Solvent-free Knoevenagel Condensations over TiO2

A study involving the scope of substrates in the Knoevenagel reaction under SFC has been conducted. Reactivity trends favored formation of the condensation product using both electron deficient and rich aryl aldehydes. A recycling study confirmed that the reaction medium could be used multiple times affording, with each run, the desired condensation product in excess of 95% conversion.     

Efficient and green synthesis of 4H-pyrans and 4H-pyrano[2,3-c] pyrazoles catalyzed by task-specific ionic liquid [bmim]OH under solvent-free conditions

Abstract

A facile and convenient procedure for the synthesis of 4H-pyrans from aldehydes, malononitrile, and ethyl acetoacetate/acetylacetone and also synthesis of 4H-pyrano[2,3-c]pyrazoles from three-component condensation of aldehydes, malononitrile, and pyrazolone or four-component condensation of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine monohydrate using [bmim]OH as task-specific ionic liquid has been described. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium.

     

Nickel‐Catalyzed α‐Allylation of Aldehydes and Tandem Aldol Condensation/Allylation Reaction with Allylic Alcohols

An additive‐free nickel‐catalyzed α‐allylation of aldehydes with allyl alcohol is reported. The reaction is promoted by 1 mol % of in situ formed nickel complex in methanol, and water is the sole by‐product of the reaction. The experimental conditions allow the conversion of various α‐branched aldehydes and α,β‐unsaturated aldehydes as nucleophiles. The same catalyst and reaction conditions enabled a tandem aldol condensation of aldehyde/α‐allylation reaction.     

Imidazole-Catalyzed Henry Reactions in Aqueous Medium

2-Nitroalkanols can be efficiently synthesized using imidazole as a mild Lewis basic catalyst in aqueous medium as well as in organic solvents. The products have been found in good yields without purification (> 95% purity by ¹H NMR) for aromatic aldehydes. Additionally, the very mild reaction conditions prevent the particular side reactions such as aldol condensation, Cannizzaro reaction, or dehydration of the 2-nitro alcohols into nitro alkenes even if aromatic aldehydes are used. This report satisfies the criteria for green synthesis in terms of reaction medium and recycling of the catalyst (imidazole).     

Highly efficient three-component Strecker-type reaction catalyzed by MgI2 etherate under solvent-free conditions

A concise, straightforward and efficient method has been developed for the synthesis of α-aminonitriles by an one-pot three-component condensation of aldehydes or ketones, amines and trimethylsilyl cyanide catalyzed by MgI₂ etherate under solvent-free conditions. This protocol has some advantages such as mild reaction condition, simple work-up, short reaction time and high product yields.     

Ultrasound-promoted,rapid, green,one-pot synthesis of 2′-aminobenzothiazolomethylnaphthols via a multi-component reaction,catalyzed by heteropolyacid in aqueous media

A one-pot, three-component condensation reaction of 2-aminobenzothiazole, 2-naphthol and appropriate aldehydes catalyzed by heteropolyacid (HPA) in an aqueous medium afforded the Mannich adduct 2′-aminobenzothiazolomethylnaphthols at 45 °C under ultrasound irradiation. This method provides several advantages such as simple work-up procedure, short reaction time and high yields.     

Bronsted acidic ionic liquid [C3SO3HDoim]HSO4 catalyzed one-pot three-component Biginelli-type reaction: An efficient and solvent-free synthesis of pyrimidinone derivatives and its mechanistic study

A series of Bronsted acidic ionic liquids(ILs) were prepared and used for Biginelli-type condensation reaction among aromatic aldehydes, urea or thiourea and cyclopentanone. Through this reaction, the synthesis of various pyrimidinones could be achieved. Of interest, it was found that the reaction was efficiently catalyzed by a novel, eco-friendly functionalized IL [C_3SO_3HDoim]HSO_4, which could be reused for at least 7 times without significantly loss of catalytic activity. The reaction proceeded efficiently at 80℃ to afford the desired products in good yield(up to 96%). In addition, a possible mechanism that accounted for the IL [C_3SO_3HDoim]HSO_4-catalyzed reaction was proposed.     

Poly(4-vinylpyridinium)hydrogen sulfate: An efficient heterogeneous catalyst for the one-pot synthesis of polyhydroquinolines via unsymmetrical Hantzsch reaction in aqueous medium

A facile and highly efficient protocol for the synthesis of polyhydroquinolines via Hantzsch multicomponent condensation of dimedone, aryl/heteryl aldehydes, ethylacetoacetate and ammonium acetate utilizing poly(4-vinylpyridinium)hydrogen sulfate as a catalyst in aqueous medium has been described. The method offers several advantages such as high yield, short reaction time, simple workup, easy separation of the catalyst and its reusability.     

