- P-Stereogenic Phosphines Directed Copper(I)-Catalyzed Enantioselective 1,3-Dipolar Cycloadditions
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A new pair of P-stereogenic ligands with multiple chiral centers were synthesized and used in the copper(I)-catalyzed enatioselective [3 + 2] cycloaddition of iminoesters with alkenes. A variety of highly functionalized pyrrolidines were obtained in excellent yield and enatioselectivity. This is the first example of a pair of P-stereogenic ligands working as pseudoenantiomers to tune the enantio- and diastereoselective 1,3-dipolar cycloaddition, and providing a pair of enantiomerically pure pyrrolidines, respectively.
- Gan, Zhenjie,Zhi, Mengna,Han, Ruiping,Li, Er-Qing,Duan, Zheng,Mathey, Fran?ois
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Read Online
- Repetition of chemistry from a recently retracted paper. A cautionary note
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The base-catalyzed condensation reaction between (E)-4-phenylbut-2-enal and phenylpropargyl aldehyde recently reported in the literature to provide formylcyclobutadiene was repeated under the published conditions. The product obtained was identified as (E)-5-phenyl-2-((E)-styryl)pent-2-en-4-ynal rather than the reported 2-phenyl-3-styrylcyclobutadiene-1-carboxaldehyde. The structure assignment is supported by NMR and IR data and a x-ray structure of the crystalline alcohol obtained by Luche reduction.
- Ryan, Wilson,Bedard, Korey,Baidilov, Daler,Tius, Marcus,Hudlicky, Tomas
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- Copper-catalyzed TEMPO addition to propargyl alcohols for the synthesis of vinylic alkoxyamines
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A variety of vinylic alkoxyamines derived from propargyl alcohols and 2, 2, 6,6-tetramethylpiperidine N-oxyl (TEMPO) were synthesized in good yields under copper-catalyzed aerobic conditions. A reaction mechanism was proposed, involving the isomerization of propargyl radicals to allenic radicals, and related mechanistic studies were performed. The kinetic isotope effect on the propargyl C-H bond cleavage (α-deprotonation) reaction was observed (kH/kD = 3.76).
- Kang, Ye-Won,Choi, Yoon-Jeong,Jang, Hye-Young
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- A practical synthesis of phenylpropargyl aldehyde from phenylacetylene and N-formylmorpholine
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A synthesis of phenylpropargyl aldehyde is described employing formylation of a phenylacetylenic Grignard reagent with N-formylmorpholine. This method afforded the product in excellent yield.
- Zanka, Atsuhiko
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- Highly efficient and mild synthesis of variously 5-substituted-4-carbaldehyde-1,2,3-triazole derivatives
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Synthesis of variously 5-substituted-4-carbaldehyde-1,2,3-triazole derivatives 2 was accomplished by reacting sodium azide with α,β-acetylenic aldehydes 1 in DMSO at room temperature. Therefore, the reaction remains basic avoiding the generation of the hazardous explosive HN3, resulting in a safe process. This mild and general reaction was instantaneous and was essentially quantitative.
- Journet, Michel,Cai, Dongwei,Kowal, Jason J.,Larsen, Robert D.
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- The use of acetylenic aldehydes in Baylis-Hillman reactions: Synthesis of versatile allyl propargyl alcohols
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The utility of acetylenic aldehydes in Baylis-Hillman reactions giving allyl propargyl alcohols in moderate to good yields is reported.
- Radha Krishna, Palakodety,Raja Sekhar, Empati,Kannan
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- Synthesis of 1,3-dioxacyclan-2-yl-substituted 1,2,3-triazoles
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A new method for preparing 4-(1,3-dioxacyclan-2-yl)-5-phenyl-1,2,3-triazoles in 30–75% yields has been developed on the basis of azide–alkyne cycloaddition to 2-phenylethinyl-1,3-dioxacyclanes. It has been shown that the best results are achieved when the reaction is carried out at 150–155°C in DMSO.
- Zlotskii,Raskil’dina,Golovanov,Bormotin,Bekin
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- Ionic liquid [Bmim][AuCl4] encapsulated in ZIF-8 as precursors to synthesize N-decorated Au catalysts for selective aerobic oxidation of alcohols
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Here we report a novel approach to synthesize Au NPs immobilized on N-doped carbon materials. In this strategy, an ionic liquid (IL) [Bmim][AuCl4] was selected as the precursor for Au NPs and porous framework of ZIF-8 as the host for the IL. Raman spectroscopy, transmission electron microscopy, N2 physical absorption and Fourier infrared spectra confirmed that the IL was successfully incorporated in the ZIF-8 pores. Followed by a thermal treatment under inert atmosphere, highly dispersed Au NPs were obtained and stabilized by nitrogen species from the carbonization of organic ligand in the metal-organic frameworks (MOFs). The [Bmim][AuCl4]@ZIF-8-6.25percent-T materials exhibited high catalytic activity for the selective aerobic oxidation of alcohols, affording excellent yields (up to >99percent) under atmospheric air and base-free conditions. Catalytic reaction along with catalyst characterization results revealed a strong interaction between Au NPs and N species. TEM, XRD and XPS characterization results further suggested that the N species could not only prevent the Au NPs from aggregation, but also further enhance the reaction activity.
- Chen, Fengfeng,Lu, Qingwen,Fan, Ting,Fang, Ruiqi,Li, Yingwei
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- Controlled reduction of activated primary and secondary amides into aldehydes with diisobutylaluminum hydride
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A practical method is disclosed for the reduction of activated primary and secondary amides into aldehydes using diisobutylaluminum hydride (DIBAL-H) in toluene. A wide range of aryl and alkyl N-Boc, N,N-diBoc and N-tosyl amides were converted into the corresponding aldehydes in good to excellent yields. Reduction susceptible functional groups such as nitro, cyano, alkene and alkyne groups were found to be stable. Broad substrate scope, functional group compatibility and quick conversions are the salient features of this methodology.
