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首页> 外文期刊>RSC Advances >Rhodium complex with unsymmetrical vicinal diamine ligand: excellent catalyst for asymmetric transfer hydrogenation of ketones
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Rhodium complex with unsymmetrical vicinal diamine ligand: excellent catalyst for asymmetric transfer hydrogenation of ketones

机译：具有不对称邻位二胺配体的铑配合物：酮不对称转移加氢的优异催化剂

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摘要

New unsymmetrical vicinal diamine ligands with systematic variation in the regio and stereo positions in the amine and sulphonamide groups were synthesized from cheap starting material such as norephedrine. Catalytic Asymmetric Transfer Hydrogenation (ATH) of aromatic alkyl ketones has been investigated using transition metal complexes and new derivatives of monotosylated unsymmetrical vicinal diamine ligands using sodium formate as the hydrogen source, in water and methanol. Chiral secondary alcohols were obtained with excellent enantioselectivity (>95% ee) and conversion of ketones (>95%) with [Rh(Cp*)Cl-2](2) and ligand 4 as a catalyst. Enantioselectivity was found to be slightly higher with the use of methanol as a solvent for ATH of ketones with sodium formate as the hydrogen source compared to water as a solvent and was found to be consistent with all the ketones investigated. The reaction mixture is homogeneous in methanol unlike in water, where substrate and product are insoluble in water and form separate phase, sodium formate being soluble in water. The activity and enantioselectivity obtained for ATH of ketones using [Rh(Cp*)Cl-2](2) and unsymmetrical vicinal diamine ligand as catalyst was comparable with the C2 symmetric benchmark ligands like TsDPEN ((1R, 2R)-N-(p-tolylsulfonyl)-1,2-diphenylethylene- diamine), and TsCYDN ((1R, 2R)-N-(p-tolylsulfonyl)-1,2-cyclohexyl, diamine) under similar reaction conditions. To the best of our knowledge, this is first example of the ATH of ketones with good activity and high enantioselectivity with [Rh(Cp*)Cl-2](2) and unsymmetrical vicinal diamine ligands as catalyst systems.
机译：从便宜的起始原料如去氧麻黄碱合成了新的不对称邻位二胺配体，其在胺和磺酰胺基团的区域和立体位置上都有系统性的变化。使用过渡金属络合物和以甲酸钠为氢源的单甲苯基化不对称邻二胺配体的新衍生物，在水和甲醇中，对芳香族烷基酮的催化不对称转移加氢（ATH）进行了研究。以[Rh（Cp *）Cl-2]（2）和配体4为催化剂，以优异的对映选择性（> 95％ee）和酮的转化率（> 95％）获得手性仲醇。与使用水作为溶剂相比，发现使用甲醇作为酮（以甲酸钠为氢源）进行ATH的溶剂时，对映选择性略高，并且发现与所有研究的酮相符。与在水中不同，反应混合物在甲醇中是均相的，在水中，底物和产物不溶于水并形成分离的相，而甲酸钠则溶于水。使用[Rh（Cp *）Cl-2]（2）和不对称邻位二胺配体作为催化剂获得的酮的ATH活性和对映选择性与TsDPEN（（1R，2R）-N-（对甲苯磺酰基）-1,2-二苯基乙二胺）和TsCYDN（（1R，2R）-N-（对甲苯磺酰基）-1,2-环己基二胺）。据我们所知，这是酮的ATH的第一个例子，该酮以[Rh（Cp *）Cl-2]（2）和不对称邻位二胺配体为催化剂体系，具有良好的活性和高的对映选择性。

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