cas 4265-25-2, 2-Methylbenzofuran | Articles data

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Highly Efficient Synthesis of 2-Substituted Benzo[ b ]furan Derivatives from the Cross-Coupling Reactions of 2-Halobenzo[ b ]furans with Organoalane Reagents
A highly efficient and simple route for the synthesis of 2-substituted benzo[ b ]furans has been developed by palladium-catalyzed cross-coupling reaction of 2-halobenzo[ b ]furans with aryl, alkynyl, and alkylaluminum reagents. Various 2-aryl-, 2-alkynyl-, and 2-alkyl-substituted benzo[ b ]furan derivatives can be obtained in 23-97% isolated yields using 2-3 mol% PdCl 2/4-6 mol% XantPhos as the catalyst under mild reaction conditions. The aryls bearing electron-donating or electron-withdrawing groups in 2-halobenzo[ b ]furans gave products in 40-97% isolated yields. In addition, aluminum reagents containing thienyl, furanyl, trimethylsilanyl, and benzyl groups worked efficiently with 2-halobenzo[ b ]furans as well, and three bioactive molecules with 2-substituted benzo[ b ]furan skeleton were synthesized. Furthermore, the broad substrates scope and the typical maintenance of vigorous efficiency on gram scale make this protocol a potentially practical method to synthesize 2-substituted benzo[ b ]furan derivatives. On the basis of the experimental results, a possible catalytic cycle has been proposed.
Wen, Chang,Wu, Chuan,Luo, Ruiqiang,Li, Qinghan,Chen, Feng
p. 3847 - 3861
(2021/07/02)

Enantio- and Diastereoselective, Complete Hydrogenation of Benzofurans by Cascade Catalysis
We report an enantio- and diastereoselective, complete hydrogenation of multiply substituted benzofurans in a one-pot cascade catalysis. The developed protocol facilitates the controlled installation of up to six new defined stereocenters and produces architecturally complex octahydrobenzofurans, prevalent in many bioactive molecules. A unique match of a chiral homogeneous ruthenium-N-heterocyclic carbene complex and an in situ activated rhodium catalyst from a complex precursor act in sequence to enable the presented process.
Gallagher, Timothy,Glorius, Frank,Hu, Tianjiao,Moock, Daniel,Wagener, Tobias
supporting information
p. 13677 - 13681
(2021/05/10)

Synthesis of Chiral Polycyclic Tetrahydrocarbazoles by Enantioselective Aminocatalytic Double Activation of 2-Hydroxycinnamaldehydes with Dienals
An efficient aminocatalytic enantioselective double-activation strategy has been developed that combines several different aminocatalytic modes in a cascade process, such as iminium ion, vinylogous iminium ion, trienamine, and dienamine activations. By using this strategy, 2-hydroxycinnamaldehydes worked well with various dienals via [4 + 2] cycloaddition and the oxa-Michael reaction-initiated cascade, respectively, leading to chiral polycyclic tetrahydrocarbazole and chromane derivatives with excellent diastereo- and enantioselectivities.
Ming, Yong-Chao,Lv, Xue-Jiao,Liu, Ming,Liu, Yan-Kai
supporting information
p. 6515 - 6519
(2021/09/02)

Discovery of orthogonal synthesis using artificial intelligence: Pd(OAc)2-catalyzed one-pot synthesis of benzofuran and bicyclo[3.3.1]nonane scaffolds
A synthetic route for the common intermediate, methyl 2-formylbenzofuran-7-carboxylate (7a), to efficiently assemble three bioactive benzofurans 4–6 was explored using the artificial intelligence system SYNSUP. Among the routes proposed by SYNSUP, we investigated a three-step synthesis of 7a using methyl 4-ally-3-oxohept-6-enoate (10). A new catalytic reaction was found in which 7a was directly obtained from 10 in a single step with a yield of 24percent. It was found that this chemical yield could be increased to 74percent when methyl 3-allyl-2-hydroxybenzoate (9a), an intermediate of the above one-pot transformation, was subjected to the catalytic process. In addition, in this catalytic process, 8a (76percent) and 11 (77percent) were each selectively synthesized from 10 by changing only the solvent. Therefore, we created a novel orthogonal synthesis of methyl 2-methylbenzofuran-7-carboxylate (8a) and methyl 9-oxobicyclo[3.3.1]nona-3,6-diene-1-carboxylate (11). Finally, the total syntheses of bioactive benzofurans 4–6 were completed smoothly using 7a and 8a.
Takabatake, Tetsuhiko,Fujiwara, Keisuke,Okamoto, Sho,Kishimoto, Ryo,Kagawa, Natsuko,Toyota, Masahiro
(2020/08/10)

