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1737 KiB

Open AccessArticle

A Sustainable Approach to the Stereoselective Synthesis of Diazaheptacyclic Cage Systems Based on a Multicomponent Strategy in an Ionic Liquid

by Raju Suresh Kumar, Abdulrahman I. Almansour, Natarajan Arumugam, Mohammad Altaf, José Carlos Menéndez, Raju Ranjith Kumar and Hasnah Osman

Molecules 2016, 21(2), 165; https://doi.org/10.3390/molecules21020165 - 29 Jan 2016

Cited by 4 | Viewed by 4547

Abstract

The microwave-assisted three-component reactions of 3,5-bis(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones, acenaphthenequinone and cyclic α-amino acids in an ionic liquid, 1-butyl-3-methylimidazolium bromide, occurred through a domino sequence affording structurally intriguing diazaheptacyclic cage-like compounds in excellent yields. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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1023 KiB

Open AccessArticle

Unimolecular Solvolyses in Ionic Liquid: Alcohol Dual Solvent Systems

by Elizabeth D. Kochly, Nicole Jean Lemon and Anne Marie Deh-Lee

Molecules 2016, 21(1), 60; https://doi.org/10.3390/molecules21010060 - 06 Jan 2016

Cited by 8 | Viewed by 4335

Abstract

A study was undertaken of the solvolysis of pivaloyl triflate in a variety of ionic liquid:alcohol solvent mixtures. The solvolysis is a k_Δ process (i.e., a process in which ionization occurs with rearrangement), and the resulting rearranged carbocation intermediate reacts [...] Read more.

A study was undertaken of the solvolysis of pivaloyl triflate in a variety of ionic liquid:alcohol solvent mixtures. The solvolysis is a k_Δ process (i.e., a process in which ionization occurs with rearrangement), and the resulting rearranged carbocation intermediate reacts with the alcohol cosolvent via two competing pathways: nucleophilic attack or elimination of a proton. Five different ionic liquids and three different alcohol cosolvents were investigated to give a total of fifteen dual solvent systems. ¹H-NMR analysis was used to determine relative amounts of elimination and substitution products. It was found, not surprisingly, that increasing the bulkiness of alcohol cosolvent led to increased elimination product. The change in the amount of elimination product with increasing ionic liquid concentration, however, varied greatly between ionic liquids. These differences correlate strongly, though not completely, to the Kamlet–Taft solvatochromic parameters of the hydrogen bond donating and accepting ability of the solvent systems. An additional factor playing into these differences is the bulkiness of the ionic liquid anion. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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983 KiB

Open AccessArticle

Reduced Reactivity of Amines against Nucleophilic Substitution via Reversible Reaction with Carbon Dioxide

by Fiaz S. Mohammed and Christopher L. Kitchens

Molecules 2016, 21(1), 24; https://doi.org/10.3390/molecules21010024 - 23 Dec 2015

Cited by 6 | Viewed by 11614

Abstract

The reversible reaction of carbon dioxide (CO₂) with primary amines to form alkyl-ammonium carbamates is demonstrated in this work to reduce amine reactivity against nucleophilic substitution reactions with benzophenone and phenyl isocyanate. The reversible formation of carbamates has been recently exploited [...] Read more.

The reversible reaction of carbon dioxide (CO₂) with primary amines to form alkyl-ammonium carbamates is demonstrated in this work to reduce amine reactivity against nucleophilic substitution reactions with benzophenone and phenyl isocyanate. The reversible formation of carbamates has been recently exploited for a number of unique applications including the formation of reversible ionic liquids and surfactants. For these applications, reduced reactivity of the carbamate is imperative, particularly for applications in reactions and separations. In this work, carbamate formation resulted in a 67% reduction in yield for urea synthesis and 55% reduction for imine synthesis. Furthermore, the amine reactivity can be recovered upon reversal of the carbamate reaction, demonstrating reversibility. The strong nucleophilic properties of amines often require protection/de-protection schemes during bi-functional coupling reactions. This typically requires three separate reaction steps to achieve a single transformation, which is the motivation behind Green Chemistry Principle #8: Reduce Derivatives. Based upon the reduced reactivity, there is potential to employ the reversible carbamate reaction as an alternative method for amine protection in the presence of competing reactions. For the context of this work, CO₂ is envisioned as a green protecting agent to suppress formation of n-phenyl benzophenoneimine and various n-phenyl–n-alky ureas. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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1292 KiB

