Mechanistic aspects of the rhodium-catalyzed enantioselective transfer hydrogenation of [alpha],[beta]-unsaturated carboxylic acids using formic acid/triethylamine (5:2) as the hydrogen source

Journal Article · Tue Jan 12 23:00:00 EST 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00054a021· OSTI ID:6483189

Leitner, W ^[1]; Brown, J M ^[2]; Brunner, H ^[3]

---

1. Univ. of Oxford (United Kingdom) Universitaet Regensburg (Germany)
2. Univ. of Oxford (United Kingdom)
3. Universitaet Regensburg (Germany)

The mechanism of the rhodium-catalyzed enantioselective transfer hydrogenation of methylenebutanedioic acid (itaconic acid) (1) and related [alpha],[beta]-unsaturated carboxylic acids using formic acid/triethylamine (5:2) as the hydrogen source is investigated. Kinetic studies using [sup 1]H NMR spectroscopy are presented. Formic acid decomposition is shown to be the rate-limiting step with 1 as the substrate, while hydrogen transfer turns out to be rate determining in the case of (E)-(phenylmethylene)butanedioic acid ((E)-phenylitaconic acid) (3). Furthermore, extensive use is made of deuterium labeling and the analysis of part-deuterated products by [sup 1]H and [sup 13]C[l brace][sup 1]H,[sup 2]H[r brace] NMR spectroscopy. Taken together, these results indicate that the mechanism of rhodium-catalyzed transfer hydrogenation with formic acid/triethylamine as the hydrogen source most likely involves decarboxylation of a transient formate species to form hydridic complexes of rhodium, in which the Rh-H entity has a long lifetime relative to hydrogen transfer to the substrate. 40 refs., 5 figs., 1 tab.

• OSTI ID: 6483189
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:1; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CARBOXYLIC ACIDS
CATALYSIS
CATALYTIC EFFECTS
CHEMICAL REACTIONS
COMPLEXES
DICARBOXYLIC ACIDS
HOMOGENEOUS CATALYSIS
HYDROGEN TRANSFER
HYDROGENATION
ITACONIC ACID
LABELLED COMPOUNDS
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
RESONANCE
RHODIUM COMPLEXES
STEREOCHEMISTRY
TRANSITION ELEMENT COMPLEXES