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Perfluoroalkyl Cobaloximes: Preparation Using Hypervalent Iodine Reagents, Molecular Structures, Thermal and Photochemical Reactivity
Treatment of cobaloximes(II), [Co(Hdmg)2(L)2] (Hdmg = dimethylglyoximate, L = neutral ligand), with perfluoroalkyl iodane reagents leads to the formation of perfluoroalkyl cobaloximes(III), [CoRF(Hdmg)2(L)] (RF = CF3, C2F5, n-C3F7, CF2CF2Ph; L = Py, NH3, MeNH2, PhNH2, MeOH). The synthetic protocol can be significantly simplified to a one-pot procedure starting from cobalt(II) acetate-tetrahydrate. The products have been fully characterized by NMR, IR, and UV/vis spectroscopy as well as single-crystal X-ray diffraction, and the thermal and photochemical reactivity has been studied. According to the Co-L distances in the crystal, the trans influence of the RF- ligands can be rated as C2F5- ≈ n-C3F7- 2CF2Ph- ≈ CF3- 3-. The thermal decomposition of the complexes is different from that of nonfluorinated analogues, probably including perfluoroalkylation of an Hdmg- ligand as the initial step. In the CF3 complexes, the Co-C bond is very resistant against photolysis, but the ligand L is readily exchanged by MeOH upon exposure to blue light. In the complexes with longer RF chains, the Co-C bond is more readily cleaved, and the product distribution depends strongly on the presence of O2. Thus, the alkane RFH is the main product under exclusion of O2, while a fluorinated methyl ester and HF are formed in a methanol solution exposed to air.
Liebing, Phil,Oehler, Florian,Wagner, Mona,Tripet, Pascal F.,Togni, Antonio
p. 570 - 583
(2018)
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Aerobic oxidation of aldehydes to carboxylic acids catalyzed by recyclable ag/c3 n4 catalyst
The oxidation of aldehydes is an efficient methodology for the synthesis of carboxylic acids. Herein we hope to report a simple, efficient and recyclable protocol for aerobic oxidation of aldehydes to carboxylic acid by using C3N4 supported silver nanoparticles (Ag/C3N4) as a catalyst in aqueous solution under mild conditions. Under standard conditions, the corresponding carboxylic acids can be obtained in good to excellent yields. In addition, Ag/C3N4 is convenient for recovery and could be reused three times with satisfactory yields.
Wu, Chaolong,Yao, Xiaoquan,Yu, Min,Zhou, Li,Zhu, Li
p. 167 - 175
(2021/03/19)

Mechanistic Investigation of the Iron-Catalyzed Azidation of Alkyl C(sp3)-H Bonds with Zhdankin’s λ3-Azidoiodane
An in-depth study of the mechanism of the azidation of C(sp3)-H bonds with Zhdankin’s λ3-azidoiodane reagent catalyzed by iron(II)(pybox) complexes is reported. Previously, it was shown that tertiary and benzylic C(sp3)-H bonds of a range of complex molecules underwent highly site-selective azidation by reaction with a λ3-azidoiodane reagent and an iron(II)(pybox) catalyst under mild conditions. However, the mechanism of this reaction was unclear. Here, a series of mechanistic experiments are presented that reveal critical features responsible for the high selectivity and broad scope of this reaction. These experiments demonstrate the ability of the λ3-azidoiodane reagent to undergo I-N bond homolysis under mild conditions to form λ2-iodanyl and azidyl radicals that undergo highly site-selective and rate-limiting abstraction of a hydrogen atom from the substrate. The resultant alkyl radical then combines rapidly with a resting state iron(III)-azide complex, which is generated by the reaction of the λ3-azidoiodane with the iron(II)(pybox) complex, to form the C(sp3)-N3bond. This mechanism is supported by the independent synthesis of well-defined iron complexes characterized by cyclic voltammetry, X-ray diffraction, and EPR spectroscopy, and by the reaction of the iron complexes with alkanes and the λ3-azidoiodane. Reaction monitoring and kinetic studies further reveal an unusual effect of the catalyst on the rate of formation of product and consumption of reactants and suggest a blueprint for the development of new processes leading to late-stage functionalization of C(sp3)-H bonds.
Chatterjee, Ruchira,Day, Craig S.,Fawcett, Alexander,Hartwig, John F.
supporting information
p. 16184 - 16196
(2021/10/12)

Togni-II Reagent Mediated Selective Hydrotrifluoromethylation and Hydrothiolation of Alkenes?
Based on the redox reactions of Togni-II reagent and thiols, a thiol-tuned selective functionalization of unactivated olefins was disclosed. In combination with aryl thiols, stoichiometric amount of Togni-II reagent prompted a hydrotrifluoromethylation of alkenes, in which, aryl thiols played as reductant and hydrogen source; while by utilization of alkyl thiols, catalytic amount of Togni-II reagent initiated thiol-ene and thiol-yne reactions. The reported applications are characterized by their operational simplicity and wide functional group tolerance.
Teng, Shuang,Meng, Lingkui,Xu, Bingbing,Tu, Guangsheng,Wu, Peng,Liao, Zhiwen,Tan, Yulin,Guo, Jian,Zeng, Jing,Wan, Qian
supporting information
p. 3429 - 3434
(2021/11/08)

Efficiency of lithium cations in hydrolysis reactions of esters in aqueous tetrahydrofuran
Lithium cations were observed to accelerate the hydrolysis of esters with hydroxides (KOH, NaOH, LiOH) in a water/tetrahydrofuran (THF) two-phase system. Yields in the hydrolysis of substituted benzoates and aliphatic esters using the various hydroxides were compared, and the effects of the addition of lithium salt were examined. Moreover, it was presumed that a certain amount of LiOH was dissolved in THF by the coordination of THF with lithium cation and hydrolyzed esters even in the THF layer, as in the reaction by a phase-transfer catalyst.
Harada, Yumi,Hayashi, Kazuhiko,Ichimaru, Yoshimi,Imai, Masanori,Kojima, Yuki,Maeda, Azusa,Nakayama, Kanae,Sugiura, Kirara
p. 581 - 594
(2021/06/06)

