Synthesis and Modifications of Dendrimers on Polymer System Supported on Montmorillonite and Their Use in Organic Synthesis

ABSTRACT

Molecules with dendrimeric structure (cascade molecules) were attached to a polymer-montmorillonite system. The supported dendrimeric molecules were modified to produce ammonium and phosphonium salts. The catalytic phase-transfer activities of these systems have been investigated. The results from the catalytic activity studies showed that the dendrimeric system is highly activating the selected organic reactions. This was attributed to the dendrimeric structure of the system which consequently increase the weight efficiency. It is worth mentioning that this is the first report in the literature describing the formation of dendrimers on polymer-montmorillonite system and their use as phase-transfer catalysts.

     

Phase-Transfer Reactions Catalyzed by Polymer-Supported Imidazoles

Abstract

Polymer-supported imidazoles were prepared by copolymerization of vinyl monomers containing imidazole moiety, styrene, and divinylbenzene with AIBN. The resulting polymers accelerated the reaction of octyl bromide with potassium thiocyanate, and the alkylation of an active methylene compound, benzyl cyanide, under phase-transfer conditions. The latter catalytic reaction afforded monoalkylated compound exclusively, although dialkylated compound was also obtained in monomeric alkylimidazole catalyzed reaction. Further, these polymers served as phase-transfer catalysts for the reduction of acetophenone by sodium borohydride. The relationship between the structure and catalytic activity, and the factors governing these catalytic reactions were examined.     

Chitosan-SO3H (CTSA) an efficient and biodegradable polymeric catalyst for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) and α-amidoalkyl-β-naphthol’s

Abstract

An efficient, green procedure for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) and α-amidoalkyl-β-naphthol’s using biodegradable polymeric catalyst chitosan-SO₃H (CTSA), is operationally easy to prepare by mixing chitosan and chlorosulfonic acid. This catalyst displays excellent catalytic activity and reusable for five subsequent reactions without significant loss of catalytic activity. This protocol proceeds with short reaction times, at mild temperatures, in a solvent-free reaction, and generally with high yields. We present herein a practical, efficient and simple procedure with a broad substrate scope that allows access to two different reactions 1H-pyrazole-5-ol and α-amidoalkyl-β-naphthol’s core unit.     

O-Alkylation of a lignite humic acid by phase-transfer catalysis

A mild phase-transfer catalytic reaction has been conducted to O-alkylate the acidic functions of a lignite humic acid (HA), using tetrabutylammonium hydroxide as the phase-transfer catalyst. The HA acidic functional groups were made to react, in tetrahydrofuran, by nucleophilic substitution with several alkyl halides—methyl iodide, and ethyl, propyl, and butyl, and benzyl bromide. The occurrence of the O-alkylation reaction was assessed by elemental analysis and ¹H NMR, CPMAS ¹³C NMR, and FTIR spectroscopy. Bonding of alkyl groups increased the carbon and hydrogen content and the H/C ratios of all the humic reaction products. Increased nitrogen in the reaction products suggested incomplete removal of the phase-transfer catalyst after purification of the alkylated HA. ¹H NMR and CPMAS ¹³C NMR spectra of alkylated products provided evidence of the successful occurrence of the alkylation reactions. Infrared spectra confirmed the NMR results, revealing the characteristic absorption of newly formed alkyl and aryl ethers and esters in the alkylated products and C–H stretching in the aromatic ring of the benzylated derivative. These findings indicate that humic matter can be successfully alkylated with several different alkylating groups by catalysed phase-transfer reaction. This O-alkylation reaction has the advantage of being mild, versatile, and high-yielding compared with traditional methylation reactions applied to HA. The possibility of introducing different alkyl groups into the HA by a mild phase-transfer reaction may become useful by enabling improved fractionation of humic supramolecular associations and further understanding of the molecular nature of humic substances.     

A Facile Synthesis of Substituted N-Benzoylthiourea

Abstract

One pot reaction of benzoyl isothiocyanate and Tris(hydroxy- methyl)aminomethane (Tris) at room temperature with polyethylene glycol-400 (PEG-400) as solid–liquid phase-transfer catalyst produced substituted N-benzoylthioureas with high yield. A reasonable pathway for their formation has been suggested.     

Amphiphilic Graft Copolymers as Phase-Transfer Catalysts in a Solid-Liquid System

Abstract

Amphiphilic graft copolymers consisting of a hydrophobic backbone and poly(oxyethylene) (PEO) side chains were employed as solidliquid phase-transfer catalysts (PTC) in the substitution of octylbromide by solid potassium phenoxide in toluene. A wide variety of structures were synthesized via ester substitution of poly(phthalimidoacrylate) (PPIA) or poly(phthalimidoacrylate-co-styrene) [poly(PIA-co-St)] with amino-functionalized methoxy-PEO (MPEO-NH₂). The phase-transfer catalytic activity (PTA) of these soluble graft copolymers was studied as a function of the structure of the backbone, the length of the side chains, and the graft density. The graft copolymers of a high degree of grafting showed PTA higher than that of parent PEOs. GPC was used to study the behavior of the graft copolymers in toluene at 90°C. It is believed that the phase-transfer reaction is accelerated in the PEO microphase.     