- Azeez, Sadaf,Kandasamy, Jeyakumar,Sabiah, Shahulhameed,Sureshbabu, Popuri
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supporting information
p. 2048 - 2053
(2022/03/31)
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- Synthesis of Chiral Propargylamines, Chiral 1,2-Dihydronaphtho[2,1-b]furans and Naphtho[2,1-b]furans with C-Alkynyl N,N′-di-(tert-butoxycarbonyl)-aminals and β-Naphthols
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Chiral phosphoric acid-catalyzed couplings of C-alkynyl N,N′-di-(tert-butoxycarbonyl)-aminals with β-naphthols led to chiral propargylamines in moderate to high yields with high to excellent enantioselectivity, in which the reactions underwent sequential chiral phosphoric acid-catalyzed in situ formation of N-(tert-butoxycarbonyl)-imines (N-Boc-imines) from the aminals, and 1,2-addition of β-naphthols to the N-Boc-imines. Chiral 1,2-dihydronaphtho[2,1-b]furans and naphtho[2,1-b]furans were prepared with satisfactory results when 10 mol% AgOAc and 20 mol% 2,6-lutidine or 1.2 equiv. of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were added to the resulting chiral propargylamines solution, respectively.
- Man, Ningning,Li, Yuming,Jie, Jiyang,Li, Hongyun,Yang, Haijun,Zhao, Yufen,Fu, Hua
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supporting information
p. 12884 - 12889
(2021/07/28)
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- Latent Nucleophilic Carbenes
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Using DFT and ab initio calculations, we demonstrate that noncyclic formamidines can undergo thermal rearrangement into their isomeric aminocarbenes under rather mild conditions. We synthesized the silylformamidine, for which the lowest activation energy in this process was predicted. Experimental studies proved it to serve as a very reactive nucleophilic carbene. The reactions with acetylenes, benzenes, and trifluoromethane proceeded via insertion into sp, sp2, and spCH bonds. The carbene also reacted with the functional groups, such as CHO, COR, and CN at double or triple bonds, displaying high mobility of the trimethylsilyl group. The obtained silylformamidine can be considered as a latent nucleophilic carbene. It can be prepared in bulk quantities, stored, and used when the need arises. Calculation results predict similar behavior for some other silylated formamidines and related compounds.
- Hurieva, Anastasiya,Koidan, Georgyi,Kostyuk, Aleksandr,Kyrylchuk, Andrii A.,Marchenko, Anatoliy,Rozhenko, Alexander B.,Rusanov, Eduard B.,Shvydenko, Kostiantyn
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- Visible Light-Induced Cascade Cyclization of 3-Aminoindazoles, Ynals, and Chalcogens: Access to Chalcogen-Containing Pyrimido[1,2- b]-indazoles
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A direct cascade cyclization of 3-aminoindazoles, ynals, and accessible chalcogens facilitated by visible light has been developed. A series of fluoroactive selenium/tellurium-substituted pyrimido[1,2-b]-indazoles were easily accessed in moderate to good yields with a broad scope. Furthermore, we surveyed the spectral properties of selenide pyrimido[1,2-b]-indazoles prepared by this method.
- Zhou, Jinlei,Li, Wen,Zheng, Huitao,Pei, Yongyan,Liu, Xiang,Cao, Hua
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p. 2754 - 2759
(2021/04/12)
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- Transition-metal-free and facile synthesis of 3-alkynylpyrrole-2,4-dicarboxylates from methylene isocyanides and propiolaldehyde
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A transition-metal-free, facile and efficient method for the synthesis of 3-alkynylpyrrole-2,4-dicarboxylates from methylene isocyanides and propiolaldehyde with moderate to good yields has been developed. The direct transformation process and good tolerance of various substituents make it an alternative approach to previous protocols, and potential applications of these investigated compounds are expected with or without post-modifications.
- Chen, Xiaojuan,Fu, Liping,Huo, Xiaoli,Shao, Jiaan,Yu, Liya,Zeng, Linghui,Zhang, Chong,Zhang, Jiankang,Zhu, Huajian
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p. 16430 - 16433
(2021/10/01)
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- Synthesis of Isoselenazoles and Isothiazoles from Demethoxylative Cycloaddition of Alkynyl Oxime Ethers
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A general method for the synthesis of isoselenazoles and isothiazoles has been developed by the base-promoted demethoxylative cycloaddition of alkynyl oxime ethers using the cheap and inactive Se powder and Na2S as selenium and sulfur sources. This transformation features the direct construction of N-, Se-, and S-containing heterocycles through the formation of N-Se/S and C-Se/S bonds in one-pot reactions with excellent functional group tolerance.
- Zhang, Zhu-Zhu,Chen, Rong,Zhang, Xiao-Hong,Zhang, Xing-Guo
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p. 632 - 642
(2020/12/22)
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- Expansion of substrate scope for nitroxyl radical/copper-catalyzed aerobic oxidation of primary alcohols: A guideline for catalyst selection
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Four distinctive sets of optimum nitroxyl radical/copper salt/additive catalyst combinations have been identified for accommodating the aerobic oxidation of various types of primary alcohols to their corresponding aldehydes. Interestingly, less nucleophilic catalysts exhibited higher catalytic activities for the oxidation of particular primary allylic and propargylic alcohols to give α,β-unsaturated aldehydes that function as competent Michael acceptors. The optimum conditions identified herein were successful in the oxidation of various types of primary alcohols, including unprotected amino alcohols and divalent-sulfur-containing alcohols in good-to-high yields. Moreover, N-protected alaninol, an inefficient substrate in the nitroxyl radical/ copper-catalyzed aerobic oxidation, was oxidized in good yield. On the basis of the optimization results, a guideline for catalyst selection has been established.
