- Observations on the Unusual Stereochemistry of the Oxidative Cleavage of Palladium-Carbon Bonds
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Oxidative cleavage of palladium-carbon bonds by CuCl2 occurs with retention of configuration at the carbon atom in the palladium(II)-catalysed cyclization of allylic 2-alkynoates.
- Zhu, Guoxin,Ma, Shengming,Lu, Xiyan,Huang, Qichen
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- An air-tolerant polymer gel-immobilized iridium photocatalyst with pumping recyclability properties
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A novel methacrylate-based cross-linked polymer gel bearing an iridium photocatalyst showed air tolerance and pumping recyclability features through its tunable swelling and deswelling ability. The photocatalytic activity of the polymer gel was demonstrated through an E-to-Z isomerisation reaction and in an azide-alkene [2+3] cycloaddition.
- Abramov, Alex,Díaz Díaz, David,Maiti, Binoy,Reiser, Oliver
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supporting information
p. 7762 - 7765
(2021/08/13)
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- Oxoammonium-Mediated Allylsilane–Ether Coupling Reaction
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A new C(sp3)?H functionalization reaction consisting of the oxidative α-allylation of allyl- and benzyl- methyl ethers has been developed. The C?C coupling could be carried out under mild conditions thanks to the use of cheap and green oxoammonium salts. The scope of the reaction was studied over 27 examples, considering the nature of the substituents on the two coupling partners.
- Carlet, Federica,Bertarini, Greta,Broggini, Gianluigi,Pradal, Alexandre,Poli, Giovanni
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supporting information
p. 2162 - 2168
(2021/04/02)
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- C–C Cross-Coupling Reactions of Organosilanes with Terminal Alkenes and Allylic Acetates Using PdII Catalyst Supported on Starch Coated Magnetic Nanoparticles
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Starch coated magnetic nanoparticles supported palladium catalyst has been explored to perform C–C cross coupling reactions, such as oxidative Heck coupling and Tsuji–Trost allylic coupling using organosilicon compounds as one of the coupling partners. The biopolymer coated magnetic catalyst was very easy to recover magnetically and was efficiently recycled in the subsequent batches. All the reactions were performed in air and thus the necessity of air and moisture free reaction condition is avoided. The present protocols show wide substrate scope and good yields of the products.
- Patra, Debabrata,Panja, Subir,Saha, Amit
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supporting information
p. 878 - 883
(2020/02/13)
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- Base-induced Sommelet–Hauser rearrangement of N-(α-(2-oxyethyl)branched)benzylic glycine ester-derived ammonium salts via a chelated intermediate
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The base-induced Sommelet–Hauser (S–H) rearrangement of N-(α-branched)benzylic glycine ester-derived ammonium salts 1 was investigated. When the α-branched substituent was a simple alkyl, such as a methyl or butyl, desired S–H rearrangement product 2 was obtained in low yield with formation of the [1,2] Stevens rearranged 4 and Hofmann eliminated products 5 and 6. However, when the α-branched substituent had a 2-oxy moiety, such as 2-acetoxyethyl or 2-benzoyloxyethyl, the yields of 2 were improved. These results could be explained by formation of chelated intermediate C that stabilizes the carbanionic ylide, and the subsequent initial dearomative [2,3] sigmatropic rearrangement would be accelerated. The existence of C was supported by mechanistic experiments. This enhancement effect is not very strong or effective; however, it will expand the synthetic usefulness of ammonium ylide rearrangements.
- Baba, Souya,Hirano, Kazuki,Tayama, Eiji
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- Environmentally benign decarboxylative: N-, O-, and S-Acetylations and acylations
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An operationally simple and general method for acetylation and acylation of a wide variety of substrates (amines, alcohols, phenols, thiols, and hydrazones) has been reported. Meldrum's acid and its derivatives have been used as an air-stable, non-volatile, cost-effective, and easy to handle acetylating/acylating agent. Easily separable byproducts (CO2 and acetone) allowed the isolation of analytically pure acetylated products without the requirement of work-up and any chromatography. This journal is
- Ghosh, Santanu,Purkait, Anisha,Jana, Chandan K.
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supporting information
p. 8721 - 8727
(2020/12/30)
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- Influence of the N→Ru Coordinate Bond Length on the Activity of New Types of Hoveyda-Grubbs Olefin Metathesis Catalysts Containing a Six-Membered Chelate Ring Possessing a Ruthenium-Nitrogen Bond
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An efficient approach to the synthesis of new types of Hoveyda-Grubbs catalysts containing an N→Ru bond in a six-membered chelate ring is proposed. The synthesis of the organometallic compounds is based on the interaction of ready accessible 2-vinylbenzylamines and 1,3-bis(2,4,6-trimethylphenyl)-2-trichloromethylimidazolidine ligands with dichloro(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphane)ruthenate, and it afforded the target ruthenium complexes in 70-80% yields. Areas of practical utility and potential applications of the obtained chelates were highlighted by tests of the catalysts in different olefin cross-metathesis (CM) and ring-closing-metathesis (RCM) reactions. These experiments revealed a high catalytic performance (up to 10-2 mol %) of all the synthesized structures in a broad temperature range. The structural peculiarities of the resultant ruthenium catalysts were thoroughly investigated by X-ray crystallography, which allowed making a reliable correlation between the structure of the metallo-complexes and their catalytic properties. It was proved that the bond length between ruthenium and nitrogen in the six-membered chelate ring has the greatest effect on the stability and efficiency of the catalyst. As a rule, the shorter and stronger the N→Ru bond, the higher the stability of the complex and the worse its catalytic characteristics. In turn, the coordination N→Ru bond length can be finely tuned and varied over a wide range of values by changing the steric volume of the cyclic substituents at the nitrogen atom, which will make it possible, as appropriate, to obtain in the future metal complexes with predictable stability and the required catalytic activity. Also, it was found that complexes in which the nitrogen atom is included in the morpholine or isoquinoline rings are the most efficient catalysts in this series. An attempt to establish a correlation between the N→Ru bond length and the 1H and 13C chemical shifts in the Ru═CH fragment has been made.
