Catalytic Hydration Of Nitriles Research Articles

A CoII-Hydroxide Complex That Converts Directly to a CoII-Acetamide during Catalytic Nitrile Hydration.

In exploring structural and functional mimics of nitrile hydratases, we report the synthesis of the pseudo-trigonal bipyramidal CoII complexes (K)[CoII(DMF)(LPh)] (1(DMF)), (NMe4)2[CoII(OAc)(LPh)] (1(OAc)), and (NMe4)2[CoII(OH)(LPh)] (1(OH)) (LPh = 2,2',2''-nitrilo-tris-(N-phenylacetamide; DMF = N,N-dimethylformamide; -OAc = acetate)). The complexes were characterized using NMR, FT-IR, ESI-MS, electronic absorption spectroscopy, and X-ray crystallography, showing the LPh ligand to bind in a tetradentate tripodal fashion alongside the respective ancillary donor. One of the complexes, 1(OH), is an unusual structural and functional mimic of the Co active site in Co nitrile hydratases. 1(OH) reacted with acetonitrile to yield the CoII-acetamide complex (NMe4)2[CoII(NHC(O)CH3)(LPh)], 2, which was also thoroughly characterized. In the presence of excess hydroxide, 1(OH) was found to catalyze quantitative conversion of the added hydroxide into acetamide. Despite the differences in Co oxidation state in nitrile hydratases and 1(OH) (CoIII versus CoII, respectively), 1(OH) was nonetheless an effective nitrile hydration catalyst, selectively producing acetamide over multiple turnovers.

Hydration of nitriles using a metal-ligand cooperative ruthenium pincer catalyst.

Nitrile hydration provides access to amides that are important structural elements in organic chemistry. Here we report catalytic nitrile hydration using ruthenium catalysts based on a pincer scaffold with a dearomatized pyridine backbone. These complexes catalyze the nucleophilic addition of H2O to a wide variety of aliphatic and (hetero)aromatic nitriles in t BuOH as solvent. Reactions occur under mild conditions (room temperature) in the absence of additives. A mechanism for nitrile hydration is proposed that is initiated by metal-ligand cooperative binding of the nitrile.

Nitrile Hydration Reaction Using Copper Iodide/Cesium Carbonate/DBU in Nitromethane–Water

The catalytic nitrile hydration (amide formation) in a copper iodide/cesium carbonate/1,8-diazabicyclo[5.4.0]undec-7-ene/nitromethane–water system is described. The protocol is robust and reliable; it can be applied to a broad range of substrates with high chemoselectivity.

Synthesis of and catalytic nitrile hydration by a cationic tris(μ-hydroxo)diruthenium(II) complex having PMe3 ligands

While phenyl vinyl ether does not react with [Ru(η4-1,5-COD)(η6-1,3,5-COT)] (1)/PMe3, the C–O bond cleavage of phenyl vinyl ether occurs by 1/PMe3 in the presence of water to give a tris(μ-hydroxo)diruthenium(II) complex [(Me3P)3Ru(μ-OH)3Ru(PMe3)3]+[OPh]−·HOPh (3·HOPh) with evolution of ethylene. The molecular structure of 3·HOPh is unequivocally determined by X-ray analysis. The most likely mechanism for the formation of 3·HOPh is protonation of [Ru(η4-1,5-COD)(PMe3)3] (2c) by water and subsequent insertion of phenyl vinyl ether into the resulting Ru–H bond followed by the β-phenoxide elimination and hydrolysis and dimerization of the phenoxoruthenium(II) species. Complex 3 acts as a catalyst for nitrile hydration. As a typical example, the hydration of benzonitrile was achieved by 3 (1.0mol%) in 1,4-dioxane at 120°C for 6h to give benzamide quantitatively.

Kinetic effects of sulfur oxidation on catalytic nitrile hydration: nitrile hydratase insights from bioinspired ruthenium(II) complexes.

Kinetic investigations inspired by the metalloenzyme nitrile hydratase were performed on a series of ruthenium(II) complexes to determine the effect of sulfur oxidation on catalytic nitrile hydration. The rate of benzonitrile hydration was quantified as a function of catalyst, nitrile, and water concentrations. Precatalysts L(n)RuPPh3 (n = 1-3; L(1) = 4,7-bis(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(2) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(3) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-sulfenato-propyl)-1-thia-4,7-diazacyclononane) were activated by substitution of triphenylphosphine with substrate in hot dimethylformamide solution. Rate measurements are consistent with a dynamic equilibrium between inactive aqua (L(n)Ru-OH2) and active nitrile (L(n)Ru-NCR) derivatives with K = 21 ± 1, 9 ± 0.9, and 23 ± 3 for L(1) to L(3), respectively. Subsequent hydration of the L(n)Ru-NCR intermediate yields the amide product with measured hydration rate constants (k's) of 0.37 ± 0.01, 0.82 ± 0.07, and 1.59 ± 0.12 M(-1) h(-1) for L(1) to L(3), respectively. Temperature dependent studies reveal that sulfur oxidation lowers the enthalpic barrier by 27 kJ/mol, but increases the entropic barrier by 65 J/(mol K). Density functional theory (DFT) calculations (B3LYP/LanL2DZ (Ru); 6-31G(d) (all other atoms)) support a nitrile bound catalytic cycle with lowering of the reaction barrier as a consequence of sulfur oxidation through enhanced nitrile binding and attack of the water nucleophile through a highly organized transition state.

