Hydrosilylation iron acetate

A catalytic mechanism, which is supported by deuterium-labeling experiments in the corresponding Ru-catalyzed procedure [146], is shown in Scheme 47. Accordingly, the reactive Fe-hydride species is formed in situ by the reaction of the iron precatalyst with hydrosilane. Hydrosilylation of the carboxyl group affords the 0-silyl-A,0-acetal a, which is converted into the iminium intermediate b. Reduction of b by a second Fe-hydride species finally generates the corresponding amine and disiloxane. 

Carbonyl groups can be catalytically reduced in a two-step procedure consisting of hydrosilylation followed by acid or F" work-up. A number of iron containing catalyst systems has been described for this transformation. Hydrosilylation of preferably aromatic ketones is achieved using iron(II) acetate as catalyst in the presence of nitrogen... 

Iron(II) acetate in the presence of tricyclohexylphosphane as ligand is an efficient catalyst for the hydrosilylation of a variety of aryl, heteroaryl, alkyl, and a,P-unsaturated aldehydes to afford the corresponding primary alcohols (Scheme 4-327). Polymethyl-hydrosiloxane (PMHS) is employed as hydride source... 

Other procedures for carbonyl hydrosilylation of aldehydes and ketones are using [bis(imino)pyridine]iron dinitrogen and dialkyl complexes as precatalysts. Only 0.1-1.0 mol% catalyst are required to achieve this transformation. The reductants are either phenylsilane or diphenylsilane in this case. A number of enantioselective versions of the hydrosilylation reaction is described. This includes the application of 1,2-bis[(25, 55)-2,5-dimethylphospholano]benzene [(S,5)-Me-DuPhos] (Scheme 4-328) as chiral ligand, iron(II) acetate as a precatalyst and polymethylhydrosiloxane as hydride source. A large variety of ketones can be transformed into the corresponding alcohols in excellent yield and up to 99% enantiomeric excess. Catalytic ketone hydrosilylation is also achieved with the dialkyliron complexes (S,S)-... 

Employment of chiral bis(oxazolinylphenyl)amines such as SJS)-BopsL-dpm (Scheme 4-328) as ligands for iron catalysts leads to almost quantitative yields and high enantioselectivities for the asymmetric hydrosilylation of ketones and asymmetric conjugate hydrosilylation of enones with (diethoxy)methylsilane as reductant (Scheme 4-329). Both enantiomers of the hydrosilylation product can be obtained from the same chiral ligand by a slight variation of the reaction conditions. The mixed catalyst system of (S -Bopa-dpm and iron(II) acetate provides the (/ )-enantiomer of the alcohol... 

Hydrosilylation of vinylmethylsilane with chlorosilanes has been reported using catalytic amounts of tetracarbonyl(Ti -trimethylsilylethene)iron. A product mixture consisting of isomeric disilylethanes, monosilylethane, and disilylated ethene was obtained. Acrolein diethyl acetal can be hydrosilylated with triethylsilane in the presence of 1 mol% pentacarbonyliron to give the corresponding Markovnikov product (Scheme 4-335). Allyl alcohols afford a mixture of the allyl silyl ether and the alltyl silyl ether, whereas acrolein leads to a mixture of cis and trans silyl enol ethers. ... 

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