Hydrosilylation Of Ketones Research Articles

Iron-Catalyzed Hydrosilylation of Aldehydes and Ketones under Solvent-Free Conditions

Exposure of aldehyde or ketone to 1 mol % BIAN-Fe(C7H8) complex in the presence of diphenyl silane affords the corresponding protected alcohol in excellent yields, under mild reaction conditions. Aldehydes and ketones are reduced cleanly in the presence of a broad range of functional groups under solvent-free conditions.

ChemInform Abstract: Reversible Substrate Activation and Catalysis at an Intact Metal—Metal Bond Using a Redox‐Active Supporting Ligand.

AbstractBased on a dinuclear mode of activation, a Ni2(naphthyridine‐diimine) complex catalyzes the high‐yielding hydrosilylation of alkenes, dienes, alkynes, aldehydes, ketones, enones, and amides.

ChemInform Abstract: Syntheses and Catalytic Application of Hydrido Iron(II) Complexes with [P,S]‐Chelating Ligands in Hydrosilylation of Aldehydes and Ketones.

AbstractFour hydrido iron(II) complexes are synthesized and evaluated according to the title reactions.

ChemInform Abstract: Asymmetric Hydrosilylation of Aromatic Ketones Catalyzed by an Economical and Effective Copper‐Diphosphine Catalytic System in Air.

Abstract(R)‐1‐Arylethanols (II) are synthesized with high yields and enantioselectivities using an efficient catalyst system in situ generated from Cu(OAc)2·H2O and (R)‐BINAP as ligand with the non‐toxic reducing agent PMHS in air atmosphere and at room temperature.

E–H Bond Activations and Hydrosilylation Catalysis with Iron and Cobalt Metalloboranes

An exciting challenge in transition metal catalyst design is to explore whether earth-abundant base metals such as Fe, Co, and Ni can mediate two-electron reductive transformations that their precious metal counterparts (e.g., Ru, Rh, Ir, and Pd) are better known to catalyze. Organometallic metalloboranes are an interesting design concept in this regard because they can serve as organometallic frustrated Lewis pairs. To build on prior studies with nickel metalloboranes featuring the DPB and ^(Ph)DPB^(Mes) ligands in the context of H_2 and silane activation and catalysis (DPB = bis(o-diisopropylphosphinophenyl)phenylborane, ^(Ph)DPB^(Mes) = bis(o-diphenylphosphinophenyl)mesitylborane), we now explore the reactivity of iron, [(DPB)Fe]_2(N_2), 1, and cobalt, (DPB)Co(N_2), 2, metalloboranes toward a series of substrates with E–H bonds (E = O, S, C, N) including phenol, thiophenol, benzo[h]quinoline, and 8-aminoquinoline. In addition to displaying high stoichiometric E–H bond activation reactivity, complexes 1 and 2 prove to be more active catalysts for the hydrosilylation of ketones and aldehydes with diphenylsilane relative to (^(Ph)DPB^(Mes))Ni. Indeed, 2 appears to be the most active homogeneous cobalt catalyst reported to date for the hydrosilylation of acetophenone under the conditions studied.

A Comparison of the Stability and Reactivity of Diamido- and Diaminocarbene Copper Alkoxide and Hydride Complexes.

The mononuclear N-heterocyclic carbene (NHC) copper alkoxide complexes [(6-NHC)CuOtBu] (6-NHC = 6-MesDAC (1), 6-Mes (2)) have been prepared by addition of the free carbenes to the tetrameric tert-butoxide precursor [Cu(OtBu)]4, or by protonolysis of [(6-NHC)CuMes] (6-NHC = 6-MesDAC (3), 6-Mes (4)) with tBuOH. In contrast to the relatively stable diaminocarbene complex 2, the diamidocarbene derivative 1 proved susceptible to both thermal and hydrolytic ring-opening reactions, the latter affording [(6-MesDAC)Cu(OC(O)CMe2C(O)N(H)Mes)(CNMes)] (6). The intermediacy of [(6-MesDAC)Cu(OH)] in this reaction was supported by the generation of Cu2O as an additional product. Attempts to generate an isolable copper hydride complex of the type [(6-MesDAC)CuH] by reaction of 1 with Et3SiH resulted instead in migratory insertion to generate [(6-MesDAC-H)Cu(P(p-tolyl)3)] (9) upon trapping by P(p-tolyl)3. Migratory insertion was also observed during attempts to prepare [(6-Mes)CuH], with [(6-Mes-H)Cu(6-Mes)] (10) isolated, following a reaction that was significantly slower than in the 6-MesDAC case. The longer lifetime of [(6-Mes)CuH] allowed it to be trapped stoichiometrically by alkyne, and also employed in the catalytic semi-reduction of alkynes and hydrosilylation of ketones.