ChemInform Abstract: Mild and Selective Heterogeneous Catalytic Hydration of Nitriles to Amides by Flowing Through Manganese Dioxide.

AbstractThe reaction tolerates a wide range of aromatic, heteroaromatic, aliphatic nitriles and dinitriles.

Mild and Selective Heterogeneous Catalytic Hydration of Nitriles to Amides by Flowing through Manganese Dioxide

A sustainable flow chemistry process for the hydration of nitriles, whereby an aqueous solution of the nitrile is passed through a column containing commercially available amorphous manganese dioxide, has been developed. The product is obtained simply by concentration of the output stream without any other workup steps. The protocol described is rapid, robust, reliable, and scalable, and it has been applied to a broad range of substrates, showing a high level of chemical tolerance.

Bioinspired catalytic nitrile hydration by dithiolato, sulfinato/thiolato, and sulfenato/sulfinato ruthenium complexes

A series of Ru(II) catalysts inspired by the metalloenzyme nitrile hydratase catalyze the hydration of benzonitrile with up to 242 turnovers under neutral conditions with very low catalysts loading. Catalysts with an oxidized sulfur environment are less susceptible to product inhibition increasing the catalytic efficiency at low nitrile : water ratios.

Arene–Ruthenium(II) Complexes Containing Inexpensive Tris(dimethylamino)phosphine: Highly Efficient Catalysts for the Selective Hydration of Nitriles into Amides

The catalytic hydration of nitriles into amides, in water under neutral conditions, has been studied using a series of arene–ruthenium(II) derivatives containing the commercially available and inexpensive ligand tris(dimethylamino)phosphine. Among them, best results were obtained with the complex [RuCl2(η6-C6Me6){P(NMe2)3}], which selectively provided the desired amides in excellent yields and short times (TOF values up to 11 400 h–1). The process was operative with both aromatic, heteroaromatic, aliphatic, and α,β-unsaturated organonitriles and showed a high functional group tolerance. The stability of [RuCl2(η6-C6Me6){P(NMe2)3}] in water was evaluated, observing its progressive decomposition into the less-active dimethylamine–ruthenium(II) complex [RuCl2(η6-C6Me6)(NHMe2)] by hydrolysis of the coordinated P(NMe2)3 ligand. The X-ray crystal structure determination of the toluene complex [RuCl2(η6-C6H5Me){P(NMe2)3}] is also included.

{Au(IPr)}2(μ‐OH)]X Complexes: Synthetic, Structural and Catalytic Studies

The synthesis of a series of dinuclear gold hydroxide complexes has been achieved. These complexes of type [{Au(IPr)}(2)(μ-OH)]X (X=BF(4), NTf(2), OTf, FABA, SbF(6); IPr=2,6-bis(disopropylphenyl)imidazol-2-ylidene; NTf(2)=bis(trifluoromethanesulfonyl)imidate; OTf=trifluoromethanesulfonate; FABA=tetrakis(pentafluorophenyl)borate) are easily formed in the presence of water and prove highly efficient in the catalytic hydration of nitriles. Their facile formation in aqueous media suggests they are of relevance in gold-catalyzed reactions involving water. Additionally, a series of [Au(IPr)(NCR)][BF(4)] (R=alkyl, aryl) complexes was synthesized as they possibly occur as intermediates in the catalytic reaction mechanism. (1)H and (13)C NMR data as well as key bond lengths obtained by X-ray diffraction studies are compared and reveal an interesting structure-activity relationship. The collected data indicate a negligible effect of the nature of the nitrile on the reactivity of [Au(L)(NCR)][X] complexes in catalysis.

高活性２元機能型触媒によるニトリル類からアミド類の製造法

New bifunctional chemical catalysts for the hydration of nitriles are described. cis-Ru(acac)2(PPh2py)2 exhibited high activity, with a turnover frequency of up to 20,900 (mol of amide)/((mol of catalyst)h). Newly synthesized iridium complexes bearing a PPh2py ligand have a 16e- square planar structure. The catalytic hydration of nitriles proceeded at 80 °C within few hours to give corresponding amides in almost quantitative yield. Moreover, the iridium complexes acted as a catalyst for the hydration under solvent-free conditions. In addition, new catalysts based on palladium nanoparticles for the hydration are described. Copper compounds containing oxygen atom acted as effective co-catalysts in the catalytic system.

