Erol Gunal Sule, Dogan Ilknur
Chemistry Department, Bogazici University, Bebek, 34342 İstanbul, Turkey.
Molecules. 2016 Jun 18;21(6):788. doi: 10.3390/molecules21060788.
Axially chiral 5-methyl-2-(o-aryl)imino-3-(o-aryl)-thiazolidine-4-ones have been subjected to aldol reactions with benzaldehyde to produce secondary carbinols which have been found to be separable by HPLC on a chiral stationary phase. Based on the reaction done on a single enantiomer resolved via a chromatographic separation from a racemic mixture of 5-methyl-2-(α-naphthyl)imino-3-(α-naphthyl)-thiazolidine-4-one by HPLC on a chiral stationary phase, the aldol reaction was shown to proceed via an enolate intermediate. The axially chiral enolate of the thiazolidine-4-one was found to shield one face of the heterocyclic ring rendering face selectivity with respect to the enolate. The selectivities observed at C-5 of the ring varied from none to 11.5:1 depending on the size of the ortho substituent. Although the aldol reaction proceeded with a lack of face selectivity with respect to benzaldehyde, recrystallization returned highly diastereomerically enriched products.
轴向手性的5-甲基-2-(邻芳基)亚氨基-3-(邻芳基)噻唑烷-4-酮已与苯甲醛进行羟醛反应生成仲醇，发现这些仲醇可在手性固定相上通过高效液相色谱法分离。基于在手性固定相上通过高效液相色谱法从5-甲基-2-(α-萘基)亚氨基-3-(α-萘基)噻唑烷-4-酮的外消旋混合物中色谱分离得到的单一对映体上进行的反应，表明羟醛反应通过烯醇盐中间体进行。发现噻唑烷-4-酮的轴向手性烯醇盐屏蔽了杂环的一个面，从而对烯醇盐产生面选择性。环C-5处观察到的选择性从无到11.5:1不等，这取决于邻位取代基的大小。尽管羟醛反应对苯甲醛缺乏面选择性，但重结晶得到了高度非对映体富集的产物。