- Alekseeva, Kseniia A.,Antonova, Alexandra S.,Grigoriev, Mikhail S.,Kumandin, Pavel A.,Nikitina, Eugeniya V.,Novikov, Roman A.,Polyanskii, Kirill B.,Sinelshchikova, Anna A.,Vasilyev, Kirill A.,Zubkov, Fedor I.
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supporting information
p. 4599 - 4607
(2020/12/22)
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- Vinylethylene Carbonates as α,β-Unsaturated Aldehyde Surrogates for Regioselective [3 + 3] Cycloaddition
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Herein, we report a novel stepwise addition-controlled ring size method, to access tetrahydropyrimidines through an operationally simple [3 + 3] cycloaddition of vinylethylene carbonates with triazinanes. Interestingly, we could also use this method for a [3 + 3] oxidative cycloaddition, which allows the facile synthesis of polysubstituted terphenyls under mild conditions. Mechanistic studies suggest that vinylethylene carbonates could generate α,β-unsaturated aldehydes as 3-carbon synthons for cycloaddition via a combination process of Pd-catalyzed decarboxylation and β-H elimination.
- Xu, Yi,Chen, Lu,Yang, Yu-Wen,Zhang, Zhiqiang,Yang, Weibo
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p. 6674 - 6678
(2019/09/03)
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- Aerobic Acyloxylation of Allylic C?H Bonds Initiated by a Pd0 Precatalyst with 4,5-Diazafluoren-9-one as an Ancillary Ligand
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Palladium-catalyzed allylic C?H oxidation has been widely studied, but most precedents use acetic acid as the coupling partner. In this study, a method compatible with diverse carboxylic acid partners has been developed. Use of a Pd0 precatalyst under aerobic reaction conditions leads to oxidation of Pd0 by O2 in the presence of the desired carboxylic acid to generate a PdII dicarboxylate that promotes acyloxylation of the allylic C?H bond. Good-to-excellent yields are obtained with a roughly 1:1 ratio of the alkene and carboxylic acid reagents. Optimized reaction conditions employ 4,5-diazafluoren-9-one (DAF) as a ligand, in combination with a quinone/iron phthalocyanine cocatalyst system to support aerobic catalytic turnover.
- Kozack, Caitlin V.,Sowin, Jennifer A.,Jaworski, Jonathan N.,Iosub, Andrei V.,Stahl, Shannon S.
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p. 3003 - 3007
(2019/06/17)
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- Size-Exclusion Borane-Catalyzed Domino 1,3-Allylic/Reductive Ireland–Claisen Rearrangements: Impact of the Electronic and Structural Parameters on the 1,3-Allylic Shift Aptitude
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The reductive Ireland–Claisen rearrangement through borane-mediated hydrosilylation is reported. The method employs a borane catalyst with a special structural design and affords access to synthetically relevant products with high diastereoselectivity. Depending on electronic and structural parameters, the reaction can be coupled with a 1,3-allylic shift, thus the valence isomer of the Ireland–Claisen product is formed.
- Fegyverneki, Dániel,Kolozsvári, Natália,Molnár, Dániel,Egyed, Orsolya,Holczbauer, Tamás,Soós, Tibor
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supporting information
p. 2179 - 2183
(2019/01/04)
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- S,O-ligand-promoted palladium-catalyzed C–H olefination of arenes with allylic substrates
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An efficient catalytic system for the C–H olefination of arenes with different allylic substrates is reported. The catalytic system is based on Pd(OAc)2 and a readily accessible bidentate S,O-ligand. The methodology shows high activity with a wide range of arenes, including bulky and, electron-rich and -poor arenes. The applicability of this catalyst is demonstrated in the late-stage functionalization of the complex molecule O-methylestrone.
- Naksomboon, Kananat,álvarez-Casao, Yolanda,Uiterweerd, Michiel,Westerveld, Nick,Maciá, Beatriz,Fernández-Ibá?ez, M. ángeles
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supporting information
p. 379 - 382
(2017/12/28)
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- Formyloxyacetoxyphenylmethane and 1,1-diacylals as versatile O-formylating and O-acylating reagents for alcohols
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Formyloxyacetoxyphenylmethane, symmetric 1,1-diacylals and mixed 1-pivaloxy-1-acyloxy-1-phenylmethanes have been used as moisture stable O-formylating and O-acylating reagents for primary and secondary alcohols, allylic alcohols and phenols under solvent/catalyst free conditions to afford their corresponding esters in good yield.
