铑催化分子内不对称碳氢硅化构建硅手性机理研究

有机合成化学家致力于发展新的活化模式，以实现对反应的精准调控。 这些活化模式能够实现特定化学键或原子的选择性转化，从而合成具有重 要应用价值或挑战性的化合物。反应机理的研究是发展新活化模式中重要 的一环。合成并鉴定反应关键中间体，不仅可以验证推测的反应路径，而 且为深入理解反应提供关键线索。根据捕获的反应中间体信息，可以指导 新方法学的发展，从根本上解决反应的难点。因此，反应机理的研究对于 促进反应发展具有重要意义。这将为有机合成带来新的机遇，推动该领域 不断创新与进步。 有机硅烷是一类重要的化合物。发展高效的合成方法来制备有机硅化 合物是合成化学研究的热点之一。其中，过渡金属催化的碳氢键硅基化反 应是高效构筑有机硅烷的重要途径，近年来得到了广泛发展。然而通过不 对称催化合成手性有机硅烷仍具有挑战性，尤其是二氢硅烷的不对称碳氢/ 硅氢脱氢偶联反应。难点在于：首先，反应的化学选择性难以控制，反应 底物中含有两个硅氢键，在过渡金属的作用下，很容易发生其他竞争反应， 如脱硅，自偶联，重排等。其次，反应的立体选择性难以控制，由于产物 中还含有一个硅氢键，可以继续与金属物种发生作用，导致消旋化。为了 解决反应存在的这些问题，对于该类反应机理的深入研究显得至关重要。 本论文以铑/双膦配体催化的联芳烃二氢硅烷分子内不对称碳氢硅化为 模板反应，系统地研究了分子内不对称碳氢/硅氢脱氢偶联反应的机理。首 先，通过原位磷谱监测到反应的关键中间体。随后，通过当量反应成功分 离并表征了该关键中间体为手性硅基铑二氢络合物，其在低温核磁中观察 到两个明显的铑氢信号。同时结合机理实验和理论计算明确了单氢硅烷产 物容易消旋的内在原因，确定了对映选择性控制步以及反应决速步等关键 问题，最终提出了合理的反应途径。通过对反应机理的深入了解，在先前 串联捕获策略合成四取代手性硅烷的基础上，通过位阻控制策略，解决了 手性单氢硅烷高对映选择性构建的难题。

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