A methylation platform of unconventional inert aryl electrophiles: Trimethylboroxine as a universal methylating reagent
Methylation is one of the most fundamental conversions in medicinal and material chemistry. Extension of substrate types from aromatic halides to other unconventional aromatic electrophiles is a highly important yet challenging task in catalytic methylation. Disclosed herein is a series of transition metal-catalyzed methylations of unconventional inert aryl electrophiles using trimethylboroxine (TMB) as the methylating reagent. This transformation features a broad substrate type, including nitroarenes, benzoic amides, benzoic esters, aryl cyanides, phenol ethers, aryl pivalates and aryl fluorides. Another important merit of this work is that these widespread "inert"functionalities are capable of serving as directing or activating groups for selective functionalization of aromatic rings before methylation, which greatly expands the connotation of methylation chemistry.
Feng, Boya,Yang, Yudong,You, Jingsong
p. 6031 - 6035
(2020/07/10)

A light triggered optical and chiroptical switch based on a homochiral Eu2L3helicate
Optical and chiroptical photoswitches have found potential applications in advanced information technologies. Herein, a pair of chiral triple-stranded helicates [Eu2(o-LRR)3](TOf)6and [Eu2(o-LSS)3](TOf)6, which have chirality, luminescence and light stimuli-responsive properties, have been designed and synthesized. The ligands o-LRR/SSare composed of photochromic diarylethene moieties as spacers and two chiral 2,6-dipicolinic amides as coordination units. Through the comprehensive spectral characteristics in combination with semiempirical geometry optimization using the Sparkle/RM1 model, it was confirmed that (R/S)-1-phenylethanamines decorated at the terminals of ligands successfully controlled the stereoselective self-assembly of the helicates. Upon alternating UV and visible light irradiation, the diarylethene experienced a reversible change between a colorless open-ring state and a pink closed-ring state. This photochromic process caused variations in the electronic structure and ligand conformation, and led to the presence of light-responsive optical (UV and PL) and chiroptical (ECD and CPL) switching properties. The helicate may, therefore, be considered as a completely reversible +/- ECD and on/off CPL switch. Furthermore, on the basis of these light-switchable optical properties, the INHIBIT and IMPLICATION logic gates were fabricated.
Cheng, Zhenyu,Gao, Ting,Li, Hongfeng,Yan, Pengfei,Yao, Yuan,Zhang, Jianpeng,Zhou, Yanyan
p. 6788 - 6796
(2020/06/03)

Rhodium-Catalyzed Intermolecular Cyclopropanation of Benzofurans, Indoles, and Alkenes via Cyclopropene Ring Opening
The generation of metal carbenoids via ring opening of cyclopropenes by transition metals offers a simple entry into highly reactive intermediates. Herein, we describe a diastereoselective intermolecular rhodium-catalyzed cyclopropanation of heterocycles and alkenes using cyclopropenes as carbene precursors with a low loading of a commercially available rhodium catalyst. The reported method is scalable and could be performed with catalyst loadings as low as 0.2 mol %, with no impact to the reaction yield or selectivity.
Jeyaseelan, Rubaishan,Lautens, Mark,Ross, Rachel J.
supporting information

(2020/06/29)

Catalytic Wacker-type Oxidations Using Visible Light Photoredox Catalysis
A combined palladium/photoredox catalytic system for the efficient oxidation of terminal olefins to the corresponding methyl ketones is presented. The interplay of air, water, and light leads to a protocol in which the stoichiometric oxidants required for oxidative palladium catalysis are substituted with catalytic, single-electron transfer processes. Detailed mechanistic investigations revealed the role of the key components, in situ generated species, and catalysts. A broad range of substrates was examined in homogeneous as well as heterogeneous photoredox protocols, delivering the desired products in good yields.
Ho, Yee Ann,Paffenholz, Eva,Kim, Hyun Jin,Orgis, Benjamin,Rueping, Magnus,Fabry, David C.
p. 1889 - 1892
(2019/03/17)

Palladium-Catalyzed Methylation of Aryl, Heteroaryl, and Vinyl Boronate Esters
A method for the direct methylation of aryl, heteroaryl, and vinyl boronate esters is reported, involving the reaction of iodomethane with aryl-, heteroaryl-, and vinylboronate esters catalyzed by palladium and PtBu2Me. This transformation occurs with a remarkably broad scope and is suitable for late-stage derivatization of biologically active compounds via the boronate esters. The unique capabilities of this method are demonstrated by combining carbon-boron bond-forming reactions with palladium-catalyzed methylation in a tandem transformation.
Haydl, Alexander M.,Hartwig, John F.
supporting information
p. 1337 - 1341
(2019/02/26)

Pd-catalyzed intramolecular Heck reaction for the synthesis of 2-methylbenzofurans
A new strategy for the synthesis of 2-Methylbenzofurans via the intramolecular Heck reaction has been developed. This efficient palladium-catalyzed system showed good catalytic activity. Various substituted 2-methylbenzofurans could be afforded in good to excellent yields.
Zhou,Shi, Yuxing,Zhu, Xueyan,Zhang, Peng
p. 2005 - 2008
(2019/07/03)

