Chiral Benzyllithium Compounds: High Configurative Stability of (R)- and (S)-1-Lithioindan-1-ylN,N-Diisopropylcarbamate and Unexpected Stereochemical Course of the Substitution Reactions
作者:Christoph Derwing、Holger Frank、Dieter Hoppe
DOI:10.1002/(sici)1099-0690(199912)1999:12<3519::aid-ejoc3519>3.0.co;2-n
日期:1999.12
sec-butyllithium/TMEDA and proved to be configuratively completely stable in ethereal solution at –78 °C. Compared with open-chain analogs, the trend for stereoretentive substitution is enhanced. Even the reaction with trialkyltin chlorides leads to partial racemization due to competing front face attack. Semiempirical calculations point to an increased degree of pyramidalization and to a higher barrier for
标题化合物 6 是通过光学活性氨基甲酸酯 5 与仲丁基锂/TMEDA 的立体定向去质子化生成的,并证明在 –78 °C 的醚溶液中构型完全稳定。与开链类似物相比,立体保留取代的趋势增强。甚至与氯化三烷基锡的反应也会由于竞争性正面攻击而导致部分外消旋化。半经验计算表明,在环状苄基锂化合物中,锥体化程度的增加和平面化的障碍更高,这两者都不利于背面攻击。