Preparation of Calix[4]arene Alkylamine Derivatives by Mannich Reaction and use as Phase-Transfer Catalysts for Esterification Reaction

In this study, 5,11,17,23-tetrakis[(N-ethylpiperazine)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (3) and 5,11,17,23-tetrakis[(4-carboethoxy-N-piperidino) methyl]-25,26,27,28-tetrahydroxycalix[4]arene (4) were synthesized in one step according to the Mannich reaction by the treatment of calix[4]arene with a secondary amine (N-ethylpiperazine, ethyl-4-piperidincarboxylate) and formaldehyde. The calix[4]arene derivatives (3, 4) were characterized by a combination of FTIR, ¹H NMR and elemental analyses. The synthesized compounds were used in an esterification reaction as the phase transfer catalyst. The catalytic efficiency of the calix[4]arenes 3 and 4 was evaluated by carrying out the ester-forming reaction of alkali metal carboxylates (sodium butyrate or sodium caprylate) with p-nitrobenzyl bromide. It was observed that the ester-forming reaction of alkali metal carboxylates with p-nitrobenzyl bromide, using calix[4]arene-based catalyst 3 as a phase-transfer catalyst in dichloromethan, provided the best yields.     

Synthesis and mesomorphic behaviour of some aromatic polyesters

Abstract

Six new aromatic polyesters were synthesized by the phase-transfer catalytic polycondensation. The polymers obtained were characterized by infra-red, X-ray diffraction, D.S.C., depolarized light intensity and polarizing microscope. Poly(p,p'-hydroquinone-1,4-phenylene dioxyacetate) and poly(p,p'-hydroquinone-1,4,7-trioxaheptamethylene dibenzoate) were found to be thermotropic liquid crystals but related polyesters are not. The results are discussed on the basis of the thermodynamic data obtained.     

Efficient Method for Demethylation of Aryl Methyl Ether Using Aliquat-336

A rapid method for selective cleavage of aryl methylethers can be achieved in the presence of a protic acid and a catalytic amount of phase-transfer catalyst (Aliquat-336). Aliquat-336 accelerates the rate of reaction and affords the corresponding phenols in excellent to good yields on a wide variety of substrates.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Tungstophosphoric Acid Supported on Zirconia: A Recyclable Catalyst for the Green Synthesis on Quinoxaline Derivatives under Solvent-Free Conditions

Abstract

A green, simple, and fast procedure has been developed for the preparation of quinoxaline derivatives by a condensation of 1,2-diamines with 1,2-dicarbonyl compounds in the presence of zirconium oxide modified with tungstophosphoric acid (H₃PW₁₂O₄₀) as a heterogeneous catalyst, in a solvent-free medium using conventional heating. Quinoxaline derivatives were formed in short-time periods and excellent yields (65–100%). The reaction work-up is very simple and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions without appreciable loss of the catalytic activity.

Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text.     

Indion 190 resin: efficient,environmentally friendly,and reusable catalyst for synthesis of benzimidazoles,benzoxazoles, and benzothiazoles

Abstract

An efficient and mild protocol has been developed for the preparation of benzimidazoles, benzoxazoles, and benzothiazoles from reactions of aldehydes with o-substituted aminoaromatics in the presence of catalytic amount of Indion 190 resin. Short reaction time, ambient conditions, simple work-up procedure, high yield, easy availability, reusability, and use of an eco-friendly catalyst are some of the striking features of the present protocol.     

Catalysis of N‐Methylaniline‐Blocked Polyisocyanate‐Hydroxyl‐Terminated Polybutadiene Cure Reaction

Catalysis of cure reaction between N‐methylaniline‐blocked polyisocyanate and hydroxyl‐terminated polybutadiene was investigated using a variety of tertiary amine and organotin catalysts. The catalytic activity of amine and organotin compounds was determined from the cure‐time results. It was found that the activity of the catalyst depends upon the steric constrain around the catalytic center. The organotin compounds showed higher catalytic activity than the amine catalysts. FTIR results obtained under isothermal condition revealed that DABCO selectively catalyze the urethane formation reaction, whereas DBTDL catalyze both the allophanate formation and urethane formation reactions during curing process. The synergistic effect of amine and organotin mixed catalysts on the cure reaction was also investigated.     

