Catalyst In Benzene Research Articles

Identification of a potent palladium-aryldiphosphine catalytic system for high-performance carbonylation of alkenes

The development of stable and efficient ligands is of vital significance to enhance the catalytic performance of carbonylation reactions of alkenes. Herein, an aryldiphosphine ligand (L11) bearing the [Ph2P(ortho-C6H4)]2CH2 skeleton is reported for palladium-catalyzed regioselective carbonylation of alkenes. Compared with the industrially successful Pd/1,2-bis(di-tert-butylphosphinomethyl)benzene catalyst, catalytic efficiency catalyzed by Pd/L11 on methoxycarbonylation of ethylene is obtained, exhibiting better catalytic performance (TON: >2,390,000; TOF: 100,000 h−1; selectivity: >99%) and stronger oxygen-resistance stability. Moreover, a substrate compatibility (122 examples) including chiral and bioactive alkenes or alcohols is achieved with up to 99% yield and 99% regioselectivity. Experimental and computational investigations show that the appropriate bite angle of aryldiphosphine ligand and the favorable interaction of 1,4-dioxane with Pd/L11 synergistically contribute to high activity and selectivity while the electron deficient phosphines originated from electron delocalization endow L11 with excellent oxygen-resistance stability.

Promoting effect of Ti on MnTiOx catalysts for benzene highly efficient oxidation

MnTiOx catalysts with different quantities of Ti are synthesized with a hydrothermal method and employed in the catalytic oxidation of benzene. By controlling the relative content of Mn and Ti, the effect of Ti content has been investigated from physicochemical properties and activity points of view. Ti enables the formation of Lewis acid with electrophilic properties and simultaneously leads to the increase of Mn4+ and surface lattice oxygen numbers. Additionally, it is established that the addition of Ti4+ can lead to the partial substitution of Mn3+ in MnTiOx to create the Mn-O-Ti structure, improving the active oxygen transfer capacity, which is crucial for catalytic activity. After optimization, the best catalytic performance sample is MnTiOx-0.33 with the T90 = 258 oC at GHSV = 45000 ml·g-1·h-1. It is proposed that the catalytic oxidation of benzene takes place on the surface of MnTiOx-0.33 through the MVK mechanism.

Olefin-Supported Cationic Copper Catalysts for Photochemical Synthesis of Structurally Complex Cyclobutanes.

The sole method available for the photocycloaddition of unconjugated aliphatic alkenes is the Cu-catalyzed Salomon-Kochi reaction. The [Cu(OTf)]2 ⋅benzene catalyst that has been standard in this reaction for many decades, however, is air-sensitive, prone to photodecomposition, and poorly reactive towards sterically bulky alkene substrates. Using bench-stable precursors, an improved catalyst system with superior reactivity and photostability has been designed, and it offers significantly expanded substrate scope. The utility of this new catalyst for the preparation of sterically crowded cyclobutane structures is highlighted through the preparation of the cores of the natural products sulcatine G and perforatol.

Olefin‐Supported Cationic Copper Catalysts for Photochemical Synthesis of Structurally Complex Cyclobutanes

AbstractThe sole method available for the photocycloaddition of unconjugated aliphatic alkenes is the Cu‐catalyzed Salomon–Kochi reaction. The [Cu(OTf)]2⋅benzene catalyst that has been standard in this reaction for many decades, however, is air‐sensitive, prone to photodecomposition, and poorly reactive towards sterically bulky alkene substrates. Using bench‐stable precursors, an improved catalyst system with superior reactivity and photostability has been designed, and it offers significantly expanded substrate scope. The utility of this new catalyst for the preparation of sterically crowded cyclobutane structures is highlighted through the preparation of the cores of the natural products sulcatine G and perforatol.

Study of CeO₂ Modified AlNi Mixed Pillared Clays Supported Palladium Catalysts for Benzene Adsorption/Desorption-Catalytic Combustion.

A new functional AlNi-pillared clays (AlNi-PILC) with a large surface area and pore volume was synthesized. The performance of adsorption/desorption-catalytic combustion over CeO2-modified Pd/AlNi-PILC catalysts was also studied. The results showed that the d001-value and specific surface area (SBET) of AlNi-PILC reached 2.11 nm and 374.8 m2/g, respectively. The large SBET and the d001-value improved the high capacity for benzene adsorption. Also, the strong interaction between PdCe mixed oxides and AlNi-PILC led to the high dispersion of PdO and CeO2 on the support, which was responsible for the high catalytic performance. Especially, 0.2% Pd/12.5% Ce/AlNi-PILC presented high performance for benzene combustion at 240 °C and high CO2 selectivity. Also, the combustion temperatures were lower compared to the desorption temperatures, which demonstrated that it could accomplish benzene combustion during the desorption process. Furthermore, its activity did not decrease after continuous reaction for 1000 h in dry air, and it also displayed good resistance to water and the chlorinated compound, making it a promising catalytic material for the elimination of volatile organic compounds.