Hydrosilylation of Aldehydes and Ketones Catalyzed by a Terminal Zinc Hydride Complex, [κ3-Tptm]ZnH

Tris(2-pyridylthio)methyl zinc hydride, [κ3-Tptm]ZnH, is an effective catalyst for multiple insertions of carbonyl groups into the Si–H bonds of PhxSiH4–x (x = 1, 2). Specifically, [κ3-Tptm]ZnH catalyzes the insertion of a variety of aldehydes and ketones into the Si–H bonds of PhSiH3 and Ph2SiH2 to afford PhSi[OCH(R)R′]3 and Ph2Si[OCH(R)R′]2, respectively. The mechanism for hydrosilylation is proposed to involve insertion of the carbonyl group into the Zn–H bond to afford an alkoxy species, followed by metathesis with the silane to release the alkoxysilane and regenerate the zinc hydride catalyst. Multiple insertion of prochiral ketones results in the formation of diastereomeric mixtures of alkoxysilanes that can be identified by NMR spectroscopy.

One-pot Synthesis of Tetralin Derivatives from 3-Benzoylpropionic Acids: Indium-catalyzed Hydrosilylation of Ketones and Carboxylic Acids and Intramolecular Cyclization

Abstract This reducing system was composed of a small amount (1 mol %) of In(OAc)3, Me2PhSiH, and I2 that effectively catalyzed the hydrosilylation of two different carbonyl groups, a ketone and a carboxylic acid found in 3-benzoylpropionic acids, followed by a subsequent intramolecular cyclization that led to the one-pot preparation of tetralin derivatives.

ChemInform Abstract: Bipyridine‐ and Phenanthroline‐Based Metal—Organic Frameworks for Highly Efficient and Tandem Catalytic Organic Transformations via Directed C—H Activation.

AbstractA series of robust and porous bipyridyl‐ and phenanthryl‐based metal—organic frameworks (MOFs) of UiO topology is prepared and metalated with [Ir(cod)(OMe)]2 to provide Ir—MOF complexes which are highly active catalysts for tandem hydrosilylation of aryl ketones and aldehydes followed by dehydrogenative ortho‐silylation as well as C—H boration of arenes.

ChemInform Abstract: Stable and Easily Handled FeIII Catalysts for Hydrosilylation of Ketones and Aldehydes.

The amine–bis(phenolate) iron(III)-catalysed reduction of ketones and aldehydes to the corresponding secondary and primary alcohols by a consecutive hydrosilylation/hydrolysis process is reported. The amine–bis(phenolate) iron(III) catalyst is easily accessible, stable towards moisture and air and has a broad substrate scope.

ChemInform Abstract: Iron Achieves Noble Metal Reactivity and Selectivity: Highly Reactive and Enantioselective Iron Complexes as Catalysts in the Hydrosilylation of Ketones.

AbstractThe first Fe‐catalyzed enantioselective hydrosilylation for a broad range of aryl and alkyl ketones is presented.

Nickel and iron pincer complexes as catalysts for the reduction of carbonyl compounds.

