Transfer Hydrogenation of Acetophenone Catalyzed by Half-Sandwich Ruthenium(II) Complexes Containing Amino Amide Ligands. Detection of the Catalytic Intermediates by Electrospray Ionization Mass Spect

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• 作者：Paolo Pelagatti ; Mauro Carcelli ; Francesca Calbiani ; Claudio Cassi ; Lisa Elviri ; Corrado Pelizzi ; Umberto Rizzotti ; and Dominga Rogolino
• 刊名：Organometallics
• 出版年：2005
• 出版时间：November 21, 2005
• 年：2005
• 卷：24
• 期：24
• 页码：5836 - 5844
• 全文大小：180K
• 年卷期：v.24,no.24(November 21, 2005)
• ISSN：1520-6041

文摘

A series of natural amino acid (alanine, valine, phenylalanine, and isoleucine) amideshave been synthesized and fully characterized. They have been used as supporting ligandsin the Ru(II)-catalyzed asymmetric transfer hydrogenation (ath) of acetophenone in thepresence of i-PrOH/KOH. Secondary amides impart high reactivity to the correspondingRu(II) complexes, with TOFs up to 1680 h^-1 and ee's up to 47%. The amino acid and thesubstituents of the amide nitrogen govern the activity and the enantioselectivity of thecatalytic processes. The precatalysts obtained by reacting (L)-phenylalanine p-anisidineamideand (L)-valine o-anisidineamide with [Ru(p-cymene)Cl₂]₂ have been isolated and characterizedas the half-sandwich complexes [(es/gifchars/eta.gif" BORDER=0 >⁶-p-cymene)Ru(es/gifchars/kappa.gif" BORDER=0 >²-N,N'-aminoamidato)Cl] (10 and 11,respectively). An ESI-MS study conducted on the acetophenone reduction catalyzed by 11has led to the detection of the organometallic intermediates involved in the catalytic cycle:the precatalyst 11, the 16e^- complex [(es/gifchars/eta.gif" BORDER=0 >⁶-p-cymene)Ru(es/gifchars/kappa.gif" BORDER=0 >²-N,N'-diamide)] 12, and the hydride[(es/gifchars/eta.gif" BORDER=0 >⁶-p-cymene)Ru(es/gifchars/kappa.gif" BORDER=0 >²-N,N'-aminoamidato)H] 13.