Preparation method of benzofuran compound
The invention relates to a preparation method of a benzofuran compound. The preparation method comprises the following steps: putting a furan compound, acetic acid and a Lewis acid catalyst in a reaction vessel, reacting for 0.5-24 h at 80-160 DEG C, and separating and purifying to obtain the benzofuran compound. According to the preparation method provided by the invention, the furan compound isused as a reaction raw material, an acetic acid water solution is used as a solvent, Lewis acid is used as a catalyst, and at a mild reaction temperature (80-160 DEG C), the benzofuran compound is directly obtained through one-step reaction. The preparation method provided by the invention can synthesize the benzofuran compound with a corresponding structure and functional groups based on the structure and functional groups of the furan compound as a raw material, the raw material components are simple , and the process is convenient to operate; wherein the selectivity of the obtained benzofuran is as high as 99% in the process of synthesizing benzofuran by using furan, so that the method has industrial application prospects.
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Paragraph 0106-0109

(2019/04/04)

A 2 - substituted benzofuran compound of the catalytic synthesis method
The invention discloses a 2 - substituted benzofuran compound of the catalytic synthesis method, comprises the following steps: normal temperature and pressure, the 2 - alkynyl substituted phenol dissolved in acetonitrile, wherein the 2 - alkynyl substituted phenol with acetonitrile molar volume ratio of 1: 1mmol/mL, to obtain 2 - alkynyl substituted phenol acetonitrile solution; and then to the acetonitrile solution in adding cuprous chloride and cesium carbonate, wherein the cuprous chloride and cesium carbonate of respectively the molar consumption of 2 - alkynyl-substituted phenol mole amount of 5%; after, room temperature stirring 6 hours, produced by the reaction of 2 - substituted benzofuran compound. The invention 2 - substituted benzofuran compound of the catalytic method for synthesis of low cost, high yield, its preparation 1 g of 2 - substituted benzofuran compounds required the cost of the catalyst the prior by iridium catalyst is a catalyst of the synthetic method has lowered 2 orders of magnitude, to improve the yield of the 88.5 - 95.8%.
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Paragraph 0010; 0011; 0012

(2019/05/22)

Trimethylphosphate as a Methylating Agent for Cross Coupling: A Slow-Release Mechanism for the Methylation of Arylboronic Esters
A methyl group on an arene, despite its small size, can have a profound influence on biologically active molecules. Typical methods to form a methylarene involve strong nucleophiles or strong and often toxic electrophiles. We report a strategy for a new, highly efficient, copper and iodide co-catalyzed methylation of aryl- and heteroarylboronic esters with the mild, nontoxic reagent trimethylphosphate, which has not been used previously in coupling reactions. We show that it reacts in all cases tested in yields that are higher than those of analogous copper-catalyzed reactions of MeOTs or MeI. The combination of C-H borylation and this methylation with trimethylphosphate provides a new approach to the functionalization of inert C-H bonds and is illustrated by late-stage methylation of four medicinally active compounds. In addition, reaction on a 200 mmol scale demonstrates reliability of this method. Mechanistic studies show that the reaction occurs by a slow release of methyl iodide by reaction of PO(OMe)3 with iodide catalyst, rather than the typical direct oxidative addition to a metal center. The low concentration of the reactive electrophile enables selective reaction with an arylcopper intermediate, rather than nucleophilic groups on the arylboronate, and binding of tert-butoxide to the boronate inhibits reaction of the electrophile with the tert-butoxide activator to form methyl ether.
He, Zhi-Tao,Li, Haoquan,Haydl, Alexander M.,Whiteker, Gregory T.,Hartwig, John F.
supporting information
p. 17197 - 17202
(2018/12/14)

Preparation method of 2-substituted-benzofuran compound
The invention relates to a preparation method of a 2-substituted-benzofuran compound. The method comprises the following specific steps that at the room temperature, after salicylaldehyde and nitroethane are mixed, sodium bisulfite (NaHSO3/SiO2) loaded by silica gel is added, the temperature is increased to 70-80 DEG C for 6-8 h, and 2-methylbenzofuran is obtained. The compound is shown in the description.
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Paragraph 0034-0042

(2018/10/11)

Novel synthesis method of benzofuran ring
The invention relates to a novel synthesis method of a benzofuran ring. The novel synthesis method comprises the following steps: carrying out a process shown in the description; after mixing salicylic aldehyde and nitromethane at room temperature; adding silica gel loaded sodium bisulfite (NaHSO3/SiO2); raising the temperature to 60 to 80 DEG C and reacting for 4 to 6h to obtain the benzofuran ring.
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Paragraph 0036; 0037; 0038; 0039

(2018/11/22)

Direct Synthesis of 2-Methylbenzofurans from Calcium Carbide and Salicylaldehyde p -Tosylhydrazones
A new methodology for the construction of methyl-substituted benzofuran rings from the reactions of calcium carbide with salicylaldehyde p-tosylhydrazones/2-hydroxyacetophenone p-tosylhydrazones is described. Various 2-methylbenzofurans and 2,3-dimethylbenzofurans could be obtained in satisfactory yield by using a cuprous chloride catalyst. The advantages of this protocol include the use of a readily available and easy-to-handle acetylene source and simple workup procedure.
Fu, Rugang,Li, Zheng
supporting information
p. 2342 - 2345
(2018/04/30)

