Hydroxyl ionic liquid (HIL)-immobilized quinuclidine for Baylis–Hillman catalysis: synergistic effect of ionic liquids as organocatalyst supports

Elucidating structure–property relationships in imidazolium-based halide ionic liquids: crystal structures and thermal behavior

A set of imidazolium-based ionic liquids (ILs), 1-(2-hydroxyethyl)-3-methylimidazolium chloride (1), 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2), and 1-butyl-2,3,4,5-tetramethylimidazolium bromide (3), has been synthesized and their structural and thermal behavior studied. Organic halides are well-known IL formers with imidazolium halides being the most prominent ones. Functionalization of the imidazolium cation by enhancing its hydrogen bonding capacity, i.e. through introduction of –OH groups or by diminishing it, i.e. through substitution of the ring hydrogen atoms by methyl groups is expected to change the inter-ionic interactions. Consequently, the solid-state structures of 1–3 have been characterized with means of single X-ray diffraction to shed light on preferential inter-ionic interactions for obtaining valuable information on anti-crystal engineering, i.e. designing ion combinations that favor a low melting point and exhibit a low tendency for crystallization. The study reveals that endowing IL forming ions with an enhanced hydrogen bonding capacity leads to a depression in melting points and kinetically hinders crystallization. This study provides hints towards new design concepts for IL design, similar to the common strategy of employing conformationally flexible ions.

Vinyl-1,2,4-oxadiazoles Behave as Nucleophilic Partners in Morita-Baylis-Hillman Reactions

We describe that vinyl-oxadiazoles function as a new and efficient nucleophilic partner for the Morita-Baylis-Hillman (MBH) reaction. The reaction between 5-vinyl-3-aryl-1,2,4-oxadiazoles and aromatic and aliphatic aldehydes, catalyzed by DABCO in the absence of solvent, showed high efficiency to afford a new class of heterocyclic MBH adducts with potential biological activity on yields up to 99% and short reaction times. These synthetically attractive adducts bear a heterocyclic scaffold of large pharmaceutical and commercial interest associated with a plethora of biological effects and technological applications. We also demonstrate their synthetic usefulness by a photoinduced addition reaction to a polyfunctionalized amino alcohol.

Synthesis, Structural Analysis, and Biological Activities of Some Imidazolium Salts

Four newly synthesized imidazolium salts were characterized by nuclear magnetic resonance, vibrational spectra, and mass spectra. Then, the density functional theory calculations were performed to obtain the molecular configurations on which the theoretical nuclear magnetic resonance and infrared spectra were consequently obtained. The comparison of calculated spectra with the experimental spectra for each molecule leads to the conclusion that the theoretical results can be assumed to be a good approach to their molecular configurations. The in vitro biological activities of the salts on the selected bacteria and cancer cell lines were determined by using the broth dilution method according to Clinical and Laboratory Standards Institute guidelines. The 1,3-bis(2-hydroxyethyl) imidazolidinium bromide and 3-(2-ethoxy-2-oxoethly)-1-(3-aminopropyl)-1H-imidazol-3-ium bromide showed efficiency on Bacillus cereus ATCC 11778. The 3-bis(2-carboxyethyl)-4-methyl-1-H-imidazol-3-ium bromide was effective on HeLa while a similar effect was observed on Hep G2 with 3-(2-carboxyethyl)-1-(3-aminopropyl)-1H-imidazol-3-ium bromide.

Morita–Baylis–Hillman reaction in eutectic solvent under aqueous medium

Aqueous solvent-catalyst system formed by DES (1ChCl/2Gly) and DABCO is more useful and practical to the Morita–Baylis–Hillman reaction.

Preparation of Poly(ionic liquid)s-Supported Recyclable Organocatalysts for the Asymmetric Nitroaldol (Henry) Reaction

A novel strategy for the embedding of quinine-based organocatalysts in polymerized ionic liquids-based hydrogels is presented. With this technique, the encapsulated organocatalyst was successfully recovered and reused for four cycles without any loss of enantioselectivity (up to 91% ee) for the asymmetric nitroaldol (Henry) reaction. In this study, high catalyst leaching was significantly reduced (<0.01%) by controlling the water content. After catalyst removal, evaporation of the solvent affords the product in 98% purity without any further purification.

Kinetic and mechanistic investigations of the Baylis–Hillman reaction in ionic liquids

We report here a quantitative study of the kinetics and mechanism of the Baylis–Hillman reaction in the presence of ionic liquids as solvent media.

