Chiral Ligands Derived from <i>Abrine</i> 8. An Experimental and Theoretical Study of Free Ligand Conformational Preferences and the Addition of Diethylzinc to Benzaldehyde
作者:H. J. Zhu、J. X. Jiang、S. Saebo、C. U. Pittman
DOI:10.1021/jo049754c
日期:2005.1.1
Three structurally similar series of 1,2,3,4-tetrahydro-β-carboline ligands, 4a−d, 6a−d and 7a−d, and two series of chiral oxazolidines, 8a−d and 9a−g, were synthesized and used as chiral catalysts in the addition of diethylzinc to benzaldehyde. The enantioselectivities of the resulting 1-phenyl-1-propanol were obtained in each case, and these ee values were, in most cases, related to the conformational
三个结构相似的1,2,3,4-四氢-β-咔啉配体系列4a - d,6a - d和7a - d,以及两个系列的手性恶唑烷,8a - d和9a - g合成了α-己内酯并将其用作在苯甲醛中添加二乙基锌的手性催化剂。在每种情况下都获得了生成的1-苯基-1-丙醇的对映选择性,这些ee值在大多数情况下与游离配体的构象种群有关,如通过计算出的配体构象能差来表示氮转化形成的。这表明可能存在线性自由能关系。对(1)位于4a - d,6a - d和7a - d的C-3取代基上的R基团的碳链长度的对映选择性的影响或(2)位于8a - d中的C-5处的(2)对对映选择性的影响对9a - g进行了详细研究。根据观察到的相关性和配体的结构特征,提出了使用配体8a - d进行乙基转移时的过渡态结构。此外,当在该手性加成物中比较非对映体配体11和12时,成功预测了对映选择性的变化。