Wacker Oxidation of Terminal Alkenes Over ZrO2-Supported Pd Nanoparticles Under Acid- and Cocatalyst-Free Conditions
Highly efficient Wacker oxidation of aromatic or aliphatic terminal alkenes into methyl ketones and benzofurans is developed by using reusable Pd0 nanoparticles (NPs) supported on ZrO2 under acid- and cocatalyst-free conditions. Molecular oxygen or air can be utilized as the terminal oxidant, which results in the formation of H2O as the only theoretical byproduct. The activation of the Pd NPs by O2 plays an important role in promoting this reaction. Interestingly, PdO supported on ZrO2 showed no activity. Additionally, the Pd particle size significantly affects the catalytic activity, with an apparent optimal diameter of 4–12 nm. In addition to the heterogeneous catalyst forms, the Pd NPs can be generated from a Pd0 complex during the reaction, and these particles are even recyclable.
Zhang, Zhenzhong,Kumamoto, Yuhya,Hashiguchi, Taishin,Mamba, Tetsuya,Murayama, Haruno,Yamamoto, Eiji,Ishida, Tamao,Honma, Tetsuo,Tokunaga, Makoto
p. 3482 - 3489
(2017/09/15)

Cyclopenta[b]annulation of Heteroarenes by Organocatalytic γ′[C(sp3)?H] Functionalization of Ynones
A new approach for the cyclopenta[b]annulation of heteroarenes through metal-free and directing-group-free γ′[C(sp3)?H] functionalization and intramolecular hydroalkylation of ynones has been developed. In an unprecedented event, nucleophilic addition of an organophosphine to the designed ynones triggers γ′[C(sp3)?H] functionalization, leading to the formation of heteroaryl-based ortho-quinodimethane (oQDM) intermediates that undergo carbocyclization to provide cyclopentannulated heteroarenes in good yields and excellent stereoselectivities. Deuterium-labeling experiments substantiated the proposed reaction mechanism as well as the speculated epimerization.
Raghu, Moluguri,Grover, Jagdeep,Ramasastry
supporting information
p. 18316 - 18321
(2016/12/16)

Lead optimization studies of cinnamic amide EP2 antagonists
Prostanoid receptor EP2 can play a proinflammatory role, exacerbating disease pathology in a variety of central nervous system and peripheral diseases. A highly selective EP2 antagonist could be useful as a drug to mitigate the inflammatory consequences of EP2 activation. We recently identified a cinnamic amide class of EP2 antagonists. The lead compound in this class (5d) displays anti-inflammatory and neuroprotective actions. However, this compound exhibited moderate selectivity to EP2 over the DP1 prostanoid receptor (～10-fold) and low aqueous solubility. We now report compounds that display up to 180-fold selectivity against DP1 and up to 9-fold higher aqueous solubility than our previous lead. The newly developed compounds also display higher selectivity against EP4 and IP receptors and a comparable plasma pharmacokinetics. Thus, these compounds are useful for proof of concept studies in a variety of models where EP2 activation is playing a deleterious role.
Ganesh, Thota,Jiang, Jianxiong,Yang, Myung-Soon,Dingledine, Ray
supporting information
p. 4173 - 4184
(2014/06/09)

Selective catalytic transfer dehydrogenation of alkanes and heterocycles by an iridium pincer complex
Catalytic alkane dehydrogenation is a reaction with tremendous potential for application. We describe a highly active PSCOP-pincer iridium catalyst for transfer dehydrogenation of cyclic and linear alkanes. The dehydrogenation of linear alkanes occurs under relatively mild conditions with high regioselectivity for a-olefin formation. In addition, the catalyst system is very effective in the dehydrogenation of heterocycles to form heteroarenes and olefinic products.
Yao, Wubing,Zhang, Yuxuan,Jia, Xiangqing,Huang, Zheng
supporting information
p. 1390 - 1394
(2014/03/21)

Indoles synthesized from amines via copper catalysis
N-Substituted indoles are synthesized from primary amines through a tandem reaction sequence. Initial condensation of the amine with an α-(o-haloaryl)ketone or aldehyde is followed by intramolecular aryl amination catalyzed by CuI. A variety of anilines and alkyl amines, including those with significant steric demands, are converted to indoles in high yields and with varying indole substitution.
Besandre, Ronald,Jaimes, Miguel,May, Jeremy A.
p. 1666 - 1669
(2013/06/26)

An efficient solid-phase synthesis of substituted benzofuran using selenium-bound resin
A very efficient solid-phase synthesis of substituted benzofuran using polymer-supported selenium resin is described. The advantages of the new method are good yields, high purity, straightforward operations, broad range and high diversity of products, lack of odor, and good stability of the resins. The easy work-up procedure makes the method suitable for building parallel libraries.
Zhang, Yin Jun,Wang, Yu Guang
experimental part
p. 212 - 216
(2012/07/13)

Ruthenium NHC catalyzed highly asymmetric hydrogenation of benzofurans
H2-O-T! Aromatic O-heterocycles are a challenging substrates for asymmetric hydrogenation (H2). An in situ formed chiral N-heterocyclic carbene (NHC) ruthenium complex allows the high yielding, completely regioselective, and highly asymmetric hydrogenation of substituted benzofurans at room Temperature, giving valuable 2,3-dihydrobenzofurans (see scheme). Copyright
Ortega, Nuria,Urban, Slawomir,Beiring, Bernhard,Glorius, Frank
supporting information; experimental part
p. 1710 - 1713
(2012/04/05)

