Fries Rearrangement Research Articles

FTIR analysis on aging characteristics of ABS/PC blend under UV-irradiation in air

Fourier Transform Infrared Spectroscopy (FTIR) is adopted to study the aging characteristics of poly(acrylonitrile–butadiene–styrene)/polycarbonate (ABS/PC) blend under UV-irradiation in air by analyzing the variation of the three main absorbance at about 967cm−1, 1720cm−1 and 3420cm−1 associated with carbon-hydrogen bonds belonging to 1,4 butadiene, carbonyl and hydroxyl groups, respectively. Results indicate that, under UV-irradiation in air, the photo-oxidation of the blend is not a simple combination of the photo-oxidation of corresponding ABS and PC themselves and takes place predominantly at the ABS component. Due to the interaction between the two components and the Fries rearrangement taken place in the PC component during the UV-irradiation in air, the ABS/PC blends behave higher photo-stability than ABS has.

The photochemical behavior of polyhydroxy styrene with azofragments containing free methacrylic double bounds

ABSTRACTPolymer material which combines advantages of photoaligning azo-compounds with thermal stability of the induced anisotropy provided by free methacryloyl groups was synthesised. FTIR spectroscopy was employed for clarification its photochemical behavior. Two Fries rearrangements in arylester groups and photoinitiated cross-linking in methacryloyl functional groups were established after the action of UV-irradiation.

Bismuth(III) triflate catalyzed tandem esterification–Fries–oxa-Michael route to 4-chromanones

An efficient tandem reaction approach is described to prepare 4-chromanones from electron-rich phenols and 3,3-dimethylacrylic acid or trans-crotonic acid in boiling toluene using 20mol% bismuth(III) triflate as the catalyst. The reaction is also successful from the corresponding aryl esters of each of these acids under the same conditions. The procedure is convenient to perform, and 25–90% yields of products are realized following chromatography. A range of substrates is included (14 substrates for each acid) to help define the scope of the process. Additional experiments are reported, which confirm that the sequence of events involves (1) esterification, (2) Fries rearrangement and (3) oxa-Michael ring closure.

Acid generation by 1,4-bis(phenylsulfonyloxy)benzene and their photochemical mechanism

Photochemical studies on 1,4-bis(phenylsulfonyloxy)benzene were performed in acetonitrile by steady-state photolysis at 254 nm. Analysis of photoproducts demonstrate that 1,4-bis(phenylsulfonyloxy)benzene undergoes S–O cleavage leading to the formation of phenylsulfonyl radical and phenylsulfonyloxyphenoxy radical which result in the formation of Fries rearrangement products or escape from the solvent cage to undergo further transformations. The involvement of triplet state in the photo-Fries rearrangement was detected. During the irradiation process, a large amount of acidic species were observed and the formation of benzenesulfonic acid was confirmed. Involvement of O2 in the acid generation was proved to be a primary pathway by comparative experiments. Another pathway of acid generation could be explained as a result of disproportionation of sulfonyl radicals due to the formation of thiobenzenesulfonate. The quantification of the acid was determined by the acid–base titration and investigation on steady-state photolysis was carried out by HPLC analysis and GC–MS.

Naphthacenodithiophene Based Polymers—New Members of the Acenodithiophene Family Exhibiting High Mobility and Power Conversion Efficiency

Wide‐bandgap conjugated polymers with a linear naphthacenodithiophene (NDT) donor unit are herein reported along with their performance in both transistor and solar cell devices. The monomer is synthesized starting from 2,6‐dihydroxynaphthalene with a double Fries rearrangement as the key step. By copolymerization with 2,1,3‐benzothiadiazole (BT) via a palladium‐catalyzed Suzuki coupling reaction, NDT‐BT co‐polymers with high molecular weights and narrow polydispersities are afforded. These novel wide‐bandgap polymers are evaluated as the semiconducting polymer in both organic field effect transistor and organic photovoltaic applications. The synthesized polymers reveal an optical bandgap in the range of 1.8 eV with an electron affinity of 3.6 eV which provides sufficient energy offset for electron transfer to PC70BM acceptors. In organic field effect transistors, the synthesized polymers demonstrate high hole mobilities of around 0.4 cm2 V–1 s–1. By using a blend of NDT‐BT with PC70BM as absorber layer in organic bulk heterojunction solar cells, power conversion efficiencies of 7.5% are obtained. This value is among the highest obtained for polymers with a wider bandgap (larger than 1.7 eV), making this polymer also interesting for application in tandem or multijunction solar cells.

ChemInform Abstract: Submillisecond Organic Synthesis: Outpacing Fries Rearrangement Through Microfluidic Rapid Mixing.

AbstractA microfluidic technique that outpaces the very rapid anionic Fries rearrangement to chemoselectively functionalize iodophenyl carbamates at the ortho position is reported.

