Solid-liquid Phase Transfer Catalysis Research Articles

A study of the sequential Michael addition-ring closure reaction of ethyl acetoacetate with chalcone: influence of quaternary ammonium cations as phase transfer catalysts

The Michael addition of ethyl acetoacetate 1 to chalcone 2 under Solid/Liquid Phase Transfer Catalysis (SL-PTC), solvent free, afforded Michael adduct 3 and an annulated compound 4 in good yield. The cyclic compound 4 was obtained in the majority via an annulation process of the Michael adduct 3. The proportion of 4 in the ratio of 3/4 was dependant on the structure of the quaternary ammonium cation. The results were interpreted on the basis of the organophilicity and accessibility of the catalysts as well as by invoking a 6-membered ring transition state for the formation of 4 due to the chelation level with Q+.

Novelties of selective synthesis of 3-methyl-4′-nitro-diphenyl ether under solid–liquid phase transfer catalysis

3-Methyl-4′-nitro-diphenyl ether, an important agrochemical, is normally synthesized by employing aprotic polar solvents, or Ullmann reaction at elevated temperatures leading to a number of by-products and the process is costly. The current paper presents a cost effective and simpler process of synthesis of 3-methyl-4′-nitro-diphenyl ether from sodium salt of m-cresol and p-chloronitrobenzene (PCNB) by using o-xylene as a solvent under solid–liquid phase transfer catalysis (S–L PTC), at 120 °C, which is 100% selective. The liquid–liquid (L–L) PTC process does not work at the same conditions due to poor reactivity of the ion-pair. A novel mathematical model is developed to determine simultaneously the rate constant and anion exchange equilibrium constant from the same set of data. This will be helpful in reactor design and scale up. The activation energy and Gibb's free energy for a combined ion exchange and partitioning of ion pairs is are also calculated. The reactivity of sodium salts of o- and p-cresol with PCNB is also tested.

Kinetic study of synthesizing N-butylphthalimide under solid–liquid phase-transfer catalysis conditions

The synthesis of N-butylphthalimide (PTR) from the reaction of 1-bromobutane and potassium salt of phthalimide (PTK) was carried out successfully in a solid–liquid phase-transfer catalytic condition (SL-PTC) instead of reaction in a liquid–liquid two-phase medium. No water is required in the reaction system. The advantage of using SL-PTC to synthesize organic chemicals is to avoid a serious hydration of potassium salt of phthalimide from the reaction of 1-bromobutane and potassium salt of phthalimide in a liquid–liquid two-phase solution. The reaction is greatly enhanced in the solid–liquid solution catalyzed by quaternary ammonium salts. The reaction mechanism is proposed and verified by examining the experimental evidence. A kinetic model is proposed in which a pseudo first-order rate law is sufficient to describe the results. Kinetics of the reaction, including the effects of agitation speed, amount of acetonitrile, organic solvents, amount of tetrabutylammonium bromide, quaternary ammonium salts, amount of water and temperature on the conversion of 1-bromobutane and the apparent rate constant ( k app) were investigated in detail. Rational explanations to account for the phenomena on the results were made.

Synthesis of New Surfactants Mono and Bipolar Derived from 1,2,4‐Triazole‐5‐thione.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of 2,6‐Disubstituted Morpholines Through Regioselective Oxiranes Ring Opening by Tosylamide under PTC Conditions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novelties of solid–liquid phase transfer catalysed synthesis of p-toluenesulfonyl fluoride from p-toluenesulfonyl chloride

Organic sulfonyl fluorides are of interest owing to their insecticidal, germicidal and enzyme inhibitory properties. In the current work, synthesis of p-toluenesufonyl fluoride was accomplished by reacting p-toluenesulfonyl chloride with solid potassium fluoride using PEG-400 as a catalyst under solid–liquid phase transfer catalysis (S–L PTC) at 30 °C. p-Toluenesulfonyl fluoride is used as peroxygen bleach activator. It also finds use in the treatment of Alzheimer's disease. The mechanism is based on homogeneous solubilization of solid. PEG forms a complex with metal cation which associates with the nucleophile and it participates in SN 2 type reactions. The reaction is intrinsically kinetically controlled. A complete theoretical analysis is done to determine both the rate constant and equilibrium constant from the same set of data. The activation energy and Gibbs free energy are also calculated.