- Iwabuchi, Yoshiharu,Nagasawa, Shota,Sasaki, Ryota,Sasano, Yusuke,Yamaichi, Aoto
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p. 488 - 497
(2021/05/27)
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- A new catalytic approach for aerobic oxidation of primary alcohols based on a Copper(I)-thiophene carbaldimines
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We report here novel Cu(I) thiophene carbaldimine catalysts for the selective aerobic oxidation of primary alcohols to their corresponding aldehydes and various diols to lactones or lactols. In the presence of the in situ generated Cu(I) species, a persistent radical (2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO)) and N-methylimidazole (NMI) as an auxiliary ligand, the reaction proceeds under aerobic conditions and at ambient temperature. Especially the catalytic system of 1-(thiophen-2-yl)-N-(4-(trifluoromethoxy)phenyl)methanimine (ligand L2) with copper(I)-iodide showed high reactivity for all kind of alcohols (benzylic, allylic and aliphatic). In the case of benzyl alcohol even 2.5 mol% of copper loading gave quantitative yield. Beside high activity under aerobic conditions, the catalysts ability to oxidize 1,5-pentadiol to the corresponding lactol (86% in 4 h) and N-phenyldiethanolamine to the corresponding morpholine derivate lactol (86% in 24 h) is particularly noteworthy.
- Lagerspets, Emi,Valbonetti, Evelyn,Eronen, Aleksi,Repo, Timo
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- Organocatalytic Regio- and Enantioselective N-Alkylation of Isoxazol-5-ones
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A chiral phosphoric acid catalyzed regio- and enantioselective reaction between 1-acylamino-3-arylprop-2-yn-1-ols and isoxazol-5-ones has been developed for the first time. With the established protocol, N-alkylation of isoxazol-5-ones was achieved, affording enantioenriched N,N-acetals in 74–99 % yield with 72–88 % ee.
- Li, Pengfei,Liu, Meiwen,Qian, Chenxiao
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supporting information
p. 6777 - 6780
(2021/12/31)
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- NHC-catalyzed enantioselective C2-functionalization of 3-hydroxychromenonesviaα,β-unsaturated acyl azoliums
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A novel synthetic method for enantioselective C2-functionalization of 3-hydroxychromenones promoted by N-heterocyclic carbenesviathe formation of α,β-unsaturated acyl azolium intermediates, which occurs with Coates-Claisen rearrangement is established. This synthetic strategy enabled the rapid assembly of enantiomerically enriched δ-hydroxychromenone-derived esters/amides under mild conditions with good to excellent yields and broad substrate scope.
- Dzieszkowski, Krzysztof,S?otwiński, Micha?,Rafińska, Katarzyna,Muzio?, Tadeusz M.,Rafiński, Zbigniew
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supporting information
p. 9999 - 10002
(2021/10/06)
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- Palladium-Catalyzed Diastereoselective Synthesis of (Z)-Conjugated Enynyl Homoallylic Alcohols
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The diastereoselective synthesis of anti-homoallylic alcohols bearing conjugated (Z)-enynes through a palladium-catalyzed three-component reaction is described. This reaction features a broad substrate scope, good functional group compatibility, and high levels of (Z)-alkene stereocontrol. In this reaction, Pd(0) functions as a catalyst in two fundamental steps of the tandem sequence: 1) the generation of a borylated π-allylpalladium species from bifunctional conjunctive reagents, inducing umpolung allylation of aldehydes, and 2) C(sp2)?C(sp) cross-coupling. Further transformations of the obtained products highlight their synthetic utility. (Figure presented.).
- Horino, Yoshikazu,Ishibashi, Mayo,Sakamoto, Juri,Murakami, Miki,Korenaga, Toshinobu
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supporting information
p. 3592 - 3599
(2021/06/15)
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- Synthesis of silyl formates, formamides, and aldehydesviasolvent-free organocatalytic hydrosilylation of CO2
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Carbon dioxide (CO2) was used as a C1 source to prepare silyl formates, formamides, and aldehydes. Tetrabutylammonium acetate (TBAA) catalyzed the solvent-freeN-formylation of amines with CO2and hydrosilane to give formamides including Weinreb formamide, Me(MeO)NCHO, which was successively converted into aldehydes by one-pot reactions with Grignard reagents.
- Ema, Tadashi,Hasegawa, Jun-Ya,Hiyoshi, Mahoko,Murata, Takumi,Ratanasak, Manussada
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supporting information
p. 5783 - 5786
(2020/06/03)
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- RET INHIBITORS, PHARMACEUTICAL COMPOSITIONS AND USES THEREOF
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Provided herein are a RET inhibitor, a pharmaceutical composition thereof and uses thereof. In particular, provided is a compound having Formula (I) or a stereoisomer, a geometric isomer, a tautomer, an N-oxide, a solvate, a metabolite, a pharmaceutically acceptable salt or a prodrug thereof. Provided is a pharmaceutical composition comprising the compound, and uses of the compound and pharmaceutical composition thereof for the preparation of a medicament, in particular for treatment and prevention of RET-related diseases and conditions, including cancer, irritable bowel syndrome, and/or pain associated with irritable bowel syndrome.
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- Synthesis of Pyrrolo[2,1,5- cd]indolizine Rings via Visible-Light-Induced Intermolecular [3+2] Cycloaddition of Indolizines and Alkynes
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A range of indolizine smoothly underwent visible-light-induced intermolecular [3+2] annulations with internal alkynes to afford pyrrolo[2,1,5-cd]indolizine in good to excellent yields with high regioselectivity. Through this cascade reaction, a series of fluoroactive fused indolizines with a large π-system were conveniently synthesized. The usage of visible light as energy source with air as a stoichiometric oxidant under simple conditions makes this process attractive and practical.
- Zhang, Yu,Yu, Yue,Liang, Bing-Bing,Pei, Yong-Yan,Liu, Xiang,Yao, Hua-Gang,Cao, Hua
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p. 10719 - 10727
(2020/09/18)
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- Regiodivergent Hydration-Cyclization of Diynones under Gold Catalysis
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Skipped diynones, efficiently prepared from biomass-derived ethyl lactate, undergo a tandem hydration-oxacyclization reaction under gold(I) catalysis. Reaction conditions have been developed for a switchable process that allows selective access to 4-pyrones or 3(2H)-furanones from the same starting diynones. Further application of this methodology in the total synthesis of polyporapyranone B was demonstrated.