- Chapman, Robert S.L.,Francis, Molly,Lawrence, Ruth,Tibbetts, Joshua D.,Bull, Steven D.
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p. 6442 - 6452
(2018/10/02)
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- Stereodivergent Alkyne Reduction by using Water as the Hydrogen Source
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A homogeneous Pd-catalyzed stereodivergent reduction of alkynes to Z and E alkenes by using H2O as the H2 source is presented. Mediated by a diboron reagent, the transfer hydrogenation has been accomplished to yield the desired geometrical isomer by rational ligand selection. The switchable stereoselectivity achieved using simple phosphine ligands is generally excellent. D2O has also been used as a D2 source for synthesizing the corresponding deuterated olefins. Supported by a gram-scale synthesis, the reaction can easily be scaled up making it an efficient way to prepare alkenes commercially as well. Mechanistic studies suggest formation of H?PdL2?OAc as the crucial step leading to the presence of two pathways involving H?Pd?B(OR)2 and molecular H2 as active intermediates.
- Rao, Santhosh,Prabhu, Kandikere Ramaiah
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supporting information
p. 13954 - 13962
(2018/09/14)
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- Efficient Pd-Catalyzed Regio- and Stereoselective Carboxylation of Allylic Alcohols with Formic Acid
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Formic acid is efficiently used as a C1 source to directly carboxylate allylic alcohols in the presence of a low loading of palladium catalyst and acetic anhydride as additive to afford β,γ-unsaturated carboxylic acids with excellent chemo-, regio-, and stereoselectivity. The reaction proceeds through a carbonylation process with in situ-generated carbon monoxide under mild conditions, avoiding the use of high-pressure gaseous CO. A bisphosphine ligand with a large bite angle (4,5-bis{diphenylphosphino}-9,9-dimethylxanthene, Xantphos) was found to be uniquely effective for this transformation. The regio- and stereoconvergence of this reaction is ascribed to the thermodynamically favored isomerization of the allylic electrophile in the presence of the palladium catalyst.
- Fu, Ming-Chen,Shang, Rui,Cheng, Wan-Min,Fu, Yao
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supporting information
p. 8818 - 8822
(2017/07/11)
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- Stereoselective and Site-Specific Allylic Alkylation of Amino Acids and Small Peptides via a Pd/Cu Dual Catalysis
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We report a stereoselective and site-specific allylic alkylation of Schiff base activated amino acids and small peptides via a Pd/Cu dual catalysis. A range of noncoded α,α-dialkyl α-amino acids were easily synthesized in high yields and with excellent enantioselectivities (up to >99% ee). Furthermore, a direct and highly stereoselective synthesis of small peptides with enantiopure α-alkyl or α,α-dialkyl α-amino acids residues incorporated at specific sites was accomplished using this dual catalyst system.
- Huo, Xiaohong,He, Rui,Fu, Jingke,Zhang, Jiacheng,Yang, Guoqiang,Zhang, Wanbin
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supporting information
p. 9819 - 9822
(2017/08/02)
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- Tandem Palladium and Isothiourea Relay Catalysis: Enantioselective Synthesis of α-Amino Acid Derivatives via Allylic Amination and [2,3]-Sigmatropic Rearrangement
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A tandem relay catalytic protocol using both Pd and isothiourea catalysis has been developed for the enantioselective synthesis of α-amino acid derivatives containing two stereogenic centers from readily accessible N,N-disubstituted glycine aryl esters and allylic phosphates. The optimized process uses a bench-stable succinimide-based Pd precatalyst (FurCat) to promote Pd-catalyzed allylic ammonium salt generation from the allylic phosphate and the glycine aryl ester. Subsequent in situ enantioselective [2,3]-sigmatropic rearrangement catalyzed by the isothiourea benzotetramisole forms syn-α-amino acid derivatives with high diastereo- and enantioselectivity. This methodology is most effective using 4-nitrophenylglycine esters and tolerates a variety of substituted cinnamic and styrenyl allylic ethyl phosphates. The use of challenging unsymmetrical N-allyl-N-methylglycine esters is also tolerated under the catalytic relay conditions without compromising stereoselectivity.
- Spoehrle, Stéphanie S. M.,West, Thomas H.,Taylor, James E.,Slawin, Alexandra M. Z.,Smith, Andrew D.
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supporting information
p. 11895 - 11902
(2017/09/07)
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- Palladium-catalyzed diastereoselective synthesis of homoaldol equivalent products
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A palladium-catalyzed reaction of easily accessible 3-(pinacolatoboryl)allyl acetates and aldehydes provides facile access to synthetically useful homoaldol equivalent products with high diastereoselectivity. The reaction presumably proceeds via allylation of aldehydes with α-acetoxy allylboronates that produced in situ by reductive elimination from allylic gem-palladium/boryl intermediates.
