Chlorohydrin Esters Research Articles

Finding the right balance between tertiary amine steric effect and solvent polarity for the regioselectivity and kinetics of epichlorohydrin acetolysis

AbstractThe asymmetric oxirane ring‐opening reaction leading to the formation of regioisomeric chlorohydrin esters was studied in the reaction series “acetic acid–epichlorohydrin–tetrahydrofuran (nitrobenzene)–trialkylamine” by kinetic methods and FT‐IR spectroscopy. The effect of solvent polarity and the structure of tertiary amines on the regioselectivity and reaction rate were studied. Tertiary amines with comparable basicity but different nucleophilicity and spatial structure were chosen as catalysts. It was shown that in solvents of different polarity, the components of the initial reaction system are present both as hydrogen‐bonded complexes and as individual substances. The reaction orders with respect to acid and amine in solvents of different polarity were established. Correlations between the reaction rate and the parameters of nucleophilicity and structure of amines as well as the polarity of the solvent were established. The regioselectivity of the reaction was studied by 1H NMR spectroscopy using the ratio of regioisomeric reaction products. It was shown that the regioselectivity and rate of catalytic acetolysis of epichlorohydrin are effectively controlled by the structure of tertiary amines and the polarity of the solvent. The scheme of reaction regio‐flows was detailed.

Reaction Kinetics of Dehydrochlorination of the Chlorohydrin Esters of Bisphenol A

The results of a study of the reaction kinetics of dehydrochlorination of the chlorohydrin esters of bisphenol A in the production of ED-20 epoxy resin are reported. The reaction was studied in a methyl isobutyl ketone solvent. An equation was derived to adequately describe the reaction kinetics and to determine the activation energy.

Preparation of chiral glycerol derivatives using chemoenzymatic approaches

Following our preparation of dissymmetric chlorohydrin esters from glycerol, we have used several lipases and whole cells to examine the kinetic resolution (KR) and dynamic kinetic resolution (DKR) of 3-chloro-2-hydroxypropyl esters. Regarding the KR, PS-IM, MmL and CALB lipases and whole cells of Aspergillus flavus showed the best selectivity and activity, depending on the compound studied. PS-IM allowed the isolation of (R)-3-chloro-2-hydroxypropyl pivaloate in 34% yield and with >99% enantiomeric excess (ee). DKR was carried out combining the biocatalysts that performed best for KR and suitable reaction conditions for racemization. Whole cells of A. flavus allowed the preparation of enantioenriched (S)-3-chloro-2-acetoxypropyl-2-methyl-2-phenyl propanoate in 43% yield and with 79% ee. Lipozyme from Mucor miehei used in a reaction subsequent to DKR allowed the purification of the corresponding enantioenriched (S)-3-chloro-2-acetoxypropyl pivaloate.

From Symmetric Glycerol Derivatives to Dissymmetric Chlorohydrins

The anticipated worldwide increase in biodiesel production will result in an accumulation of glycerol for which there are insufficient conventional uses. The surplus of this by-product has increased rapidly during the last decade, prompting a search for new glycerol applications. We describe here the synthesis of dissymmetric chlorohydrin esters from symmetric 1,3-dichloro-2-propyl esters obtained from glycerol. We studied the influence of two solvents: 1,4-dioxane and 1-butanol and two bases: sodium carbonate and 1-butylimidazole, on the synthesis of dissymmetric chlorohydrin esters. In addition, we studied the influence of other bases (potassium and lithium carbonates) in the reaction using 1,4-dioxane as the solvent. The highest yield was obtained using 1,4-dioxane and sodium carbonate.

From Symmetric Glycerol Derivatives to Dissymmetric Chlorohydrins

The anticipated worldwide increase in biodiesel production will result in an accumulation of glycerol for which there are insufficient conventional uses. The surplus of this by-product has increased rapidly during the last decade, prompting a search for new glycerol applications. We describe here the synthesis of dissymmetric chlorohydrin esters from symmetric 1,3-dichloro-2-propyl esters obtained from glycerol. We studied the influence of two solvents: 1,4-dioxane and 1-butanol and two bases: sodium carbonate and 1-butylimidazole, on the synthesis of dissymmetric chlorohydrin esters. In addition, we studied the influence of other bases (potassium and lithium carbonates) in the reaction using 1,4-dioxane as the solvent. The highest yield was obtained using 1,4-dioxane and sodium carbonate.

From glycerol to chlorohydrin esters using a solvent-free system. Microwave irradiation versus conventional heating

Esterification–chlorination of glycerol provides chlorohydrin esters in high yields. A ratio of reagents close to equivalence can be used, so that atom economy of the reaction is optimized. The reaction can be carried out using either classical or microwave heating, and no solvent is required. 2-Chloro-1-(chloromethyl)ethyl esters can be obtained in high regioisomeric relationship when either low or moderate temperature is used. In contrast, microwave irradiation allows the use of higher reaction temperatures that render mixtures of both regioisomers in variable relationships. Kinetic control of the process is proposed for classical heating, and experimental results are analyzed with the aid of ab initio calculated values. Non-thermal phenomena can be used to explain the high efficiency of microwave irradiation at low temperature.

Combining AlCl 3·6H 2O and an ionic liquid to prepare chlorohydrin esters from glycerol

We describe here the first example in which glycerol has been transformed into chlorohydrin esters using an ionic liquid and hydrated aluminium chloride. The method avoids using Crown-18 ether, which was needed to obtain a similar yield when KCl was used. Alkyl and aryl acids can be used, although yields are very dependent on the carboxylic acid used.

