Aydin Juhanes, Kumar K Senthil, Sayah Mahmoud J, Wallner Olov A, Szabó Kálmán J
Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
J Org Chem. 2007 Jun 22;72(13):4689-97. doi: 10.1021/jo070288b. Epub 2007 May 25.
New easily accessible 1,1'-bi-2-naphthol- (BINOL-) and biphenanthrol-based chiral pincer complex catalysts were prepared for selective (up to 85% enantiomeric excess) allylation of sulfonimines. The chiral pincer complexes were prepared by a flexible modular approach allowing an efficient tuning of the selectivity of the catalysts. By employment of the different enantiomeric forms of the catalysts, both enantiomers of the homoallylic amines could be selectively obtained. Both allyl stannanes and allyl trifluoroborates can be employed as allyl sources in the reactions. The biphenanthrol-based complexes gave higher selectivity than the substituted BINOL-based analogues, probably because of the well-shaped chiral pocket generated by employment of the biphenanthrol complexes. The enantioselective allylation of sulfonimines presented in this study has important implications for the mechanism given for the pincer complex-catalyzed allylation reactions, confirming that this process takes place without involvement of palladium(0) species.
制备了新型易于获得的基于1,1'-联-2-萘酚（BINOL）和联菲罗啉的手性钳形配合物催化剂，用于亚磺酰亚胺的选择性烯丙基化反应（对映体过量高达85%）。通过灵活的模块化方法制备手性钳形配合物，可有效调节催化剂的选择性。通过使用不同对映体形式的催化剂，可以选择性地获得高烯丙基胺的两种对映体。烯丙基锡烷和烯丙基三氟硼酸盐均可作为反应中的烯丙基源。基于联菲罗啉的配合物比取代的基于BINOL的类似物具有更高的选择性，这可能是由于使用联菲罗啉配合物产生了形状良好的手性口袋。本研究中提出的亚磺酰亚胺的对映选择性烯丙基化反应对钳形配合物催化的烯丙基化反应机理具有重要意义，证实了该过程在没有零价钯物种参与的情况下发生。