N-Alkenylation of hydroxamic acid derivatives with ethynyl benziodoxolone to synthesizecis-enamides through vinyl benziodoxolones
The stereoselective synthesis ofcis-β-N-alkoxyamidevinyl benziodoxolones (cis-β-N-RO-amide-VBXs) fromO-alkyl hydroxamic acids in the presence of an ethynyl benziodoxolone-acetonitrile complex (EBX-MeCN) is reported herein. The reaction was performed under mild conditions including an aqueous solvent, a mild base, and room temperature. The reaction tolerated variousO-alkyl hydroxamic acids derived from carboxylic acids, such as amino acids, pharmaceuticals, and natural products. Vinyl dideuteratedcis-β-N-MeO-amide-VBXs were also synthesized using deuterium oxide as the deuterium source. Valine-derivedcis-β-N-MeO-amide-VBX was stereospecifically derivatized to hydroxamic acid-derivedcis-enamides without the loss of stereoselectivity or reduction in the deuterium/hydrogen ratio.
Shimbo, Daisuke,Maruyama, Toshifumi,Tada, Norihiro,Itoh, Akichika
supporting information
p. 2442 - 2447
(2021/04/02)

IrIII-Catalyzed Selective ortho-Monoiodination of Benzoic Acids with Unbiased C?H Bonds
An iridium-catalyzed selective ortho-monoiodination of benzoic acids with two equivalent C?H bonds is presented. A wide range of electron-rich and electron-poor substrates undergo the reaction under mild conditions, with >20:1 mono/di selectivity. Importantly, the C?H iodination occurs selectively ortho to the carboxylic acid moiety in substrates bearing competing coordinating directing groups. The reaction is performed at room temperature and no inert atmosphere or exclusion of moisture is required. Mechanistic investigations revealed a substrate-dependent reversible C?H activation/protodemetalation step, a substrate-dependent turnover-limiting step, and the crucial role of the AgI additive in the deactivation of the iodination product towards further reaction.
Weis, Erik,Johansson, Magnus J.,Martín-Matute, Belén
supporting information
p. 10185 - 10190
(2020/07/31)

Palladium Supported on Silk Fibroin for Suzuki–Miyaura Cross-Coupling Reactions
Silk fibroin supported Pd (Pd/SF) has been prepared and used as catalyst in Suzuki–Miyaura cross-coupling reactions in water/ethanol (4:1 v/v) mixture. The reactions proceed rapidly with aryl iodides and boronic acids with different electronic properties using low metal loading (0.38 mol-%). Pd/SF exhibits better recyclability compared to other biopolymer-supported Pd catalysts, up to nineteen cycles without loss of activity.
Albano, Gianluigi,Farinola, Gianluca M.,Lo Presti, Marco,Milella, Antonella,Omenetto, Fiorenzo G.,Rizzo, Giorgio
supporting information
p. 6992 - 6996
(2020/11/30)

Direct Intermolecular Anti-Markovnikov Hydroazidation of Unactivated Olefins
We herein report a direct intermolecular anti-Markovnikov hydroazidation method for unactivated olefins, which is promoted by a catalytic amount of bench-stable benziodoxole at ambient temperature. This method facilitates previously difficult, direct addition of hydrazoic acid across a wide variety of unactivated olefins in both complex molecules and unfunctionalized commodity chemicals. It conveniently fills a synthetic chemistry gap of existing olefin hydroazidation procedures, and thereby provides a valuable tool for azido-group labeling in organic synthesis and chemical biology studies.
Li, Hongze,Shen, Shou-Jie,Zhu, Cheng-Liang,Xu, Hao
supporting information
p. 9415 - 9421
(2019/06/21)

Iodide as a Nucleophilic Trigger in Aryne Three-Component Coupling for the Synthesis of 2-Iodobenzyl Alcohols
The synthetic potential of KI as the iodide source in aryne three-component coupling has been demonstrated using aldehydes as the third component. This mild and transition-metal-free coupling reaction allowed the straightforward synthesis of 2-iodobenzyl alcohols in moderate to good yields with good functional group compatibility. Moreover, KBr and KCl could be used as the nucleophilic trigger in this aryne multicomponent coupling (MCC) and N-methylisatin and CO2 could be used as the electrophilic third components.
Bhattacharjee, Subrata,Guin, Avishek,Gaykar, Rahul N.,Biju, Akkattu T.
supporting information
p. 4383 - 4387
(2019/06/08)

Base- and Additive-Free Ir-Catalyzed ortho-Iodination of Benzoic Acids: Scope and Mechanistic Investigations
A protocol for the C-H activation/iodination of benzoic acids catalyzed by a simple iridium complex has been developed. The method described in this paper allows the ortho-selective iodination of a variety of benzoic acids under extraordinarily mild conditions in the absence of any additive or base in 1,1,1,3,3,3-hexafluoroisopropanol as the solvent. The iridium catalyst used tolerates air and moisture, and selectively gives ortho-iodobenzoic acids with high conversions. Mechanistic investigations revealed that an Ir(III)/Ir(V) catalytic cycle operates, and that the unique properties of HFIP enables the C-H iodination using the carboxylic moiety as a directing group.
Erbing, Elis,Sanz-Marco, Amparo,Vázquez-Romero, Ana,Malmberg, Jesper,Johansson, Magnus J.,Gómez-Bengoa, Enrique,Martín-Matute, Belén
p. 920 - 925
(2018/02/14)

Direct Transformation of Arylamines to Aryl Halides via Sodium Nitrite and N-Halosuccinimide
A one-pot universal approach for transforming arylamines to aryl halides via reaction with sodium nitrite (NaNO2) and N-halosuccinimide (NXS) in DMF at room temperature under metal- and acid-free condition is described. This new protocol that is complementary to the Sandmeyer reaction, is suggested to involve the in situ generation of nitryl halide induce nitrosylation of aryl amine to form the diazo intermediate which is halogenated to furnish the aryl halide.
Mukhopadhyay, Sushobhan,Batra, Sanjay
supporting information
p. 14622 - 14626
(2018/09/21)