Synthesis and Characterization of Some New Morpholine Derivatives

In this paper a new series of morpholine derivatives was prepared by reacting the morpholine with ethyl chloro acetate in the presence triethylamine as a catalyst in benzene gave morpholin-N-ethyl acetate(1) which reacted with hydrazine hydrate in ethanol, and gave morpholin-N-ethyl acetohydrazide (2) . Morpholin-N-aceto semithiocarbazide (3) were prepared by reacting compound(2) with ammonium thiocyanate , concentrated hydrochloric acid and ethanol as a solvent .Compound (3) reacted with sodium hydroxide and hydrochloric acid to give 5-(morpholin-N-methylene)-1H-1,2,4-triazole-3-thiol (4) .The new series of 1,2,4-triazol derivatives (5-8) was synthesized by reaction of compound(4) with formaldehyde , DMF as a solvent and different secondary amines. Preparation of new 1,2,4-triazoline derivatives (9) by reaction compound (4) with bromo acetic acid . Reaction of compound (9) with different aromatic aldehyde and dimethyl sulfoxide as a solvent obtained compounds (10-13).

The effect of copper on benzene hydrogenation to cyclohexane over Ni/Al2O3 catalyst

The effect of a copper modifier on physicochemical properties of coprecipitated precursors and final Ni–Cu/Al2O3 catalysts for benzene to cyclohexane hydrogenation was investigated. Based on the studies of physicochemical properties, the influence of copper on the catalytic activity and selectivity of Ni–Cu/Al2O3 systems was discussed. The addition of copper resulted in a decrease of the specific and nickel surface area, improvement of the selectivity and a slight decrease of the benzene hydrogenation activity compared to the reference catalyst. A decrease of methylcyclopentane and methylcyclohexane by-products formation on the surface of Ni–Cu/Al2O3 catalyst containing 10–17wt% CuO by, respectively, 70% and 10% was observed. The results reveal a distinct, beneficial effect of the Ni/Al2O3 modification by copper on the catalyst selectivity. However, this effect depends on temperature and is limited to ca. 20wt% CuO, above this content the activity was found to decrease considerably.

Catalytic Removal of Volatile Organic Compounds

The degradation of air quality by the release of volatile organic compounds (VOCs) into the air particularly harms human health and our environment. [...]

Synthesis and Characterization of Some New Morpholine Derivatives

In this paper a new series of morpholine derivatives was prepared by reacting the morpholine with ethyl chloro acetate in the presence triethylamine as a catalyst in benzene gave morpholin-N-ethyl acetate(1) which reacted with hydrazine hydrate in ethanol, and gave morpholin-N-ethyl acetohydrazide (2) . Morpholin-N-aceto semithiocarbazide (3) were prepared by reacting compound(2) with ammonium thiocyanate , concentrated hydrochloric acid and ethanol as a solvent .Compound (3) reacted with sodium hydroxide and hydrochloric acid to give 5-(morpholin-N-methylene)-1H-1,2,4-triazole-3-thiol (4) .The new series of 1,2,4-triazol derivatives (5-8) was synthesized by reaction of compound(4) with formaldehyde , DMF as a solvent and different secondary amines. Preparation of new 1,2,4-triazoline derivatives (9) by reaction compound (4) with bromo acetic acid . Reaction of compound (9) with different aromatic aldehyde and dimethyl sulfoxide as a solvent obtained compounds (10-13).

Effect of ZrO<SUB>2</SUB> Addition on the Properties of CuMn<SUB>2</SUB>/Al-Ti Monolithic Catalysts for Benzene Catalytic Combustion

Effect of ZrO<SUB>2</SUB> Addition on the Properties of CuMn<SUB>2</SUB>/Al-Ti Monolithic Catalysts for Benzene Catalytic Combustion

2-Cyanomethylbenzaldehyde – useful substrate for preparation of some 1,3-di- and 1,2,3-trisubstituted naphthalenes or substituted 1-cyanobenzobicyclo[2.2.2]octenes

Cyanomethylbenzaldehyde reacts in the presence of concentrated aqueous solution of sodium hydroxide or powdered potassium carbonate and a quaternary ammonium salt as a catalyst in benzene (phase-transfer catalysis) with 2-chloroethyl aryl ketones or electrophilic alkenes affording 1-cyano-3-acylnaphthalenes, 1-(2-cyano)- and 1-(2-phenylsulfonyl)ethyl-3-substituted naphthalenes or 1-cyano-5,8-diaroyl-benzobicyclo(2.2.2)octenes. Further cyclization of the corresponding 5,8-diacetyl derivative of 1-cyanobenzobicyclooctene gives 1-cyano-10- methyltetracyclo(7.5.1.0 2,7 .0 8,13 )pentadeca-2,4,6,10-tetraen-12-one. Formation of these products is rationalized.

