Aryl Acetates Research Articles

Asymmetric Synthesis of Carboxylic Acid Derivatives Having an All-Carbon α-Quaternary Center through Cu-Catalyzed 1,4-Addition of Dialkylzinc Reagents to 2-Aryl Acetate Derivatives

The asymmetric synthesis of carboxylic acid derivatives having an all-carbon alpha-quaternary center has been achieved via copper-catalyzed 1,4-addition of dialkylzinc reagents to aryl acetate derivatives in the presence of phosphoramidite ligand. High isolated yields and enantioselectivities were obtained. It was demonstrated that the Meldrum's acid and ester moieties present on the all-carbon quaternary center allow for a wide variety of subsequent transformations, leading to the expedient preparation of succinimides, succinate esters and succinic acids, gamma-butyrolactones, and beta-amino acid derivatives.

Reaction of poly‐L‐lysine with aryl acetates and aryl methyl carbonates. A mechanistic study

AbstractThe pH profile (log k vs. pH) of the reactions of poly‐L‐lysine (PL) with a series of aryl acetates and aryl methyl carbonates in aqueous solution show the same conformational changes as those determined by potentiometric titrations. When PL is a random coil, the most probable mechanism for the reactions studied is through the formation of a tetrahedral intermediate and its breakdown to products as the rate‐determining step. The tetrahedral intermediate is stabilized by a hydrogen bond interaction between the nitro groups in the substrate and the NH group of the principal chain or some NH2 groups of the lateral chains. Copyright © 2007 John Wiley & Sons, Ltd.

On the mechanism of the reaction between aryl acetates and hydroxylamine

The reaction of aryl acetates and hydroxylamine produces O-acylhydroxylamine and N- acylhydroxylamine, the latter being essentially observed for good leaving group esters and the former for poor leaving esters. For both acylation reactions, kinetics studies suggested a tetrahedral intermediate intervention for nucleofuges in a pKa range of 1 to 9. Esters having leaving groups with a pKa value less than 7 react by a rate-determining step inferred to be the tetrahedral intermediate formation, while for esters having leaving groups with a pKa value equal to or higher than 7, the rate-limiting step has been proposed to be the tetrahedral intermediate decomposition. General bifunctional acid-base catalysis by a second hydroxylamine molecule was identified as one of the components of the reaction for the intermediate collapse to products in the poor leaving group ester

Regioselective One Pot Synthesis of 2‐Alkyl/Aryl‐4H‐benzo[1,4]thiazine‐3‐one via Microwave Irradiation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Regioselective one pot synthesis of 2‐alkyl/aryl‐4h‐benzo[1,4] thiazine‐3‐one via microwave irradiation

Abstractmagnified imageA series of 2‐alkyl/aryl‐4H‐benzo[1,4]thiazine‐3‐ones have been synthesized by microwave irradiation of ethyl‐2‐bromo‐2‐alkyl/aryl acetate and 2‐amino thiophenol in the presence of 1,8‐diazabicyclo‐[5.4.0] undec‐7‐ene and N‐methylpiperidine. All compounds were characterized by 1H NMR, 13C NMR and elemental analyses, and by X‐ray crystallography in the case of 2‐methyl‐4H‐benzo[1,4]thiazin‐3‐one.

Inhibition of Human Phenol and Estrogen Sulfotransferase by Certain Non-Steroidal Anti-Inflammatory Agents

We hypothesized that aryl acetate- and aryl carboxylate-containing drugs would inhibit human phenol sulfotransferase (SULT1A1), and that selectivity would depend upon the interaction of the aryl portion of the molecule with the sulfotransferase acceptor binding site. This hypothesis was based on results with the rat orthologue showing that oxidation of phenolic substrates to carboxylate derivatives resulted in competitive inhibition of rat phenol sulfotransferase. We chose nine structurally representative non-steroidal anti-inflammatory agents and determined their inhibitory potency and selectivity toward SULT1A1 and expressed human estrogen sulfotransferase (SULT1E1). The results show that the tested agents reversibly inhibit SULT1A1 activity with IC(50) ranging from 0.1 microM to 3800 microM. These agents also inhibited SULT1E1 (IC(50) = 6 microM to 9000 microM). The agents were clearly isoform selective, with IC(50) ratios (1E1/1A1) ranging from 0.01 to 200. Nimesulide, meclofenamate, and piroxicam were more selective towards SULT1A1 inhibition, while sulindac and ibuprofen were more selective towards SULT1E1 inhibition. Sulfotransferase inhibition was maintained after substituting the carboxylate with enolate (nimesulide) or methylsulfonamide (piroxicam). Kinetic studies determined the type of inhibition of SULT1A1 for three agents (meclofenamate, nimesulide, aspirin) to be non-competitive or partial non-competitive versus both substrate (p-nitrophenol) and cofactor (PAPS). This inhibition mechanism indicates that meclofenamate, nimesulide and aspirin bind near enough to the substrate binding site to prevent catalysis but not affect dissociation of the substrate-enzyme complex. The inhibition of SULT1A1 by meclofenamate, nimesulide, salicylate and aspirin may be clinically relevant based on ratio of inhibition constant to predicted in vivo inhibitor concentration ([I]/IC(50) > 1).

