使用的有机催化剂,用于吲哚与α, β-不饱和醛之间的对映选择性 Friedel-Crafts 反应。使用具有六氟磷酸根阴离子 [PF 6 ] - ( 20 mol %) 和三乙胺 (40 mol%) 在 25 °C 下作为 1,4-二恶烷中的基础添加剂。具有六氟磷酸阴离子的α,α-二苯基-( S )-脯氨醇三甲基甲硅烷基醚[PF 6] -被回收并重复用于 FC 反应多达七次循环,具有一致的对映选择性,但在第三次循环后观察到产品收率的相当大的损失。可能的构象异构体(亚胺中间体)的能量通过 DFT 计算。
Diarylprolinol Silyl Ether Catalyzed Asymmetric Friedel-Crafts Alkylation of Indoles with α,β-Unsaturated Aldehydes: Enhanced Enantioselectivity and Mechanistic Investigations
A highly enantioselective Friedel-Crafts alkylation of indoles with α,β-unsaturated aldehydes with excellent enantioselectivities (up to >99 % ee) has been developed, and this improved method offers substantial advantages over traditional approaches, not only by avoiding the use of acids or bases, but also in terms of the higher level of stereoselectivity. In addition, we have demonstrated through