Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Am Chem Soc. 2010 Feb 3;132(4):1264-6. doi: 10.1021/ja909689t.
The first asymmetric Kumada reactions of alkyl electrophiles are described, specifically, cross-couplings of racemic alpha-bromoketones with aryl Grignard reagents. Several features of this investigation are of interest. First, the couplings proceed at remarkably low temperature (-40 or -60 degrees C), which enables the asymmetric synthesis of racemization-prone alpha-arylketones. Second, dialkyl ketones undergo enantioselective coupling in good ee and yield. Third, readily available bis(oxazolines) are shown for the first time to be effective ligands for cross-couplings of alkyl electrophiles, thereby opening the door to new opportunities in asymmetric catalysis.
首次描述了烷基亲电试剂的不对称 Kumada 反应，具体而言，是外消旋的 α-溴代酮与芳基格氏试剂的交叉偶联。该研究有几个特点很有趣。首先，偶联反应在非常低的温度（-40 或-60°C）下进行，这使得易外消旋的α-芳基酮的不对称合成成为可能。其次，二烷基酮以良好的对映选择性ee 和产率进行偶联。第三，首次表明易于获得的双恶唑啉是烷基亲电试剂交叉偶联的有效配体，从而为不对称催化开辟了新的机会。