Eco‐friendly methodologies for the synthesis of some aromatic esters, well‐known cosmetic ingredients

Solid-liquid solvent-free phase transfer catalysis (PTC) and acidic catalysis in dry media were applied, with noticeable improvement and simplification over classical procedures in a Green Chemistry context, to the synthesis of some aromatic esters useful as cosmetic ingredients: 3-methylbutyl 4-methoxycinnamate, 2-ethylhexyl 4-methoxycinnamate, 2-ethylhexyl 4-(dimethylamino)benzoate and 2-ethylhexyl salicylate, well-known ultraviolet B sunscreen filters; 4-isopropylbenzyl salicylate, UV absorber and cutaneous antilipoperoxidant; propyl 4-hydroxybenzoate and butyl 4-hydroxybenzoate (parabens), antimicrobial agents. The reactions were performed under microwave (MW) activation and conventional heating. The best results for the synthesis of cinnamic, salicylic and 4-(dimethylamino)benzoic esters were achieved by in situ preformed carboxylates alkylation with alkyl bromides using PTC. The 4-hydroxybenzoates were obtained in good yields by classical esterification of the acid with alcohols using a simple heterogeneous mixture of reagents with catalytic amounts of p-toluenesulfonic acid (PTSA). The comparisons of yields and thermal profiles under either MW or conventional heating were studied and reported.

Synergism of Low Energy Microwave Irradiation and Solid—Liquid Phase Transfer Catalysis for Selective Alkylation of Phenols to Phenolic Ethers.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Efficient Synthesis of Polymethylene‐bis‐aroyl Thiourea Derivatives under the Condition of Phase‐Transfer Catalysis.

Reaction of polymethylene diamine with aroyl chloride and ammonium thiocyanate under the condition of solid–liquid phase-transfer catalysis using polyethylene glycol-400 (PEG-400) as the catalyst yielded polymethylene-bis-aroyl thiourea derivatives 3a–q in good-to-excellent yield. The products have been characterized by analytical and spectral (IR and H1 NMR) data.

Catalytic activity and anion activation in SN2 reactions promoted by complexes of silicon polypodands. Comparison with traditional polyethers

The catalytic activity of silicon polypodands was evaluated in anion-promoted reactions under solid–liquid phase-transfer catalysis (SL-PTC) conditions and compared with that exhibited by common PTC agents. Results showed that these many-armed ligands are particularly efficient catalysts, even comparable with the more sophisticated crown ethers. Kinetics under homogeneous conditions indicated that the anion activation realized by silicon polypodands does not appreciably change with the number of chains and is comparable or slightly lower than that of traditional polyethers. In addition, the sequence of reactivity is determined by the cation (NH4+ < K+ < Na+ < Li+), thus revealing an involvement of the metal ion in the transition state of the reactions (“metal ion electrophilic catalysis”).

Synthesis and antibacterial activity of new N-acyl-N' -(3-chloro-4- fluorophenyl)thioureas

A new series of N-acyl-N'-(3-chloro-4-fluorophenyl)thioureas have been prepared in excellent yield by the reaction of acylthiocyanates and 3-chloro-4-fluoroaniline under solid-liquid phase transfer catalysis using PEG-400. All synthesised compounds were screened against Escherichia cull and Staphylococcus aureus in DMF for evaluating their antibacterial activity. 2d, 2c, 2f and 2g showed good activity at 50 μg/ml dilution.

Synthesis of New Surfactants Mono and Bipolar Derived from 1,2,4‐Triazole‐5‐thione

3‐Phenyl‐1,2,4‐triazole‐5‐thione (PTS) and 3‐methyl‐1,2,4‐triazole‐5‐thione (MTS) are prepared in two steps. The first is a condensation of the thiosemicarbazide with the benzoyl chloride and the acetyl chloride for the PTS and MTS respectively in pyridinic medium. This step leads to the formation of 1‐benzoylthiosemicarbazide and 1‐acetylthiosemicarbazide. The 1‐acetylthiosemicarbazide is also prepared with a new method consisted of a simple solvolysis the thiosemicarbazide in acetic acid for 4 hr. The second is the intramolecular cyclization in methanol with the presence of the sodium methalate leads to the formation of the PTS and the MTS in good yields. The alkylation of MTS and PTS under the conditions of solid–liquid phase transfer catalysis (PTC) allowed us to synthesize some new mono and bipolar surfactants compounds derived from 1,2,4‐triazole‐5‐thione in good yields.

Aminoalkylation of 10‐Hydroxycamptothecin Using Methylene Chloride under Solid—Liquid Phase Transfer Catalysis: A New Approach for the Preparation of Topotecan.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novelties of solid–liquid phase transfer catalysed synthesis of p-toluenesulfonyl fluoride from p-toluenesulfonyl chloride

Organic sulfonyl fluorides are of interest owing to their insecticidal, germicidal and enzyme inhibitory properties. In the current work synthesis of p-toluenesufonyl fluoride was accomplished by reacting p-toluenesulfonyl chloride with solid potassium fluoride using PEG-400 as a catalyst under solid–liquid phase transfer catalysis (S–L PTC) at 30 °C. p-Toulenesulfonyl fluoride is used as peroxygen bleach activator. It also finds use in the treatment of Alzheimer's disease. The mechanism is based on homogeneous solubilization of solid. PEG forms a complex with metal cation which associates with the nucleophile and it participates in S N 2 type reaction. The reaction is intrinsically kinetically controlled. A complete theoretical analysis is done to determine both the rate constant and equilibrium constant from the same set of data. The activation energy and Gibbs free energy are also calculated.

