- The gold(I)-catalysed protodecarboxylation mechanism
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A mechanistic study of the gold-catalysed protodecarboxylation is described. Each reaction step has been investigated experimentally and computationally. More specifically, the activation parameters for the decarboxylation step have been determined through kinetic studies. Further experimental studies on the hydrolysis of the arylgold intermediate have revealed that the protodeauration can become competitive with the decarboxylation process at high conversions. This switch in rate-limiting step has been shown to be pKa-dependent. These studies have been supported by DFT calculations and permit a better understanding of which prevalent features of the reaction mechanism account for the decarboxylation process.
- Dupuy, St??phanie,Crawford, Luke,B??hl, Michael,Nolan, Steven P.
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- Chemical Composition and Antimicrobial Activity of Ageratina deltoidea
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The chemical study of Ageratina deltoidea afforded grandiflorenic acid (1), ent-kaurenoic acid (2), and eight benzylbenzoates (3?–?10), two of them, 3,5-dimethoxybenzyl 2,3,6-trimethoxybenzoate (5) and 4-(β-d-glucopyranosyloxy)-3-hydroxybenzyl 2,6-dimethoxybenzoate (9), described for the first time. In addition, the new sesquiterpene lactone deltoidin C (13), together with the known 11 and 12, the phenolic compounds: ayanin, 2,6-dimethoxybenzoic acid, methyl 3,4-dihydroxycinnamate, chlorogenic acid, and 3,5-dicaffeoylquinic acid were also isolated. The structures of these compounds were determined by spectroscopic methods and chemical reactions. The antibacterial and antifungal activities of compounds 1?–?12 were evaluated on Staphylococcus aureus, Escherichia coli, and Candida albicans. Deltoidin A (11) was the most active antibacterial agent (MIC 16.0?μg?ml?1) against E.?coli, and the ent-kaurenoid derivatives (1?–?2) showed activity (MIC 31.0?μg?ml?1) against S.?aureus.
- Arciniegas, Amira,Pérez-Castorena, Ana L.,Meléndez-Aguirre, Mariana,ávila, José Guillermo,García-Bores, Ana María,Villase?or, José Luis,Romo de Vivar, Alfonso
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Read Online
- Transition metal free one pot synthesis of aryl carboxylic acids via dehomologative oxidation of styrenes
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Iodine/NaOH-catalyzed one-pot dehomologative oxidation of styrenes to aryl carboxylic acids has been reported. A wide range of carboxylic acids are obtained using iodine (I2) as a catalyst, tert-butyl hydroperoxide (TBHP) as an oxidant and sodium hydroxide (NaOH) as a base. This reliable conversion involves dehomologation of styrene to aromatic aldehyde which on subsequent oxidation affords aryl carboxylic acid. This protocol was used for gram-scale synthesis as it is free from chromatographic purification. This is the first report for the oxidative transformation of styrenes into aryl carboxylic acids under transition metal-free conditions.
- Patil, Bhausaheb N.,Sathe, Pratima A.,Parade, Babasao S.,Vadagaonkar, Kamlesh S.,Chaskar, Atul C.
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supporting information
p. 4340 - 4343
(2018/11/06)
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- Metal-Free Dehomologative Oxidation of Arylacetic Acids for the Synthesis of Aryl Carboxylic Acids
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A novel I2-promoted direct conversion of arylacetic acids into aryl carboxylic acids under metal-free conditions has been described. This remarkable transformation involves decarboxylation followed by an oxidation reaction enabled just by using DMSO as the solvent as well as an oxidant. Notably, aryl carboxylic acids are isolated by simple filtration technique and obtained in good to excellent yields. This protocol is free from chromatographic purification, which makes it applicable for large-scale synthesis.
- Kalmode, Hanuman P.,Vadagaonkar, Kamlesh S.,Shinde, Suresh L.,Chaskar, Atul C.
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p. 3781 - 3786
(2017/04/11)
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- Flow carbonylation of sterically hindered ortho-substituted iodoarenes
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The flow synthesis of ortho-substituted carboxylic acids, using carbon monoxide gas, has been studied for a number of substrates. The optimised conditions make use of a simple catalyst system compromising of triphenylphosphine as the ligand and palladium acetate as the pre-catalyst. Carbon monoxide was introduced via a reverse "tube-in-tube" flow reactor at elevated pressures to give yields of carboxylated products that are much higher than those obtained under normal batch conditions.
- Mallia, Carl J.,Walter, Gary C.,Baxendale, Ian R.
