- Direct deoxygenation of active allylic alcohols via metal-free catalysis
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Direct metal-free deoxygenation of highly active allylic alcohols catalyzed by a Br?nsted acid was achieved, which avoids tedious reaction steps and eliminates metal contamination. By examining a series of Br?nsted acids, alcohols, reaction temperatures and so on, up to 94% yield was obtained with 10 mol% TsOH·H2O as the catalyst and 2 equiv. of p-methylbenzyl alcohol as the reductant at 80 °C for 2 h. The system was mainly suitable for aromatic allylic alcohols, and the yield was excellent as determined via gram-scale synthesis. The main product was double bond near the side of a more electron-rich aryl group when allylic alcohols featuring different substituents at the 1 and 3 positions were used as the substrates. Deuterium-labelled experiments clearly demonstrated that the hydrogen source was the methylene of p-methylbenzyl alcohol and other control experiments indicated the existence of two ether intermediates. Interestingly, in situ hydrogen transfer of allylic benzyl ether is a key process, but kinetic isotopic effect studies (kH/kD = 1.28) showed that the C-H bond cleavage was not the rate-determining step. A possible mechanism involving carbocations, ether intermediates and hydrogen transfer is proposed.
- Han, Feng,Ji, Na,Liu, Qiaowen,Miao, Chengxia,Zhang, Tong,Zhuang, Hongfeng
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p. 1680 - 1689
(2022/03/02)
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- P-Chiral Monophosphorus Ligands for Asymmetric Copper-Catalyzed Allylic Alkylation
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Asymmetric copper-catalyzed allylic alkylation between allyl bromides and alkyl Grignard reagents using a P-chiral monophosphorus ligand is described. A range of terminal olefins bearing tertiary or quaternary carbon centers were formed in good branched/linear selectivities and excellent enantioselectivities at copper loadings as low as 0.5 mol %.
- Xiong, Wenrui,Xu, Guangqing,Yu, Xinhong,Tang, Wenjun
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p. 4003 - 4013
(2019/06/24)
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- Photo-induced Decarboxylative Heck-Type Coupling of Unactivated Aliphatic Acids and Terminal Alkenes in the Absence of Sacrificial Hydrogen Acceptors
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1,2-Disubstituted alkenes such as vinyl arenes, vinyl silanes, and vinyl boronates are among the most versatile building blocks that can be found in every sector of chemical science. We herein report a noble-metal-free method of accessing such olefins through a photo-induced decarboxylative Heck-type coupling using alkyl carboxylic acids, one of the most ubiquitous building blocks, as the feedstocks. This transformation was achieved in the absence of external oxidants through the synergistic combination of an organo photo-redox catalyst and a cobaloxime catalyst, with H2 and CO2 as the only byproducts. Both control experiments and DFT calculations supported a radical-based mechanism, which eventually led to the development of a selective three-component coupling of aliphatic carboxylic acids, acrylates, and vinyl arenes. More than 90 olefins across a wide range of functionalities were effectively synthesized with this simple protocol.
- Cao, Hui,Jiang, Heming,Feng, Hongyu,Kwan, Jeric Mun Chung,Liu, Xiaogang,Wu, Jie
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supporting information
p. 16360 - 16367
(2018/11/27)
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- Synthetic method of diarylmethanes
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The invention discloses a synthetic method of diarylmethanes. The method is characterized in that benzyl pseudohalide and aromatic boric acid are reacted in an organic solvent under alkaline condition. The method employs easily available raw materials, conversion is realized under effect of no transition metal catalysis, water-free and oxygen-free are not required, Lewis acid catalysis is not required, the method has wide substrate universality, and various substituted diarylmethanes can be synthesized by the method.
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Paragraph 0117; 0118; 0119; 0120; 0121
(2017/08/28)
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- Coupling of arylboronic acids with benzyl halides or mesylates without adding transition metal catalysts
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We report herein a transition-metal-free coupling reaction of arylboronic acids with benzyl halides and mesylates for the construction of C(sp2)[sbnd]C(sp3) bonds. A unique feature of this coupling reaction is the formation regioisomers in some cases. Mechanistic studies suggest that this reaction may proceed via an unprecedented Friedel–Crafts-type reaction pathway under base conditions with the assistance of boronic acid moiety.
- Wu, Guojiao,Xu, Shuai,Deng, Yifan,Wu, Chaoqiang,Zhao, Xia,Ji, Wenzhi,Zhang, Yan,Wang, Jianbo
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p. 8022 - 8030
(2016/11/19)
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- Photochemical Heck benzylation of styrenes catalyzed by Na[FeCp(CO)2]
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Iron-catalyzed Heck coupling of benzyl chlorides and styrenes proceeds under photochemical conditions using the well-known anionic complex, [FeCp(CO)2]- (Fp-), as a catalyst. The reaction likely proceeds through the established SN2 mechanism for Fp- alkylation, followed by styrene migratory insertion and β-hydride elimination steps that are enabled by photochemical CO dissociation.
- Waldhart, Greyson W.,Mankad, Neal P.
