Rationalization of Enantioselectivities in Dialkylzinc Additions to Benzaldehyde Catalyzed by Fenchone Derivatives
作者:Bernd Goldfuss、Melanie Steigelmann、Saeed I. Khan、K. N. Houk
DOI:10.1021/jo991070v
日期:2000.1.1
Three (-)-fenchyl alcohol derivatives, ¿(1R,2R,4S)-exo-(2-Ar)-1,3, 3-trimethylbicyclo[2.2.1] heptan-2-ol, Ar = o-anisyl (2), 2-N-methylimidazolyl (3), 2-N,N-dimethylbenzylamine (4)¿ were synthesized, characterized by X-ray analyses, and employed as precatalysts in diethyl zinc additions to benzaldehyde. Directions and relative degrees of enantioselectivities are rationalized by QM/MM ONIOM computations
三个(-)-酚醇衍生物,(1R,2R,4S)-exo-(2-Ar)-1,3,3-三甲基双环[2.2.1]庚烷-2-醇,Ar =邻茴香基( 2)合成了2-N-甲基咪唑基(3),2-N,N-二甲基苄基胺(4),通过X射线分析表征,并用作苯甲醛中二乙基锌加成中的前催化剂。通过mu-O过渡结构模型的QM / MM ONIOM计算可合理化对映选择性的方向和相对程度。对映选择性是由锌中心的“转移”或“被动”烷基与供体基团或双环[2.2.1]庚烷基团上的取代基之间的排斥性相互作用引起的。这些结果使得能够进行配体调节以提高在醛中的二烷基锌加成中基于内酯的配体的催化剂效率的预测。