School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom.
J Org Chem. 2020 Apr 3;85(7):4838-4847. doi: 10.1021/acs.joc.9b03342. Epub 2020 Mar 13.
All four possible diastereoisomers of phosphinoferrocenyloxazoline (Phosferrox type) ligands containing three elements of chirality were synthesized as single enantiomers. The configured oxazoline moiety (R = Me, -Pr) was used to control the generation of planar chirality by lithiation, with the alternative diastereoisomer formed by use of a deuterium blocking group. In each case subsequent addition of PhPCl followed by -TolMgBr resulted in a single -stereogenic diastereoisomer (,, and ,,, respectively). The alternative diastereoisomers were formed selectively by addition of -TolPCl followed by PhMgBr ((,, and ,,, respectively). Preliminary application of these four ligand diastereoisomers, together with (,) and (,) Phosferrox (PPh), to palladium catalyzed allylic alkylation of -1,3-diphenylallyl acetate revealed a stepwise increase/decrease in ee, with the configuration of the matched/matched diastereoisomer as ,, (97% ee).
所有四个可能的膦代二茂铁氧氮唑（Phosferrox 型）配体的非对映异构体都被合成了单一对映异构体，这些配体含有三个手性元素。构型的噁唑啉部分（R = Me，-Pr）被用来通过锂化控制平面手性的产生，形成的另一种非对映异构体则通过使用氘阻断基团来形成。在每种情况下，随后加入 PhPCl ，然后加入-TolMgBr ，得到单一的-手性非对映异构体（，和，，分别）。通过加入-TolPCl ，然后加入 PhMgBr ，可以选择性地形成另一种非对映异构体（，，和，，分别）。这四种配体非对映异构体与（，）和（，）Phosferrox（PPh）一起初步应用于钯催化的-1,3-二苯基烯丙基醋酸酯的烯丙基烷基化反应，发现 ee 值呈逐步增加/减少的趋势，匹配/匹配非对映异构体的构型为，，（97%ee）。
