Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans
作者:Noha M. Hilmy Elnagdi、Noura Saad Al-Hokbany
DOI:10.3390/molecules17044300
日期:——
The multicomponent reaction (MCR) of aromatic aldehydes 1 and malononitrile (2) with active methylenes 5a–h in the presence of L-proline produced pyrans and thiopyrans 6a–h stereospecifically and in good yields. Moreover a novel MCR of ethyl propiolate (8) with 1 and 2 in the presence of L-proline to afford (R)-polysubstituted pyran is also reported. X-ray structures, e.e. and optical activity of the synthesized compounds indicated that L-proline as a catalyst is responsible for the observed enantioselectivity in the studied reactions.
在有 L-脯氨酸存在的情况下,芳香醛 1 和丙二腈 (2) 与活性亚甲基 5a-h 发生多组分反应 (MCR),以良好的产率立体定向地生成了吡喃和硫代吡喃 6a-h。此外,还报道了在 L-脯氨酸存在下,丙炔酸乙酯(8)与 1 和 2 的新型 MCR 反应,生成 (R)-多取代吡喃。合成化合物的 X 射线结构、电子显微镜和光学活性表明,L-脯氨酸作为催化剂是所研究反应中观察到的对映体选择性的原因。