Aliphatic Acid Esters Research Articles

Organosilicon synthesis of isocyanates: IV. Synthesis of isocyanates from aliphatic and alkylaromatic amino acid esters

Treatment of an alcoholic suspension of amino acids with trimethylchlorosilane yielded phenylglycine, valine, β-phenylalanine, and homovaline ester hydrochlorides. Their saccharin-catalyzed silylation with hexamethyldisilazane proceeds quantitatively and involves only one proton of the amino group. The best conversion of the amino acid esters to the corresponding isocyanates was achieved by phosgene treatment of their monosilyl urethanes, rather than of the silylated amino esters. Monosilyl urethanes are formed quantitatively by treatment of the amino acid ester hydrochlorides with the hexamethyldisilazane-CO2 system. The 1H NMR spectra show that monosilyl urethanes derived from α-and β-amino acid esters are characterized by intramolecular interaction of the silicon atom and the oxygen atom of the carboxy group.

BF3-H2O catalyzed Fries rearrangement of phenolic esters

BF3-H2O catalyzed Fries rearrangement is reported. Aliphatic and aromatic carboxylic acid esters of phenols react smoothly under mild conditions to provide the corresponding hydroxyketones in high yield, selectivity and purity.

Structure and reactivity in the hydrolyses of aliphatic carboxylic acid esters and chlorides

AbstractFor hexanoic acid and its seven isomers, relative rates have been determined for acid catalysed esterification with methanol, and compared with those for saponification of the methyl esters. A good correlation between logarithms of relative rates for the two reactions is obtained, and it is suggested that the eight isomers provide a test set of compounds in which steric effects alone act on reactivity at the acyl carbon. A full set of steric parameters ($E_{\rm s}^\prime$ values) are presented. Rates of solvolyses of the acid chlorides of the isomers have been determined conductometrically in 3:1 wt:wt acetonitrile water. Logarithms of relative rates show a poor correlation with $E_{\rm s}^\prime$, and, taking into account the solvent dependence of the rates, the pattern excludes both rate‐limiting formation of a tetrahedral intermediate and rate‐limiting dissociation of chloride to form acylium ions. The remaining possibilities, a concerted process (AND) and rapid reversible formation of a hydrate followed by rate‐limiting dissociation of chloride (AN + D) are considered. Copyright © 2007 John Wiley & Sons, Ltd.

Aliphatic acid esters of (2-hydroxypropyl) cellulose—Effect of side chain length on properties of cholesteric liquid crystals

A series of aliphatic acid esters of (2-hydroxypropyl) cellulose (CnPC) were synthesized via the esterification of aliphatic acid chloride and (2-hydroxypropyl) cellulose (HPC). The liquid crystalline (LC) phases and transitions were investigated using differential scanning calorimetry, wide-angle X-ray diffraction (WAXD), and polarized light microscope (PLM) techniques. This series of CnPC polymers exhibited characteristic features of cholesteric LC phases between their glass transition and isotropization temperatures. The cholesteric LC characteristics were studied utilizing an ultraviolet/visible/near infrared spectrometer in a reflection mode. It was confirmed that, with an increase in the number of methylene units in the side chains of this series of CnPC polymers, there was an increase, on the scale of nanometers, in the layer spacing values for the cholesteric LC phases measured by WAXD. This periodic layer spacing represents the thickness of the neighboring twisted layers in a helical structure. Based on a unique significant red shift of the maximum reflection peak for the LC phases in this series of CnPCs, it is evident that the pitch distance in the helical structure also increases with an increase in the length of methylene units in the side chains.

Synthesis of S‐(3‐Chloroquinoxalin‐2‐yl) Esters of Aliphatic and Aromatic Thiosulfonic Acids.