Synthesis and evaluation of anticancer activity of 6-pyrazolinylcoumarin derivatives

A series of novel 6-pyrazolinylcoumarins has been synthesized via multi-step protocol. The synthetic procedure was based on the acetylation of hydroxycoumarins; Fries rearrangement and Claisen–Schmidt condensation; the target 6-[5-aryl-4,5-dihydropyrazol-3-yl]-5-hydroxy-7-methylcoumarins (33–49) were obtained under reactions of hydrazine and 2-aryl-5-methyl-2,3-dihydropyrano[2,3-f]chromen-4,8-diones as the last phase of the protocol. Anticancer activity screening in NCI60-cell lines assay allowed identification of compound 47 with the highest level of antimitotic activity with mean GI50 value of 10.20μM and certain sensitivity profile toward the Leukemia cell lines CCRF-CEM and MOLT-4 (GI50/TGI values 1.88/5.06μM and 1.92/4.04μM respectively).

Submillisecond organic synthesis: Outpacing Fries rearrangement through microfluidic rapid mixing.

In chemical synthesis, rapid intramolecular rearrangements often foil attempts at site-selective bimolecular functionalization. We developed a microfluidic technique that outpaces the very rapid anionic Fries rearrangement to chemoselectively functionalize iodophenyl carbamates at the ortho position. Central to the technique is a chip microreactor of our design, which can deliver a reaction time in the submillisecond range even at cryogenic temperatures. The microreactor was applied to the synthesis of afesal, a bioactive molecule exhibiting anthelmintic activity, to demonstrate its potential for practical synthesis and production.

Nucleophilic Aromatic Substitution Reactions for the Synthesis of Ferrocenyl Aryl Ethers

A range of ferrocenyl aryl ethers of type Fc–O–Ar (Fc = Fe(η5-C5H5)(η5-C5HnX4–n); n = 2–4; X = H, P(O)(OEt)2, SO2CF3; Ar = 2,4-(NO2)2-C6H3, 4-NO2-C6H4) have been successfully prepared by using the nucleophilic aromatic substitution reaction (SNAr) of Fc–OLi (1a–Li) and electron-deficient aryl fluorides, enabling a new pathway to this rarely described family of organometallic compounds. Initial studies of 1a–Li and o-phosphonato-substituted hydroxyferrocenes (1b–Li) have also been performed, indicating a low nucleophilicity of the oxygen atom. The SNAr reaction protocol tolerates ortho substituents, e.g. phosphonato and sulfonyl groups, resulting in 1,2-X,O (X = S, P) ferrocenyl ethers that can be obtained in a one-pot synthesis procedure including 1,3-O → C anionic phospho- and thia-Fries rearrangements. Within these studies, the first 1,3-diortho-functionalized ferrocenyl aryl ether could be synthesized. An electrochemical study of the redox potentials of the obtained compounds allows conclusions on the reactivity of the varying electronic properties and the electrophilicity of different aryl fluorides and the nucleophilicity of the functionalized hydroxyl ferrocenes, which is directly reflected by the potential of the first ferrocene related redox processes. Chiral-pool-based phosphonates rearrange to the aryl ethers with diastereomeric excesses of 74 and 81% after the anionic Fries rearrangement. The usage of aryl 1,2-/1,3-difluorides resulted in the synthesis of the first examples of bis(FcO)-substituted benzenes. Their electrochemical investigations reveal a splitting of the two redox processes of the ferrocenyls that decreases from 155 mV (1,2-substitution) to 130 mV (1,3-substitution) on the basis of electrostatic interactions.

ChemInform Abstract: Alternative Routes to the Acylphloroglucinol Rhodomyrtone.

Two novel routes to the acylphloroglucinol rhodomyrtone (1) which has antibiotic properties are presented. In the first route an ortho-quinone methide, generated from dioxaborinine 23, is reacted with syncarpic acid (10) leading to xanthenedione 25. Cleavage of the methyl ether functions led to the known rhodomyrtone precursor 16. In the second route the bis-ester derivative 28 of trihydroxybenzaldehyde 26 is condensed with syncarpic acid (10) to give tricyclic hemiacetal 29. Acetalization and cuprate addition to the enone function led to bis-ester 32 which gave rhodomyrtone (1) by TiCl4-induced regioselective Fries rearrangement.

Zeolite Catalysts for Phenol Benzoylation with Benzoic Acid: Exploring the Synthesis of Hydroxybenzophenones

In this paper, we report on the reaction of phenol benzoylation with benzoic acid, which was carried out in the absence of solvent. The aim of this reaction is the synthesis of hydroxybenzophenones, which are important intermediates for the chemical industry. H-beta zeolites offered superior performance compared to H-Y, with a remarkably high conversion of phenol and high yields to the desired compounds, when using a stoichiometric amount of benzoic acid. It was found that the reaction mechanism did not include the intramolecular Fries rearrangement of the primary product phenyl benzoate, but indeed, the bimolecular reaction between phenyl benzoate and phenol mainly contributed to the formation of hydroxybenzophenones. The product distribution was greatly affected by the presence of Lewis-type acid sites in H-beta; it was suggested that the interaction between the aromatic ring and the electrophilic Al3+ species led to the preferred formation of o-hydroxybenzophenone, because of the decreased charge density on the C atom at the para position of the phenolic ring. H-Y zeolites were efficient than H-beta in phenyl benzoate transformation into hydroxybenzophenones.