Method for preparing axitinib and intermediates thereof
The invention discloses a method for preparing axitinib and intermediates thereof. A chemical name of the axitinib is N-methyl-2-[(3-(1E-2-(pyridine-2-yl)ethylene)-1H-indazole-6-yl)sulfur]benzamide, and a chemical formula of the axitinib is C22H18N4OS. The preparation process disclosed by the invention is simple in process, readily available in raw materials, economic, environmentally friendly, high in product yield and product purity, contributes to realizing industrialization, reduces the production cost and is suitable for mass production. The provided novel intermediates and the preparation method thereof have significance on the economic technology of the axitinib.
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(2018/05/30)

N-Heterocycle-Stabilized Iodanes: From Structure to Reactivity
Pseudocyclic aryl-λ3-iodanes are superior reagents for a variety of oxidative transformations due to a well-balanced relation between stability, solubility and reactivity. Their properties are substantially influenced by a dative interaction between a Lewis base, in general the oxygen atom of a carboxylic acid or an amide, and the central hypervalent iodine atom. This work presents the first systematic investigation of pseudocyclic N-heterocycle-stabilized iodanes (NHIs). The synthesis of these throughout shelf-stable solids is robust and can be achieved on a large scale. Their reactivity is highly tunable, depending on the stabilizing heterocycle. Solid state structures of selected derivatives are reported and their reactivity in a model oxygen transfer reaction is compared. Further derivatization reactions to N-heterocycle-stabilized pseudocyclic diaryliodonium salts and cyclic iodoso species are presented as well.
Boelke, Andreas,Lork, Enno,Nachtsheim, Boris J.
supporting information
p. 18653 - 18657
(2018/11/23)

Transition metal free one pot synthesis of aryl carboxylic acids via dehomologative oxidation of styrenes
Iodine/NaOH-catalyzed one-pot dehomologative oxidation of styrenes to aryl carboxylic acids has been reported. A wide range of carboxylic acids are obtained using iodine (I2) as a catalyst, tert-butyl hydroperoxide (TBHP) as an oxidant and sodium hydroxide (NaOH) as a base. This reliable conversion involves dehomologation of styrene to aromatic aldehyde which on subsequent oxidation affords aryl carboxylic acid. This protocol was used for gram-scale synthesis as it is free from chromatographic purification. This is the first report for the oxidative transformation of styrenes into aryl carboxylic acids under transition metal-free conditions.
Patil, Bhausaheb N.,Sathe, Pratima A.,Parade, Babasao S.,Vadagaonkar, Kamlesh S.,Chaskar, Atul C.
supporting information
p. 4340 - 4343
(2018/11/06)

Iron(II)-Catalyzed Azidotrifluoromethylation of Olefins and N-Heterocycles for Expedient Vicinal Trifluoromethyl Amine Synthesis
We report herein an iron-catalyzed azidotrifluoromethylation method for expedient vicinal trifluoromethyl primary-amine synthesis. This method is effective for a broad range of olefins and N-heterocycles, and it facilitates efficient synthesis of a wide variety of vicinal trifluoromethyl primary amines, including those that prove difficult to synthesize with existing approaches. Our preliminary mechanistic studies revealed that the catalyst-promoted azido-group transfer proceeds through a carbo-radical instead of a carbocation species. Characterization of an active iron catalyst through X-ray crystallographic studies suggests that in situ generated, structurally novel iron-azide complexes promote the oxidant activation and selective azido-group transfer.
Zhu, Cheng-Liang,Wang, Cheng,Qin, Qi-Xue,Yruegas, Sam,Martin, Caleb D.,Xu, Hao
p. 5032 - 5037
(2018/05/14)

Enantioselective Synthesis of Oseltamivir Phosphate (Tamiflu) via the Iron-Catalyzed Stereoselective Olefin Diazidation
We herein report a gram-scale, enantioselective synthesis of Tamiflu, in which the key trans-diamino moiety has been efficiently installed via an iron-catalyzed stereoselective olefin diazidation. This significantly improved, iron-catalyzed method is uniquely effective for highly functionalized yet electronically deactivated substrates that have been previously problematic. Preliminary catalyst structure-reactivity-stereoselectivity relationship studies revealed that both the iron catalyst and the complex substrate cooperatively modulate the stereoselectivity for diazidation. Safety assessment using both differential scanning calorimetry (DSC) and the drop weight test (DWT) has also demonstrated the feasibility of carrying out this iron-catalyzed olefin diazidation for large-scale Tamiflu synthesis.
Li, Hongze,Shen, Shou-Jie,Zhu, Cheng-Liang,Xu, Hao
supporting information
p. 10619 - 10626
(2018/08/03)

Light-Driven Intermolecular Charge Transfer Induced Reactivity of Ethynylbenziodoxol(on)e and Phenols
Ethynylbenziodoxol(on)es (EBXs) have been widely used in organic synthesis as electrophilic alkyne-transfer reagents involving carbon- and heteroatom-based nucleophiles. However, potential reactions of EBXs with phenols remain uninvestigated. Here, we present the formation of (Z)-2-iodovinyl phenyl ethers with excellent regio- and stereoselectivity through the reactivity between EBXs and phenols driven by visible light. We propose that this light-activated transformation proceeds through electron donor-acceptor complexes to enable new reactivity beyond existing mechanisms for alkynylation of carbon- and heteroatom-based nucleophiles. This operationally robust process was employed for the synthesis of diverse (Z)-2-iodovinyl phenyl ethers through irradiating a solution containing a phenyl-EBX, a phenol, and the base Cs2CO3 with a commercially available blue LED at room temperature. The (Z)-2-iodovinyl phenyl ether products can be further stereospecifically functionalized to form trisubstituted alkenes, demonstrating the potential of these products en route to chemical complexity.
Liu, Bin,Lim, Chern-Hooi,Miyake, Garret M.
p. 12829 - 12835
(2018/10/15)