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Organosilicon synthesis of isocyanates: III. Synthesis of aliphatic, carbocyclic, aromatic, and alkylaromatic isocyanatocatboxylic acid esters

A series of aminoacid esters was prepared by treating the aminoacid suspensions in ethanol with thionyl chloride. Best conversion of aminoacid esters to corresponding isocyanates was achieved in the case of aromatic and carbocyclic aminoesters by phosgeneation of their N-silyl derivatives, and in the case of aliphatic and alkylaromatic aminoesters by phosgeneation of O-silyl or N,O-bissilylurethanes on their basis. In the last case additional step of esterification of the by-products isocyanatoalkylcarboxylic acid chlorides is required after phosgeneation. Unusual generation of cynnamates and intramolecular N→O-migration of trimethylsilyl group in the solutions of silylated alkylaromatic β-aminoacid esters were found.

Catalyst-Free Chemoselective N-tert-Butyloxycarbonylation of Amines in Water

[Structure: see text] Catalyst-free N-tert-butyloxycarbonylation of amines in water is reported. The N-t-Boc derivatives were formed chemoselectively without any isocyanate, urea, N,N-di-t-Boc, and O/S-t-Boc as side products. Chiral amines, esters of alpha-amino acids, and beta-amino alcohol afforded optically pure N-t-Boc derivatives. Amino alcohol and 2-aminophenol afforded the N-t-Boc derivative without oxazolidinone formation. Selectivity was observed during competition of aromatic amine vs aliphatic amine, amine vs amino acid ester, amine vs amino alcohol, and primary amine vs secondary amine.

Glycerol esters from the reaction of glycerol with dicarboxylic acid esters

AbstractMono‐ and di‐esterified glycerols were synthesized by the base catalyzed reaction of glycerol with aliphatic dicarboxylic acid esters (C2−C9): 2,3‐dihydroxy‐propyl oxalate (2), 1,3 dioxalyloxy propan‐2‐ol (3), 1,3‐dimethoxyoxalyloxy propan‐2‐ol (5), 2,3‐dihydroxy‐propyl malonate (6), 2,3‐dihydroxy‐propyl methyl malonate (7), 2,3‐dihydroxy‐propyl methyl succinate (8), 1,3‐dimethoxysuccinyloxy propan‐2‐ol (9), 2,3‐dihydroxy‐propyl methyl glutarate (10), 1,3‐dimethoxyglutaryloxy propan‐2‐ol (11), 2,3‐dihydroxy‐propyl methyl azelate (14), and 1,3‐dimethoxyazelyloxy propan‐2‐ol (15). Their structures were elucidated by spectrometric methods. Compounds 8, 10, 2,3‐dihydroxy‐propl methyl adipate (12) and 14 were found to possess surface active properties and the ability to reduce the interfacial tension between paraffin and water.

An Efficient Method for Determination of the Degree of Substitution of Cellulose Esters of Long Chain Aliphatic Acids

The determination of the degree of substitution (DS) of fatty acid cellulose esters, representing a broad range of substituents (C6, C12, C18 and C22), was performed by alkaline hydrolysis of the ester groups and the quantification of fatty acids by gas chromatography-mass spectrometry (GC-MS) as their trimethylsilyl derivatives. The method was optimized and compared with established techniques for the DS determination (elemental analysis and alkaline hydrolysis/titrimetry). The results demonstrated that alkaline hydrolysis/GC-MS is a rapid, reliable and powerful method for analysis of fatty acid cellulose esters, particularly when different acyl substituents are present.

Vanilline Alkanoates in the Synthesis of Hexahydrobenzacridine and Octahydroxanthene Derivatives

Cascade heterocyclization of 1,3-cyclohexanedione and dimedone with 2-naphthylamine and vanilline esters gave derivatives of 2-methoxy-4-(alkyl-11-oxo-7,8,9,10,11,12-hexahydrobenz[a]acridin-12-yl)- and 2-methoxy-4-(alkyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)phenyl esters of aliphatic (C1– C4 ) carboxylic acids.