Alternative routes to the acylphloroglucinol rhodomyrtone

Two novel routes to the acylphloroglucinol rhodomyrtone (1) which has antibiotic properties are presented. In the first route an ortho-quinone methide, generated from dioxaborinine 23, is reacted with syncarpic acid (10) leading to xanthenedione 25. Cleavage of the methyl ether functions led to the known rhodomyrtone precursor 16. In the second route the bis-ester derivative 28 of trihydroxybenzaldehyde 26 is condensed with syncarpic acid (10) to give tricyclic hemiacetal 29. Acetalization and cuprate addition to the enone function led to bis-ester 32 which gave rhodomyrtone (1) by TiCl4-induced regioselective Fries rearrangement.

Synthesis of 8-Bromoflavone and Its Buchwald–Hartwig Reaction with Amines

Simple and convenient synthesis of 8-bromoflavone was achieved, starting from 2-bromophenol through 3′-bromo-2′-hydroxyacetophenone whose preparation was managed to be solved by optimized Fries rearrangement. The Buchwald–Hartwig reaction of 8-bromoflavone with different type of primary and secondary amines was carried out.

Synthesis and characterization of monoaryl esters of l-tartaric acid and their process for fries rearrangement

Chiral protected monoaryl esters (2a–2h) were synthesized from monoester of l-tartaric acid, having two asymmetric centers and C2 axis of symmetry. l-tartaric acid was protected and partially hydrolyzed to give the corresponding monoester. Monoester upon treatment with different substituted phenols gave desired monoaryl esters (2a–2h). Fries rearrangement of monoaryl esters was then tried under various conditions by using different Lewis acids. All the compounds were purified and characterized by using spectroscopic techniques like IR, 1H-NMR, 13C-NMR, HRMS-ESI, and elemental analysis. The structure of compound 2e was obtained by X-ray crystallography.

ChemInform Abstract: Lithiation of a Silyl Ether: Anionic Si→C Alkyl Migration

AbstractReview: [10 refs.

Regioselective Friedel–Crafts acylation of calix[4]arenes

Friedel–Crafts acylation of 25,27-dialkoxycalix[4]arenes has been studied. Direct acylation of de-tert-butylated calixarene using acyl chlorides and AlCl3 in 1,2-dichloroethane provided the corresponding diacyl derivatives regioselectively in high yields. Furthermore, ipso-substitution in the tert-butylated series under the same reaction conditions is possible, albeit in lower yields. As indicated by the unsuccessful application of this chemistry to O-acyl derivatives, the ipso-acylation reaction of calix[4]arenes proceeds by direct attack at the upper rim and not by a Fries rearrangement mechanism.

Aryne generation vs. Truce-Smiles and fries rearrangements during the Kobayashi fragmentation reaction: a new bi-aryl synthesis.

Treatment of (ortho-trimethysilyl)aryl phenylsulfonates with a soluble fluoride source initiates a Truce-Smiles rearrangement leading to the formation of functionalized bi-aryls. This new carbon-carbon bond-forming reaction proceeds without recourse to transition metal catalysis, under mild reaction conditions and with good functional group compatibility.

Synthesis and Antimicrobial Activity of Some New Chalcones Containing Benzofuran and Benzofuran Schiff Bases

Benzofuran nucleus frequently occurs in natural products. In the present course of study an attempt is made for synthesis of new Benzofuran derivatives. 5-chloro-2-hydroxy acetophenone 2 was prepared by the Fries rearrangement with anhydrous aluminium chloride at 1300c for 3 hrs. The compound 2 was treated with chloroacetone in presence of anhydrous acetone and potassium carbonate gave 5-chloro-3-methyl-2-acetyl Benzofuran 3. Compound 3 underwent condensation with aromatic aldehyde and aromatic amines to furnished chalcone and Schiff derivatives 4a-e and 5a-e respectively. The synthesized compounds were screened for their antimicrobial activities.

Submicron ZnO raspberries as effective catalysts for Fries rearrangement

Water/o-xylene interface offers a viable platform for the synthesis of raspberry-like ZnO microstructures that act as environmentally benign catalysts for Fries rearrangement.

Lithiation of a Silyl Ether: Anionic Si→C Alkyl Migration

This article describes a new synthetic utility of silyl ethers, the lithiation of which leads to an alkyl group migration from the silyl ether to the carbonyl group of the amide in the ortho position, forming a ketone. Additionally, the combination of the well-established anionic Fries rearrangement of lithiated carbamates to give hydroxyamides is discussed herein.