Tert-Butyl Nitrite-Mediated Synthesis of N-Nitrosoamides, Carboxylic Acids, Benzocoumarins, and Isocoumarins from Amides
This work reports tert-butyl nitrite (TBN) as a multitask reagent for (1) the controlled synthesis of N-nitrosoamide from N-alkyl amides, (2) hydrolysis of N-methoxyamides to carboxylic acids, (3) metal- and oxidant-free benzocoumarin synthesis from ortho-aryl-N-methoxyamides via N-H, C-N, and C-H bond activation, and (4) isocoumarin synthesis using Ru(II)/PEG as a recyclable catalytic system via ortho-C-H activation and TBN as an oxygen source. The sequential functional group interconversion of amide to acid has also been examined using IR spectroscopic analysis. Additionally, this methodology is highly advantageous due to short reaction time, gram scale synthesis, and broad substrate scope.
Yedage, Subhash L.,Bhanage, Bhalchandra M.
p. 5769 - 5781
(2017/06/07)

Copper-Catalyzed C(sp3)-S Bond and C(sp2)-S Bond Cross-Coupling of 2-(2-Iodobenzoyl) Substituted or 2-(2-Iodobenzyl) Substituted 1,2,3,4-Tetrahydroisoquinolines with Potassium Sulfide: Synthesis of Isoquinoline-Fused 1,3-Benzothiazine Scaffolds
The sulfuration reaction of 2-(2-iodobenzoyl) substituted, or 2-(2-iodobenzyl) substituted 1,2,3,4-tetrahydroisoquinolines with potassium sulfide proceeded in the presence of copper catalysts to give tetrahydroisoquinoline-fused 1,3-benzothiazine scaffolds in moderate to appropriate yields. This protocol provided an efficient and simple strategy to construct the corresponding benzothiazine derivatives via formation of C(sp3)-S bond and C(sp2)-S bond, which the C-S bonds formed via different routes in this reaction (traditional cross-coupling reaction via the cleavage of C-I bond and oxidative cross-coupling reaction via C(sp3)-H bond functionalization).
Dang, Pan,Zheng, Zhilei,Liang, Yun
p. 2263 - 2268
(2017/02/26)

Desyl and phenacyl as versatile, photocatalytically cleavable protecting groups: A classic approach in a different (visible) light
A highly efficient, catalytic strategy for the deprotection of classical phenacyl (Pac) as well as desyl (Dsy) protection groups has been developed using visible light photoredox catalysis. The deliberate use of a neutral two-phase acetonitrile/water mixture with K3PO4 applying catalytic amounts of [Ru(bpy)3](PF6)2 in combination with ascorbic acid is the key to this truly catalytic deprotection of Pac- and Dsy-protected carboxylic acids. Our mild yet robust protocol allows for fast and selective liberation of the free carboxylic acids in very good to quantitative yields, while only low catalyst loadings (1 mol %) are required. Both Pac and Dsy, easily introduced from commercially available precursors, can be applied for the direct protection of carboxylic acids and amino acids, offering orthogonality to a great variety of other common protecting groups. We further demonstrate the general applicability and versatility of these formerly underrated protecting groups in combination with our catalytic cleavage conditions, as underscored by the gained high functional group tolerance. Moreover, this method could successfully be adapted to the requirements of solidphase synthesis. As a proof of principle for an efficient visible light, photocatalytic linker cleavage, a Boc-protected tripeptide was split off from commercially available brominated Wang resin.
Speckmeier, Elisabeth,Zeitler, Kirsten
p. 6821 - 6826
(2017/11/06)

Metal-Free Dehomologative Oxidation of Arylacetic Acids for the Synthesis of Aryl Carboxylic Acids
A novel I2-promoted direct conversion of arylacetic acids into aryl carboxylic acids under metal-free conditions has been described. This remarkable transformation involves decarboxylation followed by an oxidation reaction enabled just by using DMSO as the solvent as well as an oxidant. Notably, aryl carboxylic acids are isolated by simple filtration technique and obtained in good to excellent yields. This protocol is free from chromatographic purification, which makes it applicable for large-scale synthesis.
Kalmode, Hanuman P.,Vadagaonkar, Kamlesh S.,Shinde, Suresh L.,Chaskar, Atul C.
p. 3781 - 3786
(2017/04/11)

Bimane: A Visible Light Induced Fluorescent Photoremovable Protecting Group for the Single and Dual Release of Carboxylic and Amino Acids
A series of ester conjugates of carboxylic and amino acids were synthesized based on bimane fluorescent photoremovable protecting group (FPRPG). The photorelease of single and dual (same as well as different) carboxylic and amino acids is demonstrated from a single bimane molecule on irradiation with visible light (λ ≥ 410 nm). The detailed mechanistic study of photorelease revealed that the release of two caged acids is simultaneous but in a stepwise pathway.
Chaudhuri, Amrita,Venkatesh, Yarra,Behara, Krishna Kalyani,Singh, N. D. Pradeep
supporting information
p. 1598 - 1601
(2017/04/13)

Metal-free and light-promoted radical iodotrifluoromethylation of alkenes with Togni reagent as the source of CF3 and iodine
A light-promoted methodology for the iodotrifluoromethylation of alkenes was developed. For the first time a Togni reagent was exploited as the source of both the CF3 group and iodine atom. Preliminary mechanistic studies suggest that both CF3I and 2-iodobenzoic acid are direct sources of the iodine atom that is transferred to the products.
Beniazza, Redouane,Douarre, Maxime,Lastécouères, Dominique,Vincent, Jean-Marc
supporting information
p. 3547 - 3550
(2017/03/31)