- Horino, Yoshikazu,Sugata, Miki,Sugita, Tetsu,Aimono, Ataru,Abe, Hitoshi
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p. 2131 - 2134
(2017/05/09)
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- Ruthenium-Catalyzed Cross-Metathesis of Allyl Acetate and Styrenes: A Practical Approach to the Synthesis of Tripolinolate A and Its Analogs
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The scope of the Ru-catalyzed cross-metathesis of allyl acetates and styrenes was explored. A variety of electronically and structurally divergent styrenes were tolerated, and the resultant products were obtained in reasonable yields. The reported method was utilized in the synthesis of inhibitors of the proliferation of glioma and colorectal cancer cells, tripolinolate A and its diacetate analog.
- Araki, Yasuhiro,Topolov?an, Nikola,Kotora, Martin
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supporting information
p. 1736 - 1739
(2017/04/13)
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- Allylic C–H acetoxylation of terminal alkenes over TiO2 supported palladium nanoparticles using molecular oxygen as the oxidant
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A method for synthesizing linear allylic acetates from terminal alkenes over TiO2 supported Pd nanoparticles (NPs) has been developed, in which O2 serves as the sole oxidant. Good catalytic activity was performed when using allylbenzene as a substrate and the catalyst can be reused at least five times without activity losing. The catalytic system has a broad substrate scope including transformation of 1,3-butadiene into 1,4-diacetoxy-2-butene, which is an important industrial intermediate for production of 1,4-butanediol. In contrast to previous reports that the Pd-catalyzed allylic acetoxylation is generally promoted by PdII species, the XAFS measurements suggest that this reaction is catalyzed over Pd0 NPs. Additionally, XPS analysis of the catalyst confirms the interaction between Pd and TiO2, which probably promote the initial catalytic procedure.
- Zhang, Zhenzhong,Wu, Qixun,Hashiguchi, Taishin,Ishida, Tamao,Murayama, Haruno,Tokunaga, Makoto
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- Practical Photocatalytic Trifluoromethylation and Hydrotrifluoromethylation of Styrenes in Batch and Flow
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Styrenes represent a challenging class of substrates for current radical trifluoromethylation and hydrotrifluoromethylation methods due to a myriad of potential side reactions. Herein, we describe the development of mild, selective and broadly applicable photocatalytic trifluoromethylation and hydrotrifluoromethylation protocols for these challenging substrates. The methods use fac-Ir(ppy)3, visible light and inexpensive CF3I and can be applied to a diverse set of vinylarene substrates. The use of continuous-flow photochemical reaction conditions allowed to reduce the reaction time and increase the reaction selectivity.
- Straathof, Natan J. W.,Cramer, Sten E.,Hessel, Volker,No?l, Timothy
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supporting information
p. 15549 - 15553
(2016/12/09)
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- Oxidative cleavage of allyl ethers by an oxoammonium salt
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A method to oxidatively cleave allyl ethers to their corresponding aldehydes mediated by an oxoammonium salt is described. Using a biphasic solvent system and mild heating, cleavage proceeds readily, furnishing a variety of α,β-unsaturated aldehydes and ketones.
- Kelly, Christopher B.,Ovian, John M.,Cywar, Robin M.,Gosselin, Taylor R.,Wiles, Rebecca J.,Leadbeater, Nicholas E.
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supporting information
p. 4255 - 4259
(2015/04/14)
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- Toward a Unified Mechanism for Oxoammonium Salt-Mediated Oxidation Reactions: A Theoretical and Experimental Study Using a Hydride Transfer Model
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A range of oxoammonium salt-based oxidation reactions have been explored computationally using density functional theory (DFT), and the results have been correlated with experimentally derived trends in reactivity. Mechanistically, most reactions involve a formal hydride transfer from an activated C-H bond to the oxygen atom of the oxoammonium cation. Several new potential modes of reactivity have been uncovered and validated experimentally.
- Hamlin, Trevor A.,Kelly, Christopher B.,Ovian, John M.,Wiles, Rebecca J.,Tilley, Leon J.,Leadbeater, Nicholas E.
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p. 8150 - 8167
(2015/09/02)
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- Metal-free, regio- and stereoselective synthesis of linear (E)-allylic compounds using C, N, O, and S nucleophiles
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A variety of allylic acetates and derivatives were synthesized by an efficient two-step protocol that employs readily available terminal alkenes as starting materials. This method is highly regio- and stereoselective, affording the linear (E)- isomer as the sole adduct. This process tolerates several functional groups including halogen-containing molecules, and it is general for weak oxygen, carbon, nitrogen, and sulfur nucleophiles. Furthermore, adducts were obtained in good to excellent yields.
- Huang, Xiaojun,Fulton, Brandon,White, Kana,Bugarin, Alejandro
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supporting information
p. 2594 - 2597
(2015/06/16)
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- Facile synthesis of Z -alkenes via uphill catalysis
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Catalytic access to thermodynamically less stable Z-alkenes has recently received considerable attention. These approaches have relied upon kinetic control of the reaction to arrive at the thermodynamically less stable geometrical isomer. Herein, we present an orthogonal approach which proceeds via photochemically catalyzed isomerization of the thermodynamic E-alkene to the less stable Z-isomer which occurs via a photochemical pumping mechanism. We consider two potential mechanisms. Importantly, the reaction conditions are mild, tolerant, and operationally simple and will be easily implemented.