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supporting information
p. 1503 - 1511
(2016/08/02)
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- Method for estimating SN1 rate constants: Solvolytic reactivity of benzoates
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Nucleofugalities of pentafluorobenzoate (PFB) and 2,4,6-trifluorobenzoate (TFB) leaving groups have been derived from the solvolysis rate constants of X,Y-substituted benzhydryl PFBs and TFBs measured in a series of aqueous solvents, by applying the LFER equation: log k = sf(Ef + Nf). The heterolysis rate constants of dianisylmethyl PFB and TFB, and those determined for 10 more dianisylmethyl benzoates in aqueous ethanol, constitute a set of reference benzoates whose experimental ΔG ? have been correlated with the ΔH? (calculated by PCM quantum-chemical method) of the model epoxy ring formation. Because of the excellent correlation (r = 0.997), the method for calculating the nucleofugalities of substituted benzoate LGs have been established, ultimately providing a method for determination of the SN1 reactivity for any benzoate in a given solvent. Using the ΔG? vs ΔH? correlation, and taking sf based on similarity, the nucleofugality parameters for about 70 benzoates have been determined in 90%, 80%, and 70% aqueous ethanol. The calculated intrinsic barriers for substituted benzoate leaving groups show that substrates producing more stabilized LGs proceed over lower intrinsic barriers. Substituents on the phenyl ring affect the solvolysis rate of benzhydryl benzoates by both field and inductive effects.
- Matic, Mirela,Denegri, Bernard,Kronja, Olga
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supporting information
p. 8986 - 8998,13
(2012/12/12)
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- Palladium-catalyzed hydroxycarbonylation of aryl and vinyl triflates by in situ generated carbon monoxide under microwave irradiation
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An operationally simple hydroxycarbonylation of aryl and vinyl inflates to the corresponding carboxylic acids with a palladium-mediated microwave system was carried out in water. Georg Thieme Verlag Stuttgart.
- Lesma, Giordano,Sacchetti, Alessandro,Silvani, Alessandra
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p. 594 - 596
(2007/10/03)
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- A scaleable synthesis of fiduxosin
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Fiduxosin (1) has been under development at Abbott Laboratories for the treatment of benign prostatic hyperplasia. A convergent strategy required methodologies for preparation of an enantiomerically pure 3,4-cis-disubstituted pyrrolidine and a 2,3,5-trisubstituted thienopyrazine in a regiospecific manner. A [3+2] cycloaddition of an enantiopure azomethine ylide followed by a diastereoselective crystallization was employed to prepare the benzopyranopyrrolidine in high diastereomeric and enantiomeric purity. Conditions for reduction of an O-aryl lactone susceptible to epimerization were developed, and cyclization of the alcohol/phenol to the ether was accomplished in high yield. The thienopyrazine was prepared by condensation of methyl thioglycolate and a regiospecifically prepared 2-bromo-3-cyano-5-phenylpyrazine. Conditions for effective halogen substitutive deamination to prepare regiospecific trisubstituted pyrazines will be described.
- Haight, Anthony R.,Bailey, Anne E.,Baker, William S.,Cain, Michael H.,Copp, Richard R.,Demattei, John A.,Ford, Kelley L.,Henry, Rodger F.,Hsu, Margaret C.,Keyes, Robert F.,King, Steven A.,McLaughlin, Maureen A.,Melcher, Laura M.,Nadler, William R.,Oliver, Patricia A.,Parekh, Shyamal I.,Patel, Hemant H.,Seif, Louis S.,Staeger, Mike A.,Wayne, Gregory S.,Wittenberger, Steven J.,Zhang, Weijiang
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supporting information
p. 897 - 902
(2013/09/03)
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- Synergistic compositions for the selective control of tumor tissue
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According to the invention, compositions are made available which have a strong cytotoxic effect which is largely selective on tumor tissue. The invention is based on the fact that certain benzoic acid derivatives have a strong synergistic effect as a mixture and destroy cancer cells selectively in a pH range of 7 or below, such as from 6.5 to 7.
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- Synergistically acting compositions for selectively combating tumor tissue
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According to the invention, compositions are made available which have a strong cytotoxic effect which is largely selective on tumor tissue. The invention is based on the fact that certain benzoic acid derivatives have a strong synergistic effect as a mixture and destroy cancer cells selectively in a pH range of 7 or below, such as from 6.5 to 7.
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- Method for orthometalation of a carbocyclic aromatic derivative bearing at least an electron donor group
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The invention concerns a method for orthometalation of a carbocyclic aromatic derivative bearing at least an electron donor group, characterised in that it consists in reacting said carbocyclic aromatic derivative with an efficient amount of at least one alkaline metal in the presence of a compound of formula (I): RX, wherein: R represents a hydrocarbon radical having 1 to 20 carbon atoms which can be a saturated or unsaturated, linear or branched, acyclic aliphatic radical; a saturated or unsaturated, monocyclic or polycyclic cycloaliphatic radical; a saturated or unsaturated, linear or branched aliphatic radical bearing a cyclic substituent; and X represents a bromine or chlorine atom.