A Practical Method for the Synthesis of Indolylaryl- and Bisindolylmaleimides

[reaction: see text] Indolylaryl and indolylheteroarylmaleimides, including bisindolylmaleimides, are easily prepared by the reaction of N-methylindole-3-glyoxylamide with methyl aryl acetates in the presence of potassium tert-butoxide in THF.

Kinetics and mechanism of the reactions of polyallylamine with aryl acetates and aryl methyl carbonates

AbstractThe reactions of polyallylamine (PAA) with 4‐nitrophenyl acetate (NPA), 2,4‐dinitrophenyl acetate (DNPA), 2,4,6‐trinitrophenyl acetate (TNPA), 4‐nitrophenyl methyl carbonate (NPC), 2,4‐dinitrophenyl methyl carbonate (DNPC) and 2,4,6‐trinitrophenyl methyl carbonate (TNPC) at pH 7.0–11.5 were subjected to a kinetic investigation in aqueous solution at 25.0 °C and an ionic strength of 0.1 M (KCl). Potentiometric titration curves were obtained at different polymer concentrations under the same conditions as for the kinetic measurements. The degree of dissociation (α) and pKapp values for PAA at each pH were found from the titration curves. The shape of these curves shows a conformational change of the polymer at α > 0.7. Similar behavior was observed through the dependence of logkN on either pH or α, where kN is the second‐order rate constant for the title reactions. The kN value is influenced by the electrostatic interactions in the polymer chain and the conformational changes that PAA undergoes in solution. The Brønsted‐type plots (logkN vs pKapp) are linear with slopes (β values) of 0.5, 0.4, 0.5, 0.7, 0.6 and 0.7 for the reactions of PAA with NPA, DNPA, TNPA, NPC, DNPC and TNPC, respectively. These data are consistent with concerted mechanisms. The kN values increase in the sequence TNPA > DNPA > NPA and TNPC > DNPC > NPC. These results are in accordance with those found for the reactions with monomeric amines, which are due to the increasing nucleofugality of the leaving groups, and also the increasing electrophilic character of the carbonyl carbon, as more nitro groups are added to the substrate. Acetates are more reactive than the corresponding methyl carbonates, which can be explained by the larger electron‐releasing effect exerted by MeO relative to Me. PAA destabilizes the putative tetrahedral intermediate relative to the monomeric amines and the stability of tetrahedral intermediates would decrease in the sequence pyridines > anilines > secondary alicyclic amines > quinuclidines > PAA. Copyright © 2006 John Wiley & Sons, Ltd.

Bismuth Triflate Catalyzed Fries Rearrangement of Aryl Acetates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel Synthesis of Calix[n]arene Amide Supramolecular Receptor.

In the system of K2CO3/KI/acetone, eight p-tert-butylcalix[n]arene amide products (n = 6, 8) were prepared by the O-alkylation of calixarenes with N, N-dialkyl α-chloroacetamides in high yields (HNR2 = dipropylamine, isopropylamine, pepridine, morphine). These amide products can also be synthesised by the amination reaction of the correspond ethyl calix[n]aryl acetates.

Novel Synthesis of Calix[n]Arene Amide Supramolecular Receptor

In the system of K2CO3/KI/acetone, eight p-tert-butylcalix[ n]arene amide products ( n = 6, 8) were prepared by the O-alkylation of calixarenes with N, N-dialkyl α-chloroacetamides in high yields (HNR2 = dipropylamine, isopropylamine, pepridine, morphine). These amide products can also be synthesised by the amination reaction of the correspond ethyl calix[n]aryl acetates.

Facile and Selective Deprotection of Aryl Acetates Using Sodium Perborate under Mild and Neutral Conditions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A convenient, rapid, highly selective and eco-friendly method for deprotection of aryl acetates using silica gel supported ammonium formate under microwave irradiationPart 20 in the series ‘Studies on Novel Synthetic Methodologies’, for part 19, see ref. 1

Several aryl acetates were rapidly and selectively deprotected to the corresponding phenols in excellent yields using silica gel supported ammonium formate under microwave irradiation. The process is environmentally benign.