The reductions of aldehydes, ketones, and esters to alcohols are important processes for the synthesis of chemicals that are vital to our daily life, and the reduction of CO2 to methanol is expected to provide key technology for carbon management and energy storage in our future. Catalysts that affect the reduction of carbonyl compounds often contain ruthenium, osmium, or other precious metals. The high and fluctuating price, and the limited availability of these metals, calls for efforts to develop catalysts based on more abundant and less expensive first-row transition metals, such as nickel and iron. The challenge, however, is to identify ligand systems that can increase the thermal stability of the catalysts, enhance their reactivity, and bypass the one-electron pathways that are commonly observed for first-row transition metal complexes. Although many other strategies exist, this Account describes how we have utilized pincer ligands along with other ancillary ligands to accomplish these goals. The bis(phosphinite)-based pincer ligands (also known as POCOP-pincer ligands) create well-defined nickel hydride complexes as efficient catalysts for the hydrosilylation of aldehydes and ketones and the hydroboration of CO2 to methanol derivatives. The hydride ligands in these complexes are substantially nucleophilic, largely due to the enhancement by the strongly trans-influencing aryl groups. Under the same principle, the pincer-ligated nickel cyanomethyl complexes exhibit remarkably high activity (turnover numbers up to 82,000) for catalytically activating acetonitrile and the addition of H-CH2CN across the C═O bonds of aldehydes without requiring a base additive. Cyclometalation of bis(phosphinite)-based pincer ligands with low-valent iron species "Fe(PR3)4" results in diamagnetic Fe(II) hydride complexes, which are active catalysts for the hydrosilylation of aldehydes and ketones. Mechanistic investigation suggests that the hydride ligand is not delivered to the carbonyl substrates but is important to facilitate ligand dissociation prior to substrate activation. In the presence of CO, the amine-bis(phosphine)-based pincer ligands are also able to stabilize low-spin Fe(II) species. Iron dihydride complexes supported by these ligands are bifunctional as both the FeH and NH moieties participate in the reduction of C═O bonds. These iron pincer complexes are among the first iron-based catalysts for the hydrogenation of esters, including fatty acid methyl esters, which find broad applications in industry. Our studies demonstrate that pincer ligands are promising candidates for promoting the first-row transition metal-catalyzed reduction of carbonyl compounds with high efficiency. Further efforts in this research area are likely to lead to more efficient and practical catalysts.

Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations.

Ketones are efficiently deoxygenated in the presence of silane using highly electrophilic phosphonium cation (EPC) salts as catalysts, thus affording the corresponding alkane and siloxane. The influence of distinct substitution patterns on the catalytic effectiveness of several EPCs was evaluated. The deoxygenation mechanism was probed by DFT methods.

Synthesis of BINAM‐Based Chiral Di‐1,2,3‐triazolylidene Complexes and Application of the Di‐NHC RhI Catalyst in Enantioselective Hydrosilylation

AbstractDespite the prolific use of (di‐)NHC complexes in homogeneous catalysis, there are relatively few reports on their successful application in asymmetric transformations. In this work the atropisomeric binaphthyl backbone was combined with readily obtainable 1,2,3‐triazolylidenes to develop a strongly electron‐donating C2‐symmetric ligand. The ligand was efficiently synthesized in a three‐step procedure in an overall yield of 91 % starting from commercially available materials. Strategies for the synthesis of the corresponding di‐NHC silver(I), palladium(II), rhodium(I), and iridium(I) complexes have been developed. The rhodium(I) complex was employed in the catalytic asymmetric hydrosilylation of ketones, providing good conversions at catalyst loadings as low as 0.2 mol‐% and giving chiral inductions of up to 51 % ee.

Synthesis of Iron Hydrides by Selective C–F/C–H Bond Activation in Fluoroarylimines and Their Applications in Catalytic Reduction Reactions

AbstractThe reactions of Fe(PMe3)4 with different 2,6‐diflurophenylarylimines 1–5 were explored. Fluoroarylimines 1–3, the aryl rings of which are substituted with electron‐withdrawing groups, reacted with Fe(PMe3)4 to afford the C–H activation products 6–8. However, if the aryl rings of the fluoroarylimines were substituted with electron‐donating groups, the iron hydrides 9 and 10 were obtained from the reactions of the fluoroarylimines with Fe(PMe3)4 through C–F bond activation. In a further study, silanes, especially triethoxysilane, were found to benefit the reactions and improve the yields of the hydridoiron complexes. The three‐component reaction of Fe(PMe3)4, a fluoroarylimine, and a silane could also be utilized in reactions involving 2,6‐(CH3)2C6H3–C(=NH)–2,6‐F2C6H3 (13) and 2,6‐F2C6H3–C(=NH)–C6F5 (16) to synthesize iron hydrides (15 and 18). The hydridoiron complexes could be utilized as efficient catalysts in the hydrosilylation of aldehydes and ketones. Furthermore, cinnamaldehydes were selectively reduced to the corresponding cinnamyl alcohols in high yields. The mechanism of the catalytic reduction reaction was studied extensively through operando IR spectroscopy.

