110-47-4Relevant articles and documents
Cyanoethylation of alcohols by activated Mg-Al layered double hydroxides: Influence of rehydration conditions and Mg/Al molar ratio on Broensted basicity
Valente, Jaime S.,Pfeiffer, Heriberto,Lima, Enrique,Prince, Julia,Flores, Jorge
, p. 196 - 204 (2011)
Activated Mg-Al layered double hydroxides (LDHs) with varying Mg/Al molar ratios are tested as heterogeneous catalysts for the cyanoethylation of methanol and 2-propanol. The activation procedure is performed by calcination of the LDH precursors, followed by gas-phase rehydration on an H2O/N 2 flow. In this case, rehydration is carried out at 80 °C, instead of room temperature as usual. Increased temperature has a very significant effect on the reconstruction speed, shortening the process from ～12 to 0.5 h. Good conversions and yields to alkoxypropionitriles are obtained with thus activated LDHs. Correlations are established between basic strength, as determined by CDCl3 adsorption followed by FTIR, and catalytic activity. Depending on alcohol acidity, greatest conversions are obtained over catalysts with Mg/Al molar ratios of 2 or 3. Solids are further characterized by X-ray diffraction, thermal gravimetric analyses, and 27Al MAS NMR.
Effect of pressure on sterically congested cyanoalkylation reactions of alcohols
Jenner
, p. 4311 - 4317 (2002)
The pressure effect on the phosphine-catalyzed nucleophilic addition of alcohols to unsaturated nitriles is examined. As a general result, pressure promotes these reactions. Their sensitivity to pressure increases with increasing steric congestion of either the alcohol or the nitrile. Activation volumes are found to be very negative pointing not only to a late transition state, but essentially to a considerable electrostriction contribution depending on steric hindrance to ionization. This means that pressures favors formation of the carbanion and attack of the nitrile. The results highlight the synthetic utility of high pressure to remove steric inhibition.
Formation of a New, Strongly Basic Nitrogen Anion by Metal Oxide Modification
Tamura, Masazumi,Kishi, Ryota,Nakayama, Akira,Nakagawa, Yoshinao,Hasegawa, Jun-Ya,Tomishige, Keiichi
, p. 11857 - 11867 (2017)
Development of new hybrid materials having unique and unprecedented catalytic properties is a challenge for chemists, and heterogeneous-homogeneous hybrid catalysts have attracted much attention because of the preferable and exceptional properties that are highly expected to result from combination of the components. Base catalysts are widely used in organic synthesis as key materials, and a new class of base catalysts has made a large impact from academic and industrial viewpoints. Here, a principle for creating a new strong base by hybridization of homogeneous and heterogeneous components is presented. It is based on the modification of organic compounds with metal oxides by using the acid-base property of metal oxides. Based on kinetic and DFT studies, combination of CeO2 and 2-cyanopyridine drastically enhanced the basicity of 2-cyanopyridine by a factor of about 109 (～9 by pKa (in CH3CN)), and the pKa was estimated to be ～21, which locates it in the superbase category. 2-Cyanopyridine and CeO2 formed a unique adsorption complex via two interaction modes: (i) coordinative interaction between the Ce atom of CeO2 and the N atom of the pyridine ring in 2-cyanopyridine, and (ii) covalent interaction between the surface O atom of CeO2 and the C atom of the CN group in 2-cyanopyridine by addition of the lattice oxygen of CeO2 to the CN group of 2-cyanopyridine. These interactions established a new, strongly basic site of N- over the CeO2 surface.
Template catalysis by manganese pincer complexes: Oxa- and aza-Michael additions to unsaturated nitriles
Tang, Shan,Milstein, David
, p. 8990 - 8994 (2019)
Activation of CN bonds by metal-ligand cooperation provides a new route for the functionalization of nitriles. Herein, we report the electrophilic activation of unsaturated nitriles by dearomatized manganese pincer complexes for the oxa- and aza-Michael addition reactions under very mild and neutral conditions. Derivatives of acrylonitrile and allyl cyanide furnished the corresponding β-addition products by reacting with alcohols and amines. Mechanistically, the catalysis is mostly ligand based. Reaction of the dearomatized PNN-Mn complex with 2-pentenenitrile or 3-pentenenitrile furnished an enamido-Mn complex. The equilibrium between an enamido complex and a ketimido complex, and reversible C-C bond formation with the ligand are proposed to play central roles in the catalysis.