[HyEtPy]Cl–H2O: an efficient and versatile solvent system for the DABCO-catalyzed Morita–Baylis–Hillman reaction

A very efficient and versatile solvent system, [HyEtPy]Cl–H₂O, has been developed and used in the DABCO-catalyzed Morita–Baylis–Hillman reaction.

Insights into the Morita–Baylis–Hillman reaction of isomeric dibenzofuran carbaldehydes: a theoretical and mass spectral study

Systematic theoretical and mass spectral investigations on the faster Morita–Baylis–Hillman (MBH) reaction of dibenzofuran-4-carbaldehyde (2) compared to its isomer, dibenzofuran-2-carbaldehyde (1) are described.

Recent advances in carbon dioxide capture, fixation, and activation by using N-heterocyclic carbenes

In the last two decades, CO2 emission has caused a lot of environmental problems. To mitigate the concentration of CO2 in the atmosphere, various strategies have been implemented, one of which is the use of N-heterocyclic carbenes (NHCs) and related complexes to accomplish the capture, fixation, and activation of CO2 effectively. In this review, we summarize CO2 capture, fixation, and activation by utilizing NHCs and related complexes; homogeneous reactions and their reaction mechanisms are discussed. Free NHCs and NHC salts can capture CO2 in both direct and indirect ways to form imidazolium carboxylates, and they can also catalyze the reaction of aromatic aldehydes with CO2 to form carboxylic acids and derivatives. Moreover, associated with transition metals (TMs), NHCs can form NHC-TM complexes to transform CO2 into industrial acid or esters. Non-metal-NHC complexes can also catalyze the reactions of silicon and boron complexes with CO2 . In addition, catalytic cycloaddition of epoxides with CO2 is another effective function of NHC complexes, and NHC ionic liquids perform excellently in this aspect.

Reactions of nitroxides XIII: Synthesis of the Morita-Baylis-Hillman adducts bearing a nitroxyl moiety using 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a starting compound, and DABCO and quinuclidine as catalysts

The Morita-Baylis-Hillman adducts bearing a nitroxyl moiety were synthesized from 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl and aliphatic, aryl and heterocyclic aldehydes.

An Efficient and Recyclable DMAP-Based Ionic Liquid/Water System for Morita–Baylis–Hillman Reactions

The efficient and recyclable system, DMAP-based ionic liquid/water, has been developed and used in the Morita– Baylis–Hillman reaction of aromatic aldehydes with acrylates. The coupling reactions under the described basic reaction conditions proceed quickly with good to excellent yields. The ionic liquid could be reused at least five times without significant loss of activity.

Ether- and alcohol-functionalized task-specific ionic liquids: attractive properties and applications

In recent years, the designer nature of ionic liquids (ILs) has driven their exploration and exploitation in countless fields among the physical and chemical sciences. A fair measure of the tremendous attention placed on these fluids has been attributed to their inherent designer nature. And yet, there are relatively few examples of reviews that emphasize this vital aspect in an exhaustive or meaningful way. In this critical review, we systematically survey the physicochemical properties of the collective library of ether- and alcohol-functionalized ILs, highlighting the impact of ionic structure on features such as viscosity, phase behavior/transitions, density, thermostability, electrochemical properties, and polarity (e.g. hydrophilicity, hydrogen bonding capability). In the latter portions of this review, we emphasize the attractive applications of these functionalized ILs across a range of disciplines, including their use as electrolytes or functional fluids for electrochemistry, extractions, biphasic systems, gas separations, carbon capture, carbohydrate dissolution (particularly, the (ligno)celluloses), polymer chemistry, antimicrobial and antielectrostatic agents, organic synthesis, biomolecular stabilization and activation, and nanoscience. Finally, this review discusses anion-functionalized ILs, including sulfur- and oxygen-functionalized analogs, as well as choline-based deep eutectic solvents (DESs), an emerging class of fluids which can be sensibly categorized as semi-molecular cousins to the IL. Finally, the toxicity and biodegradability of ether- and alcohol-functionalized ILs are discussed and cautiously evaluated in light of recent reports. By carefully summarizing literature examples on the properties and applications of oxy-functional designer ILs up till now, it is our intent that this review offers a barometer for gauging future advances in the field as well as a trigger to spur further contemplation of these seemingly inexhaustible and--relative to their potential--virtually untouched fluids. It is abundantly clear that these remarkable fluidic materials are here to stay, just as certain design rules are slowly beginning to emerge. However, in fairness, serendipity also still plays an undeniable role, highlighting the need for both expanded in silico studies and a beacon to attract bright, young researchers to the field (406 references).