Reporting the release of caged species by a combination of two sequential photoreactions, a molecular switch, and one color of light
In the right light: UV light triggers bond breaking, liberates a caged carboxylic acid, and generates the central C=C double bond in the photoresponsive hexatriene molecule of a dithienylethene molecular switch. Light of the same wavelength converts the colorless isomer into its colored counterpart (see picture) in a visually convenient method to report on the success of the release event. Copyright
Wu, Tuoqi,Tang, Hao,Bohne, Cornelia,Branda, Neil R.
supporting information; experimental part
p. 2741 - 2744
(2012/05/04)

Palladium-catalyzed selective Heck-type diarylation of allylic esters with aryl halides involving a β-OAc elimination process
Palladium-catalyzed selective Heck-type diarylation of allylic esters with aryl halides has been developed. Allylic esters are reacted with aryl iodides to provide the corresponding 1,3-diaryl propenes through a β-OAc elimination process. It is noteworthy that the methodology can be applied in constructing the indole and benzofuran skeletons.(Figure Presented)
Liu, Yan,Yao, Bo,Deng, Chen-Liang,Tang, Ri-Yuan,Zhang, Xing-Guo,Li, Jin-Heng
scheme or table
p. 1126 - 1129
(2011/04/23)

A novel photochemical Wittig reaction for the synthesis of 2-aryl/alkylbenzofurans
The synthesis of 2-aryl/alkylbenzofurans has been achieved in high yields under photochemical conditions from readily accessible and suitably substituted phosphonium bromides by an intramolecular photochemical Wittig reaction onto aryloxycarbonyl groups.
Ghosh, Somnath,Das, Jhantu
p. 1112 - 1116
(2011/03/22)

Erratum: A novel photochemical Wittig reaction for the synthesis of 2-aryl/alkylbenzofurans (Tetrahedron Letters (2011) 52 (1112-1116))
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Ghosh, Somnath,Das, Jhantu
p. 2423 - 2423
(2011/05/09)

Switching reaction pathways of benzo[b]thiophen-3-yllithium and benzo[b]furan-3-yllithium based on high-resolution residence-time and temperature control in a flow microreactor
Reaction-pathway control of benzo[b]thiophen-3-yllithium and benzo[b]furan-3-yllithium was accomplished in flow microreactor systems. We could switch between the reaction with an electrophile before ring-opening and that after ring-opening at will by choosing an appropriate residence-time and temperature.
Asai, Tatsuro,Takata, Atsushi,Ushiogi, Yousuke,Iinuma, Yoshiharu,Nagaki, Aiichiro,Yoshida, Jun-Ichi
supporting information; experimental part
p. 393 - 395
(2011/05/03)

Synthesis of benzofuran, benzothiophene, and benzothiazole-based thioamides and their evaluation as KATP channel openers
Several series of benzofurans, benzothiophenes, and benzothiazoles, all featuring the thioamide group, were synthesized and tested as novel K ATP channel openers in artificial cell systems: CHO cells transfected with SUR1/Kir6.2, and HEK 293 cells transfected with SUR2B/Kir6.1; these served as model systems for insulin-secreting pancreatic β cells and smooth muscle cells, respectively. All compounds were investigated with respect to their binding affinity for the SUR2B-type KATP channels using [ 3H]P1075 as radioligand. Selected compounds were also tested as agonists in intact cells using DiBAC4(3) and DyeB (R7260) as membrane potential dyes. Remarkable affinity for SUR2B/Kir6.1 channels in the single-digit micromolar range was observed. In addition, benzothiazole-derived thioamides with sterically demanding, lipophilic substituents showed >100-fold selectivity in favor of SUR2B/Kir6.1. A one-carbon spacer between the heterocyclic skeleton and the thioamide moiety was observed to be crucial for affinity and selectivity. Two of the most potent and selective compounds were studied by crystal structure analyses.
Fischer, Andreas,Schmidt, Claas,Lachenicht, Stefan,Grittner, Dagmar,Winkler, Marcus,Wrobel, Thomas,Rood, Achim,Lemoine, Horst,Frank, Walter,Braun, Manfred
scheme or table
p. 1749 - 1759
(2012/01/02)

Gold catalysis: benzanellation versus alkylidenecyclopentenone synthesis
A series of different furan-yn-ols were prepared by a three-step sequence. Their reaction with Gagosz's catalyst Ph3PAuNTf2 depends strongly on the substitution pattern of the substrate and the quality of the leaving group. Benzofurans, alkylidenecyclopentenones or Meyer-Schuster type products can be obtained. Improving the leaving group quality leads to the preferred formation of benzofurans.
Hashmi, A. Stephen K.,W?lfle, Michael
scheme or table
p. 9021 - 9029
(2009/12/08)

