Diastereoselective Hydroformylation of 2-Substituted Allylic o-DPPB-Esters—On the Origin of 1,2-Asymmetric Induction
作者:Bernhard Breit、Golo Heckmann、Stephan K. Zahn
DOI:10.1002/chem.200390044
日期:2003.1.20
addition, a crystal structure analysis of the hydroformylation product 2 d provided further confirmation of the relative configuration. Replacement of the ester carbonyl group of the o-DPPB by a methylene unit resulted in significantly worse diastereoselectivity in the course of the hydroformylation (34-->35), which indicates a decisive role for the ester carbonyl function. All the experimental observations
已经制备了2-取代的仲醇o-DPPB酯(o-DPPB =邻-二苯基膦基苯甲酰基),并研究了它们的o-DPPB指导的非对映选择性加氢甲酰基化。已经发现,在立体形成中心和在烯烃2-位上,非对映选择性随取代基的空间需求的增加而增加。通过-内酯29-相应的内酯30提供o-DPPB基团的水解裂解,其邻位立体异构中心的相对构型可通过2D-NOESY光谱法确定。另外,对加氢甲酰化产物2d的晶体结构分析提供了相对构型的进一步确认。O-DPPB的酯羰基被亚甲基取代会导致加氢甲酰化过程中的非对映选择性显着变差(34-> 35),这表明酯羰基功能起着决定性作用。将所有实验观察结果合并到标题反应过程中1,2-不对称诱导的起源模型中。关键特征是考虑非对映体的三角-双锥体铑-氢化-烯烃复合物I和II,它们能够基于Hammond假设充当决定选择性加氢金属化步骤过渡态的良好模型。通过力场方法对这些配合物的研究表明,理论上