Cyanosilylation Of Ketones Research Articles

Efficient cyanosilylation of carbonyls using a well-defined dimeric sodium complex

We present the synthesis and structural characterization of a novel dimeric sodium complex with the chemical composition [{Ph2Si(H)PhN}Na(THF)2]2 (Na-1) supported by N,1,1-triphenylsilanamine fragment. The single-crystal X-ray diffraction analysis of complex Na-1 in the solid state reveals the coordination of sodium ion with N and O atoms of the triphenylsilanamine unit, forming a four-membered ring. The sodium complex also demonstrates excellent activity as a pre-catalyst towards the cyanosilylation of a wide array of ketones with trimethylsilyl cyanide (TMSCN) to afford trimethylsilyloxypropanenitriles in excellent yield (up to 99 %) in a shorter time under mild and solvent-free reaction conditions and exhibits a greater tolerance to a variety of ketones bearing electron-withdrawing and electron-donating functional groups. The plausible mechanism of cyanosilylation of ketones catalyzed by the complex Na-1 is also proposed.

ATI Stabilized Germylene Cation as a Cyanosilylation Catalyst for Aldehydes and Ketones.

The aminotroponiminate (ATI) ligand stabilized germylene cation [(i-Bu)2ATIGe][B(C6F5)4] (2) is found to be an efficient low-valent main-group catalyst for the cyanosilylation of aldehydes and ketones (ATI=aminotroponiminate). It was synthesized by reacting [(i-Bu)2ATIGeCl] (1) with Na[B(C6F5)4]. The catalytic cyanosilylation of diverse aliphatic and aromatic carbonyl compounds (aldehydes and ketones) using 0.075-0.75 mol% of compound 2 was completed within 5-45 min. The catalytic efficiency seen with aliphatic aldehydes was around 15,800 h-1, making compound 2 a capable low-valent main-group catalyst for the aldehyde and ketone cyanosilylation reactions. Further, DFT calculations reveal a pronounced charge localization at the germanium atom of compound 2, leading to its superior catalytic performance.

Synthesis and catalytic application of a donor-free bismuthenium cation.

Herein, we report the synthesis and catalytic application of a new N,N'-dineopentyl-1,2-phenylenediamine-based bismuthenium cation (3). 3 has been synthesized via the treatment of chlorobismuthane LBiCl [L = 1,2-C6H4{N(CH2tBu)}2] (2) with AgSbF6, and was further used as a robust catalyst for the cyanosilylation of ketones under mild reaction conditions. Experimental studies and DFT calculations were performed to understand the mechanistic pathway.

Synthesis of asymmetrical β-diketiminate magnesium methyl complexes and their catalytic application in cyanosilylation of ketones

Two asymmetrical β-diketiminate magnesium methyl complexes [(DippArNacnac)MgMe(THF)] have been synthesized in high yields and structurally characterized via single crystal X-ray diffraction etc. Subsequently, they have been successfully employed as highly efficient catalysts in the cyanosilylation of ketones including natural products with low catalyst loading (0.2 mol %) under the solvent-free condition at room temperature. A plausible mechanism was proposed base on the corresponding stoichiometric experiments and density functional theory (DFT) calculations.

Catalytic cyanosilylation of ketones utilizing air-stable zinc complexes supported by amidophosphine chalcogenide ligands

We report the synthesis and structural characterization of a series of novel zinc (II) and cadmium (II) complexes with the chemical composition, [κ2-N,E-{C5H4NCH2N(H)PPh2(E)}MX2] (M = Zn; E = Se, X = Cl (1a), Br (1b), I (1c); E = S, X = Cl (2a), Br (2b), I (2c) and M = Cd; E = Se, X = Cl (3a), I (3b); E = S, X = Cl (4a), I (4b)). These complexes are easy to prepare and air-stable. The single-crystal X-ray diffraction analysis of the complexes 1a-1c, 2a-2c, 3b, and 4b reveals that these complexes are isostructural and involve a seven-membered ring formed by the coordination of soft donor atoms (S/Se), pyridine nitrogen atom, and zinc/cadmium metal. The zinc metal complexes 1a-1c and 2a-2c were explored as pre-catalysts for the cyanosilylation of ketones with trimethylsilyl cyanide. The catalyst 1c showed excellent activity at room temperature under solvent-free conditions and demonstrated high tolerance toward a number of functional groups.