Adsorption parameters in solutions of ethyl esters of aliphatic acids

Based on the regression analysis of electrocapillary curves (ECC) in solutions of ethyl esters of aliphatic acids (from acetic to valeric), it is shown that the adsorption of these compounds on a mercury electrode from aqueous solutions corresponds in the first approximation to the model of two parallel capacitors. Moreover, to describe experimental ECC, the knowledge of only five main parameters of this model is necessary. The dependence of the adsorption parameters found on the number of carbon atoms in an ester molecule is analyzed.

Vanillin Esters of Aliphatic Acids in the Synthesis of 4,7‐Phenanthroline Derivatives.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Comparison of mesophilic and thermophilic feruloyl esterases: Characterization of their substrate specificity for methyl phenylalkanoates

The active sites of feruloyl esterases from mesophilic and thermophilic sources were probed using methyl esters of phenylalkanoic acids. Only 13 out of 26 substrates tested were significant substrates for all the enzymes. Lengthening or shortening the aliphatic side chain while maintaining the same aromatic substitutions completely abolished activity for both enzymes, which demonstrates the importance of the correct distance between the aromatic group and the ester bond. Maintaining the phenylpropanoate structure but altering the substitutions of the aromatic ring demonstrated that the type-A esterase from the mesophilic fungus Fusarium oxysporum (FoFaeA) showed a preference for methoxylated substrates, in contrast to the type-B esterase from the same source (FoFaeB) and the thermophilic type-B (StFaeB) and type-C (StFaeC) from Sporotrichum thermophile, which preferred hydroxylated substrates. All four esterases hydrolyzed short chain aliphatic acid (C 2–C 4) esters of p-nitrophenol, but not the C 12 ester of laurate. All the feruloyl esterases were able to release ferulic acid from the plant cell wall material in conjunction with a xylanase, but only the type-A esterase FoFaeA was effective in releasing the 5,5′ form of diferulic acid. The thermophilic type-B esterase had a lower catalytic efficiency than its mesophilic counterpart, but released more ferulic acid from plant cell walls.

Gas-Chromatographic Determination of Organic Compounds in Water with the Use of Supercritical Fluid Extraction

Procedures were developed for the determination of some organic compounds (n-alkanes, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, Cl,P,N-pesticides, phthalic acid esters, chlorophenols, aliphatic acids, and methyl esters of aliphatic acids) in water on the basis of direct supercritical fluid extraction with the subsequent gas-chromatographic analysis of the entire extract without using organic solvents. The detection limits were 10–11–10–7% depending on the nature of the analyte.

Vanillin Esters of Aliphatic Acids in the Synthesis of 4,7-Phenanthroline Derivatives

Condensation of vanillin esters of aliphatic acids with 6-aminoquinoline and cyclic c-diketones (1,3-cyclohexanedione and dimedone) afforded new 2-methoxy-4-(11-oxo-7,8,9,10,11,12-hexahydrobenzo[b][4,7]phenanthrolin-12-yl)phenyl esters of carboxylic acids.

How is chemical interesterification initiated: Nucleophilic substitution or α‐proton abstraction?

AbstractEsters of carboxylic acids including 2‐methylhexanoic, 2‐methylbutyric, 2,2‐dimethyl‐4‐pentenoic, palmitic, and oleic acids were tested as substrates in methoxide‐catalyzed interesterification and transesterification. The aliphatic acid esters participated in the ester‐ester interchange upon addition of catalytic sodium methoxide. Their isopropyl esters also produced methyl esters on heating with sodium methoxide. The esters of α‐methyl‐substituted acids did not participate in the ester‐ester interchange. Their isopropyl esters did not react with methoxide to produce methyl esters. However, upon addition of methanol with sodium methoxide, their methyl esters were produced. These results indicate that the first step in interesterification is possibly that methoxide abstracts the α‐hydrogen of an ester to form a carbanion. Interesterification is then likely completed via a Claisen condensation mechanism involving the β‐keto ester anion as the active intermediate. The β‐keto ester anion contains positively charged ketone and acyl carbons that are active sites for nucleophilic attack by anions such as methoxide and glycerinate, which would produce a methyl ester or rearrange acyls randomly. On the other hand, transesterification is a nucleophilic substitution by methoxide at the acyl carbon in the presence of methanol.

