Halide-free Conditions Research Articles

Synthesis of Encapsulant by Clean Oxidation Under Halide-Free Conditions

Synthesis of Encapsulant by Clean Oxidation Under Halide-Free Conditions

Amino acids/superbases as eco-friendly catalyst system for the synthesis of cyclic carbonates under metal-free and halide-free conditions

ABSTRACTAn eco-friendly and efficient binary catalyst system of superbases and amino acids was developed for the synthesis of cyclic carbonates from epoxides and CO2 under metal-free and halide-free conditions. Among the various amino acids and superbases systems tested, the L-histidine/1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) system achieved the highest conversion of propylene oxide and selectivity of propylene carbonate. The effect of various reaction parameters was evaluated. A possible catalyst mechanism for L-histidine synergized with DBU in the ring opening of epoxide and DBU introduced CO2 activation. The process herein represents a green, simple, and cost-effective route for the chemical fixation of CO2 into cyclic carbonates.

Superbase/saccharide: An ecologically benign catalyst for efficient fixation of CO2 into cyclic carbonates

ABSTRACTAn ecologically benign catalytic system consisting of superbase and saccharide was developed for CO2 chemical fixation with epoxides under metal-free and halide-free conditions. Because of the synergistic effect played by superbase and saccharide on the activations of CO2 and epoxide, the reaction could be performed with good activity and selectivity. A possible catalytic mechanism of the hydrogen-bonding of saccharide and activation of the carbon atom by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was proposed. The process is a simple, biocompatible, and ecological route for CO2 chemical fixation into high-value chemicals.

Silica-Grafted Basic Amino Acids as Environmentally Benign Catalysts for the Solventless Synthesis of Cyclic Carbonates from Epoxides and CO2 under Metal-Free and Halide-Free Conditions

A series of basic amino acids immobilized onto solid supports that can play cooperative roles was developed and applied as environmentally benign catalytic systems for the solventless synthesis of cyclic carbonates from epoxides and carbon dioxide under metal-free and halide-free conditions. The highest yield of styrene carbonate was achieved with silica supported l -histidine, associated with the acidic nature of silica: Si–OH groups on the silica surface act as a weak acid to activate the epoxide for the synergetic effect with the basic amino acid. The influence of various reaction parameters on catalytic activity was investigated. Moreover, the catalyst exhibited good recyclability.

Iron-catalyzed clean dehydrogenative coupling of alcohols with P(O)-H compounds: a new protocol for ROH phosphorylation.

An efficient oxygen-phosphoryl bond-forming reaction via iron-catalyzed cross dehydrogenative coupling has been developed. This transformation proceeds efficiently under oxidant- and halide-free reaction conditions with H2 liberation, and represents a straightforward method to prepare valuable organophosphoryl compounds from the readily available alcohols and P(O)-H compounds.

Niobate salts of organic base catalyzed chemical fixation of carbon dioxide with epoxides to form cyclic carbonates

Peroxoniobate salts of amidine and guanidine have been utilized as halogen-free catalysts for the synthesis of cyclic carbonates from epoxides and CO2 under solvent-free and halide-free conditions.

The unprecedented catalytic activity of alkanolamine CO2 scrubbers in the cycloaddition of CO2 and oxiranes: a DFT endorsed study.

A novel application of alkanolamines, widely employed as CO2 scrubbers in catalyzing the insertion of CO2 into epoxides generating cyclic carbonates in excellent yield and selectivity via the synergistic activity of hydroxyl and amine groups, is unravelled along with computational studies.

Superbase/cellulose: an environmentally benign catalyst for chemical fixation of carbon dioxide into cyclic carbonates

An environmentally benign catalytic system consisting of 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) and cellulose was developed for CO2 chemical fixation with epoxides under metal-free and halide-free conditions. Due to the dual roles played by DBU and cellulose on the activations of CO2 and epoxide, the reaction could be performed with high activity and selectivity. A possible catalytic cycle for the hydrogen bond assisted ring-opening of epoxide and the activation of CO2 induced by DBU was proposed. The process herein represents a simple, ecologically safe and efficient route for CO2 chemical fixation into high value chemicals.

