Effect of Linker Length on Selectivity and Cooperative Reactivity in Platinum-Catalyzed Asymmetric Alkylation of Bis(phenylphosphino)alkanes
作者:Brian J. Anderson、Samantha C. Reynolds、Marites A. Guino-o、Zhiming Xu、David S. Glueck
DOI:10.1021/acscatal.6b03004
日期:2016.12.2
centers and then catalytically alkylated to give 2a,b,d. From the diastereoselectivity and enantioselectivity of the transformations 1 → 2 and 3 → 2, the selectivity of each individual alkylation step (1 → 3R or 3S; 3R → 2RR or 2RS; 3S → 2SS or 2SR) could be determined as a function of linker length and compared to the selectivity of alkylation of the model monophosphines 4. The two alkylations of bis(secondary
双功能对称底物的催化不对称转化的选择性通常取决于两个反应位点之间的连接基。如果催化剂控制两个位点的反应选择性,则rac产物将通过不对称扩增以高对映体比率(er)形成。底物控制可能会增加此选择性(正合作性)或降低选择性(负合作性)。在这里,我们使用NaOSiMe 3碱研究了接头长度对双(仲膦)PhHP(CH 2)n PHPh(n = 2–6; 1a – e)与苄基溴的催化不对称烷基化反应选择性的影响。催化剂前体Pt((R,R)-Me-DuPhos)(Ph)(Cl)。这些反应,得到非对映体和对映体富集双(叔膦)PH(物理信道2)P(CH 2)Ñ P(CH 2 PH)博士(N = 2-6,图2a - ë)。Pt催化的模型膦PH(Ph)((CH 2)n H)(n = 2–6; 4a – e)苄基化得到对映体富集的P(CH 2 Ph)(Ph)((CH 2)n H )(n = 2–6; 5a – e)