Water as an efficient medium for the synthesis of tetrahydro-β-carbolines via Pictet-Spengler reactions

A mild and efficient protocol for the Pictet-Spengler reaction in water using an acid catalyst has been described. The condensation of tryptophan, tryptamine, and N_b-benzyl tryptophan with different aldehydes having both electron-withdrawing and -donating substituents in the presence of a catalytic amount of TFA in water furnished tetrahydro-β-carbolines in good isolated yields. A salient feature of the water mediated Pictet-Spengler reaction was the general trend observed during the condensation of Trp-OMe and aryl/aliphatic aldehydes furnishing diastereomeric mixtures with a preference for the cis-isomer.     

SYNTHESIS OF NOVEL SULPHONAMIDES AND EVALUATION OF THEIR ANTIBACTERIAL EFFICACY

4-(4′-sulphanilyl)-1-phenyl pipearzine (2) has been prepared by ther reaction of N-acetyl sulphanilyl chloride (ASC) with 1-phenyl piperazine followed by the hydrolysis of the product by ethanolic HCl. The hydrolyze product on facile condensation reaction with aromatic aldehydes yields Schiff bases/anils/azomethines (3a–h). These anils on cyclo condensation reaction with chloro acetyl chloride and thio glycolic acid (mercapto acetic acid) yields 2-azetidinones and 4-thiazolidinones respectively. Biological screening of the prepared compounds have been screened on some strains of bacteria.     

Microwave-assisted Knoevenagel condensation in aqueous over triazine-based microporous network

A high nitrogen-containing triazine-based microporous polymeric (TMP) network was used as an efficient metal-free catalyst for Knoevenagel condensation of ethylcyanoacetate with aromatic aldehydes. The reactions were performed in water as an environmentally benign medium, under microwave irradiation within a short reaction time of 10 min. The conversions of substituted aromatic aldehydes and selectivities for Knoevenagel products were found to be in the ranges of 44–99 and 65–99 %, respectively. The electron-withdrawing substituent showed higher conversion and selectivity as compared to electron-donating substituents. The TMP network can be readily recovered and reused up to three runs without loss in catalytic activity and selectivity.     

Branched Tertiary Amines from Aldehydes and α-Olefins by Combined Multiphase Tandem Reactions

This study presents the transformation of olefins to branched amines by combining a hydroformylation/aldol condensation tandem reaction with the reductive amination in a combined multiphase system that can be recycled 9 times. The products are branched amines that are precursors for surfactants. Since the multiphase hydrofomylation/aldol condensation system has already been studied, the first step was to develop the partial hydrogenation of unsaturated aldehydes together with a subsequent reductive amination. The rhodium/phosphine catalyst is immobilized in a polar polyethylene phase which separates from the product phase after the reaction. Reaction and catalyst recycling are demonstrated by the conversion of the C₁₄-aldehyde 2-pentylnonenal with the dimethylamine surrogate dimethylammonium dimethylcarbamate to the corresponding tertiary amine with yields up to 88 % and an average rhodium leaching of less than 0.1 % per recycling run. Furthermore, the positive influence of a Bronsted acid and carbon monoxide on the selectivity are discussed. Finally, the two PEG based systems have been merged in one recycling approach, by using the product phase of the hydroformylation aldol condensation reaction for the reductive amination reaction. The yields are stable during a nine recycling runs and the leaching low with 0.09 % over the two recycling stages.     

Ethylene diamine post‐synthesis modification on open metal site Cr‐MOF to access efficient bifunctional catalyst for the Hantzsch condensation reaction

Ethylene diamine functionalized MIL‐101(Cr) was established to be an efficient organocatalyst for single‐pot synthesis of polyhydroquinolines via four‐component condensation reaction between aldehydes, dimedone, β‐ketoecters and ammonium acetate in aqueous medium. Ethylene diamine of the parent open metal site MIL‐101(Cr) has been carried out through a post‐synthetic modification (PSM) technique. Efficient transformation, mild condition, easy product isolation and the potential high recycbility of the organocatalyst are the key feature of this protocol.     