Open AccessArticle

Development of an Analytical Method Based on Temperature Controlled Solid-Liquid Extraction Using an Ionic Liquid as Solid Solvent

by Zhongwei Pan, Zhengquan Wang, Linna Zhu, Zhiming Zhu, Jinying Cai, Xiaoman Shen, Tingli Fan, Yingnan Zhang and Zhixiu Chen

Molecules 2015, 20(12), 22137-22145; https://doi.org/10.3390/molecules201219842 - 10 Dec 2015

Cited by 1 | Viewed by 4537

Abstract

At the present paper, an analytical method based on temperature controlled solid-liquid extraction (TC-SLE) utilizing a synthesized ionic liquid, (N-butylpyridinium hexafluorophosphate, [BPy]PF₆), as solid solvent and phenanthroline (PT) as an extractant was developed to determine micro levels of Fe [...] Read more.

At the present paper, an analytical method based on temperature controlled solid-liquid extraction (TC-SLE) utilizing a synthesized ionic liquid, (N-butylpyridinium hexafluorophosphate, [BPy]PF₆), as solid solvent and phenanthroline (PT) as an extractant was developed to determine micro levels of Fe²⁺ in tea by PT spectrophotometry. TC-SLE was carried out in two continuous steps: Fe²⁺ can be completely extracted by PT-[BPy]PF₆ or back-extracted at 80 °C and the two phases were separated automatically by cooling to room temperature. Fe²⁺, after back-extraction, needs 2 mol/L HNO₃ as stripping agent and the whole process was determined by PT spectrophotometry at room temperature. The extracted species was neutral Fe(PT)_mCl₂ (m = 1) according to slope analysis in the Fe²⁺-[BPy]PF₆-PT TC-SLE system. The calibration curve was Y = 0.20856X − 0.000775 (correlation coefficient = 0.99991). The linear calibration range was 0.10–4.50 μg/mL and the limit of detection for Fe²⁺ is 7.0 × 10⁻² μg/mL. In this method, the contents of Fe²⁺ in Tieguanyin tea were determined with RSDs (n = 5) 3.05% and recoveries in range of 90.6%–108.6%. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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2451 KiB

Open AccessArticle

Adsorption Kinetics at Silica Gel/Ionic Liquid Solution Interface

by Jolanta Flieger, Małgorzata Tatarczak-Michalewska, Anna Groszek, Eliza Blicharska and Ryszard Kocjan

Molecules 2015, 20(12), 22058-22068; https://doi.org/10.3390/molecules201219833 - 10 Dec 2015

Cited by 3 | Viewed by 5559

Abstract

A series of imidazolium and pyridinium ionic liquids with different anions (Cl⁻, Br⁻, BF₄⁻, PF₆⁻) has been evaluated for their adsorption activity on silica gel. Quantification of the ionic liquids has been performed [...] Read more.

A series of imidazolium and pyridinium ionic liquids with different anions (Cl⁻, Br⁻, BF₄⁻, PF₆⁻) has been evaluated for their adsorption activity on silica gel. Quantification of the ionic liquids has been performed by the use of RP-HPLC with organic-aqueous eluents containing an acidic buffer and a chaotropic salt. Pseudo-second order kinetic models were applied to the experimental data in order to investigate the kinetics of the adsorption process. The experimental data showed good fitting with this model, confirmed by considerably high correlation coefficients. The adsorption kinetic parameters were determined and analyzed. The relative error between the calculated and experimental amount of ionic liquid adsorbed at equilibrium was within 7%. The effect of various factors such as initial ionic liquid concentration, temperature, kind of solvent, kind of ionic liquid anion and cation on adsorption efficiency were all examined in a lab-scale study. Consequently, silica gel showed better adsorptive characteristics for imidazolium-based ionic liquids with chaotropic anions from aqueous solutions in comparison to pyridinium ionic liquids. The adsorption was found to decrease with the addition of organic solvents (methanol, acetonitrile) but it was not sensitive to the change of temperature in the range of 5–40 °C. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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3586 KiB

