The reaction mechanism of Brønsted acid-catalyzed silane-dependent P═O reduction has been elucidated through combined computational and experimental methods. Due to its remarkable chemo- and stereoselective nature, the Brønsted acid/silane reduction system has been widely employed in organophosphine-catalyzed transformations involving P(V)/P(III) redox cycle. However, the full mechanistic profile of this type of P═O reduction has yet to be clearly established to date. Supported by both DFT and experimental studies, our research reveals that the reaction likely proceeds through mechanisms other than the widely accepted “dual activation mode by silyl ester” or “acid-mediated direct P═O activation” mechanism. We propose that although the reduction mechanisms may vary with the substitution patterns of silane species, Brønsted acid generally activates the silane rather than the P═O group in transition structures. The proposed activation mode differs significantly from that associated with traditional Brønsted acid-catalyzed C═O reduction. The uniqueness of P═O reduction originates from the dominant Si/O═P orbital interactions in transition structures rather than the P/H–Si interactions. The comprehensive mechanistic landscape provided by us will serve as a guidance for the rational design and development of more efficient P═O reduction systems as well as novel organophosphine-catalyzed reactions involving P(V)/P(III) redox cycle.

中文翻译：

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计算和实验相结合的研究揭示了布朗斯台德酸催化硅烷依赖性 P=O 还原的复杂机理


通过计算和实验相结合的方法，阐明了布朗斯台德酸催化的硅烷依赖性 P=O 还原的反应机理。由于其显着的化学和立体选择性性质，布朗斯台德酸/硅烷还原体系已广泛应用于涉及 P(V)/P(III) 氧化还原循环的有机膦催化转化中。然而，迄今为止，这种 P=O 还原的完整机制尚未明确。在 DFT 和实验研究的支持下，我们的研究表明，该反应可能通过广泛接受的“甲硅烷基酯双重活化模式”或“酸介导的直接 P=O 活化”机制以外的机制进行。我们提出，尽管还原机制可能随硅烷种类的取代模式而变化，但布朗斯台德酸通常会激活硅烷而不是过渡结构中的 P=O 基团。所提出的活化模式与传统的布朗斯台德酸催化 C=O 还原相关的活化模式显着不同。 P=O还原的独特性源于过渡结构中占主导地位的Si/O=P轨道相互作用，而不是P/H-Si相互作用。我们提供的综合机理景观将为合理设计和开发更高效的P=O还原系统以及涉及P(V)/P(III)氧化还原循环的新型有机膦催化反应提供指导。