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Page column 7-8
(2010/01/31)
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- Directed ortho-metalation, a new insight into organosodium chemistry
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Finely dispersed metallic sodium in combination with an alkyl chloride RCcan replace organolithium reagents in the ortho-metalation of aromatic compounds (see scheme). The in situ generated base is consumed as soon as it is formed, which avoids Wurtz coupling, the usual side reaction, and the handling and storage of highly reactive alkyl sodium bases. Reaction conditions are mild, the reaction is easy to scale up, and the reagents needed are inexpensive.
- Gissot, Arnaud,Becht, Jean-Michel,Desmurs, Jean Roger,Pevere, Virginie,Wagner, Alain,Mioskowski, Charles
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p. 340 - 343
(2007/10/03)
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- A new practical method for regioselective nucleophilic aromatic alkylation of ortho- or para-methoxy-substituted aromatic esters with Grignard reagents
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A new practical method for the regioselective nucleophilic aromatic alkylation of o- or p-methoxy-substituted aromatic carboxylic acids via their triethylcarbinyl ester derivatives by conducting the reactions with alkyl/aryl Grignard reagents in toluene has been developed.
- Kojima, Tomoyuki,Ohishi, Takeshi,Yamamoto, Izumi,Matsuoka, Tatsuomi,Kotsuki, Hiyoshizo
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p. 1709 - 1712
(2007/10/03)
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- The cooperative effect of electrostatic and hydrophobic forces in the complexation of cationic molecules by a water-soluble resorcin[4]arene derivative
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A new water-soluble resorcin[4]arene derivative 4 was synthesized and the complexation of cationic guests in D2O was studied by 1H NMR spectroscopy. A 1:1 binding mode was elucidated by a Job's plot. The cooperative effect of electrostatic and hydrophobic interactions acts as a binding force for a strong complex formation with appropriate cationic guests in water. The thermodynamic parameters of complexation of guest I determined by a van't Hoff plot indicate that the complexation process is both enthalpically and entropically driven. (C) 2000 Elsevier Science Ltd.
- Park,Hong
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p. 8311 - 8315
(2007/10/03)
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- An efficient and general method for ester hydrolysis on the surface of silica gel catalyzed by indium triiodide under microwave irradiation
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Carboxylic esters are hydrolyzed to the corresponding carboxylic acids in high yields through a simple microwave assisted operation on the surface of silica gel moistened with few drops of water in presence of indium triiodide.
- Ranu,Dutta,Sarkar
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p. 4167 - 4171
(2007/10/03)
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- UNEXPECTED HYDROLYSIS OF 5-AMINOISOXAZOLBENZOYLAMIDE HERBICIDE ISOXABEN INTO 5-ISOXAZOLINONE
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The benzoylamide derivative of 5-aminoisoxazol, i.e. the herbicide isoxaben 1 (N--2,6-dimethoxybenzamide) was transformed by aqueous acid hydrolysis into the unexpected 5-isoxazolinone 3 (3-(1-ethyl-1-methylpropyl)isoxazolin 5-one) plus mainly 2,6-dimethoxybenzamide 4.The expected 5-aminoisoxazol 7 (5-amino-3-(1-ethyl-1-methylpropyl)isoxazol) was not generated, except in very low amounts when high acid concentrations were used.In separate hydrolysis trials made in similar aqueous acid conditions, it was observed that the 5-aminoisoxazol 7 and 5-isoxazolinone 3 were not transformed.The 5-isoxazolinone 3 formed by isoxaben 1 acid hydrolysis thus was the first generated product, and was not formed by the consecutive nucleophilic substitution of 5-aminoisoxazol 7 which would have been formed in a first step.This unexpected 5-amino C-N bond cleavage by nucleophilic attack of H2O at the 5-C of the isoxazol ring of isoxaben 1 -instead of the usual amide CO-N bond cleavage- probably is due to the positive charge existing at the 5-C atom of the isoxazol ring.The acid hydrolysis pathway observed for isoxaben 1 also is the main soil metabolism pathway.The absence of formation of an aromatic amino compound by chemical hydrolysis reduces the concern as to their potential transformation into carcinogenic nitroso or azo compounds in soil.On the other hand, isoxaben 1 was not hydrolyzed in aqueous dilute alkali.
- Rouchaud, J.,Gustin, F.,Moulard, C.,Plisnier, M.
