151-10-0Relevant articles and documents
Enantioselective total synthesis of (-)-blennolide A
Tietze, Lutz F.,Ma, Ling,Reiner, Johannes R.,Jackenkroll, Stefan,Heidemann, Sven
, p. 8610 - 8614 (2013)
Blennolide A can be synthesized through an enantioselective domino-Wacker/carbonylation/methoxylation reaction of 7 a with 96 % ee and an enantioselective Wacker oxidation of 7 b with 89 % ee. Further transformations led to the α,β-unsaturated ester (E)-17, which was subjected to a highly selective Michael addition, introducing a methyl group to give 18 a. After a threefold oxidation and an intramolecular acylation, the tetrahydroxanthenone 4 was obtained, which could be transformed into (-)-blennolide A (ent-1) in a few steps. Domino effect: An enantioselective domino-Wacker/carbonylation/methoxylation process and an enantioselective Wacker oxidation are the key steps in the first total synthesis of the fungal metabolite blennolide A (see scheme). Copyright
Facile C-S Bond Cleavage of Aryl Sulfoxides Promoted by Bronsted Acid
Brutiu, Bogdan R.,Klose, Immo,Maulide, Nuno
, p. 488 - 490 (2021)
A method for the Bronsted acid promoted desulfination of aryl sulfoxides is presented. In the presence of a thiol, electron-rich sulfoxides undergo C-S bond cleavage to give the corresponding protodesulfinated arenes and disulfides.
Carbon Kinetic Isotope Effects and the Mechanisms of Acid-Catalyzed Decarboxylation of 2,4-Dimethoxybenzoic Acid and CO2 Incorporation into 1,3-Dimethoxybenzene
Vandersteen, Adelle A.,Howe, Graeme W.,Sherwood Lollar, Barbara,Kluger, Ronald
, p. 15049 - 15053 (2017)
The rate of decarboxylation of 2,4-dimethoxybenzoic acid (1) is accelerated in parallel to the extent that the carboxyl group acquires a second proton (1H+). However, the conjugate acid would resist C-C bond breaking as that would lead to formation of doubly protonated CO2. An alternative via formation of a higher-energy protonated phenyl tautomer (2H+) prior to C-C bond breaking would produce protonated CO2, an energetically inaccessible species that can be avoided by transfer of the carboxyl proton to water in the same step. Headspace sampling of CO2 that evolves in the acid-catalyzed process and analysis by GC-IRMS gives a smaller than expected value of 1.022 for the carbon kinetic isotope (CKIE), k12/k13. While this value establishes that C-C cleavage is part of the rate-determining process, intrinsic CKIEs for decarboxylation reactions are typically greater than 1.03. Computational analysis of the C-C bond cleavage from 2H+ gives an intrinsic CKIE of 1.051 and suggests two partially rate-determining steps in the decarboxylation of 1: transfer of the second carboxyl proton to the adjacent phenyl carbon and C-C cleavage in which the carboxyl proton is also transferred to water. Applying the principle of microscopic reversibility to fixation of CO2 in acidic solutions reveals the importance of proton transfers to both carbon and oxygen in the overall fixation process.
The molecular and electronic structure of octahedral tris(phenolato)iron(III) complexes and their phenoxyl radical analogues: A Mossbauer and resonance Raman spectroscopic study
Snodin, Michael D.,Ould-Moussa, Lynda,Wallmann, Ursula,Lecomte, Sophie,Bachler, Vinzenz,Bill, Eckhard,Hummel, Helga,Weyhermueller, Thomas,Hildebrandt, Peter,Wieghardt, Karl
, p. 2554 - 2565 (1999)
Hexadentate macrocyclic ligands containing a 1,4,7-triazacyclononane backbone and three N-bound pendent-arm phenolares form extremely stable neutral complexes with Fe(III)Cl3. The octahedral complexes [Fe(III)L] undergo three reversible one-electron oxidation processes to yield the mono- and dications, [FeL]+ and [FeL]2+, which are stable in solution for hours, whereas the trications, [FeL]3+, are only stable in solution on the time scale of a cyclic voltammetric experiment. These oxidations are shown to be ligand- rather than metal-centered. Three coordinated phenoxyl radicals are formed successively as shown conclusively by Mossbauer spectroscopy. The neutral, mono-, di-, and tricationic species each contain an octahedral, high-spin ferric ion (S(Fe) = 5/2), which is intramolecularly, antiferromagnetically coupled to the spin (S = 1/2 ) of the bound phenoxyl ligands to yield an S(t) = 2 ground state for the monocation, and an S(t) = 3/2 ground state for the dications as shown by EPR spectroscopy. The vibrations of the coordinated phenolate are observed by resonance Raman (RR) spectroscopy by excitation in resonance with the phenolate-to-iron charge- transfer (CT) transition above 500 nm or, alternatively, of the coordinated phenoxyl by excitation in resonance with the intraligand π → π* transition at about 410 nm. Use of 18O isotopomers selectively labeled at the phenolic oxygen allowed the identification of the C-O stretching and Fe-O stretching and bending modes. It is shown that the substitution pattern of phenolates and phenoxyls in their respective ortho and para positions and the charge of the complexes have a pronounced influence on the vibrational modes observed.