- Mu?oz, Miguel A.,Sanz, Roberto,Solas, Marta,Suárez-Pantiga, Samuel
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supporting information
p. 7681 - 7687
(2020/10/12)
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- Catalyst-Free Annulation of 2-Pyridylacetates and Ynals with Molecular Oxygen: An Access to 3-Acylated Indolizines
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A catalyst and additive-free annulation of 2-pyridylacetates and ynals under molecular oxygen was the first developed, affording 3-acylated indolizines in good to excellent yields. Molecular oxygen was used as the source of the carbonyl oxygen atom in indolizines. This approach was compatible with a wide range of functional groups, and especially it has been successfully extended to unsaturated double bonds and triple bonds, which were difficult to prepare by previous methods in a single step.
- Chen, Zhengwang,Liang, Pei,Ma, Xiaoyue,Luo, Haiqing,Xu, Guohai,Liu, Tanggao,Wen, Xiaowei,Zheng, Jing,Ye, Hui
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p. 1630 - 1639
(2019/01/26)
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- Applications of Thermal Activation, Ball-milling and Aqueous Medium in Stereoselective Michael Addition of Nitromethane to Enynones Catalyzed by Chiral Squaramides
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Stereoselective addition of nitromethane to conjugated en-ynones was performed through the application of chiral squaramides. Three non-classical approaches to promote the addition reaction were tested, including activation of the nucleophile by inorganic base in a biphasic aqueous system, thermal activation, and ball-milling. Hydrogen-bonding catalysis was effective in all these methods, providing 1,4-addition products in high yields and stereoselectivities of up to 98% requiring 1–5 mol% of Cinchona alkaloid squaramide. (Figure presented.).
- Ignatiuk, ?aneta A.,Janicki, Miko?aj J.,Góra, Robert W.,Konieczny, Krzysztof,Kowalczyk, Rafa?
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p. 1108 - 1116
(2019/01/30)
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- A Simple, Mild and General Oxidation of Alcohols to Aldehydes or Ketones by SO2F2/K2CO3 Using DMSO as Solvent and Oxidant
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A practical, general and mild oxidation of primary and secondary alcohols to carbonyl compounds proceeds in yields of up to 99% using SO2F2 as electrophile in DMSO as both the oxidant and the solvent at ambient temperature. No moisture- and oxygen-free conditions are required. Stoichiometric amount of inexpensive K2CO3, which generates easy to separate by-products, is used as the base. Thus, 5-gram scale runs proceeded in nearly quantitative yields by a simple filtration as the work-up. The use of a polar solvent such as DMSO, which usually promotes competing Pummerer rearrangement, is also noteworthy. This protocol is compatible with a variety of common N-, O-, and S-functional groups on (hetero)arene, alkene and alkyne substrates (68 examples). The protocol was applied (99% yield) to a formal synthesis of the important cholesterol-lowering drug Rosuvastatin. (Figure presented.).
- Zha, Gao-Feng,Fang, Wan-Yin,Leng, Jing,Qin, Hua-Li
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supporting information
p. 2262 - 2267
(2019/04/17)
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- Iron-Catalyzed Aerobic Oxidation of Alcohols: Lower Cost and Improved Selectivity
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An aerobic oxidation reaction of alcohols toward aldehydes or ketones using catalytic amounts of Fe(NO3)3·9H2O, 4-OH-TEMPO, and NaCl has been developed. Compared with the former catalytic system with TEMPO developed in this group, the new protocol using 4-OH-TEMPO, which is much cheaper on an industrial scale, accomplished the transformation with a higher selectivity, especially for aliphatic alcohols toward aldehydes. α,β-Unsaturated alkynals or alkynones can be efficiently synthesized from propargyl alcohols, which has been much less studied in the literature.
- Jiang, Xingguo,Liu, Jinxian,Ma, Shengming
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p. 825 - 835
(2019/05/02)
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- Chemoselective Biohydrogenation of Alkenes in the Presence of Alkynes for the Homologation of 2-Alkynals/3-Alkyn-2-ones into 4-Alkynals/Alkynols
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The chemoselective hydrogenation of alkenes in the presence of alkynes is a very challenging transformation to achieve with traditional chemical methods. The development of an effective procedure to perform this transformation would enrich the tool-kit available to organic chemists for the development of useful synthetic routes, and the creation of novel structural motifs. The reduction of activated alkene bonds by ene-reductases (ERs) is completely chemoselective, because of the mechanism of the reaction. Thus, we investigated the use of ERs belonging to the Old Yellow Enzyme family for the reduction of α,β-unsaturated aldehydes with a conjugated C≡C triple bond at the γ position. This reaction was exploited as the key step for the development of an effective homologation route to convert aryl and alkyl substituted propynals and butynones into 4-alkynals and 4-alkynols, avoiding some troublesome or hazardous steps of known synthetic routes. (Figure presented.).
- Colombo, Danilo,Brenna, Elisabetta,Gatti, Francesco G.,Ghezzi, Maria Chiara,Monti, Daniela,Parmeggiani, Fabio,Tentori, Francesca
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supporting information
p. 2638 - 2648
(2019/05/16)
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- Schiff base Cu(I) catalyst for aerobic oxidation of primary alcohols
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We report here new copper(I)-Schiff base complexes for the selective oxidation of primary alcohols to aldehydes under ambient conditions (with 2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO), N-methylimidazole (NMI), ambient air, acetonitril and RT). Particularly, the copper(I) complex bearing N-(4-fluorophenyl)-1-(furan-2-yl)methanimine (L2) showed high activity in the series and gave near- quantitative yields in the oxidations of benzyl alcohol (99% yield in 1 h) and 1-octanol (96% yield in 24 h). Based on the X-ray structure determination, the complex has a square pyramidal coordination accomplished by two L2 ligands and bromide as a counter anion. The oxidation reactions were monitored with UV–vis and in situ ATR-IR spectroscopy to study the changes in the catalytic structure and to elucidate the catalytic properties and the mechanistic details. Accordingly, detachment of one of the L2 ligands from the complexes is related to the oxidation activity.