Synthesis of 2,6-disubstituted morpholines through regioselective oxiranes ring opening by tosylamide under PTC conditions

Symmetric and non-symmetric 2,6-disubstituted morpholines were synthesized through regioselective nucleophilic ring opening of oxiranes with tosylamide under solid–liquid phase transfer catalysis (SL-PTC) conditions followed by cyclization of the tosylamido diols thus obtained and final deprotection of the corresponding N-tosyl morpholines. The morpholines prepared are interesting building blocks in the synthesis of pharmaceuticals and agrochemicals.

AN EFFICIENT SYNTHESIS OF POLYMETHYLENE-BIS-AROYL THIOUREA DERIVATIVES UNDER THE CONDITION OF PHASE-TRANSFER CATALYSIS

Reaction of polymethylene diamine with aroyl chloride and ammonium thiocyanate under the condition of solid–liquid phase-transfer catalysis using polyethylene glycol-400 (PEG-400) as the catalyst yielded polymethylene-bis-aroyl thiourea derivatives 3a–q in good-to-excellent yield. The products have been characterized by analytical and spectral (IR and H1 NMR) data.

Silicon polypodands: a new class of efficient solid–liquid phase-transfer catalysts

Silicon polypodands 1– 7 were found to be powerful complexing agents of alkali metal salts, even in low polarity media (chlorobenzene) and hence very efficient phase-transfer catalysts. Their catalytic activity was measured in typical anion-promoted reactions under solid–liquid phase-transfer catalysis (SL-PTC) conditions. It is mainly determined by the complexing ability of the ligand, increasing with the number of silicon atoms and binding sites. Comparison with traditional phase-transfer catalysts showed that these polypodands are better catalysts not only than open-chain PEG400Me 2 and TRIDENT, but even than more sophisticated macrocyclic polyethers such as DCH18C6.

Novelties of microwave irradiated solid–liquid phase transfer catalysis (MISL-PTC) in synthesis of 2′-benzyloxyacetophenone

2′-Benzyloxyacetophenone is an important pharmaceutical intermediate for the manufacture of drugs used as diuretics, antihypertensive, platelet, antiaggregant, lipoxygenase, analgesics and prostaglandin, and for treatment of metabolic disorders. Microwave irradiation has been widely used for the rapid synthesis of a variety of compounds. In the current work, for the first time, novelties of low power microwave irradiated solid–liquid phase transfer catalysis, named as MISL-PTC, has been brought out in enhancements of the rates of selective O-alkylation of sodium salt of o-hydroxyacetophenone (OHAP) with benzyl chloride by using tetra-n-butylammonium bromide as a catalyst. The advantages of solid–liquid (S–L) PTC are that the reaction is conducted at controllable temperatures, the rates of reaction are increased by orders of magnitude and the reaction is 100% selective at 80 °C, in comparison with the liquid–liquid (L–L) PTC which is slow and produces by-products. The microwave irradiation further enhances the rates of reaction. The system elegantly forms a synergistic combination of S–L PTC and microwave irradiation. The mechanism based on homogeneous solubilization of solid resulting in the formation of an active ion pair with the nucleophile was found to prevail in the system. A new theoretical analysis is presented to determine both the rate constant and equilibrium constant from the same set of data. The reaction is intrinsically kinetically controlled. The Gibbs free energy for solid dissolution with anion exchange reaction could be also evaluated.

PHASE TRANSFER CATALYZED SYNTHESIS OF THIOSEMICARBAZIDE AND bis-THIOSEMICARBAZIDE DERIVATIVES OF 2-ETHOXYBENZOIC ACID

Reaction of aryloxyacetic acid hydrazide or arenedioxydiacetic acid hydrazide with 2-ethoxybenzoy chloride and ammonium thiocyanate under the condition of solid–liquid phase transfer catalysis using polyethylene glycol-400 (PEG-400) as the catalyst yielded the corresponding thiosemicarbazide or bisthiosemicarbazide derivatives of 2-ethoxybenzoic acid in good-to-excellent yield.

Aminoalkylation of 10‐Hydroxycamptothecin Using Methylene Chloride Under Solid–Liquid Phase Transfer Catalysis: A New Approach for the Preparation of Topotecan#

The use of dichloromethane as a reagent, for the preparation of Topotecan {(4S)‐10‐(dimethylamino)methyl‐4‐ethyl‐4,9‐dihydroxy‐1‐H‐pyrano[3′,4′:6,7]indolizino‐[1,2‐b]quinoline‐3,14(4H,12H)dione} from 10‐hydroxy‐camptothecin under solid–liquid phase transfer catalysis, which behaves both as a solvent and a reagent serving as for C‐1 unit source for amino‐alkylation of 10‐hydroxy‐(4S)‐camptothecin. #US Patent no. 6,660,861 December 9, 2003.