- Dearomatization-Rearomatization Strategy for ortho-Selective Alkylation of Phenols with Primary Alcohols
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Phenols are common precursors and core structures of a variety of industrial chemicals ranging from pharmaceuticals to polymers. However, the synthesis of site-specifically substituted phenols is challenging, and thus the development of new methods for this purpose would be highly desirable. Reported here is a protocol for palladium-catalyzed ortho-selective alkylation reactions of phenols with primary alcohols by a dearomatization-rearomatization strategy, with water as the sole by-product. Various substituted phenols and primary alcohols were compatible with the standard reaction conditions. The detailed mechanism of this transformation was also investigated.
- Yu, Jianjin,Li, Chao-Jun,Zeng, Huiying
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supporting information
p. 4043 - 4048
(2020/12/18)
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- α,β-Unsaturated ketones via copper(II) bromide mediated oxidation
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A protocol for effecting a rapid Saegusa-type oxidation of enol acetates is reported. This new method relies on the in situ elimination of an α-bromo intermediate to generate α,β-unsaturated ketones using copper(II) bromide. The methodology developed was applied to a range of substrates including a cyclohexanone, which could be directly converted to the corresponding phenol derivative. A catalytic system in which a non-masked ketone was successfully oxidised using substoichiometric CuBr2 was also developed as a proof of principle.
- Sharley, James S.,Collado Pérez, Ana María,Ferri, Estela Espinos,Miranda, Amadeo Fernandez,Baxendale, Ian R.
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p. 2947 - 2954
(2016/05/19)
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- THIOSEMICARBAZONES INHIBITORS OF LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE AND USES THEREOF
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Lysophosphatidic acid acyltransferase-beta (LPAAT-β) catalyzes the production of phosphatidic acid (PA) from lysophosphatidic acid (LPA). The lipid cofactor PA contributes to the activation of c-Raf, BRAF, mTOR and PKC-ζ. LPAAT-β expression is a prognostic factor in gynecologic malignancies and is being investigated as a therapeutic target in a variety of tumor types. A class of thiosemicarbazones was identified as inhibitors of LPAAT-β from a screen of a library of small molecules. A focused library of thiosemicarbazones derivatives was prepared and led to the development of compounds which potently inhibit LPAAT-β and inhibit the growth of MiaPaCa2 human pancreatic cancer cells.
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Page/Page column 16
(2015/11/17)
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- A 'meta effect' in the fragmentation reactions of ionised alkyl phenols and alkyl anisoles
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The competition between benzylic cleavage (simple bond fission [SBF]) and retro-ene rearrangement (RER) from ionised ortho, meta and para RC 6H4OH and RC6H4OCH3 (R = n-C3H7, n-C4H9, n-C5H11, n-C7H15, n-C9H19, n-C 15H31) is examined. It is observed that the SBF/RER ratio is significantly influenced by the position of the substituent on the aromatic ring. As a rule, phenols and anisoles substituted by an alkyl group in meta position lead to more abundant methylene-2,4-cyclohexadiene cations (RER fragmentation) than their ortho and para homologues. This 'meta effect' is explained on the basis of energetic and kinetic of the two reaction channels. Quantum chemistry computations have been used to provide estimate of the thermochemistry associated with these two fragmentation routes. G3B3 calculation shows that a hydroxy or a methoxy group in the meta position destabilises the SBF and stabilises the RER product ions. Modelling of the SBF/RER intensities ratio has been performed assuming two single reaction rates for both fragmentation processes and computing them within the statistical RRKM formalism in the case of ortho, meta and para butyl phenols. It is clearly demonstrated that, combining thermochemistry and kinetics, the inequality (SBF/RER) metaorthopara holds for the butyl phenols series. It is expected that the 'meta effect' described in this study enables unequivocal identification of meta isomers from ortho and para isomers not only of alkyl phenols and alkyl anisoles but also in other alkyl benzene series. Copyright
- Bouchoux, Guy,Sablier, Michel,Miyakoshi, Tetsuo,Honda, Takashi
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experimental part
p. 539 - 546
(2012/09/22)
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- Reductive lithiation of alkoxy-substituted benzyl methyl ethers and connection with cross-coupling reactions
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2-and 4-Ethoxymethoxybenzyl methyl ethers were employied as useful starting materials for the synthesis of 1,2- or 1,4-dicarbo-substituted benzenes. The proposed reaction sequence involves connection between the reductive lithiation of benzyl alkyl ethers and the metal-catalyzed cross-coupling reaction of aromatic triflates.
