- Rh-Catalyzed Decarbonylative Addition of Salicylaldehydes with Vinyl Ketones: Synthesis of Taccabulins A–E
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A rhodium-catalyzed decarbonylative addition of salicylaldehydes with vinyl ketones was developed to synthesize o-hydroxydihydrochalcones (2-hydroxyphenethyl ketones). These decarbonylative addition reactions afforded various functionalized o-hydroxydihydrochalcones in moderate to good yields with broad functional group tolerance and selectivity. This method was also applied further in the divergent synthesis of dihydrochalcone derived taccabulins A–E.
- Rao, Maddali L. N.,Ramakrishna, Boddu S.
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p. 7545 - 7554
(2019/12/15)
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- Chemoselective transfer hydrogenation of Α,Β-unsaturated carbonyls catalyzed by a reusable supported Pd nanoparticles on biomass-derived carbon
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We herein report highly chemoselective transfer hydrogenation of α,β-unsaturated carbonyl compounds to saturated carbonyls with formic acid as a hydrogen donor over a stable and recyclable heterogeneous Pd nanoparticles (NPs) on N,O-dual doped hierarchical porous biomass-derived carbon. The synergistic effect between Pd NPs and incorporated heteroatoms on carbon plays a critical role on promoting the reaction efficiency. A series of α,β-aromatic and aliphatic unsaturated carbonyl compounds was selectively reduced to their corresponding saturated carbonyls in up to 97% isolated yields with good tolerance of various functional groups. In addition, the catalyst can be successively reused for at least 6 times without significant loss in reaction efficiency.
- Song, Tao,Duan, Yanan,Yang, Yong
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- Chemoselective Hydrogenation of α,β-Unsaturated Carbonyls Catalyzed by Biomass-Derived Cobalt Nanoparticles in Water
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Herein, we report highly chemoselective hydrogenation of α,β-unsaturated carbonyls to saturated carbonyls catalyzed by cobalt nanoparticles supported on the biomass-derived carbon from bamboo shoots with molecular hydrogen in water, which is the first prototype using a heterogeneous non-noble metal catalyst for such organic transformation as far as we know. The optimal cobalt nanocatalyst, CoOx@NC-800, manifested remarkable activity and selectivity for hydrogenation of C=C in α,β-unsaturated carbonyls under mild conditions. A broad set of α,β-aromatic and aliphatic unsaturated carbonyls were selectively reduced to their corresponding saturated carbonyls in up to 99 % yields with good tolerance of various functional groups. Meanwhile, a new straightforward one-pot cascade synthesis of saturated carbonyls was realized with high activity and selectivity via the cross-aldol condensation of ketones with aldehydes followed by selective hydrogenation. More importantly, this one-pot strategy is applicable for the expedient synthesis of Loureirin A, a versatile bioactive and medicinal molecule, from readily available starting materials, further highlighting the practical utility of the catalyst. In addition, the catalyst can be easily separated for successive reuses without significant loss in both activity and selectivity.
- Song, Tao,Ma, Zhiming,Yang, Yong
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p. 1313 - 1319
(2019/01/25)
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- One-Pot Synthesis of O-Heterocycles or Aryl Ketones Using an InCl3/Et3SiH System by Switching the Solvent
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An efficient one-pot synthesis of O-heterocycles or aryl ketones has been achieved using Et3SiH in the presence of InCl3 via a sequential ionic hydrogenation reaction by switching the solvent. This methodology can be used to construct C-O bonds and to prepare conjugate reduction products, including chromans, tetrahydrofurans, tetrahydropyrans, dihydroisobenzofurans, dihydrochalcones, and 1,4-diones in a facile manner. In addition, a novel plausible mechanism involving a conjugate reduction and a tandem reductive cyclization was verified by experimental investigations.
- Jia, Wenqiang,Xi, Qiumu,Liu, Tianqi,Yang, Minjian,Chen, Yonghui,Yin, Dali,Wang, Xiaojian
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p. 5141 - 5149
(2019/05/10)
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- A Modular Synthesis of 2-Alkyl- and 2-Arylchromans via a Three-Step Sequence
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A convergent three-step method for the synthesis of 2-substituted chromans is described. These results have been accomplished via the Heck coupling of readily accessible allylic alcohols and 2-iodophenols, followed by reduction and Mitsunobu cyclization. The utility and generality of this method is demonstrated through the synthesis of a series of 2-aryl-, 2-heteroaryl- and 2-alkylchromans, as well as an azachroman derivative. The asymmetric version of this approach via a Noyori-catalyzed ketone reduction and subsequent cyclization is likewise highlighted.