過酸化水素を用いるハロゲンフリーエポキシ化

過酸化水素を用いるハロゲンフリーエポキシ化

Pt-Catalyzed Oxidative Rearrangement of Cyclic Tertiary Allylic Alcohols to Enones Using Aqueous Hydrogen Peroxide

Abstract An oxidative rearrangement of cyclic tertiary allylic alcohols to β-disubstituted α,β-unsaturated ketones by Pt black catalyst with aqueous hydrogen peroxide is described. The reaction proceeds under organic solvent- and halide-free conditions and gives only water as a coproduct. The Pt black catalyst is commercially available and can be reused at least four times.

An Effective Synthesis of Acid-Sensitive Epoxides via Oxidation of Terpenes and Styrenes Using Hydrogen Peroxide under Organic Solvent-Free Conditions

An efficient epoxidation process for various terpenes and styrenesusing a hydrogen peroxide-tungsten catalytic system with organicsolvent- and halide-free conditions was developed. In the presenceof the catalytic system, Na 2 WO 4 , PhP(O)(OH) 2 ,and [Me( N-C 8 H 17 ) 3 N]HSO 4 ,and under weak acidic conditions, hydrogen peroxide successfullyepoxidized α-pinene to α-pinene oxide in 95% selectivityat 91% conversion, while the previously published conditionsutilizing NH 2 CH 2 P(O)(OH) 2 as apromoter provided no epoxide.

ChemInform Abstract: A Practical Method for Alcohol Oxidation with Aqueous Hydrogen Peroxide under Organic Solvent- and Halide-Free Conditions.

A catalytic system consisting of sodium tungstate and methyltrioctylammonium hydrogensulfate effects oxidation of simple secondary alcohols to ketones using 3—30% H2O2 without any organic solvents. The oxidation can be conducted under entirely halide-free, mildly acidic conditions. A combination of tungstic acid and an appropriate quaternary ammonium salt also effects the alcohol dehydrogenation. The organic/aqueous biphasic reaction allows easy product/catalyst separation. The turnover number, defined as mols of product per mol of catalyst, approaches 77700 (2-octanol) or 179000 (1-phenylethanol), two orders of magnitude higher than any previously reported. Ester, alkyl and t-butyldimethylsilyl ether, epoxy, carbonyl, N-alkyl carboxamide, and nitrile groups are tolerated under the reaction conditions. Secondary alcohols are preferentially oxidized over terminal olefins. Primary alkanols are oxidized directly to carboxylic acids in a moderate to high yield. Benzylic alcohols are selectively oxidized to be...

Green Oxidation with Aqueous Hydrogen Peroxide

Aqueous H202 is an ideal oxidant, when coupled with a tungstate complex and a quaternary ammonium hydrogen sulphate as an acidic phase-transfer catalyst. It oxidizes alcohols, olefins, and sulfides under organic solvent- and halide-free conditions in aneconomically, technically and environmentally satisfying manner.

Chemoselective Oxidation of Alcohols by a H2O2–Pt Black System under Organic Solvent‐ and Halide‐Free Conditions

Environmentally benign oxidation of allylic alcohols by platinum black catalyst with aqueous hydrogen peroxide to give the corresponding alpha,beta-unsaturated carbonyl compounds in high yield is presented. Reactions are carried out under organic solvent- and halide-free conditions. The platinum black catalyst is commercially available and is found to be reusable at least seven times before significant loss of catalytic activity. The operation is very simple, even in a hectogram-scale synthesis, and gives corresponding carbonyl compounds in over 90 % yield. The effective oxidation of benzyl and secondary alcohols are also described.