Synthesis and Application of Amino‐1H‐1,2,3‐triazolium Salts

AbstractHerein, we developed a fluoride‐mediated nucleophilic aromatic amination of chloro‐1H‐1,2,3‐triazolium salts. Various functional groups were tolerated in this reaction, which enabled the synthesis of functionalized amino‐1H‐1,2,3‐triazolium salts. In addition, we investigated the catalytic properties of triazolium‐based N‐heterocyclic imines (NHIs) for cyanosilylation of ketones. The substituent was found to play a crucial role for inducing high catalytic activity.

Chalcogen Bonding Catalysis with Phosphonium Chalcogenide (PCH).

ConspectusThe exploration of new catalysis concepts and strategies to drive chemical reactions is of vital importance for the sustainable development of organic synthesis. Recently, chalcogen bonding catalysis has emerged as a new concept for organic synthesis and has been demonstrated to be an important synthetic tool capable of addressing elusive reactivity and selectivity issues. This Account describes our progress in the research field of chalcogen bonding catalysis, including (1) the discovery of phosphonium chalcogenide (PCH) as highly efficient chalcogen bonding catalyst; (2) the development of "chalcogen-chalcogen bonding catalysis" and "chalcogen···π bonding catalysis" modes; (3) the demonstration that chalcogen bonding catalysis with PCH can activate hydrocarbons to achieve cyclization and coupling reactions of alkenes; (4) the discovery of unusual results that chalcogen bonding catalysis with PCH can solve elusive reactivity and selectivity issues that are inaccessible by classic catalysis approaches; and (5) the elucidation of chalcogen bonding mechanisms.With PCH catalysts, we systematically studied their chalcogen bonding properties, the relationship between structure and catalysis, and their application in facilitating a diverse array of reactions. Enabled by chalcogen-chalcogen bonding catalysis, an efficient assembly reaction of three molecules of β-ketoaldehyde and one indole derivative in a single operation was realized, delivering heterocycles with a newly constructed seven-membered ring. In addition, a Se···O bonding catalysis approach achieved an efficient synthesis of calix[4]pyrroles. We developed a "dual chalcogen bonding catalysis" strategy to solve reactivity and selectivity issues in the Rauhut-Currier-type reactions and related cascade cyclizations, thus shifting conventionally covalent Lewis base catalysis to a cooperative Se···O bonding catalysis approach. This strategy enables the cyanosilylation of ketones to take place in the presence of a ppm-level amount of PCH catalyst loading. Furthermore, we established chalcogen···π bonding catalysis for catalytic transformation of alkenes. In the research field of supramolecular catalysis, the activation of hydrocarbons such as alkenes by weak interactions is a highly interesting unresolved topic. We showed that the Se···π bonding catalysis approach could efficiently activate alkenes to achieve both coupling and cyclization reactions. Chalcogen···π bonding catalysis with PCH catalysts is particularly highlighted by the capability of facilitating strong Lewis-acid inaccessible transformations, such as the controlled cross coupling of triple alkenes. Overall, this Account presents a panoramic view of our research on chalcogen bonding catalysis with PCH catalysts. The works described in this Account provide a significant platform to solve synthetic problems.

Sustainable organocatalytic cyanosilylation of ketones by PPM-level loading of triphenylcarbenium tetrakis(pentafluorophenyl)borate

We report herein solvent-free cyanosilylation of ketones catalyzed by 50 ppm of tritylium tetrakis(pentafluorophenyl)borate ([Ph3C]+[B(C6F5)4]−) as an extremely active organocatalyst.

Germanium Hydride Catalyzed Selective Hydroboration and Cyanosilylation of Ketones

AbstractTwo new examples of β‐diketiminate or NacNac analogues, i. e., conjugated bis‐guanidinate (CBG) stabilized low valent germanium chloride (1) and germanium hydride (2) complexes, are reported. Deprotonation of LH upon treatment with n‐BuLi and an in situ generated LLi further treated with GeCl2⋅dioxane afforded LGeCl in 79 % yield. Compound 1 reacted with hydride source NaHBEt3 in toluene, afforded Ge (II) hydride (2) in 76 % yield. Both compounds 1 and 2 were characterized by NMR and mass spectroscopic methods. Further, germanium hydride catalyzed hydroboration and cyanosilylation of a wide range of ketones have been investigated. Control reactions suggest hydroboration reactions occurred via insertion and Ge−O/B−H bond metathesis pathways. It is worthy of mentioning that, in the case of hydroboration of ketones, reducible groups such as alkene, alkyne, halide, ester, nitro, and heterocycles were untouched. Furthermore, compound 2 was employed for the reduction of carbonate, formate, and anhydride substrates via the hydroboration technique.

A Sacrificial Iminato Ligand in the Catalytic Cyanosilylation of Ketones Promoted by Organoactinide Complexes.

