- 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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- Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
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We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
- Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
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p. 13337 - 13347
(2021/11/20)
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- Solvent-Controlled Hydrogenation of 2’-Hydroxychalcones: A Simple Solution to the Total Synthesis of Bussealins
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A solvent-controlled hydrogenation of 2’-hydroxychalcones to selectively obtain different hydrogenation products is herein reported. Thus, hydrogenation of 2’-hydroxychalcones using EtOH as solvent provided the corresponding 1,3-diarylpropanes in excellent yields. On the contrary, when the hydrogenation was performed in DCM, the corresponding dihydrochalcones were isolated. Switching the reaction solvent to n-BuOH/H2O (1:1), afforded 1,3-diarylpropanols from moderate to good yields. The methodology here reported offers a straightforward, simple and cost-effective method for the preparation of a wide variety of 2’-hydroxy-1,3-diarylpropanes derivatives, and was also applied to the preparation of natural Bussealins C and D. (Figure presented.).
- Soto, Martín,Soengas, Raquel G.,Rodríguez-Solla, Humberto
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p. 5422 - 5431
(2020/10/06)
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- Palladium-catalyzed aerobic synthesis of: Ortho -substituted phenols from cyclohexanones and primary alcohols
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Due to the importance of phenols as structural cores and precursors of chemical products, synthesis of site-specific substituted phenols is highly desirable and a significant challenge. An aerobic palladium-catalyzed site-specific synthesis of ortho-substituted phenols from cyclohexanones and primary alcohols via an oxidation/aldol/dehydration/aromatization process has been developed. Various substituted cyclohexanones and primary alcohols are successfully transformed into ortho-substituted phenols. In addition, this catalytic reaction uses air as the terminal oxidant and generates water as the sole by-product. Furthermore, the method can also be extended to polyhydroxyl substituted substrates with high chemoselectivity between primary and secondary alcohols. This method provides a greener tool for synthesizing primary alkyl ortho-substituted phenols.
- Zeng, Huiying,Yu, Jianjin,Li, Chao-Jun
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supporting information
p. 1239 - 1242
(2020/02/04)
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- Scope and Mechanistic Analysis for Chemoselective Hydrogenolysis of Carbonyl Compounds Catalyzed by a Cationic Ruthenium Hydride Complex with a Tunable Phenol Ligand
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A cationic ruthenium hydride complex, [(C6H6)(PCy3)(CO)RuH]+BF4- (1), with a phenol ligand was found to exhibit high catalytic activity for the hydrogenolysis of carbonyl compounds to yield the corresponding aliphatic products. The catalytic method showed exceptionally high chemoselectivity toward the carbonyl reduction over alkene hydrogenation. Kinetic and spectroscopic studies revealed a strong electronic influence of the phenol ligand on the catalyst activity. The Hammett plot of the hydrogenolysis of 4-methoxyacetophenone displayed two opposite linear slopes for the catalytic system 1/p-X-C6H4OH (ρ = -3.3 for X = OMe, t-Bu, Et, and Me; ρ = +1.5 for X = F, Cl, and CF3). A normal deuterium isotope effect was observed for the hydrogenolysis reaction catalyzed by 1/p-X-C6H4OH with an electron-releasing group (kH/kD = 1.7-2.5; X = OMe, Et), whereas an inverse isotope effect was measured for 1/p-X-C6H4OH with an electron-withdrawing group (kH/kD = 0.6-0.7; X = Cl, CF3). The empirical rate law was determined from the hydrogenolysis of 4-methoxyacetophenone: rate = kobsd[Ru][ketone][H2]-1 for the reaction catalyzed by 1/p-OMe-C6H4OH, and rate = kobsd[Ru][ketone][H2]0 for the reaction catalyzed by 1/p-CF3-C6H4OH. Catalytically relevant dinuclear ruthenium hydride and hydroxo complexes were synthesized, and their structures were established by X-ray crystallography. Two distinct mechanistic pathways are presented for the hydrogenolysis reaction on the basis of these kinetic and spectroscopic data. (Chemical Equation Presented).
- Kalutharage, Nishantha,Yi, Chae S.
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supporting information
p. 11105 - 11114
(2015/09/15)
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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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- Ring-opening of cyclic ethers with carbon-carbon bond formation by Grignard reagents
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The ring-opening of cyclic ethers with concomitant C-C bond formation was studied with a number of Grignard reagents. The transformation was performed in a sealed vial by heating to ~160 °C in an aluminum block or at 180 °C in a microwave oven. Good yields of the product alcohols were obtained with allyl- and benzylmagnesium halides when the ether was tetrahydrofuran or 3,3-dimethyloxetane. Lower yields were obtained with substituted tetrahydrofurans while no ring-opening was observed with tetrahydropyran. Only highly reactive allyl and benzyl Grignard reagents participated in the transformation while no reaction occurred with other alkylmagnesium halides.
- Christensen, Stig Holden,Holm, Torkil,Madsen, Robert
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p. 4942 - 4946
(2014/07/07)
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- Deoxygenation of α,β-unsaturated acylphenols through ethyl o-acylphenylcarbonates with Luche reduction
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An efficient protocol for deoxygenation of α,β-unsaturated acylphenols through ethyl o-acylphenylcarbonates with Luche reduction is described. The reaction shows very good selectivity and tolerates a wide range of functionalities on α,β-unsaturated acylphenols, giving corresponding 2-allylphenols in good to excellent yields.