Organic Solvent- and Halide-Free Oxidation with Hydrogen Peroxide

A number of environmentally benign oxidation reactions with aqueous hydrogen peroxide were carried out, including chemoselective oxidation of allylic alcohols to corresponding α, β-unsaturated carbonyl compounds by using platinum black catalyst, 1, 2-dihydroxylation of olefins in the presence of catalytic amount of resin-supported sulfonic acid, and the oxidation of cycloalkanone with tungstic acid catalyst. These reactions were carried out under organic solvent- and halide-free conditions, and they successfully gave the desired products in high yield. Platinum black and resin-supported sulfonic acid catalysts could be easily recovered and reused several times without significant loss of activity. Immobilization of quaternary ammonium and phosphonium salts, and crown etherr on the magnetic nanoparticles (MNP), and their catalytic activities in the phase-transfer reaction were also investigated. The MNP-supported catalysts showed activity comparable to those of non-supported ones. Further, they could be easily recovered by using an external magnet, and reused several times without loss of activity.

A catalytic, environmentally benign method for the epoxidation of unsaturated terpenes with hydrogen peroxide

Various unsaturated terpenes were selectively oxidised to the corresponding epoxides in good yields using phosphate buffered hydrogen peroxide and catalytic amounts of tungstate under halide free conditions. The selectivity of the reaction to epoxides was significantly increased with respect to the ionic strength of the aqueous phase of the system.

Green Oxidation with Aqueous Hydrogen Peroxide.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Green oxidation with aqueous hydrogen peroxide

Aqueous H2O2 is an ideal oxidant, when coupled with a tungstate complex and a quaternary ammonium hydrogensulfate as an acidic phase-transfer catalyst. It oxidizes alcohols, olefins, and sulfides under organic solvent- and halide-free conditions in an economically, technically, and environmentally satisfying manner.

A green method of adipic acid synthesis: organic solvent- and halide-free oxidation of cycloalkanones with 30% hydrogen peroxide

Cyclohexanone and cyclohexanol are oxidized to adipic acid in high yield with aqueous 30% H2O2 in the presence of H2WO4 as a catalyst under organic solvent- and halide-free conditions. It is important that no solvent is used in order to achieve high reactivity in this heterogeneous reaction. The use of t-butyl alcohol or dioxane as a solvent (homogeneous conditions) significantly decreases the yield of adipic acid from cyclohexanone. This ketone-to-dicarboxylic acid conversion is applicable to five- to eight-membered cyclic ketones. No operational problems are foreseen for a large-scale version of this green process.

A Practical Method for Alcohol Oxidation with Aqueous Hydrogen Peroxide under Organic Solvent- and Halide-Free Conditions

Abstract A catalytic system consisting of sodium tungstate and methyltrioctylammonium hydrogensulfate effects oxidation of simple secondary alcohols to ketones using 3—30% H2O2 without any organic solvents. The oxidation can be conducted under entirely halide-free, mildly acidic conditions. A combination of tungstic acid and an appropriate quaternary ammonium salt also effects the alcohol dehydrogenation. The organic/aqueous biphasic reaction allows easy product/catalyst separation. The turnover number, defined as mols of product per mol of catalyst, approaches 77700 (2-octanol) or 179000 (1-phenylethanol), two orders of magnitude higher than any previously reported. Ester, alkyl and t-butyldimethylsilyl ether, epoxy, carbonyl, N-alkyl carboxamide, and nitrile groups are tolerated under the reaction conditions. Secondary alcohols are preferentially oxidized over terminal olefins. Primary alkanols are oxidized directly to carboxylic acids in a moderate to high yield. Benzylic alcohols are selectively oxidized to benzaldehydes or benzoic acids under suitable conditions. This method is high-yielding, clean, safe, operationally simple, and cost-effective, and therefore suitable for practical organic synthesis. The mechanistic origin of the catalytic efficiency is discussed.