Enantioselective synthesis and application to the allylic imidate rearrangement of amine-coordinated palladacycle catalysts of cobalt sandwich complexes.
Enantioselective synthesis and application to the allylic imidate rearrangement of amine-coordinated palladacycle catalysts of cobalt sandwich complexes.
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DOI：
10.1002/chem.201302922
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发表时间：
2013-12-23
期刊：
影响因子：
--
通讯作者：
Richards CJ
中科院分区：
文献类型：
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作者：
Cassar DJ;Ilyashenko G;Ismail M;Woods J;Hughes DL;Richards CJ
（η5-（N，N-二甲氨基甲基）环戊二烯基）（η4-四苯基环丁二烯）钴与四氯钯酸钠和（R）-N-乙酰基苯丙氨酸反应，合成了平面手性二μ-氯代钯双[（η5-（Sp）-2-（N，N-二甲氨基甲基）环戊二烯基，1-C，3′-N）（η4-四苯基环丁二烯）钴]二钯[（Sp）-Me 2-CAP-Cl]，ee = 92%，收率64%。通过纯化单体（R）-脯氨酸加合物并转化回氯化物二聚体来实现对映体纯度（> 98%ee）。用AgOAc处理得到（Sp）-Me 2-CAP-OAc，其用于不对称反式环钯化（高达78%ee）。（R）-N-乙酰基苯丙氨酸介导的钯化方法也适用于相应的N，N-二乙基（82%ee，39%产率）和吡咯烷基（> 98%ee，43%产率）钴夹心络合物。5摩尔%的后者[（Sp）-Pyrr-CAP-Cl]和AgNO 3（3.8当量）的组合是用于（E）-N-芳基三氟乙酰亚胺酯的烯丙基亚氨酸酯重排的催化剂（高达83%ee），并且该催化剂体系也适用于一系列（E）-三氯乙酰亚胺酯的重排（高达99%ee）。这种不对称效率与催化剂合成的简单性相结合，为生成非外消旋烯丙基胺衍生物提供了可获得的解决方案。
The reaction of (η5-(N,N-dimethylaminomethyl)cyclopentadien-yl)(η4-tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (R)-N-acetylphenylalanine gave planar chiral palladacycle di-μ-chloridebis[(η5-(Sp)-2-(N,N-dimethylaminomethyl)cyclopentadienyl,1-C,3′-N)(η4-tetraphenylcyclobutadiene)cobalt]dipalladium [(Sp)-Me2-CAP-Cl] in 92 % ee and 64 % yield. Enantiopurity (>98 % ee) was achieved by purification of the monomeric (R)-proline adducts and conversion back to the chloride dimer. Treatment with AgOAc gave (Sp)-Me2-CAP-OAc which was applied to asymmetric transcyclopalladation (up to 78 % ee). The (R)-N-acetylphenylalanine mediated palladation methodology was applicable also to the corresponding N,N-diethyl (82 % ee, 39 % yield) and pyrrolidinyl (>98 % ee, 43 % yield) cobalt sandwich complexes. A combination of 5 mol % of the latter [(Sp)-Pyrr-CAP-Cl] and AgNO3 (3.8 equiv) is a catalyst for the allylic imidate rearrangement of an (E)-N-aryltrifluoroacetimidate (up to 83 % ee), and this catalyst system is also applicable to the rearrangement of a range of (E)-trichloroacetimidates (up to 99 % ee). This asymmetric efficiency combined with the simplicity of catalyst synthesis provides accessible solutions to the generation of non-racemic allylic amine derivatives.