- Singh, Kamaljeet,Staig, Shannon J.,Weaver, Jimmie D.
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supporting information
p. 5275 - 5278
(2014/05/06)
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- O2-promoted allylic acetoxylation of alkenes: Assessment of "push" versus "pull" mechanisms and comparison between O2 and benzoquinone
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Palladium-catalyzed acetoxylation of allylic C-H bonds has been the subject of extensive study. These reactions proceed via allyl-palladium(II) intermediates that react with acetate to afford the allyl acetate product. Benzoquinone and molecular oxygen are two common oxidants for these reactions. Benzoquinone has been shown to promote allyl acetate formation from well-defined π-allyl palladium(II) complexes. Here, we assess the ability of O2 to promote similar reactions with a series of "unligated" π-allyl palladium(II) complexes (i.e., in the absence of ancillary phosphorus, nitrogen or related donor ligands). Stoichiometric and catalytic allyl acetate formation is observed under aerobic conditions with several different alkenes. Mechanistic studies are most consistent with a "pull" mechanism in which O2 traps the Pd0 intermediate following reversible C-O bond formation from an allyl-palladium(II) species. A "push" mechanism, involving oxidatively induced C-O bond formation, does not appear to participate. These results and conclusions are compared with benzoquinone-promoted allylic acetoxylation, in which a "push" mechanism seems to be operative.
- Diao, Tianning,Stahl, Shannon S.
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- Access to cinnamyl derivatives from arenes and allyl esters by a biomimetic aerobic oxidative dehydrogenative coupling
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An efficient biomimetic aerobic oxidative dehydrogenative alkenylation of arenes with allyl esters is presented. The reaction proceeds under an ambient pressure of oxygen with relatively low catalyst loading of palladium acetate, employing catalytic amounts of electron-transfer mediators (ETMs). This study represents a new environmentally friendly method for the synthesis of cinnamyl derivatives.
- Gigant, Nicolas,Baeckvall, Jan-E.
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supporting information
p. 1664 - 1667
(2014/04/17)
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- Achieving control over the branched/linear selectivity in palladium-catalyzed allylic amination
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Palladium-catalyzed reaction of unsymmetrical allylic electrophiles with amines gives rise to regioisomeric allylic amines. We have found that linear products result from the thermodynamically controlled isomerization of the initially formed branched products. The isomerization is promoted by protic acid and active palladium catalyst. The use of base shuts down the isomerization pathway and allows for the preparation and isolation of branched allylic amines. Solvent plays a key role in achieving high kinetic regioselectivity and in controlling the rate of isomerization. The isomerization can be combined with ring-closing metathesis to afford the synthesis of exocyclic allylic amines from their endocyclic precursors.
- Dubovyk, Igor,Watson, Iain D. G.,Yudin, Andrei K.
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p. 1559 - 1575
(2013/03/28)
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- A survey of sulfide ligands for allylic C-H oxidations of terminal olefins
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Perfect to a THT! Screening a diverse library of thioether ligands led to the discovery of tetrahydrothiophene (THT) as a highly reactive and selective ligand for Pd-catalyzed allylic C-H oxidation reactions (see scheme). This novel ligand system provides some of the highest reported yields for the formation of (E)-linear allylic acetates through allylic C-H activation chemistry (BQ = 1,4-benzoquinone). Copyright
- Le, Chichip Q.,Kunchithapatham, Kamala,Henderson, William H.,Check, Christopher T.,Stambuli, James P.
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supporting information
p. 11153 - 11157
(2013/09/02)
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- An efficient palladium(II) catalyst for oxidative Heck-type reaction under base-free conditions
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An efficient catalytic system for the palladium-catalyzed oxidative Heck reaction between arylboronic acids and various alkenes has been developed. Using the bis(aminoalkoxy)palladium complex of N,N-dimethylethanolamine as a catalyst, a series of substituted alkenes were obtained in moderate to excellent yields under mild reaction conditions. This protocol could be tolerated to arylboronic acids containing electron-donating or withdrawing groups and a wide range of olefins, such as acrylate, allyl esters, allyl ethers and alkenylphosphonate. A plausible reaction mechanism of the oxidative Heck reaction was proposed.
- Mi, Xia,Huang, Mengmeng,Guo, Hai,Wu, Yangjie
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p. 5123 - 5128
(2013/06/27)
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- Pentafluorophenylammonium triflate as a mild and new organocatalyst for acylation of alcohols, phenols, and amines under solvent-free condition
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A simple, inexpensive, environmentally friendly and efficient route for the acylation of a number of alcohols, phenols and amines using pentafluorophenylammonium triflate (PFPAT) as a catalyst is described. PFPAT organocatalyst is air-stable, cost-effective, easy to handle, and easily removed from the reaction mixtures.
