The alkyl glycidyl ether as synthetic building blocks

Alkyl glycidyl ether is one of the most useful key materials for industrial applications because the addition reaction of various kinds of nucleophilic reagents to the reactive epoxy bond of the glycidyl ethers has led to glyceryl ether derivatives. Glyceryl ether exhibits many interesting physical and pharmacological properties. The alkyl glycidyl ether can presently be produced at an industrial scale under the phase-transfer catalytic Williamson ether synthesis. We have reviwwed some addition reactions of the alkyl glycidyl ether and possibilities for use as the building blocks for the syntheses of surfactants, pharmaceuticals, etc. that contain glyceryl ether skeletons. Typical examples of alkyl glyceryl ether derivatives include: amino ether as cosmetic material, and isodiglycerin mono- and dialkyl ethers and triglycerin monoalkyl ether as a cosmetic or a pharmacologically useful material, respectively. Another interesting reaction is the rearrangement of the epoxy bond of the alkyl glycidyl ether, which gives alkoxy ketone in a one-pot synthesis.     

A perspective on the contribution of surfactants and lipids toward “Green Chemistry”: Present states and future potential

“Green Chemistry” has become a subject of increasing interest in recent years. The goal of efforts in this area is to develop environmentally friendly methods and processes to replace traditional reactions that use organic solvents, consume much energy, and generate undesirable by-products and/or waste. Utilization of renewable resources is an important component of Green Chemistry. Fats and oils represent one such resource. They can give rise to many types of surfactants and lipids that can modify properties of boundary phases between different phases. Thus, phase-transfer catalysts (PTC) based on surfactants or lipids have been reported to be useful in reactions such as oxidation and hydration reactions and in glycidyl ether formation. Another approach to satisfying Green Chemistry requirements is the recovery and recycling of reactants and/or substrates used. In the preparation of alkyl glyceryl ethers, the intermediate 1,3-dioxolane compounds prepared by addition of acetone to alkyl glycidyl ethers can be hydrolyzed to regenerate reusable acetone. Other examples of methodologies based on surfactants or lipids are summarized, and their potential contribution to Green Chemistry is discussed.     

Improvement of the phase-transfer catalysis method for synthesis of glycidyl ether

A convenient procedure for the synthesis of aliphatic alkylglycidyl ether has been studied. It has been found that the improved preparation of the alkylglycidyl ether can be achieved by using fatty alcohol such as octanol and octadecanol with epichlorohydrin in the presence of phase-transfer catalyst (PTC) such as 1-alkyloxypropan-2-ol-3-trimethyl ammonium methylsulfate, 1-alkyloxypropan-2-ol-3-methyldiethanolammonium methylsulfate, alkyloxy-2-hydroxypropyldimethylamine and alkyloxy-2-hydroxypropyldiethanolamine, tetrabutylammonium bromide, etc. without water and other organic solvents. This method, carried out in solid phase/organic phase (reactants and product themselves), has the following merits: (i) producing the solid by-products such as sodium chloride and sodium hydroxide which are easily removed by simple filtration, (ii) saving the amount of reactants used such as sodium chloride and phase-transfer catalyst, and (iii) increasing the yields of glycidyl ethers. The yields of octylglycidyl ether and octadecylglycidyl ether are 92.0 and 91.7%, respectively. The amount of sodium hydroxide used can be saved by from 1.5 to 0.7 molar ratio with respect to octanol in comparison with those in the conventional method using PTC.     

Ether lipids based on the glyceryl ether skeleton: Present state,future potential

Lipids from natural sources consist mainly of saponifiable substances, such as glycerides, along with some unsaponifiable lipids, some of which are ether lipids. Typical ether lipids are monoalkyl ethers of glycerin, also called alkyl/alkenyl glyceryl ethers. Alkyl/alkenyl glyceryl ethers have also been reported in marine organisms and in human feces. Several chemical syntheses of such ether lipids have been reported. Typical examples are alkyl glyceryl ether formation by the addition reaction of alkyl glycidyl ether and the telomerization reaction of butadiene with glycerin and a transition metal catalyst. Characteristic chemical structures, such as terpene alkyl glyceryl ethers, archaebacterial macrocyclic ether lipids, and glyceryl ethers of condensed cyclic planar molecules, have been obtained as well. Over the past few decades, industry has shown much interest in the chemistry and application of highly branched fatty acids. For example, isostearyl glyceryl ether (GE-IS) with methyl branching in the middle chain was already known, but it is now prepared at an industrial scale by proprietary alkyl glycidyl ether methods. The characteristic behavior of GE-IS toward water, such as formation of water-in-oil emulsions containing large amounts of water and of liquid crystals, has made it applicable for use in hair and skin-care cosmetics. Based on these studies and considerations, glyceryl ether lipids, which are rarely investigated, may become one of the most important and useful lipids in the industry.     

