Roca Francesc X, Motevalli Majid, Richards Christopher J
Department of Chemistry, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK.
J Am Chem Soc. 2005 Mar 2;127(8):2388-9. doi: 10.1021/ja042930e.
The first highly enantioselective synthesis of planar chiral ferrocene phosphapalladacycles was performed by high-yielding asymmetric transcyclopalladation with cobalt oxazoline palladacycles (COP). Use of di-mu-acetatobis[(eta5-(S)-(pR)-2-(2'-(4'-isopropyl)oxazolinyl)cyclopentadienyl-C1,N3')(eta4-tetraphenylcyclobutadiene)cobalt]dipalladium(II), followed by acetate/chloride ligand exchange, gave (pS)-di-mu-chloro[2-(2-dicyclohexylphosphino)phenylferroene-C1,P)dipalladium(II) (95% ee). Similarly, diastereomeric di-mu-acetatobis[(eta5-(S)-(pS)-2-(2'-(4'-tert-butyl)oxazolinyl)cyclopentadienyl-C1,N3')(eta4-tetraphenylcyclobutadiene)cobalt]dipalladium(II) led to the enantiomeric (pR)-phosphapalladacycle (95% ee), revealing the control of these reactions by the element of planar chirality in COP. The reactions were extended to the synthesis of (pS)- and (pR)-di-mu-chloro[2-(2-diphenylphosphino)phenylferroene-C1,P)dipalladium(II) (78 and 92% ee, respectively). In all cases, the palladium-free precursors to COP were recovered for recycling.
通过与钴恶唑啉钯环配合物（COP）进行高产率的不对称反式环钯化反应，首次实现了平面手性二茂铁磷钯环配合物的高对映选择性合成。使用二-μ-乙酸双[(η5-(S)-(pR)-2-(2'-(4'-异丙基)恶唑啉基)环戊二烯基-C1,N3')(η4-四苯基环丁二烯)钴]二钯(II)，随后进行乙酸根/氯离子配体交换，得到(pS)-二-μ-氯[2-(2-二环己基膦基)苯基二茂铁-C1,P]二钯(II)（对映体过量95%）。类似地，非对映体二-μ-乙酸双[(η5-(S)-(pS)-2-(2'-(4'-叔丁基)恶唑啉基)环戊二烯基-C1,N3')(η4-四苯基环丁二烯)钴]二钯(II)生成对映体(pR)-磷钯环配合物（对映体过量95%），揭示了COP中平面手性元素对这些反应的控制。该反应扩展到了(pS)-和(pR)-二-μ-氯[2-(2-二苯基膦基)苯基二茂铁-C1,P]二钯(II)的合成（分别为对映体过量78%和92%）。在所有情况下，COP的无钯前体均可回收再利用。