Copper‐Catalyzed Conjugate Addition of Diboron Reagents to α,β‐Unsaturated Amides: Highly Reactive Copper‐1,2‐ Bis(diphenylphosphino)benzene Catalyst System

Abstractmagnified imageAn efficient copper catalyst system for the β‐boration of α,β‐unsaturated amides has been developed. Copper‐bisphosphine complexes with small bite angles generate efficient catalyst systems for the successful conjugate addition of bis(pinacolato)diboron to a variety α,β‐unsaturated amides under mild conditions. This method was utilized in the formal synthesis of (S)‐fluoxetine.

Rhodium-Catalyzed Hydroarylation and Hydroalkenylation of Alkynes Using Organo[2-(hydroxymethyl)phenyl]dimethylsilanes

The title reaction was found to proceed in the presence of a rhodium/1,2-bis(diphenylphosphino)benzene catalyst. Variously substituted arylethenes and 1,3-dienes were obtained in good yields.

Carbon-bridged diphosphine ligands for chromium-catalysed ethylene tetramerisation and trimerisation reactions

The use of carbon-bridged diphosphine ligands in chromium-catalysed ethylene tri- and tetramerisation reactions has been investigated. Two- and three-carbon spacer ligands all showed activity for selective oligomerisation, with a structure–selectivity correlation between P–Cr–P bite angle and 1-octene:1-hexene ratio evident. Activated chromium complexes of single carbon spacer diphosphines were also shown to be effective tetramerisation catalysts, provided that the ligand is innocent under the conditions of catalyst activation. A catalyst with the bis(diphenylphosphino)benzene ligand was found to be exceptionally active, although the combined 1-hexene and 1-octene selectivity was lower than with the best diphosphinoamine (PNP) ligands. The yield losses to by-products can to an extent be minimised by the use of high reaction temperatures and pressures. Unlike with the PNP-based systems, attempts to activate the Cr/bis(diphenylphosphino)benzene catalyst in situ from a chromium salt and free ligand resulted in low activity and high polymer formation. The effect of different phosphine substitution on catalyst selectivity was explored. Steric constraints around the catalytic centre ( ortho-alkylphenyl phosphines) resulted in a shift towards 1-hexene formation, as with PNP catalysts. Additionally, the basicity of the phosphines appears to influence catalyst selectivity, with alkyl phosphines favouring trimerisation. An interplay between phosphine basicity and bridge structure is in evidence, however, as a catalyst containing a ligand with both basic phosphine atoms and a small bite angle was shown to be selective towards 1-octene.

Reaction of difluorocarbene with anions from amides and oximes: Synthesis of N-difluoromethyl substituted amides, O-difluoromethylimidates or O-difluoromethyl substituted oximes under phase-transfer catalysis conditions

N-Aryl substituted amides react with chlorodifluoromethane in the presence of concentrated aqueous sodium hydroxide and benzyltriethylammonium chloride (TEBAC) as a catalyst in benzene (phase-transfer catalysis, PTC), affording mixtures of N- and O-difluoromethyl substituted derivatives. Amide anions are involved in this process. The reaction carried out with oximes gives O-difluoromethyl oxime ethers.

Anionic Synthesis of Primary Amine Functionalized Polystyrenes via Hydrosilation of Allylamines with Silyl Hydride Functionalized Polystyrenes

A general anionic ω-chain-end functionalization methodology is described and illustrated by the synthesis of ω-primary amine functionalized polystyrenes. First, the quantitative ω-silyl hydride functionalization of well-defined poly(styryl)lithium (Mn = 2200 and 14 100 g/mol) was effected with dimethylchlorosilane in hydrocarbon solution at room temperature. In the second step, involving amination by hydrosilation, the silyl hydride functionalized polystyrene was added quantitatively to 3-[N,N-bis(trimethylsilylamino]-1-propene, a protected amine, using Karstedt's Pt(0) hydrosilation catalyst in benzene. One of the principal advantages of this method is the fact that it is not necessary to use protecting groups for many functional groups, as illustrated by the quantitative primary amine functionalization of ω-silyl hydride functionalized poly(styryl)lithium with allylamine using the Karstedt's hydrosilation catalyst. The silyl hydride and amine functionalized polystyrenes were characterized by SEC, FTIR, ...

