Dinuclear and ansa-titanocenes for enantioselective catalyst-controlled radical reactions and further applications

自由基反应在聚合反应中起着至关重要的作用，并且最近在明确定义的C-C键形成反应中变得越来越重要。然而，实现催化的对映选择性自由基反应仍然存在问题。最近，我们证明，自由基环化酮腈运行在手性柄型二茂钛催化剂的存在下进行特殊的对映体选择性，因此，具有良好的催化剂控制。基于我们的机理研究，我们在此提出了手性双核茂钛催化剂的发展，实现进一步的分子内和分子间的对映选择性自由基反应。这包括合成手性桥连的Cp配体的新策略。我们的方法将进一步导致快速和立体选择性合成手性柄型二茂钛和Cp-配合物的其他金属，我们将评估在典型的应用和新的反应。这将克服茂金属合成中的几个经典问题，并大大拓宽此类催化剂的应用范围。

Radical reactions play a crucial role in polymerization reactions and, more recently, are becoming increasingly important in well-defined C-C bond forming reactions. Realizing catalytic enantioselective radical reactions, however, has remained problematic. Recently, we demonstrated that radical cyclizations of ketonitriles run in presence of a chiral ansa-titanocene catalyst proceed with exceptional enantioselectivity and, thus, with excellent catalyst control. Based on our mechanistic studies, we herein propose the development of chiral dinuclear titanocene catalysts for the realization of further intra- and intermolecular enantioselective radical reactions. This includes new strategies for the synthesis of chiral-bridged cyclopentadienyl (Cp) ligands. Our approach will further lead to rapid and stereoselective syntheses of chiral ansa-titanocenes and Cp-complexes of other metals, which we will evaluate in typical applications and novel reactions. This way, we will overcome several classical problems in metallocene synthesis and significantly broaden the application range of such catalysts.