Applications of protecting groups in the synthesis of surfactants, lipids, and related compounds

Several types of alkyl ether lipids were prepared in high yield and high purity using protecting groups such as 1,3-dioxolane compounds or allyl ethers. We also succeeded in the industrial production of alkyl glyceryl ethers using the reaction of alkyl glycidyl ethers with acetone to give 1,3-dioxolane compounds, from which the desired alkyl glyceryl ethers were obtained in high quantities. 1,3-Dioxolane (ketal) compounds based on acetone were used in the enzymatic preparation of monoglyceride on an industrial scale. On the basis of these protecting groups, we extended our studies concerning both the preparations and properties of novel polyol ether compounds, beginning with alkyl glycidyl ethers. Another typical property of surfactants containing 1,3-dioxolane units and acetal is degradability under acidic conditions. Several types of destructible/cleavable surfactants based on polyols, such as carbohydrates and polyethyleneglycol, were prepared. As for natural products containing polyol skeletons, much attention has been paid to their molecular design, in which protecting groups such as 1,3-dioxolane compounds or allyl ether have contributed to synthetic strategies.     

Newer synthetic approaches to surfactants, lipids, and related compounds based on C-3 building blocks: Recent advances related to fatty chemistry

Many lipids derived from natural sources are based on the glycerin molecule. Synthetically alkyl glycidyl ether can be used as a C-3 building block for lipid molecules as well as alkyl glyceryl ether. Several glycidyl and glyceryl ethers have been studied as C-3 synthetic building blocks for lipids used in surfactants/emulsifiers, cosmetics, or toiletries. From an environmental viewpoint, several surfactants and detergents have been modified by using epichlorohydrin or glycerides as C-3 building blocks to have higher performance or biodegradability. Recently, complex lipid molecules having special bioactivities have attracted attention among chemists. Glycidyl ether would be expected to be one of the synthetic building blocks for such complex lipids.     

Synthesis of cyclic carbonate from allyl glycidyl ether and CO2 over silica-supported ionic liquid catalysts prepared by sol-gel method

A silica-supported ionic liquid (Im-IL) was proven to be an effective heterogeneous catalyst for solventless synthesis of cyclic carbonate from allyl glycidyl ether (AGE) and carbon dioxide. Im-IL catalysts were prepared by sol-gel method. The synthesis of cyclic carbonate from AGE and CO₂ was carried out in a batch autoclave reactor. Im-IL with shorter alkyl chain length showed the highest conversion of AGE, probably due to the steric hindrance for the formation of intermediate from the catalyst prepared by using longer alkyl chains and AGE. High temperature and high pressure were favorable for the conversion of AGE. Im-IL can be reused for the reaction up to two consecutive runs without any considerable loss of its catalytic activity.     

Anwendungsmöglichkeiten der homogenen Übergangsmetallkatalyse in der Fettchemie

Homogeneous Transition Metal Catalysis in Oleochemistry Numerous processes in industrial oleochemistry are carried out using transition metal catalysts. However, in most cases the catalysts applied are heterogeneous. The present review considers the huge number of possible applications of homogeneous transition metal catalysis in oleochemistry. The advantages of homogeneous transition metal catalysis are the high selectivity and the mild reaction conditions. These advantages are often used in petrochemistry, but in industrial oleochemistry exist no similar developments. The results of the laboratory research in the last two decades prove that the special properties of homogeneous transition metal catalysts can be applied in oleochemistry too. Well known chemical reactions could be improved and new reactions could be developed. The present review refers some of the most interesting reaction types, e. g. the selective hydrogenation of manifold unsaturated fatty acids or the possibilities to isomerize the double bonds selectively. Oxidation reactions, reactions with carbon monoxide, metathesis, CC-linkage reactions, telomerizations and additions to the double bonds of unsaturated fatty compounds will also be presented.     