- Lagerspets, Emi,Lagerblom, Kalle,Heli?vaara, Eeva,Hiltunen, Otto-Matti,Moslova, Karina,Nieger, Martin,Repo, Timo
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- Copper-Catalyzed Asymmetric Silylation of Propargyl Dichlorides: Access to Enantioenriched Functionalized Allenylsilanes
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A copper-catalyzed silylation of propargyl dichlorides was developed to access chloro-substituted allenylsilanes under mild reaction conditions. Moreover, enantioenriched chloro-substituted allenylsilanes can be synthesized in moderate to high yields and good enantioselectivities with this protocol.
- Liu, Zheng-Li,Yang, Chao,Xue, Qi-Yan,Zhao, Meng,Shan, Cui-Cui,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 16538 - 16542
(2019/11/11)
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- Mechanistic Divergence in the Hydrogenative Synthesis of Furans and Butenolides: Ruthenium Carbenes Formed by gem-Hydrogenation or through Carbophilic Activation of Alkynes
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Enynes with a tethered carbonyl substituent are converted into substituted furan derivatives upon hydrogenation using [Cp*RuCl]4 as the catalyst. Paradoxically, this transformation can occur along two distinct pathways, each of which proceeds via discrete pianostool ruthenium carbenes. In the first case, hydrogenation and carbene formation are synchronized (“gem-hydrogenation”), whereas the second pathway comprises carbene formation by carbophilic activation of the triple bond, followed by hydrogenative catalyst recycling. Representative carbene intermediates of either route were characterized by X-ray crystallography; the structural data prove that the attack of the carbonyl group on the electrophilic carbene center follows a Bürgi–Dunitz trajectory.
- Peil, Sebastian,Fürstner, Alois
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supporting information
p. 18476 - 18481
(2019/11/14)
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- Chemoselective Reduction of Sterically Demanding N,N-Diisopropylamides to Aldehydes
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A sequential one-pot process for chemoselectively reducing sterically demanding N,N-diisopropylamides to aldehydes has been developed. In this reaction, amides are activated with EtOTf to form imidates, which are reduced with LiAlH(OR)3 [R = t-Bu, Et] to give aldehydes by hydrolysis of the resulting hemiaminals. The non-nucleophilic base 2,6-DTBMP remarkably improves reaction efficiency. The combination of EtOTf/2,6-DTBMP and LiAlH(O-t-Bu)3 was found to be optimal for reducing alkyl, alkenyl, alkynyl, and 2-monosubstituted aryl N,N-diisopropylamides. In contrast, EtOTf and LiAlH(OEt)3 in the absence of base were found to be optimal for reducing extremely sterically demanding 2,6-disubstituted N,N-diisopropylbenzamides. The reaction tolerates various reducible functional groups, including aldehyde and ketone. 1H NMR studies confirmed the formation of imidates stable in water. The synthetic usefulness of this methodology was demonstrated with N,N-diisopropylamide-directed ortho-metalation and C-H bond activation.
- Xiao, Peihong,Tang, Zhixing,Wang, Kai,Chen, Hua,Guo, Qianyou,Chu, Yang,Gao, Lu,Song, Zhenlei
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p. 1687 - 1700
(2018/02/23)
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- One-Pot Regiospecific Synthesis of Indolizines: A Solvent-Free, Metal-Free, Three-Component Reaction of 2-(Pyridin-2-yl)acetates, Ynals, and Alcohols or Thiols
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A novel approach for the synthesis of indolizines from 2-(pyridin-2-yl)acetates, ynals, and alcohols or thiols has been developed. This MCR (multicomponent reaction) that proceeds under the solvent- and metal-free conditions has provided a straightforward path to construct indolizines. Furthermore, this reaction demonstrates other attractive features such as widely available starting materials, mild conditions, good functional group tolerance, and high efficiency.
- Yang, Daji,Yu, Yue,Wu, Yuanheng,Feng, Huiyi,Li, Xuechen,Cao, Hua
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p. 2477 - 2480
(2018/04/25)
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- Cycloaddition Reaction of α,β-Alkynic Hydrazones and KSCN under Transition-Metal-Free Conditions: Synthesis of N-Iminoisothiazolium Ylides
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A novel heteroannulation reaction between α,β-alkynic hydrazones and potassium thiocyanate has been developed for the synthesis of N-iminoisothiazolium ylides. The transformation features wide substrate scope, functional tolerance, and easy operation. This investigation involves a [4 + 1]-type cycloaddition reaction and C-S/S-N bond formation under transition-metal-free conditions. The application of this transformation to the gram-scale preparation of the N-imide ylide is also accomplished.
- Liu, Bei-Bei,Cao, Wen-Bin,Wang, Fei,Wang, Shun-Yi,Ji, Shun-Jun
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supporting information
p. 11118 - 11124
(2018/09/06)
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- Fe(NO3)3/2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ): An efficient catalyst system for selective oxidation of alcohols under aerobic conditions
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A practical and efficient catalyst system for the oxidation of alcohols to carbonyl compounds using catalytic amounts of DDQ and Fe(NO3)3 with air as the environmentally benign oxidant has been developed. A variety of benzylic, heterocyclic, allylic and propargylic alcohols were smoothly converted into aldehydes or ketones in good to excellent yields. In case of large-scale reaction for the oxidation of benzyl alcohol, benzaldehyde was obtained in 93% isolated yield. Moreover, a possible reaction mechanism was proposed.
