- KOtBu-Catalyzed Michael Addition Reactions Under Mild and Solvent-Free Conditions
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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.
- Thiyagarajan, Subramanian,Krishnakumar, Varadhan,Gunanathan, Chidambaram
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supporting information
p. 518 - 523
(2020/02/04)
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- An Enantioselective Cross-Dehydrogenative Coupling Catalysis Approach to Substituted Tetrahydropyrans
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An enantioselective cross-dehydrogenative coupling (CDC) reaction to access tetrahydropyrans has been developed. This process combines in situ Lewis acid activation of a nucleophile in concert with the oxidative formation of a transient oxocarbenium electrophile, leading to a productive and highly enantioselective CDC. These advances represent one of the first successful applications of CDC for the enantioselective couplings of unfunctionalized ethers. This system provides efficient access to valuable tetrahydropyran motifs found in many natural products and bioactive small molecules.
- Lee, Ansoo,Betori, Rick C.,Crane, Erika A.,Scheidt, Karl A.
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supporting information
p. 6212 - 6216
(2018/05/14)
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- Formation of a New, Strongly Basic Nitrogen Anion by Metal Oxide Modification
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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.
- Tamura, Masazumi,Kishi, Ryota,Nakayama, Akira,Nakagawa, Yoshinao,Hasegawa, Jun-Ya,Tomishige, Keiichi
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p. 11857 - 11867
(2017/09/08)
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- Synthesis and fluorescence studies on menthol-coumarin conjugates
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A three-step protocol for synthesis of alcohol containing aliphatic natural products and coumarins has been described. The Blaise reaction of converting the nitrile to β-keto esters formed key-step in this protocol. The menthol-coumarin conjugates prepared for the first time are subjected to absorption and fluorescence emission studies. The studies reveal that menthol substitution has little influence on the absorption or emission characteristic of the chromophore. However, substitution of C(6)H or C(6)OMe of the coumarin with NEt2 has dramatic influence on both absorption and emission of the conjugate. Solvatochromic studies and analysis of Stoke shift data show that the menthol-coumarin conjugate with C(6)NEt2 stabilizes itself in dipolar push-pull structure in ground and excited states.
- Rao, H. Surya Prakash,Desai, Avinash
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p. 514 - 524
(2015/07/07)
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- Catalytic Olefin hydroalkoxylation by nano particles of pollucite
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The catalytic hydroalkoxylation of α,β-unsaturated esters, nitriles, and ethers with aliphatic and aromatic alcohols over pollucite using thermal and microwave-assisted methods was investigated. To study the effect of the alcohol structures on the mechanism of the hydroalkoxylation reaction, different alcohols, such as methanol to butanol, cyclohexanol, phenol, and 2-ethylhexanol were used. The activities of pollucite, in contrast to other basic solids, were scarcely affected by the presence of air and moisture. The correlation between alcohol acidity and reaction activity is discussed. The prepared pollucite was characterized by X-ray diffraction, volumetric nitrogen adsorption surface area analysis, and CO2 temperature-programmed desorption. Scanning electron microscopy analysis revealed that the size of the modified nano catalyst particles was under 40nm.
- Zamanian, Sara,Kharat, Ali Nemati
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p. 981 - 986
(2015/06/25)
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- Cyanoethylation of alcohols and amines by cesium-modified zeolite y
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Zeolite Y modified by cesium and magnesium ions was prepared by ion-exchange and impregnation methods, and its activity in the cyanoethylation of aliphatic and aromatic alcohols and amines was investigated. During the preparation of some samples, the transformation of zeolite Y into a pollucite-type phase occurred. This phase exhibited good activity in the cyanoethylation of aliphatic alcohols. The prepared solids modified by the impregnation method were more active than the ion-exchanged solids. The activities of the catalysts, in contrast to other basic solids, were scarcely affected by the presence of air or moisture. A correlation between catalyst basicity and catalytic activity is discussed. The catalysts were characterized by X-ray diffraction, volumetric nitrogen adsorption surface area measurement, and CO2 temperature-programmed desorption. Scanning electron microscopy revealed that the particles of the modified nanocatalysts were 40 nm. The reaction of acrylonitrile with linear alcohols in the presence of the catalysts was accelerated by microwave irradiation.
- Zamanian, Sara,Kharat, Ali Nemati
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p. 264 - 269
(2014/03/21)
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- Solid sodium stannate as a high-efficiency superbase catalyst for anti-Markovnikov hydroamination and hydroalkoxylation of electron-deficient olefins under mild conditions
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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.
- Zhang, Shuguo,Wei, Yudan,Yin, Shuangfeng,Au, Chak-Tong
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p. 712 - 716
(2013/01/09)
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- Omega-hydrofluoroalkyl ethers, precursor carboxylic acids and derivatives thereof, and their preparation and application
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Normally liquid, omega-hydrofluoroalkyl ether compounds (and selected mixtures thereof) have a saturated perfluoroaliphatic chain of carbon atoms interrupted by one or more ether oxygen atoms. The compounds can be prepare, e.g. by decarboxylation of the corresponding fluoroalkyl ether carboxylic acids and are useful, e.g., in cleaning and drying applications.
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- Modified Mg-Al hydrotalcite: A highly active heterogeneous base catalyst for cyanoethylation of alcohols
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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.
- Kumbhar, Pramod S.,Sanchez-Valente, Jaime,Figueras, Francois
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p. 1091 - 1092
(2007/10/03)
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- Aldose epimerization by Ni(II): effect of ether-containig alkylenediamine ligands
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Several N-substituted ethylenediamine (en) Ni(II) derivatives containing ether linkages were prepared in order to study the effect of ligand structure on C-2 epimerization of aldohexoses.The reagent consisted of a Ni(II)-alkyenediamine derivative in methanol.The presence of ether linkages in the ligand increased the solubilty of the complexes, and resulted in an increase in the rate of epimerization.Epimerization occured rapidly under mild conditions, and the same equilibrium point was reached regardless of whether the reaction was started from glucose or mannose.Among the ligands studied, N,N'-dialkylethylenediamine was the most effective in C-2 epimerization.
- Osanai, Shuichi,Inaba, Kiyoshi,Yoshikawa, Sadao
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p. 289 - 295
(2007/10/02)
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