- Azzena, Ugo,Dettori, Giovanna,Pireddu, Roberta,Pisano, Luisa
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p. 1617 - 1623
(2007/10/03)
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- Metal cation-exchanged montmorillonite (Mn+-mont)-catalysed aromatic alkylation with aldehydes and ketones
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The alkylation of aromatic compounds with aldehydes and ketones in the presence of a variety of metal cation-exchanged montmorillonites (Mn+-mont; Mn+ = Zr4+, Al3+, Fe3+, Zn2+, H+, Na+) has been investigated. Al3+- and Zr4+-Monts are revealed to be effective as catalysts, while no reaction takes place with Na+-mont. Al3+-Mont-catalysed alkylation of phenol with several aldehydes produces mainly or almost solely the corresponding gem-bis(hydroxyphenyl)alkanes (bisphenols) in good yields, while that with several ketones affords selectively the corresponding alkylphenols in moderate to good yields. The alkylation always occurs at the carbonyl carbon without any skeletal rearrangement and the kind of products depends much on the steric hindrance of an electrophilic intermediary carbocation. The alkylation of anisole, veratrole and p-cresol proceeds well, while that of toluene, benzene, chlorobenzene and nitrobenzene scarcely occurs.
- Tateiwa, Jun-Ichi,Hayama, Ei,Nishimura, Takahiro,Uemura, Sakae
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p. 1923 - 1928
(2007/10/03)
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- Interaction of alkoxides. XVIII. Utilitization of the complex base from alkyllithium and potassium alkoxides in the dimetallation of phenol, thiophenol, o-, m- and p-cresol
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Successful O- and ortho-ring metallation of phenol and side chain metallation in o-cresol has been achieved by use of a mixture of two molar equivalents of n-butyllithium, one molar equivalent of potassium t-butoxide and two molar equivalents of N,N,N',N'-tetramethylethylene diamine in hexane.Poor results were obtained with m-cresol, thiophenol and p-cresol. m-Cresol was effectively dimetallated with a mixture of two molar equivalents of tBuOK and two molar equivalents of nBuLi*TMEDA.The effectiveness of another type of complex base based on 2-ethylhexyllithium (EhexLi) and potassium alkoxides has been also investigated, especially in respect of the influence of the concentration and the ctructure of the alkoxide used.With a complex base from EhexLi and 3 equivalents of potassium 3-methyl-3-pentoxide phenol was successfuly dimetallated even in the absence of TMEDA.Thus, the enhanced reactivity of a complex base containing a higher concentration of a more branched potassium alkoxide over that of previously used complex bases has been confirmed.
- Andringa, H.,Verkruijsse, H.D.,Brandsma, L.,Lochmann, L.
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p. 307 - 314
(2007/10/02)
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- REDUCTIVE TRANSFORMATIONS WITH TRIMETHYLSILYL CHLORIDE-SODIUM IODIDE. A NEW SYNTHESIS OF 4H-1,3-OXAZINES
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1-Arylalkenes and 1-arylalkanols are reduced to arylalkanes on heating with trimethylsilyl chloride/sodium iodide in CH3CN.Under similar conditions enones, dialkylated in the β-position of the double bond, give 4H-1,3-oxazines.
- Ghera, Eugene,Maurya, Rakesh,Hassner, Alfred
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p. 4741 - 4744
(2007/10/02)
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- Preparation and Reactions of Dianions from the Cresols
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With n-BuLi/KO-t-Bu, protons are removed from the hydroxyl and methyl groups of cresols 5 to give dianions 6 in yields of 85percent (ortho), 95percent (meta), and 42percent (para).These dianions react with alkyl halides, Me3SiCl, Bu3SnCl, CO2, and oxidizing agents at carbon only and with dialkyl sulfates at both carbon and oxygen.Thus phenol derivatives bearing primary alkyl groups can be prepared from the corresponding methylphenols via dianions 6.
- Bates, Robert B.,Siahaan, Teruna J.
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p. 1432 - 1434
(2007/10/02)
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