Ionic Liquids Derivative of 1H-Imidazole as Novel Reagents, Catalysts and Solvents

Ionic liquids are becoming widely used in chemical processes. Taking this into account we focus on recent advances in the synthesis and the investigation of 1H-imidazole derived ionic liquids. The fi rst part of this paper focuses on describing the developments in the synthesis and physical properties of 1,3-disubstituted imidazolium salts. The second part describes the application of these unique reagents, as catalysts and solvents in organic chemistry.

New Catalytic System for Preparation of Methyl 2-(3-Hydroxy-2-Oxo-2,3-Dihydro-1H-3- Indolyl)Acrylates

A novel catalyst derived from the nitrile functionalized ionic liquids and DMAP promoted the MoritaBaylis-Hillman reaction of N-substituted isatines and the methyl acrylate with moderate up to high yields.

An efficient ultrasonic-assisted synthesis of imidazolium and pyridinium salts based on the Zincke reaction

A mild and efficient method has been developed using ultrasound irradiation for the synthesis of imidazolium and pyridinium salts based on the Zincke reaction. Tertiary nitrogen nucleophiles such as pyridines and imidazoles can be alkylated with primary amine by simply using their ammonium form Zincke salts. In almost all cases, a clear yield increase results and a dramatic reduction of the reaction time accompanied by an improved quality of the products occurs.

"Nonsolvent" applications of ionic liquids in biotransformations and organocatalysis

The application of room-temperature ionic liquids (RTILs) as (co)solvents and/or reagents is well documented. However, RTILS also have "nonsolvent" applications in biotransformations and organocatalysis. Examples are the anchoring of substrates to RTILs; ionic-liquid-coated enzymes (ILCE) and enzyme-IL colyophilization; the construction of biocatalytic ternary reaction systems; the combination of enzymes, RTILs, membranes, and (bio)electrochemistry; and ionic-liquid-supported organocatalysts. These strategies provide more robust, more efficient, and more enantioselective bio- and organocatalysts with many practical applications. As shown herein, RTILs offer a wide range of promising alternatives to conventional chemistry.

An atom-efficient and practical synthesis of new pyridinium ionic liquids and application in Morita-Baylis-Hillman reaction

New ionic liquids containing (3-chloro-2-hydroxypropyl)-functionalized pyridinium cations have been synthesized by the ultrasound-assisted, atom-efficient, room temperature reaction of pyridine with acid and 3-chloro-propylene oxide, the acid providing the anionic component of the resultant ionic liquids, and under the ultrasound, a clear yield increase results and a dramatic reduction of the reaction time accompanied by an improved quality of the products occurs. Furthermore, the application of new ionic liquids were tested as solvents in Morita-Baylis-Hillman reaction, in some cases, good results were obtained.

Nonenzymatic Acylative Kinetic Resolution of Baylis−Hillman Adducts

The first efficient nonenzymatic acylative kinetic resolution of Baylis-Hillman adducts is reported. Chiral pyridine catalyst 1a and an optimized analogue 1e are capable of promoting the synthetically useful enantioselective acylation (the efficiency of which is outstanding for sp(2)-sp(2) carbinol substrates, s = 3.5-13.1, ee up to 97%) of Baylis-Hillman adducts derived from recalcitrant precursors which are currently difficult to synthesize utilizing benchmark asymmetric Baylis-Hillman reaction catalyst technology. A novel one-pot synthesis-kinetic resolution process involving a DBU-catalyzed Baylis-Hillman reaction and subsequent 1e/DBU-mediated enantioselective acylation has also been developed.

Bifunctional Polymeric Organocatalysts and Their Application in the Cooperative Catalysis of Morita–Baylis–Hillman Reactions

A series of soluble, non-cross-linked polystyrene-supported triphenylphosphane and 4-dimethylaminopyridine reagents were prepared. Some of these polymeric reagents contained either alkyl alcohol or phenol groups on the polymer backbone. The use of these materials as organocatalysts in a range of Morita-Baylis-Hillman reactions indicated that hydroxyl groups could participate in the reactions and accelerate product formation. In the cases examined, phenol groups were more effective than alkyl alcohol groups for catalyzing the reactions. This article is one of the first reports of the synthesis and use of non-natural, bifunctional polymeric reagents for use in organic synthesis in which both functional groups can cooperatively participate in the catalysis of reactions.