Open AccessArticle

Alkylation of Methyl Linoleate with Propene in Ionic Liquids in the Presence of Metal Salts

by Christian Silvio Pomelli, Tiziana Ghilardi, Cinzia Chiappe, Alberto Renato De Angelis and Vincenzo Calemma

Molecules 2015, 20(12), 21840-21853; https://doi.org/10.3390/molecules201219805 - 07 Dec 2015

Cited by 7 | Viewed by 7738

Abstract

Vegetable oils and fatty acid esters are suitable precursor molecules for the production of a variety of bio-based products and materials, such as paints and coatings, plastics, soaps, lubricants, cosmetics, pharmaceuticals, printing inks, surfactants, and biofuels. Here, we report the possibility of using [...] Read more.

Vegetable oils and fatty acid esters are suitable precursor molecules for the production of a variety of bio-based products and materials, such as paints and coatings, plastics, soaps, lubricants, cosmetics, pharmaceuticals, printing inks, surfactants, and biofuels. Here, we report the possibility of using Lewis acidic ionic liquids (ILs) to obtain polyunsaturated ester dimerization-oligomerization and/or, in the presence of another terminal alkene (propene), co-polymerization. In particular, we have tested the Lewis acidic mixtures arising from the addition of a proper amount of GaCl₃ (Χ > 0.5) to two chloride-based (1-butyl-3-methylimidazolium chloride, [bmim]Cl, and 1-butylisoquinolium chloride, [BuIsoq]Cl) or by dissolution of a smaller amount of Al(Tf₂N)₃ (Χ = 0.1) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][Tf₂N]. On the basis of product distribution studies, [bmim][Tf₂N]/Al(Tf₂N)₃ appears the most suitable medium in which methyl linoleate alkylation with propene can compete with methyl linoleate or propene oligomerization. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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873 KiB

Open AccessArticle

A Simple, Effective, Green Method for the Regioselective 3-Acylation of Unprotected Indoles

by Phuong Hoang Tran, Hai Ngoc Tran, Poul Erik Hansen, Mai Hoang Ngoc Do and Thach Ngoc Le

Molecules 2015, 20(10), 19605-19619; https://doi.org/10.3390/molecules201019605 - 27 Oct 2015

Cited by 14 | Viewed by 7091

Abstract

A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)₃ in [...] Read more.

A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)₃ in catalytic amounts is found to be the best catalyst together with the commercially available ionic liquid [BMI]BF₄ (1-butyl-3-methylimidazolium tetrafluoro-borate) as solvent. The reaction is completed in a very short time using monomode microwave irradiation. The catalyst can be reused up to four times without significant loss of activity. A range of substituted indoles are investigated as substrates, and thirteen new compounds have been synthesized. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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1745 KiB

Open AccessArticle

Preparation of Thermo-Responsive Poly(ionic liquid)s-Based Nanogels via One-Step Cross-Linking Copolymerization

by Jing Zhang, Jingjiang Liu, Yong Zuo, Rongmin Wang and Yubing Xiong

Molecules 2015, 20(9), 17378-17392; https://doi.org/10.3390/molecules200917378 - 18 Sep 2015

Cited by 16 | Viewed by 7377

Abstract

In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3′-bis-1-vinyl imidazolium bromides ([C_nVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue [...] Read more.

In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3′-bis-1-vinyl imidazolium bromides ([C_nVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue opalescent biimidazolium (BIm)-based nanogel solutions could be obtained without any precipitation when the copolymerizations were conducted in methanol. Most importantly, these novel nanogels were thermo-response, and could reversibly transform to precipitation in methanol with temperature changes. Turbidity analysis and dynamic light scatting (DLS) measurement illustrated that PIL-based nanogel solutions presented the phase transform with upper critical solution temperature (UCST) in the range of 5–25 °C. The nanogels were characterized using Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). In addition, BIm-based nanogels could also be used as highly active catalysts in the cycloaddition reaction of CO₂ and epoxides. As a result, our attributes build a robust platform suitable for the preparation of polymeric nanomaterials, as well as CO₂ conversion. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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713 KiB

Open AccessArticle

Eco-Friendly Synthesis of a New Class of Pyridinium-Based Ionic Liquids with Attractive Antimicrobial Activity

by Mouslim Messali

Molecules 2015, 20(8), 14936-14949; https://doi.org/10.3390/molecules200814936 - 14 Aug 2015

Cited by 39 | Viewed by 5725

Abstract

The present study reports a green synthesis of a new family of ionic liquids (ILs) based on functionalized 4-dimethylaminopyridinium derivatives. The structures of 23 newly synthesized ILs (2–24) were confirmed by FT-IR, ¹H-, ¹³C-, ¹¹B-, ¹⁹ [...] Read more.

