117356-99-7Relevant academic research and scientific papers
Quinone Reduction by Organo-Osmium Half-Sandwich Transfer Hydrogenation Catalysts
Bolitho, Elizabeth M.,Coverdale, James P. C.,Sadler, Peter J.,Schünemann, Volker,Wolny, Juliusz A.,Worby, Nathan G.
, p. 3012 - 3023 (2021)
Organo-osmium(II) 16-electron complexes [OsII(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 http://www.w3.org/1999/xlinkd-lactate in cancer cells. To improve the catalytic performance of these osmium complexes, we have introduced electron-donor and electron-acceptor substituents (R) into thepara(R1) ormeta(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 [OsII(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 OsII, possible CO2coordination, 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.