- Hu, Yongke,Chen, Lei,Li, Bindong
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- Selective Aerobic Oxidation of Alcohols with NO3? Activated Nitroxyl Radical/Manganese Catalyst System
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A homogeneous Mn(NO3)2/2,2,6,6-tetramethylpiperidin-1-yl)oxyl/2-picolinic acid catalyst system is highly active and versatile for the selective aerobic oxidation of alcohols (2,2,6,6-tetramethylpiperidin-1-yl)oxyl=TEMPO, 2-picolinic acid=PyCOOH). The catalytic method enables near quantitative conversion of various primary alcohols to the respective aldehydes using a very simple reaction setup and workup. This study presents findings on the catalyst stability and mechanisms of deactivation. The results show that NO3? plays a crucial catalytic role in the reaction as a source of oxygen activating NOx species. Yet, disproportionation of NO3? to the volatile NO2 during the reaction leads to catalyst deactivation under open air conditions. Catalyst deactivation through this route can be overcome by adding a catalytic amount of nitrate salt, for example NaNO3 into the reaction. This stabilizes the Mn(NO3)2/TEMPO/PyCOOH catalyst and enables oxidation of various primary alcohols to the respective aldehydes using low catalyst loadings under ambient conditions. Secondary alcohols can be oxidized with a modified catalyst utilizing sterically accessible nitroxyl radical 9-azabicyclo[3.3.1]nonane N-oxyl (ABNO) instead of TEMPO. At the end of the alcohol oxidation, pure carbonyl products and the reusable catalyst can be recovered simply by extracting with organic solvent and dilute aqueous acid, followed by evaporation of both phases.
- Lagerblom, Kalle,Keskiv?li, Juha,Parviainen, Arno,Mannisto, Jere,Repo, Timo
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p. 2908 - 2914
(2018/05/03)
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- Regioselective Synthesis of Indene from 3-Aryl Propargylic gem-Dipivalates Catalyzed by N-Heterocyclic Carbene Gold(I) Complexes
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1-Aryl-3,3-bis(pivaloyloxy)propynes can be converted in good to high yields into either 1,3- or 1,2-bis(pivaloyloxy)indenes, depending on the N-heterocyclic carbene (NHC) gold(I) hexafluoroantimonate catalyst used. Almost exclusive formation of 1,3-di(oxycarbonyl)indene derivatives was achieved with cationic gold complexes containing the embracing N,N′-1,3-bis(9-butylfluorenyl)benzimidazolylidene ligand (nBuFNHC). The regioselective issue of the reaction was rationalized by the specific spatial distribution of the steric bulk in the nBuFNHC ligand. In contrast, only modest selectivities in favor of 1,2-disubstituted indenes were observed with more classical NHC gold complexes, the best selectivity being then obtained with N,N′-1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazolylidene gold chloride (SIPrAuCl) as precatalyst. (Figure presented.).
- Hueber, Damien,Teci, Matthieu,Brenner, Eric,Matt, Dominique,Weibel, Jean-Marc,Pale, Patrick,Blanc, Aurélien
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supporting information
p. 2453 - 2459
(2018/05/14)
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- Radical Alkyne peri-Annulation Reactions for the Synthesis of Functionalized Phenalenes, Benzanthrenes, and Olympicene
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Radical cyclization reactions at a peri position were used for the synthesis of polyaromatic compounds. Depending on the choice of reaction conditions and substrate, this flexible approach led to Bu3Sn-substituted phenalene, benzanthrene, and olympicene derivatives. Subsequent reactions with electrophiles provided synthetic access to previously inaccessible functionalized polyaromatic compounds.
- Tsvetkov, Nikolay P.,Gonzalez-Rodriguez, Edgar,Hughes, Audrey,dos Passos Gomes, Gabriel,White, Frankie D.,Kuriakose, Febin,Alabugin, Igor V.
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supporting information
p. 3651 - 3655
(2018/03/06)
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- Phosphine-mediated partial reduction of alkynes to form both (E)- and (Z)-alkenes
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A mild, phosphine-mediated partial reduction of alkynyl carbonyls to the corresponding alkenes was developed. Tuning of the reaction conditions led to either the (E)- or (Z)-diastereomer with high selectivity. A range of alkynyl esters, amides, and ketones were reduced to form alkenes in good to high yields and with excellent functional group tolerance.
- Pierce, Brett M.,Simpson, Brittany F.,Ferguson, Kane H.,Whittaker, Rachel E.
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supporting information
p. 6659 - 6662
(2018/09/29)
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- Base-Promoted Tandem Cyclization for the Synthesis of Benzonitriles by C?C Bond Construction
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A facile synthesis of benzonitriles via a base-promoted tandem cyclization reaction of α,β-unsaturated enones having electron-withdrawing group (EWG) and 2-acyl-acrylonitriles was developed. This new synthetic method to access benzonitriles is suitable for a wide range of substrates. A plausible reaction mechanism is proposed on the basis of previous literature and our own investigations. (Figure presented.).
- Zhu, Cheng-Zhi,Wei, Yin,Shi, Min
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supporting information
p. 808 - 813
(2018/01/27)
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- Chemoselective Hydroalumination of 1-Aza-but-1-en-3-ynes (C-Iminoalkynes): Formation of Propargylamines by Imine Reduction and of 5-Aluminazoles and 1-Aza-butadienes by Anti-Michael Attack
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Hydroalumination of 1-aza-but-1-en-ynes 1 provides facile access to propargylamines 4 by reduction of the C=N bonds or alternatively to 1-aza-buta-1,3-dienes 6 by reduction of the triple bond. The chemoselectivity depends not only on the steric properties of both the hydroalumination agent (di-iso-butylaluminum (DIBAL-H, iBu2AlH) versus di-tert-butylaluminum hydride (tBu2AlH)) and the substrates but also on the reaction temperatures. In several cases, initial aluminum species of 5-aluminazole type 5 could be isolated and characterized by X-ray diffraction, indicating an "anti-Michael" addition of the hydride to the triple bond. Aqueous workup of those species led to 1-azabutadiene derivatives 6. High-level DFT calculations indicate that the observed chemoselectivity is only compatible with a dimeric nature of the hydroaluminating agent. Using such a dimer, the imine reduction corresponds to the kinetically controlled pathway, whereas the triple bond reduction leads to the thermodynamically much more stable 5-aluminazoles, 5.