Reversible substrate activation and catalysis at an intact metal-metal bond using a redox-active supporting ligand.

An electron rich Ni(I)-Ni(I) bond supported by a doubly reduced naphthyridine-diimine (NDI) ligand reacts rapidly and reversibly with Ph2SiH2 and Et2SiH2 to form stable adducts. The solid-state structures of these complexes reveal binding modes in which the silanes symmetrically span the Ni-Ni bond and exhibit highly distorted H-Si-H angles and elongated Si-H bonds. This process is facilitated by the release of electron density stored in the π-system of the NDI ligand. Based on this dinuclear mode of activation, [NDI]Ni2 complexes are shown to catalyze the high-yielding hydrosilylation of alkenes, dienes, alkynes, aldehydes, ketones, enones, and amides. In comparative studies of alkyne hydrosilylations, the [NDI]Ni2 catalyst is found to be significantly more active than its mononuclear counterparts for aryl-substituted substrates.

Asymmetric Hydrosilylation of Aromatic Ketones Catalyzed by an Economical and Effective Copper‐Diphosphine Catalytic System in Air

AbstractIn the presence of the inexpensive and non‐toxic polymethylhydrosiloxane, the combination of copper(II) acetate and a chiral diphosphine displayed high catalytic efficiency in the asymmetric hydrosilylation of a series of aromatic ketones in air atmosphere and at room temperature. (R)‐1‐Arylethanols were obtained with up to 99% yield and 93% enantiomeric excess. Meanwhile, the electron effect and steric hindrance of substituents on the aromatic ring had an interesting influence on both the yields and enantioselectivities. Furthermore, a possible mechanism was presented to explain the influence of some key factors on the reaction.

Highly Enantioselective Iron-Catalyzed Ketone Hydrosilylation

Highly Enantioselective Iron-Catalyzed Ketone Hydrosilylation

Synthesis and Reactivity of a Hydrido CNC Pincer Cobalt(III) Complex and Its Application in Hydrosilylation of Aldehydes and Ketones

Reaction of the N-benzylidene-1-naphthylamine with CoMe(PMe3)4 afforded the hydrido CNC pincer cobalt complex CoH(PMe3)2[(C6H4)CH═N(C10H6)] (1) via double C–H bond activation. In the 1H NMR spectrum, a triplet at −18.98 ppm is the typical signal of the hydrido ligand (Co–H). Complex 1 reacted with haloalkane (CH3I and EtBr) to deliver CoX(PMe3)2((C6H4)CH═N(C10H6)) (X = I (2); Br (3)). However, the reactions of complex 1 with HCl and trifluoroacetic acid (TFA) delivered HCoCl(PMe3)2((C6H4)CH═N(C10H7)) (4) and HCo(OCOCF3)(PMe3)2((C6H4)CH═N(C10H7)) (5) with the cleavage of the Co–C(naphthyl) bond. In the 1H NMR spectra, the signals of the hydrido ligands were found at −21.31 (4) and −18.71 (5) ppm. A reaction of complex 1 with DCl was carried out to prove that the hydrogen atom eliminated to the naphthyl carbon comes from HCl. Complex 1 reacted with acetylacetone, resulting in the formation of Co(acac)(PMe3)2((C6H5)CHNH(C10H6)) (7). Complex 1 was found to be an efficient catalyst for hydrosilylation of aldehydes and ketones. The molecular structures of complex 1, 2, 4, and 7 were determined by X-ray single-crystal diffraction.

Dual [Fe+Phosphine] Catalysis: Application in Catalytic Wittig Olefination

AbstractIron hydride complexes of the general formula P2Fe(NO)CO)H are highly active catalysts for the hydrosilylation of aldehydes or ketones and phosphine oxides. Depending on the solvent, the in situ reduction of the phosphine oxide can be faster than the corresponding hydrosilylation of a carbonyl group. This unusual activity was used within the context of catalytic Wittig olefination.