Modified Mg-Al hydrotalcite: A highly active heterogeneous base catalyst for cyanoethylation of alcohols
Kumbhar, Pramod S.,Sanchez-Valente, Jaime,Figueras, Francois
, p. 1091 - 1092 (1998)
Modified Mg-Al hydrotalcite (Mg:Al = 3:1) prepared by thermal decarbonation followed by rehydration of a conventional Mg-Al hydrotalcite is found to be a highly active, reusable and air stable catalyst for cyanoethylation of alcohols.
A metal-ligand cooperative pathway for intermolecular oxa-michael additions to unsaturated nitriles
Perdriau, Sébastien,Zijlstra, Douwe S.,Heeres, Hero J.,De Vries, Johannes G.,Otten, Edwin
, p. 4236 - 4240 (2015)
An unprecedented catalytic pathway for oxa-Michael addition reactions of alcohols to unsaturated nitriles has been revealed using a PNN pincer ruthenium catalyst with a dearomatized pyridine backbone. The isolation of a catalytically competent Ru-dieneamido complex from the reaction between the Ru catalyst and pentenenitrile in combination with DFT calculations supports a mechanism in which activation of the nitrile through metal-ligand cooperativity is a key step. The nitrile-derived Ru-N moiety is sufficiently Br?nsted basic to activate the alcohol and initiate conjugate addition of the alkoxide to the α,β-unsaturated fragment. This reaction proceeds in a concerted manner and involves a six-membered transition state. These features allow the reaction to proceed at ambient temperature in the absence of external base.
Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions
Boese, A. Daniel,Fischer, Susanne M.,Renner, Simon,Slugovc, Christian
supporting information, p. 1689 - 1697 (2021/08/03)
Electron-rich triarylphosphines, namely 4-(methoxyphenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP), outperform commonly used triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions and at room temperature. The results reveal a decisive superiority of TMTPP for converting poor and intermediate Michael acceptors such as acrylamide and acrylonitrile and for converting less acidic alcohols like isopropanol. With stronger Michael acceptors and more acidic alcohols, the impact of the more electron-rich catalysts is less pronounced. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine-Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was also evaluated and the most electron-rich TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa- Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80°C resulted in macromolecules containing a considerable share of Rauhut-Currier-type repeat units and consequently lower molar masses were obtained.
KOtBu-Catalyzed Michael Addition Reactions Under Mild and Solvent-Free Conditions
Thiyagarajan, Subramanian,Krishnakumar, Varadhan,Gunanathan, Chidambaram
supporting information, p. 518 - 523 (2020/02/04)
Designed transition metal complexes predominantly catalyze Michael addition reactions. Inorganic and organic base-catalyzed Michael addition reactions have been reported. However, known base-catalyzed reactions suffer from the requirement of solvents, additives, high pressure and also side-reactions. Herein, we demonstrate a mild and environmentally friendly strategy of readily available KOtBu-catalyzed Michael addition reactions. This simple inorganic base efficiently catalyzes the Michael addition of underexplored acrylonitriles, esters and amides with (oxa-, aza-, and thia-) heteroatom nucleophiles. This catalytic process proceeds under solvent-free conditions and at room temperature. Notably, this protocol offers an easy operational procedure, broad substrate scope with excellent selectivity, reaction scalability and excellent TON (>9900). Preliminary mechanistic studies revealed that the reaction follows an ionic mechanism. Formal synthesis of promazine is demonstrated using this catalytic protocol.
Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion
Xu, Boran,Hartigan, Elizabeth M.,Feula, Giancarlo,Huang, Zheng,Lumb, Jean-Philip,Arndtsen, Bruce A.
supporting information, p. 15802 - 15806 (2016/12/16)
We describe the use of simple copper-salt catalysts in the selective aerobic oxidation of amines to nitriles or imines. These catalysts are marked by their exceptional efficiency, operate at ambient temperature and pressure, and allow the oxidation of amines without expensive ligands or additives. This study highlights the significant role counterions can play in controlling selectivity in catalytic aerobic oxidations.
Solid sodium stannate as a high-efficiency superbase catalyst for anti-Markovnikov hydroamination and hydroalkoxylation of electron-deficient olefins under mild conditions
Zhang, Shuguo,Wei, Yudan,Yin, Shuangfeng,Au, Chak-Tong
, p. 712 - 716 (2013/01/09)
A solid superbase with H- above 26.5 has been obtained through thermal treatment of sodium stannate hydrate. It was found to be an efficient catalyst for anti-Markovnikov hydroamination and hydroalkoxylation of electron-deficient olefins under mild conditions.
