Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
Chemistry. 2011 Oct 24;17(44):12326-39. doi: 10.1002/chem.201101168. Epub 2011 Sep 16.
Good to excellent stereoselectivity has been found in the addition reactions of Grignard and organozinc reagents to N-protected aziridine-2-carboxaldehydes. Specifically, high syn selectivity was obtained with benzyl-protected cis, tert-butyloxycarbonyl-protected trans, and tosyl-protected 2,3-disubstituted aziridine-2-carboxaldehydes. Furthermore, rate and selectivity effects of ring substituents, temperature, solvent, and Lewis acid and base modifiers were studied. The diastereomeric preference of addition is dominated by the substrate aziridines' substitution pattern and especially the electronic character and conformational preferences of the nitrogen protecting groups. To help rationalize the observed stereochemical outcomes, conformational and electronic structural analyses of a series of model systems representing the various substitution patterns have been explored by density functional calculations at the B3LYP/6-31G* level of theory with the SM8 solvation model to account for solvent effects.
在 N-保护的氮丙啶-2-甲醛与格氏试剂和有机锌试剂的加成反应中，发现了极好的立体选择性。具体来说，苄基保护的顺式、叔丁氧羰基保护的反式和对甲苯磺酰基保护的 2,3-取代氮丙啶-2-甲醛具有很高的 syn 选择性。此外，还研究了环取代基、温度、溶剂、路易斯酸和碱调节剂的速率和选择性影响。加成的非对映选择性主要由底物氮丙啶的取代模式决定，特别是氮保护基团的电子性质和构象偏好。为了帮助合理化观察到的立体化学结果，通过密度泛函计算在 B3LYP/6-31G*理论水平上对一系列代表各种取代模式的模型体系进行了构象和电子结构分析，并使用 SM8 溶剂模型来考虑溶剂效应。