- Dahlkamp, J. Matthias,Tolzmann, Michael,Lucchesi, Ralph,Daniliuc, Constantin-Gabriel,Wibbeling, Birgit,Uhl, Werner,Würthwein, Ernst-Ulrich
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p. 1346 - 1357
(2018/05/23)
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- Tandem Aza Michael Addition-Vinylogous Nitroaldol Condensation: Construction of Highly Substituted N-Fused 3-Nitropyrazolopyridines
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A base-mediated tandem aza-Michael addition-vinylogous nitroaldol condensation has been described between 3,5-dialkyl 4-nitropyrazoles and alkynyl ketones/aldehydes. This transition metal-free atom economical transformation occurred via C-N and C=C bond formations in one step with the elimination of water. The construction of a variety of highly substituted N-fused 3-nitropyrazolopyridine derivatives has been demonstrated with good yields. Good to excellent regioselectivities have been achieved with unsymmetrically substituted 4-nitropyrazoles.
- Obulesu, Owk,Murugesh,Harish, Battu,Suresh, Surisetti
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supporting information
p. 6454 - 6465
(2018/05/30)
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- Gold-Catalyzed [4 + 1]-Annulation Reactions between 1,4-Diyn-3-ols and Isoxazoles to Construct a Pyrrole Core
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This work reports gold-catalyzed [4 + 1]-annulation reactions between 1,4-diyn-3-ols and isoxazoles or benzisoxazoles to yield pyrrole derivatives. The reaction chemoselectivity is controlled by an initial attack of an isoxazole at a less hindered alkyne to form gold carbenes, further inducing a 1,2-migration of a second alkyne group. A broad substrate scope of 1,4-diyn-3-ols, isoxazoles and even benzisoxazoles highlighted the reaction utility.
- Kardile, Rahul Dadabhau,Kale, Balaji S.,Sharma, Pankaj,Liu, Rai-Shung
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supporting information
p. 3806 - 3809
(2018/07/25)
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- Electrochemical properties and reactions of organoboronic acid esters containing unsaturated bonds at their α-position
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Electrochemical analyses of 2-(cynnamyl)boronic acid pinacol ester and (3-phenyl-2-propynyl)boronic acid pinacol ester, and their trimethylsilyl analogues as well as their parent compounds were comparatively studied by cyclic voltammetry measurements. We
- Ohtsuka, Kazuhiro,Inagi, Shinsuke,Fuchigami, Toshio
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p. G23 - G28
(2017/12/26)
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- Stereoselective One-Pot Sequential Dehydrochlorination/trans-Hydrofluorination Reaction of β-Chloro-α,β-unsaturated Aldehydes or Ketones: Facile Access to (Z)-β-Fluoro-β-arylenals/β-Fluoro-β-arylenones
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The monofluoroalkene substructure shows a high potential as a fluorinated synthon in organic synthesis. However, control of the Z/E stereoselectivity of multi-substituted monofluoroalkene products in one-pot reactions still remains a challenge. An unprecedented one-pot approach for the highly regio- and stereoselective preparation of functionalized (Z)-β-monofluoro tri-substituted alkenes from readily available β-chloro-α,β-unsaturated aldehydes or ketones has been explored. Mechanistic studies demonstrated that the reaction is initiated by dehydrochlorination of the substrates to give alkynyl aldehydes/ketones, followed by their trans-hydrofluorination. It is worth mentioning that a fluorinating reagent with suitable basicity and nucleophilicity plays a key role in promoting the formation of (Z)-β-fluoro-β-aryl tri-substituted monofluoroalkenes. (Figure presented.).
- Zhang, Jingli,Liu, Liran,Duan, Junxin,Gu, Lianghu,Chen, Bifeng,Sun, Taolei,Gong, Yuefa
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p. 4348 - 4358
(2017/12/26)
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- Characterization of Carboxylic Acid Reductases as Enzymes in the Toolbox for Synthetic Chemistry
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Carboxylic acid reductase enzymes (CARs) meet the demand in synthetic chemistry for a green and regiospecific route to aldehydes from their respective carboxylic acids. However, relatively few of these enzymes have been characterized. A sequence alignment with members of the ANL (Acyl-CoA synthetase/ NRPS adenylation domain/Luciferase) superfamily of enzymes shed light on CAR functional dynamics. Four unstudied enzymes were selected by using a phylogenetic analysis of known and hypothetical CARs, and for the first time, a thorough biochemical characterization was performed. Kinetic analysis of these enzymes with various substrates shows that they have a broad but similar substrate specificity. Electron-rich acids are favored, which suggests that the first step in the proposed reaction mechanism, attack by the carboxylate on the α-phosphate of adenosine triphosphate (ATP), is the step that determines the substrate specificity and reaction kinetics. The effects of pH and temperature provide a clear operational window for the use of these CARs, whereas an investigation of product inhibition by NADP+, adenosine monophosphate, and pyrophosphate indicates that the binding of substrates at the adenylation domain is ordered with ATP binding first. This study consolidates CARs as important and exciting enzymes in the toolbox for sustainable chemistry and provides specifications for their use as a biocatalyst.
- Finnigan, William,Thomas, Adam,Cromar, Holly,Gough, Ben,Snajdrova, Radka,Adams, Joseph P.,Littlechild, Jennifer A.,Harmer, Nicholas J.
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p. 1005 - 1017
(2017/03/27)
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- An Unexpected Domino Reaction of β-Keto Sulfones with Acetylene Ketones Promoted by Base: Facile Synthesis of 3(2H)-Furanones and Sulfonylbenzenes
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An unexpected domino reaction of β-keto sulfones with acetylene ketones has been developed. The domino reaction of β-keto sulfones with diynones proceeded smoothly in the presence of 30 mol% K2CO3 without other additives, and afforded the novel 3(2H)-furanone derivatives. On replacing the diynones with terminal alkyne ketones, the reaction regioselectivity was changed and sulfonylbenzenes were obtained via benzannulation in good yields. (Figure presented.).
- Tong, Wei,Li, Qian-Yu,Xu, Yan-Li,Wang, Heng-Shan,Chen, Yan-Yan,Pan, Ying-Ming
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p. 4025 - 4035
(2017/11/21)
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- Burgess Reagent Facilitated Alcohol Oxidations in DMSO
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The Burgess reagent ([methoxycarbonylsulfamoyl]triethylammonium hydroxide) has historically found utility as a dehydrating agent. Herein we show that, in the presence of dimethyl sulfoxide, the Burgess reagent efficiently and rapidly facilitates the oxidation of a broad range of primary and secondary alcohols to their corresponding aldehydes and ketones in excellent yields and under mild conditions, and can be combined with other transformations (e.g., Wittig olefinations). A mechanism similar to those described for the Pfitzner-Moffatt and Swern oxidations is proposed.