Synthetic Applications of π-Electron-Deficient Sulfones

Abstract

The use of π-electron-deficient aryl sulfones, especially 3,5-bis(trifluoromethyl) phenyl alkyl sulfones (BTFP-sulfones) as soft nucleophiles, as caboxylic acid protecting group and in Julia–Kocienski olefination reactions is described. In the case of α-(arylsulfonyl)acetates dialkylation, reactions are performed under phase-transfer analysis (PTC) conditions using K ₂ CO ₃ as base. Esters derived from 2-(arylsulfonyl)ethanol can be deprotected using aqueous NaHCO ₃ . Alkyl BTFP sulfones are coupled with carbonyl compounds using KOH or P4-t-Bu as bases to give the corresponding alkenes after Smiles rearrangement.     

Decyl(Tri-Tert-Butyl)Phosphonium Tetrafluoroborate/Palladium Acetate: An Effective Catalyst for Cross-Coupling Reaction of Arylbromides with Phenylacetylene in Copper-Free Conditions

Abstract

The phosphonium salts with sterically hindered cation and noncoordinating anion can be used as phase-transfer reagent in the Sonogashira cross-coupling reaction allowing copper- and amine-free protocol. The reactions proceed under mild conditions with good yields.     

Investigation on the Acylation of Heterocyclic Alcoholate Anions with O,O-Dialkyl Phosphorochloridothioate in Water Solvent

Abstract

The acylation of some heterocyclic alcoholate anions with O,O-dialkyl phosphorochloridothioate has been investigated. Higher yields and fewer byproducts were achieved in water at 50 °C by employing an effective phase-transfer catalyst (PTC) (benzyl triethylammonium chloride [BTEAC]), acylation catalyst (AC) (4-dimethylaminopyridine), and surfactant (sodium dodecyl sulfate), under weakly basic (pH 9.5～10) conditions. This reaction can also be applied to synthesize other insecticides with excellent yields.     

反应控制相转移催化剂的研究进展

反应控制相转移催化兼具均相和非均相催化的优点,有助于解决催化剂催化活性低及分离回收困难等问题,符合环境友好的要求,所以一直以来备受关注。反应控制相转移现象的形成与催化剂的阴、阳离子结构和溶剂等反应条件密切相关。本文就目前应用广泛的反应控制相转移催化剂的阴、阳离子的结构特点进行综述,最后就反应控制相转移催化体系可能存在的问题和创新方向作了展望。     

固载聚乙二醇催化合成异黄樟油素

以聚乙二醇和固载聚乙二醇作为相转移催化剂, 在无溶剂条件下, 黄樟油素经催化异构合成异黄樟油素. 通过正交实验, 得到固载PEG-X (polyethylene glycol-X)催化最优工艺条件为: m(88.5%黄樟油)∶m(KOH)∶m(PEG-X)＝1∶0.2∶0.25, 反应温度90 ℃, 反应时间 5 h, 在此工艺条件下, 异黄樟油素得率为99.9%. 固载PEG-X催化剂循环使用10次后其催化活性未见下降. 结果显示, 固载聚乙二醇催化工艺具有操作简便、反应温度低、时间短、产率高以及对环境友好等优点. 用¹H NMR, GC-MS对异构黄樟油素结构进行了表征, 研究了固载聚乙二醇作为相转移催化剂合成异黄樟油素的反应机理.     

Phase-Transfer Catalyzed Alkylation and Cycloalkylation of 2-Mercaptoquinazolin-4(3H)-One

Solid/liquid phase-transfer catalyzed alkylation of 2-mercaptoquinazolin-4(3H)-one at 25°C by different organohalogen compounds in the presence of tetrabutylammonium bromide as a catalyst underwent, exclusively, S-monoalkylation or S- and N-, di-, or cycloalkylation, depending on the nature of alkylating agents.     

Reaction of Red Phosphorus with Electrophilic Reagents in Superbasic Systems

Abstract

A new method for generating highly nucleophilic ions from red phosphorus in superbasic systems, such as alkali metal hydroxide-dipolar aprotic solvent (HMPA, DMSO) or solvent of moderate polarity (toluene) with or without a phase-transfer catalyst, has been developed and shown to cover non-standard convenient routes to triorganylphosphines, -phosphine oxides and their derivatives. This is illustrated by the following examples:     

Enantioselective benzylation of methyl 4-oxo-3-piperidinecarboxylate with cinchona alkaloids phase-transfer catalysts

The asymmetric benzylation of methyl 4-oxo-3-piperidinecarboxylate has been investigated, and methyl (R)-1,3-dibenzyl-4-oxopiperidine-3-carboxylate (3c) was obtained by using a phase-transfer catalyst O-allyl-N-9-anthracenemethyl-cindexnine bromide (1k). This synthetic method has the advantages of cheap materials, mild reaction conditions and moderate enantioselectivity, and is useful for preparation of biologically active compounds containing a chiral 3-benzylpiperidine backbone.