Mechanism of Catalytic Hydration of Nitriles with Hydrotris(pyrazolyl)borato (Tp) Ruthenium Complexes

The aquo-amido complexes TpRu(PPh3)(H2O)(NHC(O)R) (R = Me, Ph), which can be prepared by refluxing a THF solution of TpRu(PPh3)(RCN)H containing excess water or more conveniently by reacting TpRu(PPh3)(RCN)Cl with NaOH in THF in the presence of water, are found to be active for catalytic hydration of nitriles to amides. The catalysis proceeds via a mechanism that is distinctly different from the common ones involving intramolecular nucleophilic attack of a hydroxo (or aquo) ligand or external attack of a hydroxide ion (or water) at the carbon atom of the η1-coordinated nitrile to form the metal amide intermediate and subsequent protonation of amido ligand by an adjacent aquo ligand or solvent water. The new mechanism involves the intermediacy of a relatively stable complex containing a chelating N-imidoylimidato ligand; ring-opening nucleophilic attack of this ligand by water is the product-generating step. Formation of the N-imidoylimidato complex from TpRu(PPh3)(H2O)(NHC(O)R) involves several steps. The initial one is displacement of the H2O ligand by a nitrile molecule to yield the nitrile-amido species TpRu(PPh3)(RCN)(NHC(O)R). This is followed by an unusual linkage isomerization of the N-bonded amido ligand to an O-bonded imido, which then undergoes nucleophilic attack at the carbon atom of the nitrile ligand in the complex; facile 1,3-proton shift between the nitrogen atoms on the resulting ring completes the reaction. The N-imidoylimidato complexes TpRu(PPh3)(κ2-N,O-NH═CMeN═CMeO), TpRu(PPh3)(κ2-N,O-NH═CPhN═CPhO), and TpRu(PPh3)(κ2-N,O-NH═CMeN═CPhO) were independently prepared, and the molecular structure of TpRu(PPh3)(κ2-N,O-NH═CPhN═CPhO) was determined by X-ray crystallography. To study the feasibility of the proposed mechanism for nitrile hydration with the aquo-amido complexes, theoretical calculations were performed at the Becke3LYP level of DFT theory to examine the whole catalytic cycle. It is learned that there is a substantially high barrier for the hydrolysis of the highly stable N-imidoylimidato complex, a step involving the ring-opening nucleophilic attack of this ligand by water, and this is probably the reason for the requirement of a relatively high reaction temperature.

Phosphite‐Derivatized Ruthenium‐Carbohydrate Complexes in the Catalytic Hydration of Nitriles. Short Communication

The synthesis of metal complexes with bioligands is one option to introduce chirally defined ligands to catalysts. Herein, the hydration of nitriles to the corresponding carboxamides by use of ruthenium(II) complexes is described, which were obtained by attaching derivatives of the 3,5,6-bicyclophosphite-alpha-D-glucofuranoside ligand.

Cobalt(III) Complexes with Carboxamido-N and Sulfenato-S or Sulfinato-S Ligands Suggest that a Coordinated Sulfenate-S is Essential for the Catalytic Activity of Nitrile Hydratases

A bis(sulfenato-S)CoIII complex and its corresponding bis(sulfinato-S) complex were prepared. Their catalytic nitrile hydration activity was tested. Whereas the former catalyzes the hydration of CH3CN under mild acidic conditions, the latter is inactive. A mechanism for this reaction is proposed, in relation with nitrile hydratase activity.

The catalytic hydration of nitriles to amides using a homogeneous platinum phosphinito catalyst

New homogeneous catalysts for the hydration of nitriles to amides are described. The catalyst precursors are coordination compounds of Pt(II) with secondary phosphine oxides. They contain a hydrogen bridged mono-anionic didentate phosphinito group, together with a third phosphine oxide ligand and a monodentate anionic ligand, either hydride or chloride. Reacting the chloride with silver ion, or the hydride with water gives a cationic species which is the active catalyst. On coordination to the cation the nitrile becomes susceptible to nucleophilic attack. The hydrolysis gives the amide as the sole product, and there is no tendency towards further hydrolysis to the acid. The effects of substituents on phosphorus are investigated, and a reaction mechanism is suggested. The most active catalyst, [PtH(PMe 2OH)(PMe 2O) 2H], 2a, is derived from dimethylphosphine oxide, and this precursor catalyses the hydration of acrylonitrile to acrylamide with a turnover number of 77,000, without addition to the CC double bond.

Catalytic Hydration of Nitriles to Amides

The hydration of nitriles to amides is one of the basic transformations in organic chemistry However, it is not generally appreciated how difficult this transformation is to carry out efficiently since amides themselves undergo further hydrolysis to the acid. While nicotinamide and acrylamide are usually manufactured from the corresponding nitriles using metallic copper heterogeneous catalysts, applications in the fine chemicals industry are rare. Now, the use of a new platinum-containing homogeneous catalyst applicable to complex organic nitriles containing sensitive functional groups will create an opportunity for nitrile hydration in the fine chemical and pharmaceutical industries.

ChemInform Abstract: Catalytic Hydration of Nitriles (I) to Amides (II) with Manganese Dioxide on Silica Gel.

ChemInform Abstract: Catalytic Hydration of Nitriles (I) to Amides (II) with Manganese Dioxide on Silica Gel.

Catalytic Hydration of Nitriles to Amides with Manganese Dioxide on Silica Gel

Catalytic Hydration of Nitriles to Amides with Manganese Dioxide on Silica Gel

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