The Catalyst Precursor, Catalyst, and Intermediate in the Ru^II‐Promoted Asymmetric Hydrogen Transfer between Alcohols and Ketones

Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts

“…Although CH 3 OH has been investigated previously as a hydrogen donor in CTH (12), the nature of the oxidized products from CH 3 OH has not been previously characterized. Moreover, these previous observations when coupled with the structural information obtained from NMR provides important insights on the nature of the ions formed at m∕z 444.1118 and m∕z 460.1064 as observed by DESI.…”

“…As a catalytic version of the classical MeerweinPondorf-Verley reduction/Oppenaur oxidation (6-10), CTH provides a mild method for both ketone reduction and alcohol oxidation. Previous studies show that methanol (CH 3 OH) can serve as a hydrogen donor for (arene)Ru complexes ligated by β-amino alcohols (11), but the nature of the oxidized products from CH 3 OH has not been previously characterized (12). Additionally, some Pd and Ru (13,14) catalysts can oxidize CH 3 OH to methyl formate (HCOOCH 3 ), but selective oxidation to methyl formate has not been observed previously for a transfer hydrogenation catalysis.…”

Ligand Design for Catalytic Asymmetric Reduction

“…In many cases, therefore, formic acid, an irreversible reducing agent, with (C 2 H 5 ) 3 N for tuning the acidity of reaction media gives higher conversion and better enantioselectivity. 105 Detailed experimental 106 as well as theoretical [107][108][109][110] studies revealed the mechanism of the asymmetric transfer hydrogenation in 2-propanol. As summarized in Figure 1.24, the NH effect is evident.…”

Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones

“…The active species in catalytic cycles, Ru-hydride (31 or 34) and Ru-amido complexes (32 or 35), have not only been detected but also isolated in some cases (Abdur-Rashid et al, 2001, 2002Haack et al 1997).…”