- Yuan, Hu,Chen, Hao,Jin, Huizi,Li, Bo,Yue, Rongcai,Ye, Ji,Shen, Yunheng,Shan, Lei,Sun, Qingyan,Zhang, Weidong
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supporting information
p. 2776 - 2780
(2013/06/05)
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- Acaricidal activity of tonka bean extracts. Synthesis and structure-activity relationships of bioactive derivatives
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The acaricidal effects of tonka bean, Dipterix odorata, extracts were investigated on Dermatophagoides pteronyssinus, the European house dust mite, and compared with benzyl benzoate as a standard acaricidal compound. A cyclohexane extract was the most effective, with an EC50 = 0.075 g/m2 after a 24 h period, as compared with benzyl benzoate (0.025 g/m2). Bioassay-guided fractionation of this extract led to the isolation of coumarin (1). Pharmacomodulation of this compound led us to test 20 analogues (2-21), which were either synthesized or purchased.
- Gleye, Christophe,Lewin, Guy,Laurens, Alain,Jullian, Jean-Christophe,Loiseau, Philippe,Bories, Christian,Hocquemiller, Reynald
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p. 690 - 692
(2007/10/03)
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- Photoreactions of trans-1-o-Hydroxyphenyl-2-phenylcyclopropane
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The photochemistry of trans-1-o-hydroxyphenyl-2-phenylcyclopropane, trans-1, was studied under a variety of experimental conditions. Direct irradiation through quartz in cyclohexane gave rise mainly to ring-expanded products, 2-phenyl-3,4-dihydro-2H-benzopyran, 2, 2-benzyl-2,3-dihydrobenzofuran, 3, and 1-o-hydroxyphenylindan, 4. The major products, 2 and 3, are rationalized by intramolecular proton transfer. However, a significant fraction of 3 is formed via ring-opening to cinnamylphenol, 5. An additional product, o-(α-cyclohexylmethyl)phenol, 7, suggests fragmentation of trans-1 and (formal) insertion of o-hydroxyphenylcarbene into cyclohexane. Direct irradiation in methanol produced methanol adducts 8 and 9 instead of 2, 3,4, or 7. Finally, acetone-sensitized irradiation of trans-1 resulted in geometric isomerization to cis-1; this result can be rationalized via a biradical intermediate.
- Delgado, Julio,Espinos, Amparo,Jimenez, M. Consuelo,Miranda, Miguel A.,Roth, Heinz D.,Tormos, Rosa
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p. 6541 - 6546
(2007/10/03)
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- [2-ω-phenylalkyl)phenoxy]alkylamines: Synthesis and dual dopamine2 (D2) and 5-hydroxytryptamine2 (5-HT2) receptor antagonistic activities
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A series of [2-(ω-phenylalkyl)phenoxy]alkylamines was synthesized and their 5-hydroxytryptamine2 (5-HT2) and/or dopamine2 (D2) receptor antagonistic activities were examined in vitro. [2-(4- Phenylbutyl)phenoxy]
- Tanaka, Naoki,Goto, Riki,Ito, Rie,Hayakawa, Miho,Ogawa, Taketoshi,Fujimoto, Koichi
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p. 639 - 646
(2007/10/03)
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- ALPHA-OMEGA-DIARYLALKANE COMPOUNDS SEROTONIN-2 RECEPTOR AGONISTS
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Compounds of formula (I): STR1 [wherein: R 1 is aryl; R 2 is hydrogen, alkyl, alkoxy, halogen or cyano; R 3 is a group of formula--B--NR 4 R 5, where R 4 and R 5 are independently hydrogen, alkyl or substituted alkyl or R 4 and R 5, together with the nitr
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- Reduction of flavanones by NaBH3CN in trifluoroacetic acid.
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For our studies on the reduction of flavanones, we worked on flavanone itself and on some other derivatives, oxygenated on the B ring.Besides expected flavans and chalcanes, condensed compounds (dimers and trimers) are also obtained.Reaction begins with the reduction of carbonyl to methylene; all the other isolated products arise from the two possible and competitive reactions on the potential carbocation C-2 of the flavan system: a) reductive cleavage of heterocycle; b) electrophilic aromatic substitution.Reactivity of flavanones is correlated with substituents of B ring through their ?+ values. Key words: flavanones / sodium cyanoborhydride / trifluoroacetic acid / flavans / chalcanes / dimers
- Lewin, G.,Bert, M.,Dauguet, J. C.,Dolley, J.,Menez, P. Le,et al.
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p. 939 - 944
(2007/10/02)
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- Reactions of Flav-2-enes and Flav-2-en-4-ones (Flavones)
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Flav-2-enes, flavones, and 3-alkyl ethers of flavonols add alcohols and carboxylic acids in the presence of N-bromosuccinimide to give 2-alkoxy- and 2-acyloxy-3-bromoflavans which provide routes to cis-3-bromoflavans by reduction and to 3,4-diols by elimination and reaction with osmium tetraoxide.The 2-acyloxyflavans react with alcohols yielding 2-alkoxyflavans.Flavonols react with N-bromosuccinimide and alcohols to give bromine-free hemiacetals, the known 2,3-dialkoxy-3-hydroxyflavanones.
- Bird, T. Geoffrey C.,Brown, Ben R.,Stuart, Ian A.,Tyrrell, William R.
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p. 1831 - 1846
(2007/10/02)
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