Diastereoselective syntheses of chroman spiroketals via [4 + 2] cycloaddition of enol ethers and o-quinone methides
(Chemical Equation Presented) A variety of chroman spiroketals are synthesized via inverse-demand [4 + 2] cycloaddition of enol ethers and ortho-quinone methides (o-QMs). Low temperature o-QM generation in situ allows for the kinetic, diastereoselective construction of these motifs, providing entry to a number of unusual chroman spiroketal natural products.
Marsini, Maurice A.,Huang, Yaodong,Lindsey, Christopher C.,Wu, Kun-Liang,Pettus, Thomas R. R.
supporting information; experimental part
p. 1477 - 1480
(2009/04/10)

Ruthenium-catalyzed intramolecular cyclization of hetero-functionalized allylbenzenes
Intramolecular addition of heterofunctionalities to C{double bond, long}C double bonds without β-hydride elimination was investigated and catalyzed by ruthenium complexes. The combination of RuCl3 · nH2O (10 mol%) and 3 equiv. of AgOTf acted as a catalyst for cyclization of 2-allylphenol (1a) to 2,3-dihydro-2-methylbenzofuran (2a) in good yield in the presence of Cu(OTf)2 as a co-catalyst and PPh3 as a ligand. This catalyst system also catalyzed the cyclization of 2-allylbenzoic acid to lactone in 91% yield. Then, a new catalyst system (RuCp*Cl2)2 (1.0 mol%)/4AgOTf/4PPh3, was found to be more active even in the absence of Cu(OTf)2. Furthermore, this catalysis was applied to asymmetric reaction of 2-allylphenol (1a). When using TolBINAP as a ligand, over 60% e.e. was achieved.
Ohta, Tetsuo,Kataoka, Yohei,Miyoshi, Akio,Oe, Yohei,Furukawa, Isao,Ito, Yoshihiko
p. 671 - 677
(2008/02/06)

Efficient synthesis of benzofurans utilizing [3,3]-sigmatropic rearrangement triggered by N-trifluoroacetylation of oxime ethers: Short synthesis of natural 2-arylbenzofurans
A new synthetic method for the preparation of benzofurans has been developed. The key step of this method is the [3,3]-sigmatropic rearrangement of N-trifluoroacetyl-ene-hydroxylamines, which was triggered by acylation of oxime ethers. TFAA has been proved to be the best reagent to induce [3,3]-sigmatropic rearrangement for the synthesis of cyclic or acyclic dihydrobenzofurans. On the other hand, the TFAT-DMAP system is found to be the most effective for constructing various benzofurans. Synthetic utility of this reaction is demonstrated by the short synthesis of natural benzofurans without protection of the hydroxy group. The synthesis of Stemofuran A was accomplished via condensation of ketones with aryloxyamine and subsequent reaction with TFAT-DMAP in a four-step synthesis with 72% overall yield. Similarly, Eupomatenoid 6 and Coumestan were synthesized through the reaction of oxime ether with TFAT-DMAP. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Takeda, Norihiko,Miyata, Okiko,Naito, Takeaki
p. 1491 - 1509
(2008/09/19)

Convenient and efficient Pd-catalyzed regioselective oxyfunctionalization of terminal olefins by using molecular oxygen as sole reoxidant
(Chemical Equation Presented) Just the one: The combination of palladium dichloride and N,N-dimethylacetamide (DMA) constitutes a highly efficient and reusable catalytic system, which uses molecular oxygen as the sole reoxidant for liquid-phase Wacker oxidation and acetoxylation of terminal olefins to the corresponding methyl ketones and linear allylic acetates, respectively (see scheme). 2006 Wiley-VCH Verlag GmbH Co. KGaA.
Mitsudome, Takato,Umetani, Takuya,Nosaka, Naoya,Mori, Kohsuke,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
p. 481 - 485
(2007/10/03)

On-water chemistry: Copper-catalyzed straightforward synthesis of benzo[b]furan derivatives in neat water
A more sustainable protocol leading to 2-alkyl- or 2-aryl-substituted benzo[b]furans is reported, involving a copper-TMEDA complex which catalyzes the transformation of readily available ketone derivatives into the corresponding benzofurans in good to excellent yields. The reaction is accomplished using water as the solvent without organic cosolvents, and one example of catalyst reutilization is also presented.
Carril, Monica,SanMartin, Raul,Tellitu, Imanol,Dominguez, Esther
p. 1467 - 1470
(2007/10/03)

Expeditious synthesis of the aromatic spiroketal skeleton using hetero-Diels-Alder cycloaddition
The hetero-Diels-Alder reactions of enolic ethers generated from methylenation of various esters are described, which allow for the rapid synthesis of various substituted [6,6] aromatic spiroketal skeletons.
Zhou, Guanglian,Zheng, Deping,Da, Shijun,Xie, Zhixiang,Li, Ying
p. 3349 - 3352
(2007/10/03)

Method of making high purity phenol
A method of manufacturing a phenol product having a reduced concentration of a contaminating reaction by-product. The method includes contacting a phenol stream, having a concentration of the contaminating by-product, by contacting the phenol stream with an acidic catalyst under suitable purification reaction conditions. Also included is a composition comprising a sec-butyl benzene derived phenol product that has been purified by the removal of certain undesirable reaction by-products.
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Page 5

