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。