Highly chemoselective palladium-catalyzed conjugate reduction of. cap alpha. ,. beta. -unsaturated carbonyl compounds with silicon hydrides and zinc chloride cocatalyst
A three-component system comprised of a soluble palladium catalyst, hydridosilane, and zinc chloride is capable of efficient conjugate reduction of ..cap alpha..,..beta..-unsaturated ketones and aldehydes. The optimal set of conditions includes diphenylsilane as the most effective hydride donor, any soluble palladium complex in either the O or II oxidation state, when it is stabilized by phosphine ligands, and ZnCl/sub 2/ as the best Lewis acid cocatalyst. The reaction is very general with respect to a broad range of unsaturated ketones and aldehydes, and it is highly selective for these Michael acceptors, as reduction of ..cap alpha..,..beta..-unsaturated carboxylic acid derivatives is very sluggish under these conditions. When dideuteriodiphenylsilane is used to reduce unsaturated ketones, deuterium is stereoselectivity introduced at the less-hindered fact of the substrate and regioselectively at the ..beta..-position. Conversely, when reductions are carried out in the presence of traces of D/sub 2/O, deuterium incorporation occurs at the ..cap alpha..-position. On the basis of deuterium-incorporation experiments and /sup 1/H NMR studies a catalytic cycle is postulated in which the first step involves reversible coordination of the palladium complex to the electron-deficient olefin and oxidative addition of silicon hydride to form a hydridopalladium olefin complex.
- Research Organization:
- Weizmann Inst. of Science, Rehovot (Israel)
- OSTI ID:
- 6996830
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 108:23
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALDEHYDES
REDUCTION
KETONES
PALLADIUM
CATALYTIC EFFECTS
SILANES
ZINC CHLORIDES
CARBONYLS
CATALYSIS
CATALYSTS
EXPERIMENTAL DATA
LEWIS ACIDS
LIGANDS
VALENCE
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
DATA
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
METALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
PLATINUM METALS
SILICON COMPOUNDS
TRANSITION ELEMENTS
ZINC COMPOUNDS
ZINC HALIDES
400201* - Chemical & Physicochemical Properties