Chemistry of Ruthenium(II) Monohydride and Dihydride Complexes Containing Pyridyl Donor Ligands Including Catalytic Ketone H2-Hydrogenation1

In this study we determine the changes to the properties of dihydride catalysts for ketone H2-hydrogenation by successively replacing the amine donors in the known dach complex RuH2(PPh3)2(dach) (2a), dach = 1,2-(R,R)-diaminocyclohexane, with one pyridyl group in the corresponding 2-(aminomethyl)pyridine (ampy) complexes RuH2(PPh3)2(ampy) (2b) and with two pyridyl groups in the complexes RuH2(PPh3)2(bipy) (2c) and RuH2(PPh3)2(phen) (2d). The ruthenium monohydride complex, (OC-6-54)-RuHCl(PPh3)2(ampy), (1b with Cl trans to H) was prepared by the addition of 1 equiv of ampy to RuHCl(PPh3)3 in THF. Treatment of the monohydride complex with K[BH(sec-Bu)3] in THF or KOtBu/H2 in toluene resulted in the formation of a mixture of at least two isomers of the highly reactive, air-sensitive ruthenium dihydride complex 2b. One is the cis dihydride (OC-6-14)-2b or more simply c,t-2b with trans PPh3 groups and another is the cis dihydride c,c-2b (OC-6-42) that has PPh3 trans to H and PPh3 trans to N(pyridyl). The isomer c,c-2b slowly converts to c,t-2b in solution. The reaction of 1b with KOtBu under Ar results in the formation of a mixture that includes a complex with an imino ligand HN=CH-2-py while the same reaction under H2 leads to c,c-2b and then c,t-2b. The dach complex c,t-2a, reacts with ampy, 2,2'-bipyridine (bipy), and 1,10-phenanthroline (phen) in refluxing THF to form the substituted cis-dihydride complexes c,t-2b, (OC-6-13)-RuH2(PPh3)2(bipy) (c,t-2c with trans PPh3 groups) and (OC-6-13)-RuH2(PPh3)2(phen), c,t-2d, respectively. The dihydrides containing amino groups and cis-PPh3 groups, i.e., c,c-2a or c,c-2b, are active precatalysts for the H2-hydrogenation of acetophenone (neat or in benzene) under mild reaction conditions, whereas those with trans-PPh3 groups, c,t-2a and c,t-2b are much less active. The combination of ampy complex 1b and KOtBu also provides a catalyst in benzene that is more active than the corresponding dach system. The complexes without amino groups c,t-2c and c,t-2d are air-stable and inactive as hydrogenation catalysts under comparable conditions. The mechanism of hydrogenation of ketones catalyzed by isomers of 2a,b is thought to be similar and to proceed via a trans-dihydride complex, t,c-2a or t,c-2b, and an amido complex, neither of which are directly observed for the ampy complexes. The dihydride complex c,t-2b reacts with formic acid to give (OC-6-45)-RuH(OCHO)(PPh3)2(ampy), 3b, with formate trans to hydride. The structures of 1b, c,t-2b, c,t-2c, and 3b have been determined by single-crystal X-ray diffraction.

Allylation of Meldrum’s Acids by Allylic Alcohols Using Tetrakis[triphenylphosphine]palladium(0) Catalysts

Meldrum's acids can be allylated by allylic alcohols using tetrakis[triphenylphosphine]palladium(0) [(PPh 3 ) 4 Pd] as a catalyst in benzene at 80°C without prior activation of allylic hydroxy group.

A Convergent Synthesis of (17R,5Z,8Z,11Z,14Z)‐17‐Hydroxyeicosa‐5,8,11,14‐tetraenoic Acid Analogues and Their Tritiated Derivatives.

Abstract 17(R)-OH-AA and 14,15-dehydro-17(R)-OH-AA were synthesized from a common tetraacetylenic precursor and their azide derivatives were obtained in moderate yields via the corresponding p-toluenesulfonates. Since the azido group remained stable during tritiation procedure on Lindlar's catalyst in benzene, both 14,15-dehydro-17(S)-N3-AA and 14,15-dehydro-17(R)-OH-AA constitute useful intermediates in the synthesis of radio-labelled 17(S)-N3-AA and 17(R)-OH-AA. In contrast, reduction of azide in methanol afforded 17(S)-NH2-AA with 95% yield.

A convergent synthesis of (17 R,5 Z,8 Z,11 Z,14 Z)-17-hydroxyeicosa-5,8,11,14-tetraenoic acid analogues and their tritiated derivatives

17( R)-OH-AA and 14,15-dehydro-17( R)-OH-AA were synthesized from a common tetraacetylenic precursor and their azide derivatives were obtained in moderate yields via the corresponding p-toluenesulfonates. Since the azido group remained stable during tritiation procedure on Lindlar's catalyst in benzene, both 14,15-dehydro-17( S)-N 3-AA and 14,15-dehydro-17( R)-OH-AA constitute useful intermediates in the synthesis of radio-labelled 17( S)-N 3-AA and 17( R)-OH-AA. In contrast, reduction of azide in methanol afforded 17( S)-NH 2-AA with 95% yield.