Manganese‐Containing Periodic Mesoporous Organosilica with Ionic‐Liquid Framework (Mn@PMO‐IL): A Powerful,Durable, and Reusable Nanocatalyst for the Biginelli Reaction

The catalytic application of a novel manganese‐containing periodic mesoporous organosilica with ionic‐liquid framework (Mn@PMO‐IL) in the Biginelli reaction was investigated. First, the Mn@PMO‐IL nanocatalyst was prepared and characterized by TEM, SEM, X‐ray photoelectron spectroscopy, and nitrogen‐sorption analysis. The catalyst was then used in the one‐pot Biginelli condensation of various aldehydes with urea and alkyl acetoacetates under solvent‐free conditions. The corresponding dihydropyrimidone products were obtained in high to excellent yields and selectivities at short reaction times. Moreover, the catalyst was recovered and successfully reused many times with no notable decrease in activity and selectivity.     

Three-component condensation of α-nitroacetophenone,aromatic aldehydes,and methylurea

The three-component condensation of aromatic aldehydes, methylurea, and α-nitroacetophenone affords both N(1)-and N(3)-methyl-substituted 4,6-diaryl-5-nitro-3,4-dihydropyrimidin-2(1H)-ones depending on the structure of aldehyde. Intermediate 4,6-diaryl-4-hydroxy-3-methyl-5-nitrohexahydropyrimidin-2-ones and trisubstituted urea, which is the transformation product of the 4-hydroxy-3-methyl derivative in an acidic medium (retro-Henry reaction), were identified in the reaction mixtures. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1141–1145, June, 2007.     

离子液体1-乙基-3-丁基磺酸咪唑对甲苯磺酸盐催化合成氧杂蒽

以1-乙基咪唑为原料,合成了布朗斯特酸性离子液体--1-乙基-3-丁基磺酸咪唑对甲苯磺酸盐(IL1),并将其用于催化芳香醛与5,5-二甲基-1,3-环己二酮或1,3-环己二酮在无溶剂条件下合成了系列氧杂蒽类化合物,其结构经¹H NMR, ¹³C NMR和ESI-MS表征。研究结果表明：当IL1用量为5 mol%,于80 ℃反应40 min,收率78%~95%; IL1循环使用3次,收率86%~89%,催化活性无明显变化。     

Diastereoselective Synthesis of Functionalized Tetrahydropyrimidin‐2‐thiones via ZnCl2 Promoted One‐pot Reactions

In the presence of zinc chloride, the in situ generated β‐enamino ester from the reaction of morpholine, piperidine and pyrrolidine with methyl propiolate reacted, with aromatic aldehydes and thiourea in ethanol resulting in the functionalized tetrahydropyrimidin‐2‐thiones in satisfactory yields and with good diastereoselectivity. When aromatic aldehydes bearing electron‐withdrawing group were used in the reaction, the 4‐hydroxytetrahydropyrimidin‐2‐thione derivatives were obtained as the main product.     

A One‐pot Green Synthesis of Alkylidenesuccinimides

A mild and facile Wittig reaction between N‐substituted maleimides and aldehydes has been developed. Various synthetically valuable alkylidenesuccinimides were obtained from this one‐pot reaction in high yields (up to 99%). The product was obtained by simple filtration and no extra purification was necessary. Ethanol, an environment‐benign solvent, was found to be a suitable reaction medium.     

新型功能离子液体水相催化芳醛与5,5-二甲基-1,3-环己二酮的反应

以N,N,N′,N′-四甲基乙二胺、1,3-丙磺酸内酯为原料,经酸化合成了功能化离子液体N,N,N′,N′-四甲基N,N′-二磺丙基二硫酸氢盐(TSIL)。 TSIL离子液体兼具Bronsted 酸性官能团和季铵盐相转移催化剂的结构,能够实现水相中芳醛与5,5-二甲基-1,3-环己二酮反应,得到氢化氧杂蒽衍生物。 结果表明,合成的TSIL具有较高的催化活性,在水相中于100 ℃下回流2～3 h即可完成反应,产率可达80%～93%。 反应生成的取代氢化氧杂蒽与离子液体的水溶液不相溶,通过简单的过滤可实现产物与催化体系的分离,简化了分离过程,方法操作简便、环境友好、催化剂可回收并重复使用。     

Facile Aldol Reaction Between Unmodified Aldehydes and Ketones in Bronsted Acid Ionic Liquids

A series of condensation reactions of unmodified ketones and aromatic aldehydes to prepare α,β-unsaturated carbonyl compounds by means of Aldol reactions in Bronsted acid ionic liquids(BAILs)was explored.1-Butyl-3-methylimidazolium hydrogen sulphate(BMImHSO4)acting as an effective media and catalyst in aldol reactions was compared with other BAILs,with the advantages of high conversion and selectivity.The product was easily isolated and the left ionic liquid can be readily recovered and reused at least 3 times with almost the same efficiency.The scope and limitation of the present method were explored and the possible catalytic mechanism was speculated.