Departamento de Química, Universidad de las Islas Baleares, 07122, Palma de Mallorca, Spain.
Molecules. 2010 Feb 1;15(2):709-34. doi: 10.3390/molecules15020709.
Conscious of the importance that stereochemical issues may have on the design of efficient organocatalyts for both Morita-Baylis-Hillman and aza-Morita-Baylis-Hillman reaction we have analyzed them in this minireview. The so-called standard reactions involve "naked" enolates which therefore should lead to the syn adducts as the major products, irrespective of the E, Z stereochemistry of the enolate. Accordingly, provided the second step is rate determining step, the design of successful bifunctional or polyfunctional catalysts has to consider the geometrical requirements imposed by the transition structures of the second step of these reactions. On the other hand, MBH and aza-MBH reactions co-catalyzed by (S)-proline and a secondary or tertiary amine (co-catalyst) involve the aldol-type condensation of either a 3-amino-substituted enamine, dienamine, or both, depending on the cases. A Zimmerman-Traxler mechanism defines the stereochemical issues regarding these co-catalyzed condensations which parallel those of the well established (S)-proline catalyzed aldol-like reactions.
鉴于立体化学问题可能对 Morita-Baylis-Hillman 和氮杂-Morita-Baylis-Hillman 反应高效有机催化剂的设计具有重要意义，我们在这篇综述中对其进行了分析。所谓的标准反应涉及“裸露”烯醇盐，因此无论烯醇盐的 E、Z 立体化学如何，都应该导致顺式加合物作为主要产物。因此，只要第二步是速率决定步骤，成功的双功能或多功能催化剂的设计就必须考虑这些反应第二步过渡态所施加的几何要求。另一方面，（S）-脯氨酸和仲或叔胺（共催化剂）共同催化的 MBH 和氮杂-MBH 反应涉及 3-氨基取代烯胺、二烯胺或两者的 aldol 型缩合，具体取决于情况。Zimmerman-Traxler 机制定义了这些共催化缩合的立体化学问题，这些问题与已确立的（S）-脯氨酸催化的类似 aldol 反应的问题平行。