- Khaksar, Samad,Zakeri, Hasan
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p. 576 - 579,4
(2020/08/31)
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- Ni- and pd-catalyzed synthesis of substituted and functionalized allylic boronates
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Two highly efficient and convenient methods for the synthesis of functionalized and substituted allylic boronates are described. In one procedure, readily available allylic acetates are converted to allylic boronates catalyzed by Ni/PCy3 or Ni/PPh3 complexes with high levels of stereoselectivity and in good yields. Alternatively, the borylation can be accomplished with commercially available Pd catalysts [e.g., Pd 2(dba)3, PdCl2, Pd/C], starting with easily accessed allylic halides.
- Zhang, Ping,Roundtree, Ian A.,Morken, James P.
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supporting information; scheme or table
p. 1416 - 1419
(2012/06/01)
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- A simple and efficient method for the allylation of heteroarenes catalyzed by PdCl2
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The PdCl2-catalyzed allylation of heteroarenes is presented. Various heteroarenes including O-, N-, and S-based ones were allylated efficiently with a rich range of allylic acetates in the presence of only 2 mol % of PdCl2, without the need of bases/acids, additives, and external supporting ligands. In addition, the reactions were carried out under mild and simple conditions just by stirring the two reactants and catalyst in CH 2Cl2 at 60 °C. Moreover, the by-product produced was non-toxic acetic acid. Thus, the method presented in this work provides a general, clean, and operationally simple approach for the functionalization of heteroarenes. Finally, a preliminary mechanistic study suggested that the Pd(II) may be reduced in situ by the heteroarenes to Pd(0), which serves as the active metal center to catalyze the following allylations of heteroarenes via a Tsuji-Trost pathway.
- Yuan, Feng-Quan,Sun, Feng-Yi,Han, Fu-She
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scheme or table
p. 6837 - 6842
(2012/08/28)
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- Synthesis of pyrimidine-modified NHC ruthenium-alkylidene catalysts and their application in RCM, CM, em and ROMP reactions
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A new type of N-heterocyclic carbene bearing ruthenium olefin metathesis catalyst was prepared through the incorporation of a chelated pyrimidinyl methylene subunit, in which electron-rich substituents were attached to stabilize the ruthenium complexes. These catalysts were successfully used in various types of olefin metathesis reactions, including ring-closing metathesis (RCM), cross-metathesis (CM), enyne metathesis (EM), and ring-opening metathesis polymerization (ROMP) reactions. The results therein showed that the presence of an electron-deficient pyrimidine structure greatly enhanced the new NHC ruthenium complexes' catalytic activities. New N-heterocyclic carbene bearing ruthenium olefin metathesis catalysts were synthesized and applied in various types of olefin metathesis reactions, including ring-closing metathesis, cross-metathesis, enyne metathesis, and ring-opening metathesis polymerization reactions. Copyright
- Wu, Guang-Long,Cao, Sheng-Li,Chen, Jian,Chen, Zili
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p. 6777 - 6784
(2013/01/15)
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- Palladium-catalyzed heck-type reactions of allylic esters with arylboronic acids or potassium aryltrifluoroborates
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A selective and general route to (E)-1,3-diaryl-prop-1-enes and (E)-3-arylallyl acetates has been developed by palladium-catalyzed Heck-type reactions of allylic esters with arylboronic acids or potassium aryltrifluoroborates. The present method selectively proceeds including β-OAc elimination or β-H elimination on the basis of the boronic acids. Whereas a variety of allylic esters were reacted with arylboronic acids, palladium(II) acetate [Pd(OAc)2], tetra(n-butyl)ammonium chloride [(n-Bu)4NCl] and postassium dihydrogen phosphate (KH 2PO4) to afford the corresponding diarylation products in moderate to good yields, treatment of allylic esters with potassium aryltrifluoroborates furnished the corresponding monoarylation products. Copyright
- Yao, Bo,Liu, Yan,Wang, Meng-Ke,Li, Jin-Heng,Tang, Ri-Yuan,Zhang, Xing-Guo,Deng, Chen-Liang
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experimental part
p. 1069 - 1076
(2012/05/31)
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- Pyridine ligands as promoters in PdII/0-catalyzed C-H olefination reactions
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Commercially available pyridine ligands can significantly enhance the rate, yield, substrate scope, and site selectivity of arene C-H olefination (Fujiwara-Moritani) reactions. The use of a 1:1 ratio of Pd/pyridine proved critical to maximize reaction rates and yields.
- Kubota, Asako,Emmert, Marion H.,Sanford, Melanie S.
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supporting information; experimental part
p. 1760 - 1763
(2012/05/20)
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- New nitrochromenylmethylidene-containing ruthenium metathesis catalyst
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New Hoveyda-Grubbs type catalyst containing nitrochromenyl ligand is reported herein. The catalyst was tested in model RCM, CM and enyne reactions. Its activity was compared with that of commercially available complexes and with literature data for Grela catalyst. New catalyst appeared to be fast initiating, but less stable than other catalysts.
