Crown ether complex cation ionic liquids: preparation and applications in organic reactions
Yingying Song1, Huanwang Jing, Bo Li
1State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|June 17, 2011
Summary
New crown ether complex cation ionic liquids (CECILs) efficiently catalyze organic reactions like Michael additions and Henry reactions. These novel catalysts demonstrate excellent activity and recyclability, offering a greener approach to synthesis.
Area of Science:
- Green Chemistry
- Organic Synthesis
- Catalysis
Background:
- Ionic liquids offer unique solvent and catalytic properties.
- Crown ether complex cations (CECILs) represent a novel class of ionic liquids.
- Developing efficient and recyclable catalysts is crucial for sustainable chemistry.
Purpose of the Study:
- To design and synthesize novel crown ether complex cation ionic liquids (CECILs).
- To investigate the catalytic applications of CECILs in various organic transformations.
- To evaluate the recyclability and reusability of the developed CECIL catalysts.
Main Methods:
- Synthesis and characterization of CECILs using NMR, HRMS, TG-DTA, and elemental analysis.
- Evaluation of catalytic activity in Michael addition, Henry reaction, Knoevenagel condensation, Heck reaction, and alcohol oxidation.
- Assessment of catalyst recyclability through multiple reaction cycles.
Main Results:
- CECILs, including [15-C-5Na][OH] and [18-C-6K][OAc], efficiently catalyzed Michael additions.
- [18-C-6K][OH] and [15-C-5Na][OH] effectively promoted the Henry reaction.
- [18-C-6K][OH] showed excellent catalytic efficiency in Knoevenagel condensation and Heck reactions.
- [18-C-6K][BrO3] served as an effective oxidant and solvent for alcohol oxidation.
- CECIL catalysts ([15-C-5Na][OH] and [18-C-6K][OH]) were recycled multiple times without significant loss of activity.
Conclusions:
- Novel CECILs are effective catalysts for a range of organic reactions.
- The developed CECILs offer high catalytic activity and selectivity.
- The recyclability and simple recovery of CECIL catalysts highlight their potential for sustainable synthesis.
Related Concept Videos
02:36Crown Ethers
Crown ethers are cyclic polyethers that contain multiple oxygen atoms, usually arranged in a regular pattern. The first crown ether was synthesized by Charles Pederson while working at DuPont in 1967. For this work, Pedersen was co-awarded the 1987 Nobel Prize in Chemistry. Crown ethers are named using the formula x-crown-y, where x is the total number of atoms in the ring and y is the number of ether oxygen atoms. The term 'crown' refers to the crown-like shape that these ether molecules take.
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
02:28Structure and Nomenclature of Ethers
Structure and Bonding
Ethers are organic compounds with an ether functional group which is characterized by an oxygen atom connected to two — identical or different — alkyl, aryl, or vinyl groups. The C–O–C linkage in dimethyl ether — the simplest ether — has an approximately tetrahedral bond angle of 110.3 degrees. The oxygen atom is sp3- hybridized, with the C–O distance being about 140 pm.
Classification of Ethers
Based on their attached substituent groups, ethers can be classified into two...
Ethers are organic compounds with an ether functional group which is characterized by an oxygen atom connected to two — identical or different — alkyl, aryl, or vinyl groups. The C–O–C linkage in dimethyl ether — the simplest ether — has an approximately tetrahedral bond angle of 110.3 degrees. The oxygen atom is sp3- hybridized, with the C–O distance being about 140 pm.
Classification of Ethers
Based on their attached substituent groups, ethers can be classified into two...
02:29Ethers from Alcohols: Alcohol Dehydration and Williamson Ether Synthesis
Overview
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
01:23Reactivity of Enolate Ions
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, leading to a resonance-stabilized enolate ion where one of the contributing structures is an oxyanion, which imparts additional stability. Therefore, the proton on the α carbon is more acidic in nature than that of other sp3-hybridized C–H bonds but less acidic than those in O–H bonds where the negative charge in the conjugate base is localized on the oxygen...