(η 5 -( N , N -二甲氨基甲基)环戊二烯基)(η 4 -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得到平面手性环钯二-μ-氯化双[(η 5 - ( S p )-2-( N , N-二甲基氨基甲基)环戊二烯基,1- C ,3′- N )(η 4 -四苯基环丁二烯)钴]二钯[( S p )-Me 2 -CAP-Cl],92 % ee和 64% 的产率。通过纯化单体 ( R )-脯氨酸加合物并转化回氯化物二聚体,实现对映体纯度 (>98% ee )。AgOAc 处理得到 ( S p )-Me 2 -CAP-OAc,将其应用于不对称转环钯化(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,产率 39%)和吡咯烷基(>98% ee,产率 43%)钴夹心配合物。5 mol % 的后者 [( S p
(η 5 -( N , N -二甲氨基甲基)环戊二烯基)(η 4 -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得到平面手性环钯二-μ-氯化双[(η 5 - ( S p )-2-( N , N-二甲基氨基甲基)环戊二烯基,1- C ,3′- N )(η 4 -四苯基环丁二烯)钴]二钯[( S p )-Me 2 -CAP-Cl],92 % ee和 64% 的产率。通过纯化单体 ( R )-脯氨酸加合物并转化回氯化物二聚体,实现对映体纯度 (>98% ee )。AgOAc 处理得到 ( S p )-Me 2 -CAP-OAc,将其应用于不对称转环钯化(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,产率 39%)和吡咯烷基(>98% ee,产率 43%)钴夹心配合物。5 mol % 的后者 [( S p
Picolinamide as a Directing Group on Metal Sandwich Compounds: sp<sup>2</sup> C–H Bond Activation and sp<sup>3</sup> C–H Bond Oxidation
作者:Susanta Hazra、Mayukh Deb、Jatinder Singh、Anil J. Elias
DOI:10.1021/acs.organomet.7b00143
日期:2017.5.8
Palladium catalyzed bis-arylations, -alkylations, and -allyl-ations on the Cp ring of iron and cobalt sandwich compounds have been achieved using the bidentate picolinamide directing group. This directing group along with catalytic Pd(OAc)(2) was found to be highly efficient for C-H functionalization, giving up to 87% yields. The palladacyclic intermediate for the C-H activation of the Cp ring has been isolated and structurally characterized for the cobalt sandwich compound [eta(5)-C5H5]Co(eta(4)-C4Ph4). Attempted C-H annulation reactions using picolinamide-derived sandwich compounds did not yield the expected annulated products and instead oxidized the Cp- and picolinamide-bound CH2 unit to aldehydes. Detailed studies on this novel and unprecedented oxidation indicated that this happens only with the assistance of the picolinamide directing group. We have also shown that the sp(2) C-H functionalization and the sp(3) C-H oxidation can be effectively carried out as a one-pot reaction.