- Orr, Robert K.,Campeau, Louis-Charles,Chobanian, Harry R.,McCabe Dunn, Jamie M.,Pio, Barbara,Plummer, Christopher W.,Nolting, Andrew,Ruck, Rebecca T.
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p. 657 - 666
(2017/01/28)
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- Nanopalladium on polyethylenimine–grafted starch: An efficient and ecofriendly heterogeneous catalyst for Suzuki–Miyaura coupling and transfer hydrogenation reactions
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Functionalized natural polysaccharides are attractive supports for colloidal metal nanocatalysts due to their abundance, cheapness, biocompatibility and biodegradability. In this study, isocyanate–functionalized starch was prepared by treating with diisocyanate. Polyethylenimine grafted onto starch via the formation of urea linker. The palladium nanoparticles deposited starch PEIS@Pd(0) was obtained through a chelating–in situ reduction procedure. Characterization of these materials was done using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X–ray diffraction, and inductive coupled plasma atomic emission spectrometry. The catalytic activity of PEIS@Pd(0) was then tested in two series of model reactions: Suzuki–Miyaura coupling and transfer hydrogenation. The catalyst could be recovered by simple filtration and was reused for five times without significant loss of catalytic activity, which confirmed the good stability of the catalyst.
- Fu, Lixia,Deng, Wenxiu,Liu, Lujie,Peng, Yanqing
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- Michael additions of highly basic enolates to ortho -quinone methides
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A protocol by which ketone or ester enolates and ortho-quinone methides (o-QMs) are generated in situ in a single reaction flask from silylated precursors under the action of anhydrous fluoride is reported. The reaction partners are joined to give a variety of β-(2-hydroxyphenyl)-carbonyl compounds in 32-94% yield in a single laboratory operation. The intermediacy of o-QMs is supported by control experiments utilizing enolate precursors and conventional alkyl halides as competitive alkylating agents and the isolation of 1,5-dicarbonyl products resulting from conjugate additions that do not restore the aromatic system.
- Lewis, Robert S.,Garza, Christopher J.,Dang, Ann T.,Pedro, Te Kie A.,Chain, William J.
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p. 2278 - 2281
(2015/05/13)
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- Tosylhydrazine mediated conjugate reduction and sequential reductive coupling cyclization: Synthesis of 2-arylchromans
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Tosylhydrazine mediated conjugate reduction of 2-hydroxyl chalcones and sequential reductive coupling cyclization is described. This is an unprecedented protocol and an extremely efficient method for a one-pot domino synthesis of 2-arylchromans in good to excellent yields from commercially available, cheap starting materials. More importantly, the two-step reactions can be easily controlled to afford dihydrochalcones or 2-arylchromans by the mole amounts of tosylhydrazine. Furthermore, the operational simplicity of the process and the high functional group tolerance are remarkable.
- Shang, Xuyang,Zhou, Xiaomeng,Zhang, Wei,Wan, Changfeng,Chen, Junmin
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p. 8187 - 8193
(2015/12/30)
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- CYCLIC PEROXIDE OXIDATION OF AROMATIC COMPOUND PRODUCTION AND USE THEREOF
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The present invention provides a method for converting an aromatic hydrocarbon to a phenol by providing an aromatic hydrocarbon comprising one or more aromatic C-H bonds and one or more activated C-H bonds in a solvent; adding a phthaloyl peroxide to the solvent; converting the phthaloyl peroxide to a di-radical; contacting the di-radical with the one or more aromatic C-H bonds; oxidizing selectively one of the one or more aromatic C-H bonds in preference to the one or more activated C-H bonds; adding a hydroxyl group to the one of the one or more aromatic C-H bonds to form one or more phenols; and purifying the one or more phenols.
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Page/Page column 10
(2014/10/15)
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- A novel transition metal-free conjugate reduction of α,β-unsaturated ketones with tosylhydrazine as a hydrogen source
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A novel and efficient method has been developed for the chemoselective conjugate reduction of α,β-unsaturated ketones with tosylhydrazine as a hydrogen source to the corresponding saturated ketones in moderate to good yields. The present protocol does not require the use of transition metal, and is efficient being applicable to a wide range of substrates (25 examples).
