Centre for Nuclear Magnetic Resonance, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia.
PLIVA d.d. Prilaz Baruna Filipovića 25, 10000 Zagreb, Croatia.
Int J Mol Sci. 2024 May 20;25(10):5570. doi: 10.3390/ijms25105570.
This work investigated the cocatalytic activity of recently prepared guanidinium salts containing an oxanorbornane subunit in an ()-proline-catalyzed aldol reaction. The activity was interpreted by the diastereoselectivity of the reaction (/ ratio) and for the most interesting polycyclic guanidinium salt, the enantioselectivity of the reaction was determined. The results indicated a negative impact on the oxanorbornane unit if present as the flexible substituent. For most of the tested aldehydes, the best cocatalysts provided enantioselectivities above 90% and above 95% at room temperature and 0 °C, respectively, culminating in >99.5% for 4-chloro- and 2-nitrobenzaldehyde as the substrate. The barriers for forming four possible enantiomers were calculated and the results for two enantiomers are qualitatively consistent with the experiment. Obtained results suggest that the representatives of furfurylguanidinium and rigid polycyclic oxanorbornane-substituted guanidinium salts are good lead structures for developing new cocatalysts by tuning the chemical space around the guanidine moiety.
这项工作研究了最近制备的含氧杂降冰片烷亚基的胍盐在 ()-脯氨酸催化的Aldol 反应中的共催化活性。通过反应的非对映选择性 (/ 比) 来解释活性，对于最有趣的多环胍盐，还确定了反应的对映选择性。结果表明，如果氧杂降冰片烷单元作为柔性取代基存在，对其活性有负面影响。对于大多数测试的醛，最好的共催化剂在室温下提供了超过 90%的对映选择性，在 0°C 下提供了超过 95%的对映选择性，对于作为底物的 4-氯-和 2-硝基苯甲醛，最终达到了 >99.5%。计算了形成四个可能对映体的能垒，并且对于两个对映体的结果与实验定性一致。所得结果表明，糠基胍和刚性多环氧杂降冰片烷取代胍盐代表了通过调整胍部分周围的化学空间来开发新型共催化剂的良好先导结构。