(2010/02/08)

Method of purifying phenol
A method of purifying a phenol stream that contains a concentration of a contaminating compound is provided. The phenol stream is treated or purified by contacting the stream, under suitable process conditions, with a treatment catalyst that has a low silica content but comprises alumina and a Group VIA metal.
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Page 3

(2008/06/13)

METHOD OF PURIFYING PHENOL
A method of purifying a phenol stream that contains a concentration of a contaminating compound is provided. The phenol stream is treated or purified by contacting the stream, under suitable process conditions, with a treatment catalyst that has a low silica content but comprises alumina and a group VIA metal.
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Page 10

(2008/06/13)

Novel highly regioselective VO(acac)2/TBHP mediated oxidation of o-alkenyl phenols to o-hydroxybenzyl ketones
A novel mild methodology for the preparation of o-hydroxybenzyl ketones is described starting from o-alkenyl phenols and based on the VO(acac)2/TBHP (2 mol %/1.2 equiv) system. VO(acac)2 first catalyzes the epoxidation of o-alkenyl phenols and then the rearrangement of the epoxyphenols to ketones via the selective benzylic C-O cleavage and 1,2 hydride migration. The protocol has also been applied to set up a useful and easy one-pot conversion of o-alkenyl phenols to benzo[b]furans by means of the sequential addition of TFA, after the generation of the intermediate o-hydroxybenzyl ketones.
Lattanzi, Alessandra,Senatore, Antonello,Massa, Antonio,Scettri, Arrigo
p. 3691 - 3694
(2007/10/03)

Efficient [3,3]-sigmatropic rearrangement accelerated by a trifluoroacetyl group: Synthesis of benzofurans under mild conditions
The [3,3]-sigmatropic rearrangement took place smoothly during the course of trifluoroacetylation of O-phenyl-oxime at below room temperature to give the dihydrobenzofuran or benzofuran as a result of concomitant cyclization.
Miyata, Okiko,Takeda, Norihiko,Morikami, Yoshiaki,Naito, Takeaki
p. 254 - 256
(2007/10/03)

Revisit to the reduction of allylic chlorides to less substituted olefins by a low-valent chromium species in the presence of a proton source
Allylic chlorides have been reduced to afford less substituted olefins by a low-valent chromium species in the presence of an alcoholic proton source. This process certainly has synthetic benefits since the regio-selectivity of the reduction is high and the reaction conditions are mild and nearly neutral.
Omoto, Mineko,Kato, Nobuo,Sogon, Tetsuya,Mori, Akira
p. 939 - 941
(2007/10/03)

Evolution of products in the combustion of scrap tires in a horizontal, laboratory scale reactor
A horizontal laboratory reactor was used to study the evolution of byproducts from the combustion of scrap tires at five nominal temperatures (ranging from 650 to 1050 °C) and different oxygen:sample ratios A model was used to calculate the bulk air ratio (λ), and the oxygen consumption was discussed considering this ratio λ. More than 100 volatile and semivolatile compounds were identified and quantified by gas chromatography mass spectrometry, plotting their yields vs the bulk air ratio and temperature. Five different behaviors considering the bulk air ratio and the temperature were identified.
Fullana,Font,Conesa,Blasco
p. 2092 - 2099
(2007/10/03)

Alkylidenation of esters on solid support and traceless synthesis of 2- substituted benzofurans
Polymer-supported esters are smoothly converted into enol ethers using a titanocene alkylidene prepared by treatment of 2-tert- butyldimethylsilyloxybenzaldehyde diphenyldithioacetal with the low valent titanium species Cp2Ti[P(OEt)3]2. Treatment of the enol ethers with acid leads to the release of ketones from the Wang resin in high yield. Traceless solid-phase synthesis of 2-substituted benzofurans is achieved in a three- step termination procedure. (C) 2000 Published by Elsevier Science Ltd.
Guthrie, Emma J.,MacRitchie, Jackie,Hartley, Richard C.
p. 4987 - 4990
(2007/10/03)