O -Iodoxybenzoic Acid (IBX)-Iodine Mediated One-Pot Deacylative Sulfonylation of 1,3-Dicarbonyl Compounds: A Synthesis of β-Carbonyl Sulfones
A combination of o-iodoxybenzoic acid (IBX) and a catalytic amount of iodine is found to promote a facile one-pot deacylative sulfonylation reaction of 1,3-dicarbonyl compounds with sodium sulfinates to yield β-carbonyl sulfones. The present method provides the target products bearing a wide variety of functional groups in one step and in good yields.
Katrun, Praewpan,Songsichan, Teerawat,Soorukram, Darunee,Pohmakotr, Manat,Reutrakul, Vichai,Kuhakarn, Chutima
supporting information
p. 1109 - 1121
(2017/02/24)

One-pot synthesis of primary amines from carboxylic acids through rearrangement of in situ generated hydroxamic acid derivatives
A one-pot synthesis of primary amines from carboxylic acids through a Lossen rearrangement of hydroxamic acid derivatives, which were in situ generated by the reaction of carboxylic acids with O-trimethylsilylhydroxylamine (NH2OTMS) and carbonyl diimidazole (CDI, 1.5 equiv) in dimethyl sulfoxide at room temperature, has been achieved. This one-pot method could be applied to various carboxylic acids such as aromatic, heteroaromatic, aliphatic, and optically active substrates.
Hoshino, Yujiro,Ohtsuka, Naoya,Okada, Takuya,Honda, Kiyoshi
p. 5304 - 5307
(2016/11/16)

Nickel(II)-Mediated Regioselective C H Monoiodination of Arenes and Heteroarenes by using Molecular Iodine
The 8-aminoquinoline-directed, nickel(II)-mediated ortho-iodination of benzamides using molecular iodine has been developed. The process is highly regioselective and furnishes only monoiodinated products. A broad range of arenes and heteroarenes with diverse functional groups provided monoiodinated products in good to excellent yields. (Figure presented.) .
Khan, Bhuttu,Kant, Ruchir,Koley, Dipankar
p. 2352 - 2358
(2016/07/28)

Nickel-catalyzed ortho-halogenation of unactivated (hetero)aryl C-H bonds with lithium halides using a removable auxiliary
The first example of Ni-catalyzed halogenation of (hetero)aryl C-H bonds with lithium halides (LiX, X = Br, I, Cl) using PIP as a removable directing group is reported. This protocol provides an efficient access to ortho-halogenated (hetero)arenes with operational simplicity, good functional group tolerance, and large-scale synthesis.
Zhan, Bei-Bei,Liu, Yan-Hua,Hu, Fang,Shi, Bing-Feng
p. 4934 - 4937
(2016/04/10)

Synthesis of isocoumarins via silver(I)-mediated annulation of enol esters
Silver-mediated annulation of 2-iodo enol esters leading to 4- and 3,4-substituted isocoumarins was accomplished selectively at room temperature. Coupling of 2-iodo benzoic acids with enolates that were produced in situ from the simple esters was also performed to produce isocoumarins under analogous reaction conditions. Owing to the mildness of the current protocol, 4-acyl 3-substituted isocoumarins were efficiently produced without any deacylation.
Panda, Niranjan,Mishra, Priyadarshini,Mattan, Irshad
p. 1047 - 1056
(2016/02/19)

Visible-Light-Induced Alkoxyl Radical Generation Enables Selective C(sp3)-C(sp3) Bond Cleavage and Functionalizations
The alkoxyl radical is an important reactive intermediate in mechanistic studies and organic synthesis; however, its current generation from alcohol oxidation heavily relies on transition metal activation under strong oxidative conditions. Here we report the first visible-light-induced alcohol oxidation to generate alkoxyl radicals by cyclic iodine(III) reagent catalysis under mild reaction conditions. The β-fragmentation of alkoxyl radicals enables selective C(sp3)-C(sp3) bond cleavage and alkynylation/alkenylation reactions with various strained cycloalkanols, and for the first time with linear alcohols.
Jia, Kunfang,Zhang, Fuyuan,Huang, Hanchu,Chen, Yiyun
supporting information
p. 1514 - 1517
(2016/02/20)

Dual Hypervalent Iodine(III) Reagents and Photoredox Catalysis Enable Decarboxylative Ynonylation under Mild Conditions
A combination of hypervalent iodine(III) reagents (HIR) and photoredox catalysis with visible light has enabled chemoselective decarboxylative ynonylation to construct ynones, ynamides, and ynoates. This ynonylation occurs effectively under mild reaction conditions at room temperature and on substrates with various sensitive and reactive functional groups. The reaction represents the first HIR/photoredox dual catalysis to form acyl radicals from α-ketoacids, followed by an unprecedented acyl radical addition to HIR-bound alkynes. Its efficient construction of an mGlu5 receptor inhibitor under neutral aqueous conditions suggests future visible-light-induced biological applications.
Huang, Hanchu,Zhang, Guojin,Chen, Yiyun
p. 7872 - 7876
(2015/06/30)

Lewis Acid Catalyzed Formal Intramolecular [3 + 3] Cross-Cycloaddition of Cyclopropane 1,1-Diesters for Construction of Benzobicyclo[2.2.2]octane Skeletons
A novel Lewis acid catalyzed formal intramolecular [3 + 3] cross-cycloaddition (IMCC) of cyclopropane 1,1-diesters has been successfully developed. This supplies an efficient and conceptually new strategy for construction of bridged bicyclo[2.2.2]octane skeletons. This [3 + 3]IMCC could be run up to gram scale and from easily prepared starting materials. This [3 + 3]IMCC, together with our previously reported [3 + 2]IMCC strategy, can afford either the bicyclo[2.2.2]octane or bicyclo[3.2.1]octane skeletons from the similar starting materials by regulating the substituents on vinyl group.
Ma, Weiwei,Fang, Jie,Ren, Jun,Wang, Zhongwen
supporting information
p. 4180 - 4183
(2015/09/15)

Copper(I)-photocatalyzed trifluoromethylation of alkenes
Using the photoreducible CuII precatalyst 2, trifluoromethylation reactions of alkenes are conducted effectively at low copper loading (0.1-0.5 mol%) on exposing the reaction mixture to sunlight/ambient light.
Beniazza,Molton,Duboc,Tron,McClenaghan,Lastécouères,Vincent
supporting information
p. 9571 - 9574
(2015/06/08)