Polyfuryl(aryl)alkanes and their derivatives. 12. C-fur bond cleavage in the series of polyfuryl(aryl)alkanes
Butin,Stroganova,Kul'nevich
, p. 153 - 157 (1996)
Reactions taking place with cleavage of the C-Fur bond are examined. It was established that disproportionation in two directions, leading to the formation of tris(5-methyl-2-furyl)methane, takes place when 3,4-dimethoxyphenylbis(5-methyl-2-furyl)methane is boiled in an acidic medium. The acid-catalyzed reaction of 5-methylfurfural with ethylene glycol leads to the formation of either 2-(5-methyl-2-furyl)-1,3-dioxolane or tris(5-methyl-2-furyl)methane, depending on the catalyst. The treatment of 2-(5-methyl-2-furyl)-1,3-dioxolane or gemtris(5·methyl-2-furyl)ethane with trityl perchlorate leads to tris(5-methyl-2-furyl)carbenium or bis(5-methyl-2-furyl)methylcarbenium perchlorates respectively. 1996 Plenum Publishing Corporation.
Hollow, mesoporous, eutectic Zn1?xMgxO nano-spheres as solid acid-base catalysts for the highly regio-selectiveO-methylation of 1,2-diphenols
Liu, Jie,Ma, Xuebing,Wang, Xuri,Xie, Guangxin,Yin, Zuyong,Zhang, Jianing
, p. 7454 - 7466 (2021/11/23)
The highly regio-selectiveO-methylation of catechol with dimethyl carbonate (DMC), catalyzed by a solid acid-base catalyst, is an environmentally friendly chemical process for industrial production of guaiacol. However, a guaiacol yield below 84% and high reaction temperature above 280 °C limit its industrial application. Here, hollow, mesoporous Zn1?xMgxO nano-spheres with a eutectic structure, denoted as Zn1?xMgxO HMNSs (x= 0.012-0.089), are facilely fabricatedviathe calcination of Mg2+/Zn2+ion-adsorbing carbon spheres at 500 °C in air. In theO-methylation of catechol with DMC at 180 °C, Zn1?xMgxO HMNSs (x= 0.052) afford guaiacol in 95.5% yield with a complete catechol conversion. Furthermore, 89.0-95.3% mono-ether yields with high 1,2-diphenol conversions (94.5-100%) are also obtained for the other 1,2-diphenols bearing -CH3and -Br groups. Moreover, a plausible mechanism for highly selectiveO-methylation of catechol with DMC is proposed, in which the single-site activation and double-site activation of phenolic hydroxyls by the basic oxygen of Mg-O afford guaiacol and veratrole, respectively.
Catalytic SNAr Hydroxylation and Alkoxylation of Aryl Fluorides
Kang, Qi-Kai,Li, Ke,Li, Yuntong,Lin, Yunzhi,Shi, Hang,Xu, Lun
supporting information, p. 20391 - 20399 (2021/08/13)
Nucleophilic aromatic substitution (SNAr) is a powerful strategy for incorporating a heteroatom into an aromatic ring by displacement of a leaving group with a nucleophile, but this method is limited to electron-deficient arenes. We have now established a reliable method for accessing phenols and phenyl alkyl ethers via catalytic SNAr reactions. The method is applicable to a broad array of electron-rich and neutral aryl fluorides, which are inert under classical SNAr conditions. Although the mechanism of SNAr reactions involving metal arene complexes is hypothesized to involve a stepwise pathway (addition followed by elimination), experimental data that support this hypothesis is still under exploration. Mechanistic studies and DFT calculations suggest either a stepwise or stepwise-like energy profile. Notably, we isolated a rhodium η5-cyclohexadienyl complex intermediate with an sp3-hybridized carbon bearing both a nucleophile and a leaving group.
Methylation with Dimethyl Carbonate/Dimethyl Sulfide Mixtures: An Integrated Process without Addition of Acid/Base and Formation of Residual Salts
Chan, Bun,Lui, Matthew Y.,Lui, Yuen Wai
, (2022/01/08)
Dimethyl sulfide, a major byproduct of the Kraft pulping process, was used as an inexpensive and sustainable catalyst/co-reagent (methyl donor) for various methylations with dimethyl carbonate (as both reagent and solvent), which afforded excellent yields of O-methylated phenols and benzoic acids, and mono-C-methylated arylacetonitriles. Furthermore, these products could be isolated using a remarkably straightforward workup and purification procedure, realized by dimethyl sulfide‘s neutral and distillable nature and the absence of residual salts. The likely mechanisms of these methylations were elucidated using experimental and theoretical methods, which revealed that the key step involves the generation of a highly reactive trimethylsulfonium methylcarbonate intermediate. The phenol methylation process represents a rare example of a Williamson-type reaction that occurs without the addition of a Br?nsted base.
Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
, p. 4685 - 4696 (2021/07/12)
Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
Method for synthesizing M-hydroxyanisole
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Paragraph 0032-0033; 0052-0053; 0056-0057; 0060-0063, (2021/11/03)
The invention provides a method for synthesizing M-hydroxyanisole. Belong to organic synthesis technical field. The synthesis method comprises the following steps: a vapor phase mixture of resorcinol and methanol is subjected to alkylation reaction through a metal phosphate - alumina fixed phase catalyst to obtain m-hydroxyanisole. The method adopts the gas-solid phase alkylation method to synthesize the M-hydroxyanisole without separating the reaction product from the catalyst, has the characteristic of continuous reaction, and can realize continuous production in the industrial production process. The method utilizes the acid-base catalytic activity center on the surface of the stationary phase catalyst to catalyze the reaction of resorcinol and methanol, and has high resorcinol conversion rate. The method has the advantage of high selectivity of m-hydroxyanisole. Methanol is used as a methylation reagent, and the method is environmentally friendly, low in cost and high in economic benefit.
