Quinone Reduction by Organo-Osmium Half-Sandwich Transfer Hydrogenation Catalysts,Organometallics

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Quinone Reduction by Organo-Osmium Half-Sandwich Transfer Hydrogenation Catalysts
Organometallics ( IF 2.5 ) Pub Date : 2021-08-24 , DOI: 10.1021/acs.organomet.1c00358
Elizabeth M. Bolitho ₁ , Nathan G. Worby ₁ , James P. C. Coverdale ₁ , Juliusz A. Wolny ₂ , Volker Schünemann ₂ , Peter J. Sadler ₁

Affiliation

Organo-osmium(II) 16-electron complexes [Os^II(η⁶-arene)(R-PhDPEN)] (where η⁶-arene = para-cymene or biphenyl) can catalyze the reduction of prochiral ketones to optically pure alcohols in the presence of a hydride source. Such complexes can achieve the conversion of pyruvate to unnatural d-lactate in cancer cells. To improve the catalytic performance of these osmium complexes, we have introduced electron-donor and electron-acceptor substituents (R) into the para (R₁) or meta (R₂) positions of the chiral R-phenyl-sulfonyl-diphenylethylenediamine (R-PhDPEN) ligands and explored the reduction of quinones, potential biological substrates, which play a major role in cellular electron transfer chains. We show that the series of [Os^II(η⁶-arene)(R-PhDPEN)] derivatives exhibit high turnover frequencies, enantioselectivities (>92%), and conversions (>93%) for the asymmetric transfer hydrogenation (ATH) of acetophenone-derived substrates and reduce duroquinone and menadione to their di-alcohol derivatives. Modeling of the catalysis using density functional theory (DFT) calculations suggests a mechanism involving formic acid deprotonation assisted by the catalyst amine groups, phenyl-duroquinone stacking, hydride transfer to Os^II, possible CO₂ coordination, and tilting of the η⁶-arene ring, followed by hydride transfer to the quinone. These findings not only reveal subtle differences between Ru(II) and Os(II) catalysts, but also introduce potential biological applications.

中文翻译：

有机锇半夹心转移加氢催化剂还原醌

有机锇 (II) 16 电子配合物 [Os ^II (η ^{6 -}芳烃)(R-PhDPEN)]（其中 η ^{6 -}芳烃 =对伞花烃或联苯）可以催化前手性酮还原为光学纯醇氢化物源的存在。这种复合物可以在癌细胞中实现丙酮酸向非天然d-乳酸的转化。为了提高这些锇配合物的催化性能，我们在对位(R ₁ ) 或间位(R ₂) 手性 R-苯基-磺酰基-二苯基乙二胺 (R-PhDPEN) 配体的位置，并探索了在细胞电子转移链中起主要作用的潜在生物底物醌的还原。我们表明 [Os ^II (η ^{6 -}芳烃)(R-PhDPEN)] 系列衍生物在不对称转移氢化 (ATH) 中表现出高周转频率、对映选择性 (>92%) 和转化率 (>93%)。苯乙酮衍生的底物，并将杜罗醌和甲萘醌还原为它们的二元醇衍生物。使用密度泛函理论 (DFT) 计算的催化模型表明，涉及由催化剂胺基团辅助的甲酸去质子化、苯基-杜罗醌堆积、氢化物转移到 Os ^II、可能的 CO 的机制₂配位和 η ^{6 -}芳烃环倾斜，随后氢化物转移到醌。这些发现不仅揭示了 Ru(II) 和 Os(II) 催化剂之间的细微差别，而且还介绍了潜在的生物学应用。

更新日期：2021-09-13

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