Facile and selective deprotection of aryl acetates using sodium perborate under mild and neutral conditions

A variety of aryl acetates are cleaved to the corresponding phenols using sodium perborate in methanol under mild conditions (25 °C). The effectiveness of this protocol is manifested in its tolerance of different functional groups and selectivity of deprotection towards aryl acetates whereas alkyl acetates are found to be unreactive under these reaction conditions.

Palladium(0)-catalyzed coupling-cyclization reaction of polymer-supported aryl iodides with 1,2-allenyl carboxylic acids. Solid-phase parallel synthesis of butenolides.

In this contribution, we constructed a library of butenolides with 77 members by parallel synthesis strategy on Merrifield resin. Sixteen 2,3-allenoic acids and 12 polymer-bound aryl iodides were combined to react with each other, and then the polymer-supported products were cleaved to release butenolide derivatives. The reactions with alkyl-substituted 2,3-allenoic acids in acetonitrile afforded the corresponding products in high yields and high purities, whereas those with aryl-substituted acids in acetonitrile failed. After some reaction conditions were screened, the solid-phase reactions with aryl-substituted 2,3-allenoic acids were realized in toluene, and the products are of good purities albeit in slightly low yields. In the benzyl ether linkage, a new cleavage model was found. By adding 6 equiv of acetyl bromide, we can get single (5-oxo-2,5-dihydrofuran-3-yl)benzyl bromide other than the corresponding benzyl acetate. To further increase the diversities, a dihydropyran (DHP) linker was introduced into our combinatorial synthesis of butenolides. By reversing the addition sequence of 2,3-allenoic acids and organic base, we realized the solid-phase cyclization reaction of polymer-bound aryl iodides with the THP linkage in moderate yields and good purities. Now the library of butenolides includes (5-oxo-2,5-dihydrofuran-3-yl)benzoic acids, -aryl acetates, -benzyl bromides, -benzyl alcohols, and -phenols, which are difficult to synthesize with conventional solution methods.

ChemInform Abstract: A Mild and Chemoselective Method for Deprotection of Aryl Acetates and Benzoates under Non‐hydrolytic Condition.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Palladium catalyzed arylation of malonate accompanying in situ dealkoxycarbonylation

One-pot conversion of aryl halides into aryl acetates was achieved by the palladium catalyzed arylation of malonate accompanying in situ dealkoxycarbonylation of aryl malonates using Cs2CO3 as a base and as a catalyst.

A mild and chemoselective method for deprotection of aryl acetates and benzoates under non-hydrolytic condition

Chemoselective deprotection of aryl acetates and benzoates can be achieved under non-hydrolytic condition by treatment with K 2CO 3 in N-methyl-2-pyrrolidone (NMP) at 100°C. Selective cleavage of aryl acetates and benzoates take place in the presence of alkyl carboxylates during intramolecular competitions.

Solvent effect on the alpha-effect for the reactions of aryl acetates with butane-2,3-dione monoximate and p-chlorophenoxide in MeCN-H2O mixtures.

Second-order rate constants have been measured spectrophotometrically for the nucleophilic reactions of three substituted phenyl acetates with butane-2,3-dione monoximate (Ox(-)) as an alpha-nucleophile and p-chlorophenoxide (ClPhO(-)) as corresponding normal nucleophile, in MeCN-H2O mixtures of varying compositions at 25.0 +/- 0.1 degrees C. The reactivity of Ox(-) toward the aryl acetates decreases upon addition of MeCN to the reaction medium up to ca. 30 mol % MeCN, followed by a gradual increase in rate upon further addition of MeCN. A similar result has been obtained for the reaction of ClPhO(-) with the aryl acetates. However, the decrease in rate is more significant for the less reactive ClPhO(-) than for the more reactive Ox(-). Thus, for all the aryl acetates studied, Ox(-) exhibits a sizable alpha-effect (k(Ox)-/k(ClPhO)-) whose magnitude increases as the mol % MeCN in the reaction medium increases. The relative basicities (DeltapK(a)) of Ox(-) and ClPhO(-) have been determined spectrophotometrically using piperazine as a reference base. The DeltapK(a) values increase on increasing the mol % MeCN in the medium for both Ox(-) and ClPhO(-). The difference in the relative basicities of these nucleophiles (DeltaDeltapK(a)) becomes larger with increasing mol % MeCN. The plots of log k(Ox)-/k(ClPhO)- vs DeltaDeltapK(a) for the three substrates are linear with near-unit slope, indicating that the difference in the relative basicity of the nucleophiles is largely responsible for the increasing alpha-effect with medium composition in this system.

A mild procedure for rapid and selective deprotection of aryl acetates using natural kaolinitic clay as a reusable catalyst

A variety of aryl acetates are selectively cleaved to the corresponding phenols using natural kaolinitic clay in methanol under mild conditions (25°C).