- Sultane, Prakash R.,Bielawski, Christopher W.
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p. 1046 - 1052
(2018/06/18)
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- Practical Aerobic Oxidation of Alcohols: A Ligand-Enhanced 2,2,6,6-Tetramethylpiperidine-1-oxy/Manganese Nitrate Catalyst System
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A highly efficient, ligand-enhanced 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO)/Mn(NO3)2 catalyst system for the aerobic oxidation of alcohols is described. From the series of coordinating ligands studied herein, 2-picolinic acid (PyCOOH) improves the catalytic activity of TEMPO/Mn(NO3)2 remarkably. Under ambient air at room temperature in acetic acid, the ligand-enhanced catalyst converts aliphatic and benzylic primary alcohols that bear various functional groups into their respective aldehydes with near quantitative conversions. The applicability of the catalyst for convenient preparative synthesis was demonstrated by conducting oxidations on a gram scale. A change of TEMPO to the sterically less demanding 9-azabicyclo[3.3.1]nonane N-oxyl results in a Mn catalyst that is also able to oxidize secondary alcohols to ketones. Mechanistic studies showed that alcohols are oxidized by the oxoammonium cation derived from the nitroxyl radical. The active oxidant is regenerated by Mn(NO3)2, and this process is greatly promoted by the coordination of PyCOOH to Mn.
- Lagerblom, Kalle,Lagerspets, Emi,Keskiv?li, Juha,Cook, Chris,Ekholm, Filip,Parviainen, Arno,Repo, Timo
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p. 3880 - 3887
(2017/09/28)
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- Highly regioselective gold-catalyzed formal hydration of propargylic: Gem -difluorides
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Herein, we report a highly regioselective gold-catalyzed formal hydration of propargylic gem-difluorides. Not only does this transformation provide access to versatile fluorinated building blocks that were difficult or hardly possible to access beforehand, but it also represents a rare case of a highly regioselective gold-catalyzed hydroalkoxylation of internal alkynes and puts forward the utility of the difluoromethylene unit as a directing group in catalysis.
- Hamel, Jean-Denys,Hayashi, Tatsuru,Cloutier, Mélissa,Savoie, Paul R.,Thibeault, Olivier,Beaudoin, Meggan,Paquin, Jean-Fran?ois
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supporting information
p. 9830 - 9836
(2017/12/08)
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- Mechanically induced oxidation of alcohols to aldehydes and ketones in ambient air: Revisiting TEMPO-assisted oxidations
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The present work addresses the development of an eco-friendly and cost-efficient protocol for the oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones by mechanical processing under air. Ball milling was shown to promote the quantitative conversion of a broad set of alcohols into carbonyl compounds with no trace of an over-oxidation to carboxylic acids. The mechanochemical reaction exhibited higher yields and rates than the classical, homogeneous, TEMPO-based oxidation.
- Porcheddu, Andrea,Colacino, Evelina,Cravotto, Giancarlo,Delogu, Francesco,De Luca, Lidia
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supporting information
p. 2049 - 2055
(2017/10/16)
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- Two-Step Synthesis of (Z)-3-Aryl-5-(arylmethylidene)butenolides by an Ivanov Reaction/Silver(I)-Catalyzed Lactonization/In Situ Dehydration Sequence
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A stereoselective synthesis of the title compounds was developed. Hexane- and amine-free THF solutions of α-lithiated lithium arylacetates ('arylacetic acid dianions') were aldol-added to 3-arylpropynals. This gave 2,5-diaryl-3-hydroxypent-4-ynoic acids with up to a 72:28 preference for the anti-diastereomer (27 examples + 1 exception). When treated with Ag2CO3 (1-20 mol%) in DMF at room temperature for 2.5 days, the respective mixtures underwent regio- and stereoselective lactonizations followed by an in situ dehydration. Thereby 3-aryl-5-(arylmethylidene)butenolides were obtained with a Z-configuration of the oxygenated C=C bond. Their overall yields ranged from 46% to 83% (1 exception: 28%). Three 3-aryl-5-(arylmethylidene)butenolides contained a C-Br and/or a C-I bond. They allowed a subsequent Pd-catalyzed C-C coupling, which furnished follow-up butenolides.
- Hermann, David,Arican, Deniz,Brückner, Reinhard
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p. 326 - 352
(2016/12/24)
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- [4+2] or [4+1] Annulation: Changing the Reaction Pathway of a Rhodium-Catalyzed Process by Tuning the Cp Ligand
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A change in reaction pathway was achieved for the first time by tuning the cyclopentadienyl (Cp) ligand used for the rhodium-catalyzed cyclization of benzamides with conjugated enynones. Depending on the Cp ligand, the reaction pathway switched between [4+2] and [4+1] annulation. Electronic effects turned out to be crucial for the product distribution. The dichotomy was attributed to the alteration of the Lewis acidity of the resultant Cp-bound rhodium species.
- Hong, Seung Youn,Jeong, Jisu,Chang, Sukbok
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supporting information
p. 2408 - 2412
(2017/02/23)
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- Phosphine-Mediated Dimerization of Conjugated Ene-Yne Ketones: Stereoselective Construction of Dihydrobenzofurans
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A new strategy for the phosphine-mediated dimerization of conjugated ene-yne ketones to produce functionalized dihydrobenzofurans has been developed, affording diversified 4,5-dihydrobenzofurans in moderate to excellent yields with high diastereoselectivities under mild conditions. This new synthetic method can tolerate a variety of functional groups and can be performed on a gram scale and in an asymmetric variant using the chiral phosphine Xyl-BINAP to give the desired products with up to 94% ee. (Figure presented.).
- Zhu, Cheng-Zhi,Sun, Yao-Liang,Wei, Yin,Shi, Min
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supporting information
p. 1263 - 1270
(2017/04/18)
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