- Hryniewicka, Agnieszka,Koz?owska, Anna,Witkowski, Stanis?aw
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experimental part
p. 87 - 92
(2012/03/11)
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- Synthesis of 1,3-diarylpropenes through palladium-catalyzed mizoroki-heck and allyl cross-coupling reactions using hydrazones as ligands
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The palladium-catalyzed synthesis of unsymmetrical 1,3-diarylpropenes from allyl esters through a Mizoroki-Heck-type reaction with aryl iodides followed by allyl cross-coupling with a variety of arylboronic acids was developed; the products are obtained in moderate to good yields by using a hydrazone-Pd(OAc) 2 system. The synthesis of unsymmetrical 1,3-diarylpropenes from allyl esters by a Mizoroki-Heck-type reaction followed by allyl cross-coupling with a variety of arylboronic acids was developed; the products were obtained in moderate to good yields by using a hydrazone-Pd(OAc)2 system. Copyright
- Mino, Takashi,Koizumi, Tomoko,Suzuki, Saori,Hirai, Kiminori,Kajiwara, Kenji,Sakamoto, Masami,Fujita, Tsutomu
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scheme or table
p. 678 - 680
(2012/03/10)
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- Pd(II)-catalyzed direct olefination of arenes with allylic esters and ethers
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A convenient Pd(II)-catalyzed direct olefination of unactivated arenes with allylic esters and ethers via C-H activation was demonstrated. Under the typical conditions, various aryl-substituted allylic esters and ethers can be prepared. Georg Thieme Verlag Stuttgart - New York.
- Shang, Xiaojie,Xiong, Yun,Zhang, Yuexia,Zhang, Lei,Liu, Zhongquan
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supporting information; experimental part
p. 259 - 262
(2012/03/08)
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- Enantioselective Prevost and Woodward reactions using chiral hypervalent iodine(iii): Switchover of stereochemical course of an optically active 1,3-dioxolan-2-yl cation
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Optically active 1,3-dioxolan-2-yl cation intermediates were generated during enantioselective dioxyacetylation of alkene with chiral hypervalent iodine(III). Regioselective attack of a nucleophile toward the intermediate resulted in reversal of enantioselectivity of the dioxyacetylation. The Royal Society of Chemistry.
- Fujita, Morifumi,Wakita, Mikimasa,Sugimura, Takashi
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supporting information; experimental part
p. 3983 - 3985
(2011/05/04)
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- Cobalt-catalyzed reductive allylation of alkyl halides with allylic acetates or carbonates
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An efficient method for the direct allylation of alkyl halides catalyzed by simple cobalt(II) bromide has been developed. This reaction, using a variety of substituted allylic acetates or carbonates, provides the linear product as the major product. It displays broad substrate scope and good functional group tolerance. Copyright
- Qian, Xin,Auffrant, Audrey,Felouat, Abdellah,Gosmini, Corinne
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supporting information; experimental part
p. 10402 - 10405
(2011/12/03)
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- Palladium-catalyzed selective acyloxylation using sodium perborate as oxidant
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Sodium perborate (SPB), a principal component of washing powders, was employed as an inexpensive and eco-friendly oxidant in the palladium-catalyzed C-H acyloxylation of alkenes in excellent regio-and stereochemistry. The reactions used anhydrides as acyloxy sources. The method applies to both terminal and internal alkenes, and even benzylic C-H oxidation.(Figure Presented)
- Pilarski, Lukasz T.,Janson, Paer G.,Szabo, Kalman J.
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supporting information; experimental part
p. 1503 - 1506
(2011/04/25)
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- PdII-catalyzed highly selective arylation of allyl esters via C-H functionalization of unreactive arenes with retention of the traditional leaving group
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A highly selective Fujiwara-Moritani oxidative Heck reaction of allyl esters with unreactive arenes via C - H bond activation was developed, in which -H elimination is highly chemo-, regio- and stereoselective. Moreover, even electron-deficient arenes are tolerated in this type of C - H activation. 2010 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim.
- Pan, Delin,Yu, Miao,Chen, Wei,Jiao, Ning
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experimental part
p. 1090 - 1093
(2011/07/08)
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- Allylic C-H acetoxylation with a 4,5-diazafluorenone-ligated palladium catalyst: A ligand-based strategy to achieve aerobic catalytic turnover
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Pd-catalyzed C-H oxidation reactions often require the use of oxidants other than O2. Here we demonstrate a ligand-based strategy to replace benzoquinone with O2 as the stoichiometric oxidant in Pd-catalyzed allylic C-H acetoxylation. Use of 4,5-diazafluorenone (1) as an ancillary ligand for Pd(OAc)2 enables terminal alkenes to be converted to linear allylic acetoxylation products in good yields and selectivity under 1 atm O 2. Mechanistic studies have revealed that 1 facilitates C-O reductive elimination from a π-allyl-PdII intermediate, thereby eliminating the requirement for benzoquinone in this key catalytic step.
- Campbell, Alison N.,White, Paul B.,Guzei, Ilia A.,Stahl, Shannon S.