Four new complexes containing the bis(pentamethylcyclopentadienyl)thorium(IV) moiety, Cp*2Th(L1)(Me) (Th2), Cp*2Th(L2)(Me) (Th3), Cp*2Th(L1)Cl (Th5), and Cp*2Th(L2)Cl (Th6), were synthesized in quantitative yields via the protonolysis reaction of the metallocene precursor complexes Cp*2Th(Me)2 (Th1) and Cp*2Th(Me)Cl (Th4) and the respective six- and seven-membered N-heterocyclic neutral imine ligands L1H and L2H. The molecular structures of all the complexes were established by single-crystal X-ray structure analyses. The synthesized complexes along with the precursor complexes were employed as catalysts for the cyanosilylation reaction of ketones with trimethylsilyl cyanide (Me3SiCN). The removal of the iminato ligand is necessary to trigger the reaction, allowing the formation of the active catalyst.

Synthesis of cyanooxovanadate and cyanosilylation of ketones.

The cyanosilylation was performed by using metavanadate catalysts, and in situ measurements revealed the formation of [VO2(CN)3]2− and [VO4TMS2]− under reaction conditions. The reaction of [VO2(CN)3]2−, trimethylsilyl cyanide (TMSCN), and water afforded [VO4TMS2]− and CN−, which reacted with ketones to yield the corresponding cyanohydrin trimethylsilyl ethers over [VO2(CN)3]2−. Compound [VO2(CN)3]2− showed high catalytic performance for cyanosilylation of various carbonyl compounds. In the case of n-hexanal, turnover frequency reached up to 250 s−1.

Nanoceria as a recyclable catalyst/support for the cyanosilylation of ketones and alcohol oxidation in cascade

The cyanosilylation of carbonyl compounds is a fundamental reaction in organic synthesis, to give cyanohydrins. Ketones are particularly reluctant to cyanosilane addition and require the action of a catalyst, and despite many soluble Brönsted and Lewis acids have been employed for this task, it is difficult to find in the open literature catalytic solids able to carry out the reaction. Here, we show that commercially available nanoceria catalyzes the cyanosilylation of different ketones (21 examples) at temperatures between 0 and 50 °C, in high yields, under solventless conditions if required. The nanoceria network atoms act in a cooperative way to provide a bifunctional acid-base solid catalyst for the cyanosilylation reaction. The amorphization of nanoceria during reaction, due to acid release, does not hamper the catalytic activity and, indeed, different types of nanoceria, even with supported metal nanoparticles on surface, are active for the reaction, enabling extensive reuses after air calcination and the use of the catalytic material for the aerobic oxidation of alcohols / cyanosilylation reaction.

Xiaohua Liu.

"In a spare hour, I walk my dog … My favorite time of day is when I enjoy my walks in the garden…" Find out more about Xiaohua Liu in her Author Profile.

Carbonyl-Stabilized Phosphorus Ylide as an Organocatalyst for Cyanosilylation Reactions Using TMSCN

We report carbonyl-stabilized phosphorus ylides as general and efficient catalysts for the cyanosilylation of ketones. The N,N-diethylacetamide derived phosphorane is identified as an extremely efficient catalyst for the cyanosilylation of dialkyl ketones, alkyl aryl ketones, diaryl ketones, and α,β-unsaturated enones with catalyst loading down to 0.005 mol %, the lowest ever known for ketone cyanosilylation. Aldehydes, aldimines, and ketimines are also viable substrates. By NMR and React IR analysis, as well as electrical conductivity experiments, it is proposed that the phosphorane acts as a Lewis base in order to mediate the reaction via the desilylative nucleophilic activation of TMSCN.

A micro-environment tuning approach for enhancing the catalytic capabilities of lanthanide containing polyoxometalate in the cyanosilylation of ketones.

The as-synthesized (TBA)8H5[Nd(SiW11O39)2] manifested high catalytic activity for cyanosilylation of ketones, and its catalytic activity could be improved further through rational design of the reaction micro-environment beyond the molecular level, and the corresponding mechanism has been systematically studied.

The Hydrosilylation and Cyanosilylation of Ketones Catalyzed using Metal Borohydrides.