- Zhou, Xiaomeng,Li, Xiaokang,Zhang, Wei,Chen, Junmin
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supporting information
p. 5137 - 5140
(2015/02/19)
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- An unexpected rearrangement-hydration reaction sequence of 2H-chromenes to dihydrochalcones under catalysis of HAuCl4
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2-Aryl-2H-chromenes in aqueous DCM medium under catalysis of HAuCl 4 are converted into 3-(2-hydroxyaryl)-1-arylpropan-1-ones through hydration-rearrangement reaction sequence in very good yield. The key step probably involves the [1,5] hydride shift followed by the hydrolysis under the reaction condition. The notable advantages of this method are operational simplicity and ease of isolation of products and also provide a pathway to convert the chalcone into DHCs with the transposition of carbonyl group. 2012 Elsevier Ltd. All rights reserved.
- Maiti, Gourhari,Kayal, Utpal,Karmakar, Rajiv,Bhattacharya, Rudraksha N.
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p. 6321 - 6325,5
(2012/12/12)
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- Arylation of allyl alcohols in organic and aqueous media catalyzed by oxime-derived palladacycles: Synthesis of β-arylated carbonyl compounds
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A 4-hydroxyacetophenone oxime-derived palladacycle catalyzes the Mizoroki-Heck reaction of allyl alcohols with aryl iodides, bromides, and chlorides in aqueous and organic solvents. The reaction takes place in the presence of dicyclohexylmethylamine or cesium carbonate as bases, the addition of tetrabutylammonium bromide (TBAB) as additive for aryl bromides and chlorides being necessary. Under these reaction conditions, β-arylated aldehydes and ketones are mainly obtained using a rather low loading of palladium (0.1-1 mol%). Similar catalytic activity is shown by a Kaiser oxime resin-derived palladacycle, which allows one to perform recycling and reusing experiments with low Pd leaching. The high regio- and chemoselectivity observed supported that these palladacycles, working as a source of Pd(0) species, operates mainly through a neutral mechanism. This methodology has been applied to the synthesis of important β-arylated carbonyl compounds, such as 4-phenylbutan-2-one, 4-(4-hydroxyphenyl)butan-2-one, dihydrochalcones, the anti-inflamatory nabumetone, and the fragance β-lilial. γ-Arylation is observed in the reactions of allyl alcohol and but-3-en-2-ol with 2-iodoaniline giving mainly the corresponding quinolines. The same tendency is observed in the case of 1,1-dimethylallyl alcohol affording either γ-arylated alcohols or (E)-1-arylisoprenes.
- Alacid, Emilio,Najera, Carmen
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p. 2572 - 2584
(2008/09/19)
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- Concise Synthesis of Dihydrochalcones via Palladium-Catalyzed Coupling of Aryl Halides and 1-Aryl-2-propen-1-ols
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An expedient route to substituted dihydrochalcones is reported. The key step is a palladium-assisted arylation of 1-aryl-2-propen-1-ols. This two-step/one-purification process allows the synthesis of a wide range of compounds with original substitution patterns, including polyphenolic derivatives.
- Briot, Anne,Baehr, Corinne,Brouillard, Raymond,Wagner, Alain,Mioskowski, Charles
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p. 1374 - 1377
(2007/10/03)
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- Reactions of 2-phenyl-4H-1,3,2-benzodioxaborin, a stable ortho-quinone methide precursor
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Thermolysis of 1-phenyl-4H-1,3,2-benzodioxaborins generated the corresponding ortho-quinone methides, which were found to undergo intermolecular cycloaddition reactions with ethyl vinyl ether, dihydropyran, β-methylstyrene, cyclohexene, and 1-ethoxy-1-trimethylsiloxy-1-propenes to give various substituted chromans.Intramolecular trapping of the quinone methides with an olefin led to the syntheses of several analogs of tetrahydrocannabinols. ortho-Quinone methides, generated by treatment of the 2-phenyl-4H-1,3,2-benzodioxaborins with a Lewis acid, react with various nucleophiles to give the corresponding 1,4-addition products.Thus, alkyl and aryl thiols, alcohols, amine, hydride, allyl trimethylsilane, acetophenone, and diethyl malonate as well as some aryl compounds react with the quinone methide to give various 2-substituted phenols.Intramolecular reaction of the quinone methide with an aryl group led to the preparation of some 4-phenylchromans and tetralins.
- Chambers, Jeffrey D.,Crawford, Jason,Williams, Haydn W. R.,Dufresne, Claude,Scheigetz, John,et al.
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p. 1717 - 1732
(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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