Hypervalent iodine reagents enable chemoselective deboronative/decarboxylative alkenylation by photoredox catalysis
Chemoselective C(sp3)-C(sp2) coupling reactions under mild reaction conditions are useful for synthesizing alkyl-substituted alkenes having sensitive functional groups. Reported here is a visible-light-induced chemoselective alkenylation through a deboronation/decarboxylation sequence under neutral aqueous reaction conditions at room temperature. This reaction represents the first hypervalent-iodineenabled radical decarboxylative alkenylation reaction, and a novel benziodoxole-vinyl carboxylic acid reaction intermediate was isolated. This C(sp3/sup>)-C(sp2) coupling reaction leads to aryl-and acyl-substituted alkenes containing various sensitive functional groups. The excellent chemoselectivity, stable reactants, and neutral aqueous reaction conditions of the reaction suggest future biomolecule applications.
Huang, Hanchu,Jia, Kunfang,Chen, Yiyun
supporting information
p. 1881 - 1884
(2015/02/19)

Is carbon dioxide able to activate halogen/lithium exchange?
The unexpected effect of carbon dioxide on halogen-lithium exchange (HLE) reactions of selected haloarenes with tBuLi was investigated. In an aliphatic hydrocarbon solvent (pentane), the HLE does not occur at ca. -70 C but, surprisingly, pouring the mixture of reactants onto dry ice and subsequent aqueous acidic hydrolysis gave carboxylic acids resulting from the quench of the first-formed aryllithiums with carbon dioxide. This suggests that CO 2 acts as a promoter of the HLE and, subsequently, serves as an electrophile to trap the aryllithium intermediates that are generated in situ. Theoretical DFT calculations were used to develop a plausible mechanism for the reaction, which indicates that CO2 is a much weaker donor than tetrahydrofuran (THF) so the cleavage of inert tBuLi cubic tetramers into more reactive solvated dimeric species (tBuLi)2(CO2) 4 is disfavored by 42.8 kJ per mol of (tBuLi)4. It is possible that this deaggregation process occurs to some extent when a large excess of CO2 is used. Copyright
Durka, Krzysztof,Lulinski, Sergiusz,Dabrowski, Marek,Serwatowski, Janusz
p. 4562 - 4570
(2014/08/05)

Aryl diazonium nanomagnetic sulfate and potassium iodide: An iodination process
A simple and efficient procedure for the synthesis of iodoarenes is developed which involves the sequential diazotization-iodination of aromatic amines with sodium nitrite, nanomagnetic supported sulfonic acid, and potassium iodide under solvent-free conditions at room temperature.
Kolvari, Eskandar,Amoozadeh, Ali,Koukabi, Nadiya,Otokesh, Somayeh,Isari, Mohsen
supporting information
p. 3648 - 3651
(2014/06/23)

Direct carbocyclizations of benzoic acids: Catalyst-controlled synthesis of cyclic ketones and the development of tandem aHH (acyl Heck-Heck) reactions
The formation of exo-methylene indanones and indenones from simple ortho-allyl benzoic acid derivatives has been developed. Selective formation of the indanone or indenone products in these reactions is controlled by choice of ancillary ligand. This new process has a low environmental footprint as the products are formed in high yields using low catalyst loadings, while the only stoichiometric chemical waste generated from the reactants in the transformation is acetic acid. The conversion of the active cyclization catalyst into the Hermman-Beller palladacycle was exploited in a one-pot tandem acyl Heck-Heck (aHH) reaction, and utilized in the synthesis of donepezil. Carboxylic acids in aHH: Simple ortho-allyl benzoic acid derivatives have been utilized in an acyl Heck (aH) reaction to selectively form indanones and indenones. The conversion of the active cyclization catalyst into the Hermman-Beller palladacycle was exploited in a one-pot tandem acyl Heck-Heck (aHH) reaction to form two sp 2-sp2 bonds of (E)-trisubstituted olefins.
Miles, Kelsey C.,Le, Chi,Stambuli, James P.
supporting information
p. 11336 - 11339
(2014/10/16)

Ketene-Ketene interconversion. 6-Carbonylcyclohexa-2,4-dienone-hepta-1,2,4, 6-tetraene-1,7-dione-6-oxocyclohexa-2,4-dienylidene and wolff rearrangement to fulven-6-one
6-Carbonylcyclohexa-2,4-dienone (1) has been generated by flash vacuum thermolysis (FVT) with Ar-matrix isolation of methyl salicylate (7), 2-phenylbenzo-1,3-dioxan-4-one (8), phthalic peranhydride (9), and benzofuran-2,3-dione (11) and also by matrix photolysis of 9, 11, and 2-diazocyclohepta-4,6-dien-1,3-dione (12). In each case, FVT above 600 °C results in decarbonylation of 1 and Wolff rearrangement to fulven-6-one (13) either concertedly or via open-shell singlet 6-oxocyclohexa-2,4-dienylidene (18). Ketenes 1 and 13 were characterized by IR spectroscopy. Photolysis of matrix-isolated 1 at 254 nm also results in the slow formation of 13. The sequential formation of ketenes 1 and 13 from 7 has also been monitored by FVT-mass spectrometry, and 13 has been trapped with MeOH to afford methyl 1,3-cyclopentadiene-1- and -2-carboxylates 15 and 16. FVT of methyl salicylate-1-13C 7a revealed a deep-seated rearrangement of the 13C-labeled 1a to hepta-1,2,4,6-tetraen-1,7-dione (17a) by means of electrocyclic ring opening followed by a facile 1,5-H shift and recyclization prior to CO-elimination and ring contraction to 13C-labeled 13. The rearrangement mechanism is supported by M06-2X/6-311++G(d,p) calculations, which predict feasible barriers for the FVT rearrangements and confirm the observed labeling pattern in the isolated methyl salicylate 7a/7b and methyl cyclopentadienecarboxylates 20 and 21 resulting from trapping of 13 with MeOH.
Koch, Rainer,Blanch, Rodney J.,Wentrup, Curt
p. 6978 - 6986
(2014/08/18)