The present study reports a green synthesis of a new family of ionic liquids (ILs) based on functionalized 4-dimethylaminopyridinium derivatives. The structures of 23 newly synthesized ILs (2–24) were confirmed by FT-IR, ¹H-, ¹³C-, ¹¹B-, ¹⁹F-, and ³¹P-NMR spectroscopy and mass spectrometry. The antimicrobial activity of all novel ILs was tested against a panel of bacteria and fungi. The results prove that all tested ILs are effective antibacterial and antifungal agents, especially 4-(dimethylamino)-1-(4-phenoxybutyl) pyridinium derivatives 5 and 19. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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Review

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1632 KiB

Open AccessReview

Application of Ionic Liquids in Pot-in-Pot Reactions

by Simge Çınar, Michael D. Schulz, Stephanie Oyola-Reynoso, David K. Bwambok, Symon M. Gathiaka and Martin Thuo

Molecules 2016, 21(3), 272; https://doi.org/10.3390/molecules21030272 - 26 Feb 2016

Cited by 4 | Viewed by 7427

Abstract

Pot-in-pot reactions are designed such that two reaction media (solvents, catalysts and reagents) are isolated from each other by a polymeric membrane similar to matryoshka dolls (Russian nesting dolls). The first reaction is allowed to progress to completion before triggering the second reaction [...] Read more.

Pot-in-pot reactions are designed such that two reaction media (solvents, catalysts and reagents) are isolated from each other by a polymeric membrane similar to matryoshka dolls (Russian nesting dolls). The first reaction is allowed to progress to completion before triggering the second reaction in which all necessary solvents, reactants, or catalysts are placed except for the starting reagent for the target reaction. With the appropriate trigger, in most cases unidirectional flux, the product of the first reaction is introduced to the second medium allowing a second transformation in the same glass reaction pot—albeit separated by a polymeric membrane. The basis of these reaction systems is the controlled selective flux of one reagent over the other components of the first reaction while maintaining steady-state catalyst concentration in the first “pot”. The use of ionic liquids as tools to control chemical potential across the polymeric membranes making the first pot is discussed based on standard diffusion models—Fickian and Payne’s models. Besides chemical potential, use of ionic liquids as delivery agent for a small amount of a solvent that slightly swells the polymeric membrane, hence increasing flux, is highlighted. This review highlights the critical role ionic liquids play in site-isolation of multiple catalyzed reactions in a standard pot-in-pot reaction. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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2560 KiB

Open AccessReview

Room Temperature Ionic Liquids as Green Solvent Alternatives in the Metathesis of Oleochemical Feedstocks

by Priya A. Thomas and Bassy B. Marvey

Molecules 2016, 21(2), 184; https://doi.org/10.3390/molecules21020184 - 06 Feb 2016

Cited by 57 | Viewed by 7875

Abstract

One of the most important areas of green chemistry is the application of environmentally friendly solvents in catalysis and synthesis. Conventional organic solvents pose a threat to the environment due to the volatility, highly flammability, toxicity and carcinogenic properties they exhibit. The recently [...] Read more.

One of the most important areas of green chemistry is the application of environmentally friendly solvents in catalysis and synthesis. Conventional organic solvents pose a threat to the environment due to the volatility, highly flammability, toxicity and carcinogenic properties they exhibit. The recently emerged room temperature ionic liquids (RTILs) are promising green solvent alternatives to the volatile organic solvents due to their ease of reuse, non-volatility, thermal stability and ability to dissolve a variety of organic and organometallic compounds. This review explores the use of RTILs as green solvent media in olefin metathesis for applications in the oleochemical industry. Full article

(This article belongs to the Special Issue Ionic Liquids in Organic Synthesis)

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