The hydrosilylation reaction of carbonyl compounds has emerged as a powerful method in organic synthesis. The catalytic hydrosilylation of ketones is a valuable transformation because it generates protected cyanosilylation reaction of carbonyl compounds is an efficient procedure for the synthesis of silylated cyanohydrins, which are readily converted into useful functionalized compounds, such as cyanohydrins, α-hydroxy acids, β-amino alcohols and other biologically active compounds. A facile, economic and efficient method has been developed for the hydrosilylation and cyanosilylation of ketones using metal borohydrides. A series of silylated ethers and silylated cyanohydrins can be isolated via direct distillation. The catalytic properties of a range of metal borohydrides in the hydrosilylation reaction of acetophenone with diphenylsilane were investigated. The relative catalytic activity of the borohydride catalyst studied was as follows: (CH3)4NBH4> (PhCH2)(CH3)3NBH4> (CH2CH3)4NBH4> (CH3CH2CH2CH3)4NBH4> NaBH4> KBH4> LiBH4. The cyanosilylation of acetophenone using trimethylsilyl cyanide (TMSCN) in the presence of NaBH4 occurred under similar reaction conditions. An excellent reaction rate and high conversion were obtained. The metal borohydride-catalyzed hydrosilylation alcohols in one step. The and cyanosilylation of ketones could be carried out smoothly under mild reaction conditions. Among the metal borohydrides studied, an excellent reaction rate and high conversion were obtained using NaBH4, NaBH (CH2CH3)3 or (alkyl)4 NBH4 as the reaction catalyst.

Syntheses, Structures, and Catalytic Activities of the Anionic Heterobimetallic Rare-Earth Metal Complexes Supported by Pyrrolyl-Substituted 1,2-Diimino Ligands.

A series of the anionic heterobimetallic rare-earth metal complexes supported by trans- or chiral pyrrolyl-substituted 1,2-diimino ligands were synthesized in good yields via reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with the corresponding 1,2-diimino proligands. Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of trans-1,2-bis(pyrrol-2-ylmethylene)-1,2-diphenylethanediamine (H2L1) afforded the discrete ion-pair rare-earth metal complexes [Li(THF)4]+[(L1)2RE]- (RE = Sm(5), Dy(6), Er(7)). Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of ( R, R)-1,2-bis(pyrrol-2-ylmethylene)-1,2-diphenylethanediamine (H2L2) gave the heterobimetallic rare-earth metal complexes (L2)2RELi(THF)2 (RE = Sm(8), Y(9)). When the rare-earth metal is Er, the chiral linear rare-earth coordination polymer {(L2)2ErLi} n (10) was obtained. Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of trans-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane (H2L3) gave the heterobimetallic rare-earth metal complexes (L3)2RELi(THF)2 (RE = Pr (11), Sm(12), Eu(13)). Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of ( R, R)-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane (H2L4) also gave the heterobimetallic rare-earth metal complexes (L4)2RELi(THF)2 (Ln = Pr(14), Sm(15)). All complexes were characterized by spectroscopic methods and elemental analyses, and complexes 5-11, 13, and 14 were further determined by single-crystal X-ray diffraction. The catalytic properties of racemic rare-earth metal complexes on cyanosilylation of ketones were examined, and results showed that the above complexes could effectively catalyze the cyanosilylation of ketones. Chiral rare-earth metal complexes as catalysts for the enantioselective epoxidation of α,β-unsaturated ketones were also examined to afford the chiral epoxides in high yields with moderate enantioselectivities.

Low-valent magnesium(i)-catalyzed cyanosilylation of ketones.

The magnesium(i) complex [(XylNacnac)Mg]2 was employed as a highly efficient catalyst for the cyanosilylation of a variety of ketones with trimethylsilyl cyanide under mild conditions. In contrast to the traditional stoichiometric use of magnesium(i) complexes, 1 provides the first example of a truly catalytic application of Mg(i) complexes.

Chiral rare-earth metal complexes with a tridentate amido-fluorenyl ligand: Syntheses, structures and catalytic performance

The complexes of rare-earth metals (Y, La, Sm and Lu) with a chiral tridentate amido-fluorenyl ligand were synthesized and characterized. These complexes demonstrated high efficiency in catalyzing both the intramolecular hydroamination of non-activated olefins and the cyanosilylation of ketones under very mild conditions, however, with no enantiocontrol being achieved. 1H NMR monitoring of the reaction process suggests the weak coordination capacity of the fluorenyl moiety might be responsible for the lack of asymmetric inducing power of the chiral complexes in such transformations.

Remarkable Acceleration of Benzimidazole Synthesis and Cyanosilylation Reactions in a Supramolecular Solid Catalyst

AbstractA solid metal–organic catalyst with hydrophobic pockets and Lewis acid centers strongly accelerates the reaction rate for organic reactions. This is exemplified for the cyanosilylation of ketones and for the synthesis of benzimidazoles, for which very high selectivities are obtained. The solid can be recovered and reused and its behavior approaches that of a functional enzyme mimic.