Superacid BF3-H2O promoted benzylation of arenes with benzyl alcohols and acetates initiated by trace water
A convenient procedure employing simple starting materials benzyl alcohols and acetates as the benzyl donors to assemble a series of diarylalkanes through benzylation of arenes using in situ prepared superacid BF3-H 2O as an efficient promoter has been developed. The beneficial role of water in the reaction has been clarified with combination of control experiments and 11B NMR analysis. This reaction is a self-promoted model, which is triggered by the trace of water and continuously promoted by self released by-product water (or carboxylic acid). A wide range of substrates are investigated and the moderate to excellent yields and the good regioselectivities for secondary benzyl alcohols as well as arenes bearing electron-withdrawing groups have been achieved. As a result, moisture in the reaction system has been utilized as an efficient initiator in all benzylation cases.
Zhang, Shuting,Zhang, Xiaohui,Ling, Xuege,He, Chao,Huang, Ruofeng,Pan, Jing,Li, Jiaqiang,Xiong, Yan
p. 30768 - 30774
(2014/08/05)

Synthesis, characterization and initial evaluation of 5-nitro-1- (trifluoromethyl)-3H-1λ3,2-benziodaoxol-3-one
The synthesis of 5-nitro-1-(trifluoromethyl)-3H-1λ3,2- benziodaoxol-3-one (3), a hypervalent-iodine-based electrophilic trifluoromethylating reagent, is described. Whereas considerations based on cyclic voltammetry and X-ray structural properties would predict an inferior reactivity when compared to the non-nitrated derivative 2, 19F NMR kinetic studies showed that this new derivative is almost one order of magnitude more reactive. Furthermore, differential scanning calorimetry measurements indicated that, in addition, it is also safer to handle.
Santschi, Nico,Sarott, Roman C.,Otth, Elisabeth,Kissner, Reinhard,Togni, Antonio
p. 1 - 6
(2014/01/23)

Visible-light-induced chemoselective deboronative alkynylation under biomolecule-compatible conditions
Here, we report a visible-light-induced deboronative alkynylation reaction, which is redox-neutral and works with primary, secondary and tertiary alkyl trifluoroborates or boronic acids to generate aryl, alkyl and silyl substituted alkynes. This reaction is highly chemoselective and performs well on substrates containing alkenes, alkynes, aldehydes, ketones, esters, nitriles, azides, aryl halides, alkyl halides, alcohols, and indoles, with no detectable occurrence of side reactions. The mechanism of this novel C(sp3)-C(sp) bond coupling reaction was investigated by luminescence quenching, radical trapping, on-off light, and 13C-isotopic-labeling experiments. This reaction can be performed in neutral aqueous conditions, and it is compatible with amino acids, nucleosides, oligosaccharides, nucleic acids, proteins, and cell lysates.
Huang, Hanchu,Zhang, Guojin,Gong, Li,Zhang, Shuaiyan,Chen, Yiyun
supporting information
p. 2280 - 2283
(2014/03/21)

Design, synthesis and anticancer activity evaluation of diazepinomicin derivatives
A series of diazepinomicin derivatives were synthesized and evaluated in vitro for their growth inhibitory activity against the human carcinoma cell lines. The results indicated the anticancer selectivity of this kind of compounds. Based on the results, preliminary structure-activity relationships were discussed.
Yu, Yongguo,Wu, Jianbo,Lei, Fan,Chen, Lei,Wan, Weili,Hai, Li,Guan, Mei,Wu, Yong
p. 369 - 373
(2013/07/26)

Palladium-catalyzed insertion of N-tosylhydrazones for the synthesis of isoindolines
Isoindolines are synthesized by palladium-catalyzed coupling reaction of N-(2-iodobenzyl) anilines with α,β-unsaturated N-tosylhydrazones. The reaction has several potential advantages: (1) toleration of a wide range of functional groups, (2) easy to handle and with mild conditions, (3) enriches the isoindoline family, (4) two new bonds form in one step.
Zhou, Ping-Xin,Luo, Jian-Yi,Zhao, Lian-Biao,Ye, Yu-Ying,Liang, Yong-Min
supporting information
p. 3254 - 3256
(2013/05/08)

Palladium-catalyzed annulation reactions of methyl o-halobenzoates with azabicyclic alkenes: A general protocol for the construction of benzo[c]phenanthridine derivatives
The annulation reaction of methyl o-halobenzoates with azabicyclic alkenes proceeds efficiently to give the corresponding benzo[c]phenanthridine derivatives in good to excellent yields using a developed base-free methodology based on our preliminary studies. Thirty-seven application examples validate the compatibility of the present strategy with different groups, particularly with the electron-deficient ones, that are difficult to access using other traditional methods. In addition, annulation reactions with non-symmetric azabicyclic alkenes are achieved in high regioselectivity.
Guo, Cui,Huang, Kanglun,Wang, Bo,Xie, Longguang,Xu, Xiaohua
p. 17271 - 17280
(2013/09/24)

Kinetics and mechanism of the oxidation of substituted benzaldehydes with bis(pyridine)silver permanganate
The oxidation of thirty-six ortho-, meta- and para-substituted benzaldehydes by bis(pyridine)silver permanganate (BPSP) resulted in the formation of the corresponding benzoic acids. The reaction is first order with respect to both BPSP and aldehydes. The reaction is catalyzed by hydrogen ions. The rate of reaction increases with an increase in the amount of acetic acid in the solvent. The correlation analyses of the rate of oxidation of thirty-six aldehydes were performed in terms of Charton's LDR and LDRS equations. The rate of oxidation of meta- and para-substituted benzaldehydes showed excellent correlation with Charton's LDR equation. The rates of ortho-compounds showed excellent correlation with LDRS equation. The oxidation para-compounds is more susceptible to the delocalization effect. The oxidation of ortho- and meta-compounds exhibited a greater dependence on the field effect. The polar reaction constants are negative indicating an electron-deficient centre in the rate-determining step. A mechanism involving a nucleophilic attack on the carbonyl group by a permanganate-oxygen and a subsequent hydride transfer has been proposed.
Purohit, Trupti,Banerji, Jayshree,Kotai, Laszlo,Sajo,Banerji,Sharma, Pradeep K.
p. 1045 - 1052
(2013/01/14)