由碳酸二甲酯合成芳香醚的绿色工艺

综述了酚类化合物与碳酸二甲酯(DMC)甲基化反应合成芳香醚的绿色工艺。气相连续流动法和液相间歇法是2种有效的由DMC合成芳香醚的方法。在气液相转移催化和液固相转移催化的条件下,酚与DMC甲基化反应的产率和选择性均很高。酚与DMC甲基化反应的均相催化剂一般选择叔胺、叔膦、季铵盐及Schiff碱等有机碱,多相催化剂为碱金属碳酸盐、沸石、氧化铝及附载有金属盐的氧化铝和煅烧的Mg-Al水滑石。     

The enantioselective synthesis of alpha-amino acids by phase-transfer catalysis with achiral Schiff base esters

The development and application of chiral phase-transfer catalysis (PTC) for the enantioselective synthesis of optically active alpha-amino acid derivatives using achiral Schiff base esters developed in the author's laboratory and by others is reviewed. Phase-transfer catalysts derived from the Cinchona alkaloids have been exploited as inexpensive and attractive organocatalysts in the chiral PTC process. The recent evolution and use of these and other catalytic systems is described.     

Epoxy resins based on resorcinol and its derivatives

Schemes are presented for the synthesis of epoxy oligomers based on resorcinol and its derivatives. The properties of furfurylresorcinol glycidyl ethers (UP-63 resin), oligomeric glycidyl ethers of glycerol dihydroxydiphenyl ether (UP-67 resin), diglycidyl ether of ethylene glycol dihydroxydiphenyl ether (UP-622 resin), and oligomeric glycidyl ether of pentaerythritol and resorcinol (UP-635 resin) are considered. These resins are shown to be substantially advantageous compared to standard bisphenol A-based epoxy oligomers. Materials possessing higher thermal stability and adhesion are developed on their basis.     

Oxidative Cleavage of Long Chain Olefins to Carboxylic Acids with Hydrogen Peroxide

The role of phase-transfer catalysts (PTC) (ammonium and phosphonium salts) with various anions on the biphasic oxidative cleavage of long chain olefins with aqueous hydrogen peroxide catalyzed by Na₂WO₄/H₃PO₄/PTC system has been investigated. It was shown that the nature of PTC widely affects the catalytic activity of the above system in the conversion of alkenes, cycloalkenes and unsaturated fatty acids into carboxylic acids.     

聚乙二醇及其衍生物催化合成苯并呋咱-N-氧化物的研究

研究了在聚乙二醇或其衍生物烷基聚氧乙烯醚、脂肪醇聚氧乙烯醚介质中,用NaOCl氧化邻硝基苯胺合成苯并呋咱-N-氧化物的反应过程,揭示了在合成反应中,聚乙二醇或其衍生物不仅可作为溶剂,还可替代碱金属氢氧化物,起到良好的催化作用。苯并呋咱-N-氧化物合成反应是以聚乙二醇或其衍生物为溶剂和催化剂,在邻硝基苯胺溶液中滴加理论用量1.1～1.5倍的次氯酸钠水溶液进行反应,合成温度为25～55 ℃,产物最高收率为98%。实验还表明,聚乙二醇及其衍生物稳定性好、次氯酸钠用量较小、反应温度适宜、时间短、条件缓和、产物收率和纯度高。     

Oxidative Cleavage of Long Chain Olefins to Carboxylic Acids with Hydrogen Peroxide

The role of phase-transfer catalysts (PTC) (ammonium and phosphonium salts) with various anions on the biphasic oxidative cleavage of long chain olefins with aqueous hydrogen peroxide catalyzed by Na₂WO₄/H₃PO₄/PTC system has been investigated. It was shown that the nature of PTC widely affects the catalytic activity of the above system in the conversion of alkenes, cycloalkenes and unsaturated fatty acids into carboxylic acids.