Polymer pyrolysis and oxidation studies in a continuous feed and flow reactor: Cellulose and polystyrene
A dual-zone, continuous feed tubular reactor is developed to assess the potential for formation of products from incomplete combustion in thermal oxidation of common polymers. Solid polymer (cellulose or polystyrene) is fed continuously into a volatilization oven where it fragments and vaporizes. The gas-phase polymer fragments flow directly into a second, main flow reactor to undergo further reaction. Temperatures in the main flow reactor are varied independently to observe conditions needed to convert the initial polymer fragments to CO2 and H2O. Combustion products are monitored at main reactor temperatures from 400 to 850 °C and at 2.0-s total residence time with four on-line GC/FIDs; polymer reaction products and intermediates are further identified by GC/MS analysis. Analysis of polymer decomposition fragments at 400 °C encompasses complex oxygenated and aromatic hydrocarbon species, which range from high-molecular-weight intermediates of ca. 300 amu, through intermediate mass ranges down to C1 and C2 hydrocarbons, CO, and CO2. Approximately 41 of these species are positively identified for cellulose and 52 for polystyrene. Products from thermal oxidation of cellulose and polystyrene are shown to achieve complete combustion to CO2 and H2O at a main reactor temperature of 850 °C under fuel-lean equivalence ratio and 2.0-s reaction time. A dual-zone, continuous feed tubular reactor is developed to assess the potential for formation of products from incomplete combustion in thermal oxidation of common polymers. Solid polymer (cellulose or polystyrene) is fed continuously into a volatilization oven where it fragments and vaporizes. The gas-phase polymer fragments flow directly into a second, main flow reactor to undergo further reaction. Temperatures in the main flow reactor are varied independently to observe conditions needed to convert the initial polymer fragments to CO2 and H2O. Combustion products are monitored at main reactor temperatures from 400 to 850°C and at 2.0-s total residence time with four on-line GC/FIDs; polymer reaction products and intermediates are further identified by GC/MS analysis. Analysis of polymer decomposition fragments at 400°C encompasses complex oxygenated and aromatic hydrocarbon species, which range from high-molecular-weight intermediates of ca. 300 amu, through intermediate mass ranges down to C1 and C2 hydrocarbons, CO, and CO2. Approximately 41 of these species are positively identified for cellulose and 52 for polystyrene. Products from thermal oxidation of cellulose and polystyrene are shown to achieve complete combustion to CO2 and H2O at a main reactor temperature of 850°C under fuel-lean equivalence ratio and 2.0-s reaction time.
Park, Byung-Ik,Bozzelli, Joseph W.,Booty, Michael R.,Bernhard, Mary J.,Mesuere, Karel,Pettigrew, Charles A.,Shi, Ji-Chun,Simonich, Staci L.
p. 2584 - 2592
(2007/10/03)

Synthesis of benzofurans via Pd2+-catalyzed oxidative cyclization of 2-allylphenols
Substituted 2-methylbenzofurans were obtained from 2-allylphenols via Pd2+-catalyzed oxidative cyclization using Cu(OAc)2-LiCl as a reoxidant and wet DMF as a solvent.
Roshchin, Alexander I.,Kel'chevski, Sergey M.,Bumagin, Nikolai A.
p. 163 - 167
(2007/10/03)

Transition metal-catalyzed cyclization of 2-allylphenol to 2,3-dihydro-2-methylbenzofuran without β-elimination
The intramolecular nucleophilic addition of 2-allylphenol was catalyzed by RuCl3·nH2O/AgOTf-PPh3-Cu(OTf) 2 to afford 2,3-dihydro-2-methylbenzofuran in good yield, while 2-(3-butenyl)-phenol was converted to 3,4-dihydro-2(2H)-methylbenzopyran.
Hori, Kazushige,Kitagawa, Hideki,Miyoshi, Akio,Ohta, Tetsuo,Furukawa, Isao
p. 1083 - 1084
(2007/10/03)

Reductive, selective deoxygenation of acylbenzo[b]furans, aromatic aldehydes and ketones with NaBH3CN-TMSCl
Aromatic aldehydes, ketones and acylbenzo[b]furans have been reductively deoxygenated with sodium cyanoborohydride and the mild electrophile chlorotrimethylsilane.
Box, Vernon G.S.,Meleties, Panayiotis C.
p. 7059 - 7062
(2007/10/03)

Synthesis of fused furans by gas-phase pyrolysis of 2-allyloxyaryl-propenoic esters
Flash vacuum pyrolysis of 2-allyloxypropenoic esters (e.g. 7) gives benzo[b]furans (e.g. 32) in synthetically useful yields by sequential generation of a phenoxyl radical, cyclisation and ejection of the carboxylic ester function as a free radical leaving group. The method is compatible with a range of substituents on either the benzene ring or the propenoate chain, and is particularly effective for 2-substituted benzo[b]furans. The natural products 5-methoxybenzo[b]furan 1 and angelicin 2 have been synthesised in three and four steps respectively from commercially available starting materials by this route. Related cyclisations to give naphtho[2,1-b]furan 40 were complicated by competitive formation of naphtho[2,1-b]pyran-3-ones (e.g. 41 and 42), but the yield of the required product could be optimised by the choice of the radical precursor. Annelation of a furan ring onto a thlophene is also possible by this method, but lower yields are obtained in such pyrolyses.
Black, Michael,Cadogan,McNab, Hamish,MacPherson, Andrew D.,Roddam, V. Peter,Smith, Carol,Swenson, Helen R.
p. 2483 - 2493
(2007/10/03)

A New Preparation of Benzofurans Utilizing Trimethylsilyldiazomethane
o-Triisopropylsiloxyaryl ketones and aldehydes smoothly reacted with the lithium salt of trimethylsilyldiazomethane to give o-triisopropylsiloxyphenylacetylenes which were easily converted to benzofurans by treatment with tetra-n-butylammonium fluoride. 3-Benzofuranmethanols were also obtained when the reaction was conducted in the presence of carbonyl compounds.
Ito, Yasuko,Aoyama, Toyohiko,Shioiri, Takayuki
p. 1163 - 1164
(2007/10/03)