Synthesis of 1-[(Triisopropylsilyl)ethynyl]-1λ3,2- benziodoxol-3(1 H)-one and alkynylation of indoles, thiophenes, and anilines
An efficient procedure was developed for the synthesis of 1-[(triisopropylsilyl)ethynyl]-13,2-benziodoxol-3(1H)-one on a 100-mmol (36-g) scale. The benziodoxolone can be used for the gold-catalyzed direct alkynylation of indole, 2-hexylthiophene, or N,N-dibenzylaniline on a 5- to 10-mmol scale. Georg Thieme Verlag Stuttgart New York.
Brand, Jonathan P.,Waser, Jerome
experimental part
p. 1155 - 1158
(2012/06/04)

Ethynyl benziodoxolones for the direct alkynylation of heterocycles: Structural requirement, improved procedure for pyrroles, and insights into the mechanism
This report describes a full study of the gold-catalyzed direct alkynylation of indoles, pyrroles, and thiophenes using alkynyl hypervalent iodine reagents, especially the study of the structural requirements of alkynyl benziodoxolones for an efficient acetylene transfer to heterocycles. An improved procedure for the alkynylation of pyrroles using pyridine as additive is also reported. Nineteen alkynyl benziodoxol(on)es were synthesized and evaluated in the direct alkynylation of indoles and/or thiophenes. Bulky silyl groups as acetylene substituents were optimal. Nevertheless, transfer of aromatic acetylenes to thiophene was achieved for the first time. An accelerating effect of a methyl substituent in both the 3-and 6-position of triisopropylsilylethynyl-1,2-benziodoxol-3(1H)-one (TIPS-EBX) on the reaction rate was observed. Competitive experiments between substrates of different nucleophilicity, deuterium labeling experiments, as well as the regioselectivity observed are all in agreement with electrophilic aromatic substitution. Gold(III) 2-pyridinecarboxylate dichloride was also an efficient catalyst for the reaction. Investigations indicated that gold(III) could be eventually reduced to gold(I) during the process. As a result of these investigations, a π activation or an oxidative mechanism are most probable for the alkynylation reaction.
Brand, Jonathan P.,Chevalley, Clara,Scopelliti, Rosario,Waser, Jerome
scheme or table
p. 5655 - 5666
(2012/06/01)

Gold-catalysed oxyarylation of styrenes and mono- and gem-disubstituted olefins facilitated by an iodine(III) oxidant
1-Hydroxy-1,2-benziodoxol-3(1H)-one (IBA) is an efficient terminal oxidant for gold-catalysed, three-component oxyarylation reactions. The use of this iodine(III) reagent expands the scope of oxyarylation to include styrenes and gem-disubstituted olefins, substrates that are incompatible with the previously reported Selectfluor-based methodology. Diverse arylsilane coupling partners can be employed, and in benzotrifluoride, homocoupling is substantially reduced. In addition, the IBA-derived co-products can be recovered and recycled. The I's have it: The unprecedented use of an iodine(III) reagent as the terminal oxidant for gold-catalysed oxyarylation allows the substrate scope to be significantly expanded; in addition to monosubstituted olefins, styrenes and gem-disubstituted olefins are well tolerated (see scheme). With benzotrifluoride as solvent, unproductive homodimerisation of the arylsilane coupling partner is effectively suppressed. Copyright
Ball, Liam T.,Lloyd-Jones, Guy C.,Russell, Christopher A.
supporting information; experimental part
p. 2931 - 2937
(2012/04/23)

Structure-Reactivity correlation in the oxidation of substituted benzaldehydes by tetraethylammonium chlorochromate
Oxidation of 36 monosubstituted benzaldehydes by tetraethylammonium chlorochromate in dimethyl sulphoxide, leads to the formation of corresponding benzoic acids. The reaction is of first order with respect to chlorochromate and aldehydes. The reaction is promoted by H+; the H+ dependence has the form kobs = a + b[H+]. The oxidation of duteriated benzaldehyde exhibits substantial primary kinetic isotope effect. The reaction was studied in 19 different organic solvents and the effect of solvent was analyzed using Taft's and Swain's multiparametric equations. The rates of the oxidation of para- and meta-substituted benzaldehydes showed excellent correlation in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzaldehydes were correlated well with tetraperametric LDRS equation. The oxidation of para-substituted benzaldehydes is more susceptible to the delocalized effect than is the oxidation of ortho- and meta- substituted compounds, which display a greater dependence on the field effect. The positive value of h suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the orthosubstituents. A suitable mechanism has been proposed.
Gehlot,Prasadrao,Sharma
experimental part
p. 1173 - 1178
(2012/01/05)

A green procedure for the diazotization-iodination of aromatic amines under aqueous, strong-acid-free conditions
A convenient and mild one-pot method for the synthesis of iodoarenes in high yields by the sequential diazotization-iodination of aromatic amines with a reusable polymeric diazotization agent in the presence of p-toluenesulfonic acid at room temperature in water was developed. The method is general and is the greenest alternative of the known diazotization-iodination methods. The method is also effective for the preparation of 1H-benzo[d][1,2,3]triazole and benzo[d][1,2,3]thiadiazole. Georg Thieme Verlag Stuttgart ? New York.
Trusova, Marina E.,Krasnokutskaya, Elena A.,Postnikov, Pavel S.,Choi, Younghwa,Chi, Ki-Whan,Filimonov, Victor D.
experimental part
p. 2154 - 2158
(2011/08/05)