Reaction of Long-Chain Vanillyl Esters with CH-Acids and 2-Naphthylamine

The previously unknown 4-(alkyl-11-oxo-7,8,9,10,11,12-hexahydrobenzo[a]acridin-12-yl)- and 4-(alkyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)-2-methoxyphenyl esters of aliphatic (C5-C7, C12) carboxylic acids were synthesized via cascade heterocyclization of cyclohexane-1,3-dione and dimedone with 2-naphthylamine and long-chain vanillyl esters.

Hydrogenation of Dicarboxylic Acid Diesters to Corresponding Dialdehydes over ZrO<sub>2</sub> Based Catalysts (Part 1) Reactivity of Various Dicarboxylic Acid Diesters

Dimethyl terephthalate was hydrogenated over ZrO 2 catalyst in the vapor phase to form terephthalaldehydic acid methyl ester and terephthalaldehyde as the major products. The reactivity of the three regioisomers of benzenedicarboxylic acid dimethyl esters to hydrogenation was in the order, terephthalic > isophthalic >> phthalic. The low reactivity of dimethyl phthalate is probably due to the mutual steric hindrance of the two vicinal methoxycarbonyl groups and to catalyst deactivation caused by strong adsorption of the intermediates of dimethyl phthalate on the catalyst surface. Formation of terephthalaldehyde by hydrogenation of terephthalaldehydic acid methyl ester suggested that the hydrogenation reaction of dibasic acid diesters proceeds via successive reduction of the ester groups to formyl groups. Alicyclic acid diester dimethyl 1,4-cyclohexanedicarboxylate was also converted into the corresponding mono- and dialdehyde in a similar way. However, aliphatic dibasic acid esters such as dimethyl glutarate and dimethyl adipate were not hydrogenated at all. Modification of ZrO 2 by Cr, In or Zn improved the catalyst activity. Maximum dialdehyde selectivity in the hydrogenation of terephthalaldehydic acid methyl ester reached 72.4% by using Zn modified ZrO 2 catalyst (atomic ratio Zn/Zr = 5/100).

Esterification of aliphatic acids with olefin promoted by Brønsted acidic ionic liquids

Addition reactions of aliphatic acids with olefins to give corresponding esters have been investigated using SO3H-functionalized ionic liquids as dual catalyst–solvent. The isolation of the desired products could be achieved via simple decantation and ionic liquids could be reused continuously after dried in vacuum (5–12 mmHg) at ca. 80 °C.

Enhancing Effects of Medium Chain Aliphatic Alcohols and Esters on the Permeation of 6-Carboxyfluorescein and Indomethacin through Rat Skin

Medium chain aliphatic alcohols (C8-C12) and methyl or propyl esters of medium chain fatty acids (C8-C12) enhanced the permeation of 6-carboxyfluorescein (6-CF) and indomethacin (IND) through excised rat skin. The enhancing effects of the aliphatic alcohols for 6-CF and IND decreased with the increase in carbon chain length. The dependence on the carbon chain length was different from that exhibited by medium-chain fatty acids previously reported. In the case of fatty acid esters, the enhancing effects were lower than those of aliphatic alcohols and fatty acids. The relationship between the enhancing effects and the total number of carbon atoms in the esters was different for 6-CF and IND. The dependence on the total number of carbon atoms was similar to that in the aliphatic alcohols for 6-CF, and greater effects were observed in the shorter esters. On the other hand, no definite trends were observed for IND. Although the relationships between the structure and skin permeation-enhancing effect of the aliphatic alcohols and fatty acid esters used in this study are not yet fully understood, they are possible candidates as permeation enhancers for hydrophilic and lipophilic drugs. Further experiments, including examination of the location and environment of the lipophilic carbon chain and hydrophilic groups of such enhancers in the stratum corneum, are needed to optimize transdermal delivery systems containing them.