Selective reduction of carboxylic acids to aldehydes through manganese catalysed hydrosilylation (original) (raw)
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Advanced Synthesis & Catalysis, 2013
A palladium catalyst system that allows the reduction of carboxylic acids to the corresponding aldehydes with hydrosilanes as reducing agent and pivalic anhydride as an indispensable reagent has been developed. A simple mixture of commercially available bis(dibenzylideneacetone)palladium(0) [PdA C H T U N G T R E N N U N G (dba) 2 ], tri(para-tolyl)phosphane and methylphenylsilane realized the reduction of various aliphatic carboxylic acids as well as benzoic acids to aldehydes in good to high yields.
A Convenient and General Iron-Catalyzed Hydrosilylation of Aldehydes
Organic Letters, 2007
A general and highly chemoselective hydrosilylation of aldehydes using iron catalysts is reported. Fe(OAc) 2 in the presence of tricyclohexylphosphine as ligand and polymethylhydrosiloxane (PMHS) as an economical hydride source forms an efficient catalyst system for the hydrosilylation of a variety of aldehydes. Aryl, heteroaryl, alkyl and r, -unsaturated aldehydes are successfully reduced to the corresponding primary alcohols. Broad substrate scope and high tolerance against several functional groups make the process synthetically useful.
An Efficient Catalyst Based on Manganese Salen for Hydrosilylation of Carbonyl Compounds
Organometallics, 2013
Manganese salen complexes were prepared according to the literature. All the substrates and reagents were obtained commercially and were degasified and dried over molecular sieves prior to the reaction. The 1 H and 13 C NMR spectra were recorded on a Bruker AVANCE-500 NMR spectrometer and referenced to the residue peaks in CDCl 3 (7.26), CD 3 CN (1.94), or C 6 D 6 (7.16). GC-MS analyses were performed on an HP 5890 GC/HP 5971/B MSD system with electron impact ionization (70 eV) and a DB5 column (30m x 0.53 mm ID, 0.25 µm thick; initial temperature 50 °C, initial time 1 min; ramp rate 10 °C/min; final temperature 310 °C, final time 5 min or 20min). High resolution mass spectrometry (HRMS) was performed using high-resolution time of flight G1969A instrumentation (Agilent, Santa Clara, CA, USA). UV-vis measurement was performed on a PerkinElmer Lamda 35 spectrophotometer. Catalytic hydrosilylation. In a typical procedure, MnN catalyst 1 (2-3 mg, 0.5 mol%), substrate (~1 mmol, 2.0 equivalents), CD 3 CN (0.30-0.35 mL), and PhSiH 3 (1 equivalent) were added to a J Young NMR tube, usually in that order. Trimethylphenylsilane was used as an internal standard (5-10 mol%). This was then heated in an oil bath at ~80 °C and the reaction progress was monitored by 1 H NMR at preset times. After the reaction was complete or nearly complete, the mixture was transferred to a round bottom flask with diethylether, and hydrolyzed with aqueous HCl or TBAF (tetrabutylammonium fluoride). A small aliquot of sample was taken and analyzed by GC-MS before and after the hydrolysis. After hydrolysis, the organic layer was extracted with ether and subjected to column chromatography using silica with hexane-EtOAc as eluent. The resultant products were characterized by 1 H NMR and GC-MS analysis in comparison with literature data or authentic samples. Synthesis and Characterization of Manganese salen complex [MnN(salen-3,5-t Bu 2)] (1): The complex was prepared according to the literature. 1 The data here were obtained to verify its identity. 1
A Simple Method for the Reduction of Carboxylic Acids to Aldehydes or Alcohols Using H 2 and Pd/C
Journal of Organic Chemistry, 1999
Aldehydes are versatile compounds in organic synthesis. Despite their intrinsic benefits, there are relatively few methods for their preparation. 1 A common approach to obtain aldehydes is in fact the oxidation of primary alcohols 2 or the reduction of carboxylic acids and their derivatives. 3 This last transformation is particularly useful for the preparation of N-protected R-amino aldehydes 4 that are valuable intermediates for the synthesis of biologically active compounds. 5 Several methods employed for the preparation of protected amino aldehydes make use of complex metal hydrides as the reducing agents and esters or amides as the starting material (for example DIBAL-H on methyl esters 6 and LiAlH 4 on particularly reactive amides 7 ).
Dioxomolybdenum(vi) complexes as catalysts for the hydrosilylation of aldehydes and ketones
Dalton Trans., 2006
We report herein the possibility to perform the hydrosilylation of carbonyls, using actinide complexes as catalysts. While complexes of the uranyl ion [UO2] 2+ have been poorly considered in catalysis, we show the potentialities of the Lewis acid [UO2(OTf)2] (1) in the catalytic hydrosilylation of a series of aldehydes. [UO2(OTf)2] proved a very active catalyst affording distinct reduction products depending on the nature of the reductant. With Et3SiH, a number of aliphatic and aromatic aldehydes are reduced into symmetric ethers, while i Pr3SiH yielded silylated alcohols. Studies of the reaction mechanism led to the isolation of aldehyde/uranyl complexes, [UO2(OTf)2(4-Me2N-PhCHO)3], [UO2(- 2-OTf)2(PhCHO)]n and [UO2(- 2-OTf)(OTf)2(PhCHO)2]2 which have been fully characterized by NMR, IR and single crystal X-ray diffraction.
Journal of Organometallic Chemistry, 2000
The nickel equivalent of Karstedt catalyst CHSiMe 2 ) 2 O} 2 {m-(h-CH 2 CHSiMe 2 ) 2 O}] (1) appeared to be a very efficient catalyst for dehydrogenative coupling of vinyl derivatives (styrene, vinylsilanes, vinylsiloxanes) with trisubstituted silanes HSi(OEt) 3 , HSiMe 2 Ph. The reaction occurs via three pathways of dehydrogenative coupling, involving formation of an unsaturated compound as the main product as well as a hydrogenated olefin (DS-1) pathway, hydrogenated dimeric olefin (DS-2) and dihydrogen (DC), respectively. The reaction is accompanied by side hydrosilylation. Stoichiometric reactions of 1 with styrene and triethoxysilane, in particular synthesis of the bis(triethoxysilyl) (divinyltetramethyldisiloxane) nickel complex 3 and the first documented insertion of olefin (styrene) into Ni Si bond of complex 3, as well as all catalytic data have allowed us to propose a scheme of catalysis of this complex reaction by 1.