     

相转移催化法合成十二烷基缩水甘油醚

以十二醇和二氯丙醇为原料,用相转移催化剂直接合成了十二烷基缩水甘油醚。考察了催化剂种类、原料摩尔比、反应时间和反应温度对十二烷基缩水甘油醚收率的影响。结果表明,以四丁基溴化铵为催化剂,甲苯为溶剂,n(十二醇)∶n(二氯丙醇)=1∶1.60,反应温度50℃,反应时间4 h,十二烷基缩水甘油醚收率可达73.2%。用IR、1HNMR对产物结构进行了表征,采用测定产品环氧值的方法来计算十二烷基缩水甘油醚的收率。     

窄分布醇醚下游衍生产品的差异化

论述了窄分布脂肪醇(聚氧乙烯)醚的研究进展,从物化性能、合成及应用、国内外发展概况等方面重点介绍了脂肪醇醚羧酸盐(AEC)、脂肪醇醚磺基琥珀酸酯二钠盐(AESS)和脂肪醇醚磷酸酯(MAEP),展望了窄分布醇醚下游衍生产品的发展前景。     

Catalytic performance of pyridinium salt ionic liquid in the synthesis of cyclic carbonate from carbon dioxide and butyl glycidyl ether

The catalytic performance of pyridinium salt ionic liquids in the reaction of butyl glycidyl ether and carbon dioxide was investigated in this study. The catalytic activity was studied in a batch reactor with different 1-alkylpyridinium salt ionic liquids at 60–140°C. The conversion of butyl glycidyl ether was affected by the structure of the ionic liquid; the one with the cation of bulkier alkyl chain length showed better reactivity. The effect of carbon dioxide pressure, reaction temperature and zinc bromide co-catalyst on this reaction was also discussed.     

Formation of a Third Liquid Phase and Its Reuse for Dibenzyl Ether Synthesis in a Tetraalkylammonium Salt Phase Transfer Catalytic System

This paper describes the formation of a third liquid phase in a phase transfer catalytic system in the presence of benzyl alcohol and potassium hydroxide, where dodecane and tetraalkylammonium bromide serve as organic solvent and catalyst, respectively. In this kind of system, a symmetrical ether (dibenzyl ether) was synthesized from benzyl chloride and benzyl alcohol at 323 K. In particular, the investigation demonstrates that the observed reaction rate constant depends on the length of the alkyl group of the catalyst. Tetrabutylammonium bromide exhibits the highest catalytic activity among the catalysts explored. With respect to the reuse of the third liquid phase, the results confirm that there is no decrease in phase transfer catalytic activity in three consecutive runs.     

Catalytic performance of quaternary ammonium salts in the reaction of butyl glycidyl ether and carbon dioxide

The synthesis of cyclic carbonate from butyl glycidyl ether (BGE) and carbon dioxide was performed in the presence of quaternary ammonium salt catalysts. Quaternary ammonium salts of different alkyl group (C₃, C₄, C₆ and C₈) and anions (Cl⁻, Br⁻ and I⁻) were used for this reaction carried out in a batch autoclave reactor at 60–120 °C. The catalytic activity increased with increasing alkyl chain length in the order of C₃ < C₄ < C₆. But, the quaternary ammonium salt with longer alkyl chain length (C₈) decreased the conversion of BGE because it is too bulky to form an intermediate with BGE. For the counter anion of the tetrabutyl ammonium salt catalysts, the BGE conversion decreased in the order Cl⁻ > Br⁻ > I⁻. The effects of carbon dioxide pressure and reaction temperature on this reaction were also studied to better understand the reaction mechanism.     

KINETIC STUDY OF SYNTHESIZING 1-PHENYl-3-PROPYL ETHER UNDER LIQUID-LIQUID PHASE-TRANSFER CATALYTIC CONDITIONS

The etherification of 1-bromo-3-phenylpropane with phenol to synthesize 1-phenyl-3-propyl ether by phase-transfer catalytic conditions was successfully carried out in an alkaline solution of KOH/organic solvent two-phase medium. In this work, quaternary ammonium salts acted as the phase-transfer catalysts. The main purpose of this study was to investigate the kinetic behavior, mechanism, and activation energy of the reaction system. A rational mechanism for the etherification is proposed according to the experimental evidence. The reaction follows a pseudo first-order rate law. A pseudo steady-state hypothesis (PSSH) was proposed to describe the kinetic behaviors from which the apparent rate constant of the two-phase reaction (k_app) was obtained via experimental data. Kinetics of the reaction including the effects of agitation speed, amount of potassium hydroxide, volume of water, temperature, amount of tetrabutylammonium bromide, quaternary ammonium salts, volume of chlorobenzene, and organic solvents on the reaction rate were investigated in detail. Rational explanations to account for the unique results, especially for the water volume effect on the reaction rate, are also provided.