Stereoselective Pinacol Coupling of Chiral Formylferrocene Using Divalent Samarium Triflate: Preparation of a New Chiral Bisferrocenyl Oxazoline Ligand and Its Application to Asymmetric Diels−Alder Reactions

The pinacol coupling reaction of planar chiral ortho-oxazoline-substituted formylferrocene was smoothly mediated by SmI2 or Sm(OTf)3 to give
the (R,R) isomer selectivity (up to 76% diastereomeric excess). The combination of Yb(OTf)3 and the (R,R)-ferrocenyl diol was revealed to be
a good catalyst for the asymmetric Diels−Alder reaction of 3-acyloxazolidinone with cyclopentadiene, and the endo adduct was produced in
up to 80% enantiomeric excess.

以二碘化钐（SmI₂）或三氟甲磺酸钐(III)（Sm(OTf)₃）为介导试剂，可顺利实现平面手性邻恶唑啉取代甲酰基二茂铁的频哪醇偶联反应，产物呈现优异的(R,R)构型异构体选择性，最高非对映体过量值可达76%。研究发现，三氟甲磺酸镱(III)（Yb(OTf)₃）与(R,R)-二茂铁二醇的组合体系可作为优良催化剂，用于3-酰基恶唑烷酮与环戊二烯的不对称狄尔斯-阿尔德反应，所得内型加成产物的对映体过量值最高可达80%。