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p. 557 - 564
(2007/10/02)
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- A new method for hydrolyzing 2-aryl-4,4-dimethyl-2-oxazolines to aryl carboxylic acids
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A method of hydrolyzing 2-aryl-4,4-dimethyl-2-oxazolines with trifluoromethanesulfonic anhydride is described which works well even for highly hindered systems where alternate methods fail.
- Phillion,Pratt
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- Regioselective Reductive Electrophilic Substitution of 1,2,3-Trimethoxybenzene and Its 5-Alkyl-Substituted Homologues
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The methoxy group in the 2-position of 1,2,3-trimethoxybenzene (1) can be regioselectively removed by electron transfer from alkali metals and replaced with a variety of electrophiles in a one-pot procedure, affording 2-substituted resorcinol dimethyl ethers.The usefulness of this synthetic method is illustrated by numerous examples.This reaction procedure has been successfully extended to the 5-methyl-substituted homologue (2), but limitations occur with the higher homologue 1-pentyl-3,4,5-trimethoxybenzene (3).Investigations on the mechanism of demethoxylation, with the aid of labeling experiments, provided clear evidence for the intermediacy of aryl radicals and explained the low yields obtained in the reductive electrophilic substitution of compound 3.
- Azzena, Ugo,Denurra, Teresa,Melloni, Giovanni,Piroddi, Anna Maria
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p. 5386 - 5390
(2007/10/02)
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- Steric Enhancement of Resonance-Evidence from Kinetic Study on some Acetophenones
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The kinetics of oxidation of some mono-, di- and tri-substituted acetophenones by alkaline hexacyanoferrate(III) in 50percent (v/v) methanol-water mixture at constant ionic strength and at 20, 30 and 40 deg have been studied spectrophotometrically and the rate constants determined by least-squares analysis.Electron-withdrawing groups in the ring facilitate the oxidation of the acetyl function while electron-releasing groups retard the rate.The rate constant values for the oxidation of 3-substituted-4-alkoxy-acetophenones are computed based on the principle of additivity of group effects.The observed rate constants are significantly lower than the calculated values.This is attributed to the phenomenon of steric enhancement of resonance (SER). 3,5-Disubstituted-4-methoxyacetophenones have higher observed rate constant values than the calculated ones.The steric inhibition of resonance (SIR) operates in these systems.In the case of 3-halogeno-4-methoxyacetophenones, the importance of SER increases with increase in the bulkiness of the 3-substituents.The difference between the calculated and observed multiple substituent constants of 3-substituted-4-methoxyacetophenones also lends support for SER.
- Pillay, M. Krishna,Palanivelu, S.
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p. 1055 - 1059
(2007/10/02)
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- THE DIPHENYLMAFNESIUM/ALKALI METAL ALKOXIDE SYSTEM. HYDROCARBON-SOLUBLE ORGANOALKALI METAL REAGENTS
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Unsolvated diphenylmagnesium is solubilized in aromatic hydrocarbon solvents by an alkali metal 2-ethoxyethoxide.The mode of interaction between Ph2Mg and MOCH2CH2OEt (M=Li, Na, K) varies with M.For M=Li the complex formed has an Mg/Li ratio equal to 1.3/1.0, and is evidently different from the PhLi/Mg(OCH2CH2OEt) complex.For M=Na the metal-metal interchange apparently leads to a complex identical to thaht derived from PhNa and Mg(OCH2CH2OEt).For M=K the results are not conclusive.The width of the resonance 13C from the ipso-carbon, increases with increasing ionic radius, and for M=K the signal is too broad to be clearly observed .The ipso-carbon in the NMR spectrum of the PhNa/Mg(OCH2CH2OEt) complex has now been shown to give rise to resonance at 175.95 ppm.Metalation experiments involving Ph2Mg along with two equivalents of MOCH2CH2OEt indicated that reactivity increases in the order Li Na K.
- Screttas, Constantinos G.,Micha-Screttas, Maria
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- METALATION REACTIONS. VI. STERIC LIMITS IN THE PREPARATION OF 1,2,3-TRI-SUBSTITUTED BENZENE DERIVATIVES
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Metalation of 1,3-dialkoxy-, 1-alkoxy-3-(alkylthio)- and 1,3-bis-(alkylthio)-benzenes with n-butyllithium has been examined to verify the possibility of preparing 1,2,3-tri-substituted benzene derivatives.The reaction is affected by steric hindrance.The yields of the metalation in the position ortho to both the substituents decrease as steric requirement increases becoming zero when the bulk of both the alkyl substituent and the hetero-atom is increased.It has been shown that synthesis of 1,2,3-tri-substituted derivatives by this route is feasible only with small substituents.
- Cabiddu, Salvatore,Maccioni, Antonio,Piras, Pier Paolo,Plumitallo, Antonio
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p. 123 - 128
(2007/10/02)
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