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

Abstract

A series of natural amino acid (alanine, valine, phenylalanine, and isoleucine) amides have been synthesized and fully characterized. They have been used as supporting ligands in the Ru(II)-catalyzed asymmetric transfer hydrogenation (ath) of acetophenone in the presence of i-PrOH/KOH. Secondary amides impart high reactivity to the corresponding Ru(II) complexes, with TOFs up to 1680 h -1 and ee's up to 47%. The amino acid and the substituents of the amide nitrogen govern the activity and the enantioselectivity of the catalytic processes. The precatalysts obtained by reacting (L)-phenylalanine p-anisidineamide and (L)-valine o-anisidineamide with [Ru(p-cymene)Cl 2 ] 2 have been isolated and characterized as the half-sandwich complexes [(η 6 -p-cymene)Ru(κ 2 -N,N′-aminoamidato)Cl] (10 and 11, respectively). An ESI-MS study conducted on the acetophenone reduction catalyzed by 11 has led to the detection of the organometallic intermediates involved in the catalytic cycle: the precatalyst 11, the 16ecomplex [(η 6 -p-cymene)Ru(κ 2 -N,N′-diamide)] 12, and the hydride [(η 6 -p-cymene)Ru(κ 2 -N,N′-aminoamidato)H] 13.

Ru(II)‐η6‐benzene Complexes of Dibenzosuberenyl Appended Aroyl/Acylthiourea Ligands: In vitro Biomolecular Interaction Studies and Catalytic Transfer Hydrogenation

“…The para halo substituted aromatic ketone substrates, such as F (Table 5, entry 4), Cl (Table 5, entry 5) and Br (Table 5, entry 6) reduced the electron density around C=O bond so that the activity was enhanced, which giving growth to easier hydrogenation. [59,60] Additionally, 2-acetylthiophene and 2-acetyl furan were efficiently hydrogenated (Table 5, entries 11 and 12) to their respective alcohols and 2-adamantanone is converted to adamantan-2-ol in good manner (Table 5, entry 8). Benzhydrol is used as an essential constituent in antihistamines, antihypertensive, antiallergenic agents and a valuable synthetic intermediate in pharmaceuticals, agrochemicals, and other organic compounds.…”

The application of electrospray ionization mass spectrometry to homogeneous catalysis

“…Since then, the primary use of ESI-MS in the area of solution-phase organometallic chemistry has been in the identification of short-lived, low concentration intermediates from catalytic mixtures. Toward this end, ESI-MS has been used to study catalytic oxidations [5][6][7][8], hydrogenations [9][10][11], hydrosilylations [12] and carbon-carbon bond-forming [13][14][15] reactions with the most attention given to palladium-catalyzed carbon-carbon bond-forming reactions [14,[16][17][18][19][20][21]. A number of book chapters have been written on the subject of ESI-MS analysis of organometallic reaction intermediates [22][23][24] and this review aims to highlight more recent advances and new directions in the field.…”

New chiral phosphinite ligands with C2‐symmetric axis and their possible applications in Ru‐catalyzed asymmetric transfer hydrogenation

“…In addition, the catalytic activity of [Ru(η 6 -p-cymene)(µ-Cl)Cl] 2 under the applied experimental conditions is negligible. [51,52] However, when the temperature was increased to 82…”