The open d-shell enforces the active space in 3d metal catalysis: highly enantioselective chromium(ii) pincer catalysed hydrosilylation of ketones.
The open d-shell enforces the active space in 3d metal catalysis: highly enantioselective chromium(ii) pincer catalysed hydrosilylation of ketones.
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DOI：
10.1039/c8cc05172k
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发表时间：
2018-08
影响因子：
4.9
通讯作者：
Christian H. Schiwek;V. Vasilenko;H. Wadepohl;L. Gade
中科院分区：
文献类型：
--
作者：
Christian H. Schiwek;V. Vasilenko;H. Wadepohl;L. Gade
双（恶唑啉基二甲基甲基）吡咯（PdmBox）立体定向配体为铬（II）催化的酮的高对映选择性硅氢加成反应提供了关键。一种罕见的正方形平面，手性铬（ii）烷基络合物被发现作为一个有效的预催化剂，用于减少广泛的芳基烷基和二烷基酮衍生物。铬（II）的开放式d4壳层的立体电子偏好将分子催化剂牢牢地锁定在正方形平面几何形状中，从而产生配位球的两个受阻象限。这种富含地球的贱金属催化平台在温和的反应条件（_40 °C至室温）和低催化剂负载（低至0.5摩尔%）下以高达98%ee的优异的分离产率产生相应的手性醇。
Bis(oxazolinyldimethylmethyl)pyrrol (PdmBox) stereodirecting ligands provided the key to the chromium(ii)-catalysed highly enantioselective hydrosilylation of ketones. A rare square planar, chiral chromium(ii) alkyl complex was found to serve as a potent precatalyst for the reduction of a broad range of aryl alkyl and dialkyl ketone derivatives. The stereoelectronic preference of the open d4 shell of chromium(ii) firmly locks the molecular catalyst in a square planar geometry giving rise to two blocked quadrants of the coordination sphere. This earth-abundant base metal catalytic platform produces the corresponding chiral alcohols in excellent isolated yields with up to 98 %ee under mild reaction conditions (-40 °C to rt) and at low catalyst loadings (as low as 0.5 mol%).