The present study addresses the challenges in catalytic transfer hydrogenation using methanol/ethanol for converting biomass-derived furanic aldehydes to furfuryl alcohols. The introduction of air-stable Ru(II)-para-cymene catalysts with imidazole-based metal–ligand cooperativity represents a significant advancement. Spectroscopic, in situ monitoring, labeling, and DFT investigations reveal mechanistic details, highlighting the role of Ru–H generation through the dehydrogenation of Ru(II)-alkoxide intermediates. Hydride and proton transfers are facilitated by the interconvertible coordination mode of imidazole with Ru(II)–para-cymene, which is crucial for maintaining the catalyst’s efficiency and selectivity. Notably, the pK_a of the N–H in coordinated imidazole significantly influences the reactivity, following a specific order depending on the attached heterocycle: imidazole > pyridine > thiazole. This order correlates well with the computed activation barrier for Ru–H generation. The catalyst exhibits ease of synthesis, stability in air and moisture, use of renewable hydrogen sources, excellent selectivity for aldehydes, applicability to various furanic aldehydes, and potential for large-scale processes. These features collectively contribute to the economic and sustainable nature of both the catalyst and the protocol, providing a valuable contribution to the field of catalytic transfer hydrogenation.

中文翻译：

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明确的鲁棒咪唑基金属-配体合作Ru(II)-对伞花烃，用于使用可再生醇进行呋喃醛的转移氢化

本研究解决了使用甲醇/乙醇催化转移氢化将生物质衍生的呋喃醛转化为糠醇的挑战。具有咪唑基金属配体协同作用的空气稳定性 Ru(II)-对伞花烃催化剂的引入代表了一项重大进步。光谱、原位监测、标记和 DFT 研究揭示了机制细节，强调了通过 Ru(II)-醇盐中间体脱氢生成 Ru-H 的作用。咪唑与Ru(II)-对伞花烃的可相互转换配位模式促进了氢化物和质子的转移，这对于保持催化剂的效率和选择性至关重要。值得注意的是，配位咪唑中 N-H 的 pKa显着影响反应活性，具体顺序取决于所连接的杂环：咪唑 > 吡啶 > 噻唑_。该顺序与计算的 Ru-H 生成激活势垒密切相关。该催化剂具有易于合成、在空气和湿气中稳定、可使用可再生氢源、对醛具有优异的选择性、对各种呋喃醛的适用性以及大规模生产的潜力。这些特征共同促进了催化剂和方案的经济性和可持续性，为催化转移氢化领域做出了宝贵的贡献。