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supporting information; experimental part
p. 15116 - 15119
(2011/01/06)
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- Palladium-catalyzed allylic acyloxylation of terminal alkenes in the presence of a base
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"Chemical Equation Presentation" The efficiency and the selectivity of the Pd-catalyzed oxidation, in carboxylic acids, of terminal alkenes are strongly improved in the presence of a base. The methodology is particularly well adapted for the oxidation of homoallylic alcohols, for which the resulting acyloxylated products are obtained selectively as E-isomers in fair to good yields. 2010 American Chemical Society.
- Thiery, Emilie,Aouf, Chahinez,Belloy, Julien,Harakat, Dominique,Bras, Jean Le,Muzart, Jacques
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scheme or table
p. 1771 - 1774
(2010/05/01)
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- Allylic oxidations of terminal olefins using a palladium thioether catalyst
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"Chemical equation presented" A palladium catalyst that converts terminal olefins to linear allylic acetates at lower catalyst loadings and faster reaction times than current systems is reported. This reaction can be conducted using benzoquinone as the oxidizing agent or catalytic amounts of copper and hydroquinone under one atmosphere of oxygen. Preliminary reactivity studies of π-allylpalladium complexes under our reaction conditions do not provide results similar to those obtained in the catalytic reaction, which may suggest an alternative reaction pathway. The palladium catalyst is ligated by an aryloxyalkyl aryl sulfide, which is identified as a new ligand for homogeneous catalysis.
- Henderson, William H.,Check, Christopher T.,Proust, Nicolas,Stambuli, James P.
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supporting information; experimental part
p. 824 - 827
(2010/04/06)
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- Generally applicable and efficient oxidative Heck reaction of arylboronic acids with olefins catalyzed by cyclopalladated ferrocenylimine under base- and ligand-free conditions
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A mild and efficient method for oxidative Heck-type reaction of arylboronic acids with olefins catalyzed by cyclopalladated ferrocenylimine was developed. The results represent the first examples involving the palladacycle as the catalyst for such couplings. Moreover, the catalytic system could tolerate various functional groups, such as F, Cl, Br, NO2 and CH3O, and the substrates could be extended to a wide range of olefins from acrylic esters, α,β-unsaturated ketones to alkenes. Furthermore, the olefination could proceed well under base- and ligand-free conditions and employ oxygen as the environmentally benign oxidant.
- Leng, Yuting,Yang, Fan,Wei, Kun,Wu, Yangjie
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experimental part
p. 1244 - 1248
(2010/03/30)
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- Silica gel-mediated rearrangement of allylic acetates. Application to the synthesis of 1,3-enynes
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Silica gel was found to efficiently promote the rearrangement of allylic acetates into their most stable regioisomers under microwave irradiation. The reaction is easy to perform and eco-friendly. This method was applied to the metal-free synthesis of 1,3-enynes.
- Serra-Muns, Anna,Guerinot, Amandine,Reymond, Sebastien,Cossy, Janine
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supporting information; experimental part
p. 4178 - 4180
(2010/08/07)
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- Control of chemo-, regio-, and stereoselectivities in ligand-free Pd-catalyzed oxidative heck reactions of arylboronic acids or alkenylboronate with allyl esters
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A ligand-free Pd-catalyzed highly selective oxidative Heck reaction of organoboronic acids with allyl esters was developed. β-H elimination is highly chemoselectively controlled, leading to γ-substituted allyl esters, which is contrary to the traditional
- Su, Yijin,Jiao, Ning
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supporting information; experimental part
p. 2980 - 2983
(2009/12/05)
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- A heterogeneous cobalt(II) Salen complex as an efficient and reusable catalyst for acetylation of alcohols and phenols
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Acetylation of various alcohols and phenols was performed successfully using an immobilized cobalt(II) catalyst in high yield. The catalyst shows high thermal stability and was also recovered and reused at least 10 times without any considerable loss of activity.
- Rajabi, Fatemeh
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scheme or table
p. 395 - 397
(2009/05/07)
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- Broensted acidic ionic liquid as an efficient catalyst for acetylation of alcohols and phenols
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A novel Broensted acidic room temperature ionic liquid (1-H-3-methyl-imidazolium bisulfate) is found to catalyze efficiently the acetylation of a wide rang of alcohols as well as phenols with acetic anhydride in good to excellent yields at 50°C under solvent-free conditions. Products are easily isolated by extraction with ether and the protocol is mild and green, compared to the existing method based on toxic solvents.
- Hajipour, Abdol R.,Khazdooz, Leila,Ruoho, Arnold E.
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experimental part
p. 398 - 403
(2009/12/06)
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- On the isolation of neat allylic fluorides
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Neat cinnamyl fluoride, geranyl fluoride, 5-carbomethoxy-3-fluorocyclohexene and parent 3-fluorocyclohexene undergo spontaneous decomposition on contact with borosilicate glass or catalytic quantities of moderately strong acids that consists in polycondensation with elimination of HF initiated by electrophilic abstraction of F-. Acid sensitivity of these allylic fluorides correlates with stability of respective allylic cations, exceeds that of parent benzyl fluoride, yet can be mitigated by the use of Teflon and PFA containers that permit their isolation and handling in the neat state.
- Lee, Eunsung,Yandulov, Dmitry V.
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scheme or table
p. 474 - 483
(2009/12/06)
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