Comprehensive Experimental and Theoretical Studies of Configurationally Labile Epimeric Diamine Complexes of α-Lithiated Benzyl Carbamates
作者:Stefan Grimme、Dieter Hoppe、Heiko Lange、Robert Huenerbein、Birgit Wibbeling、Roland Fröhlich
DOI:10.1055/s-2008-1067242
日期:2008.9
Different primary benzyl-type carbamates were deprotonated by sec-butyllithium in the presence of a tert-leucinol-derived bis(oxazoline) ligand. The resulting configurationally labile epimeric complexes equilibrated and one diastereomer was strongly favored in the equilibria. After dynamic thermodynamic resolution, the complexes could be trapped with different classes of electrophiles to yield highly enantioenriched secondary benzyl carbamates. The stereochemical course of the substitution reactions was elucidated. High-level quantum chemical investigations were performed and allowed a prediction of both the favored complex and the enantiomeric excess that could be expected within the reactions.
在叔亮氨醇衍生的双(恶唑啉)配体存在下,不同主要苄基型氨基甲酸酯被仲丁基锂去质子化。由此得到的构型易变的差向异构复合物达到平衡,其中一个异构体在平衡中占优势。经过动力学热力学拆分后,这些复合物可以通过不同类别的亲电试剂捕获,生成高度对映体富集的次级苄基氨基甲酸酯。取代反应的立体化学过程被阐明。进行了高水平的量子化学研究,并能够预测出占优势的复合物和在反应中可预期的对映体过量。