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supporting information
p. 171 - 174
(2015/03/05)
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- Method for Allylating and Vinylating Aryl, Heteroaryl, Alkyl, and Alkene Halogenides Using Transition Metal Catalysis
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What is described is a process for preparing organic compounds of the general formula (I) R—R′??(I) by converting a corresponding compound of the general formula (II) R—X ??(II) in which X is fluorine, chlorine, bromine or iodine to an organomagnesium compound of the general formula (III) [M+]n[RmMgXkY1]??(III) wherein compounds of the formula (III) are reacted with a compound of the general formula (IV) characterized in that the reaction of (III) with (IV) is performed in the presence of a) catalytic amounts of an iron compound, based on the compound of the general formula (II), and optionally in the presence of b) a nitrogen-, oxygen- and/or phosphorus-containing additive in a catalytic or stoichiometric amount, based on the compound of the general formula (II).
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Paragraph 0062; 0063; 0069; 0070
(2013/07/25)
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- Selective cross-coupling of organic halides with allylic acetates
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A general protocol for the coupling of haloarenes with a variety of allylic acetates is presented. Strengths of the method are a tolerance for electrophilic (ketone, aldehyde) and acidic (sulfonamide, trifluoroacetamide) substrates and the ability to couple with a variety of substituted allylic acetates. Secondary alkyl bromides can also be allylated under slightly modified conditions, demonstrating the generality of the approach. Finally, the coupling of a reactive vinyl halide could be achieved by the use of a very hindered ligand and more reactive, branched allylic acetates.
- Anka-Lufford, Lukiana L.,Prinsell, Michael R.,Weix, Daniel J.
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supporting information
p. 9989 - 10000
(2013/01/15)
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- Rapid selective defunctionalization of the carbonyl group of α,β-unsaturated ketones with trialkoxylsilane/ZnX2
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Reduction of the carbonyl group of ketones to a methylene unit is widely applied in organic syntheses. In this article, we report that trialkoxylsilane/Zn-based catalyst systems may be applied in the reduction of the carbonyl groups of α,β-unsaturated ketones to methylene units under very mild conditions. In comparison with other Zn-based catalysts, excellent rates and high conversions of,-unsaturated ketones to methylene units are obtained using trialkoxylsilane/ZnI2 or ZnCl2. And the same time, the hydrosilylation reaction product could only be detected when using CuI, CuCl, or FeCl3. No reaction could be conducted by using trialkoxylsilane/CoCl2 or NiCl2, in comparison with Zn-based catalysts. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor &Francis Group, LLC.
- Li, Jiayun,Peng, Jiajian,Bai, Ying,Chen, Lingzhen,Lai, Guoqiao
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scheme or table
p. 1621 - 1625
(2011/10/04)
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- Practical iron-catalyzed allylations of aryl grignard reagents
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An operationally simple iron-catalyzed reductive cross-coupling reaction between aryl halides and allyl electrophiles has been developed. The underlying domino process exhibits high versatility with respect to the allylic leaving group (acetate, tosylate, diethyl phosphate, methyl carbonate, trimethylsilanolate, methanethiolate, chloride, bromide) and high economic and environmental sustainability with respect to the catalyst system (0.2-5 mol% tris(acetylacetonato)iron(III), ligand-free) and reaction conditions (tetrahydrofuran, 0°C, 45 min).
- Mayer, Matthias,Czaplik, Waldemar M.,Von Wangelin, Axel Jacobi
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supporting information; experimental part
p. 2147 - 2152
(2010/12/18)
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- An efficient 1,3-allylic carbonyl transposition of chalcones
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A very simple, convenient, and efficient procedure is reported for the 1,3-allylic carbonyl transposition of chalcones. The transposition can be achieved by reduction of chalcones to 1,3-diarylpropan-1-ols and dehydration of the latter to give 1,3-diarylpropenes followed by benzylic/allylic oxidation.
- Khurana, Jitender M.,Dawra, Kiran,Majumdar, Susruta
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experimental part
p. 69 - 72
(2010/03/24)
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- Palladium(0) complexes of a 15-membered macrocyclic triolefin as a recoverable catalyst - Monomer- and polystyrene-anchored versions
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Preparation of the 15-membered cycle (E,E,E)-1,6,11-tris[(2,4,6- triisopropylphenyl)sulfonyl]-1,6,11-triazacyclopentadeca-3,8,13-triene (8) is reported. This cyclic triolefin forms a stable Pd°complex 9 which catalyzes several cross-coupling reactions and
- Cortés, Jordi,Moreno-Ma?as, Marcial,Pleixats, Roser
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p. 239 - 243
(2007/10/03)
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- Preparation of 1,3-Diarylpropenes by Phosphine-Free Palladium(0)-Catalyzed Suzuki-Type Coupling of Allyl Bromides with Arylboronic Acids
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1,2-Diarylpropenes 3 featuring different substituents at the aryl rings are obtained in high yields by a modified Suzuki coupling between cinnamyl bromides and arylboronic acids using the phosphine-free Pd(dba)n (n = 1.5-2) as catalyst, in benzene and in
- Moreno-Manas, Marcial,Pajuelo, Francesca,Pleixats, Roser
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p. 2396 - 2397
(2007/10/02)
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- ORGANO TIN NUCLEOPHILES III. PALLADIUM CATALYZED REDUCTIVE CLEAVAGE OF ALLYLIC HETEROSUBSTITUENTS WITH TIN HYDRIDE
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Tributyl tin hydride, serving as an efficient hydride transfer agent, allows highly chemoselective palladium catalyzed reductions of allylic heterosubstituents even in presence of aldehydes, benzyl acetate and benzyl chloride.
- Keinan, Ehud,Greenspoon, Noam
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p. 241 - 244
(2007/10/02)
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