Combining regio‐ and enantioselectivity of lipases for the preparation of (R)‐4‐chloro‐2‐butanol

Preparation of 98% ee (R)-4-chloro-2-butanol was carried out by the enzymatic hydrolysis of chlorohydrin esters, using fungal resting cells and commercial enzymes. Hydrolyzes were carried out using lipases from Candida antarctica (Novozym 435), C. rugosa, Rhizomucor miehei (Lipozyme IM), Burkolia cepacia, and resting cells of Rhizopus oryzae and Aspergillus flavus. The influence of the enzyme, the solvent, the temperature, and the alkyl chain length on the selectivity of hydrolyzes of isomeric mixtures of chlorohydrin esters is described. Regioselectivity was higher than 95% for some of the tested lipases. Novozym 435 allowed preparation of the (R)-4-chloro-2-butanol after 15 min of reaction at 30-40 degrees C.

Influence of Carboxylic Acids on the Synthesis of Chlorohydrin Esters from 1,3‐Butanediol

The influence of diverse carboxylic acid on the preparation of chlorohydrin esters using a one‐pot esterification–chlorination reaction, in which one of the reagents (chlorotrimethylsilane) acts as solvent, is described. Whereas the acid with low pKa provided higher amounts of the 2‐chloro regioisomer, the ones with higher pKa rendered the 1‐chloro regioisomer in 80% yield. These results are in accordance with the mechanism proposed in a previous article.

Chlorotrimethylsilane: a suitable reagent for the synthesis of chlorohydrin esters.

A new methodology for obtaining chlorohydrin esters using a one-pot esterification-chlorination reaction, in which one of the reagents, chlorotrimethylsilane, acts as solvent, is described. The reaction is stereospecific and its regioselectivity depends on the number of carbons between the hydroxyl groups present in the starting material. A mechanism is proposed.

Synthesis of glycidyl esters

A novel method of synthesis of glycidyl carboxylates (2,3-epoxypropyl carboxylates, RCOOCH2CH-CH2O) has been developed by carrying out the reaction of epichlorhydrin with a carboxylic acid in the presence of chromium acetate catalyst and subsequent dehydrochlorination of the resulting mixture of chlorohydrin esters followed by their separation. © 1999 Society of Chemical Industry

Reactions of 1,3-dioxolanes with iodine monochloride: formation of chlorohydrin esters and diol monoesters

2-Mono-substituted 1,3-dioxolanes are oxidised by iodine monochloride to the appropriate 2-substituted 1,3-dioxolan-2-ylium ions, whose stability is dependent upon the presence and nature of substituents on C-4 and C-5. Some dioxolanylium ions are labile and under the reaction conditions afford Chlorohydrin esters, with inversion of configuration taking place at the ring carbon attacked by chloride. Others are stable under the reaction conditions and may be converted on aqueous workup to diol monoesters with retention of configuration at C-4 and C-5. The effect of substituents and reaction conditions on these competing reactions are described. The stereo- and regio-chemistry of both hydroxy- and chloro-ester formation was confirmed through NMR studies, which necessitated the prior detailed analysis of the 1H and 13C spectra associated with the acyloxy sidechains of the relevant esters.

Mechanism of formation of oil additives of the diethyldithiocarbamic acid ester type

Summaryo1.The rate of interaction of sodium diethyldithiocarbamate with chlorohydrin esters of glycerine is restricted by the formation and transformation of an equimolar complex between the reagents.2.The transformation of the intermediate complex into diethyldithiocarbamic acid esters is affected by the concentration of HO− anions in the reaction mixture. The addition of 0·2–0·25 mole sodium hydroxide per mole sodium diethyldithiocarbamate increases the reaction rate many times and permits the formation of esters at room temperature in almost quantitative yield. The rate of interaction of sodium diethyldithiocarbamate with chlorohydrin esters of glycerine is restricted by the formation and transformation of an equimolar complex between the reagents. The transformation of the intermediate complex into diethyldithiocarbamic acid esters is affected by the concentration of HO− anions in the reaction mixture. The addition of 0·2–0·25 mole sodium hydroxide per mole sodium diethyldithiocarbamate increases the reaction rate many times and permits the formation of esters at room temperature in almost quantitative yield.

Glycidyl Esters of Aromatic Acids

Abstract The reaction of substituted benzoic acids, dicarboxylic acids such as phthalic, terephthalic, and isophthalic acids, and the sodium or potassium salts of these acids with equimolar or excess epichlorohydrin in the presence of benzyltrimethylammonium chloride has been studied using various solvents such as toluene, dioxane, monochlorobenzene, and tetrachloroethylene. Use of the free carboxylic acids gave only fair to low yields of glycidyl esters, while sodium or potassium salts of the carboxylic acids gave excellent yields of materials of high oxirane content. The epoxidation of chlorohydrin esters of these acids by the dehydrochlorination was also studied using various dehydrochlorinating reagents such as NaOH, KOH, Na2CO3, and NaAlO2 in such solvents as water, dichloromethane, dioxane, and monochlorobenzene at various temperatures. Reaction time, reaction temperature, and water content were found to influence the yield of glycidyl esters. It is suggested that the reaction path involves nucleoph...