- Radical Decarboxylative Carbometalation of Benzoic Acids: A Solution to Aromatic Decarboxylative Fluorination
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Abundant aromatic carboxylic acids exist in great structural diversity from nature and synthesis. To date, the synthetically valuable decarboxylative functionalization of benzoic acids is realized mainly by transition-metal-catalyzed decarboxylative cross couplings. However, the high activation barrier for thermal decarboxylative carbometalation that often requires 140 °C reaction temperature limits both the substrate scope as well as the scope of suitable reactions that can sustain such conditions. Numerous reactions, for example, decarboxylative fluorination that is well developed for aliphatic carboxylic acids, are out of reach for the aromatic counterparts with current reaction chemistry. Here, we report a conceptually different approach through a low-barrier photoinduced ligand to metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation strategy, which generates a putative high-valent arylcopper(III) complex, from which versatile facile reductive eliminations can occur. We demonstrate the suitability of our new approach to address previously unrealized general decarboxylative fluorination of benzoic acids.
- Xu, Peng,López-Rojas, Priscila,Ritter, Tobias
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supporting information
p. 5349 - 5354
(2021/05/05)
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- Cu-Catalyzed Phenol O-Methylation with Methylboronic Acid
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A Cu-catalyzed oxidative cross-coupling of phenols with methylboronic acid to form aryl methyl ethers has been developed, expanding the scope of Chan-Evans-Lam alkylation. Electron-deficient phenol derivatives with a broad array of functional groups are methylated in high yields. Increased reaction temperature and catalyst loading enables the methylation of substrates incorporating pyridine and dihydroquinolone motifs. Electron-rich phenol derivatives are poor substrates for the methylation; the characterization of C?H homodimerization products formed from these substrates illuminates a competing mechanistic pathway.
- Bartlett, Mairead E.,Chavez, Angela K.,Gaffney, Uma Bhagwat,Gorin, David J.,Lee, Joyce,Sharew, Betemariam,Wu, Miranda,Zhu, Yingchuan
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supporting information
p. 5661 - 5664
(2021/11/11)
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- A highly stable all-in-one photocatalyst for aryl etherification: The NiIIembedded covalent organic framework
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The efficient conversion of aryl bromides to the corresponding aryl alkyl ethers by dual nickel/photocatalysis has seen great progress, but difficulties of recycling the photosensitizer or nickel complexes cause problems of sustainability. Here, we report the design of a novel, highly stable vinyl bridge 2D covalent organic framework (COF) containing Ni, which combines the role of photosensitizer and reactive site. The as-prepared sp2c-COFdpy-Ni acts as an efficient heterogeneous photocatalyst for C-O cross coupling. The sp2c-COFdpy-Ni can be completely recovered and used repeatedly without loss of activity, overcoming the limitations of the prior methods. Preliminary studies reveal that strong interlayer electron transfer may facilitate the generation of the proposed intermediate sp2c-COFdpy-NiI in a bimolecular and self-sustained manner. This all-in-one heterogeneous photocatalyst exhibits good compatibility of substrates and tolerance of functional groups. The successful attempt to expand the 2D COFs with this new catalyst into photocatalytic organic transformation opens an avenue for photoredox/transition metal mediated coupling reactions.
- Chen, Hao,Dong, Wenbo,Hu, Jianxiang,Rao, Li,Wang, Pei,Wang, Shengyao,Xiang, Yonggang,Yang, Yi
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p. 5797 - 5805
(2021/08/23)
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- Trialkylammonium salt degradation: Implications for methylation and cross-coupling
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Trialkylammonium (most notably N,N,N-trimethylanilinium) salts are known to display dual reactivity through both the aryl group and the N-methyl groups. These salts have thus been widely applied in cross-coupling, aryl etherification, fluorine radiolabelling, phase-transfer catalysis, supramolecular recognition, polymer design, and (more recently) methylation. However, their application as electrophilic methylating reagents remains somewhat underexplored, and an understanding of their arylation versus methylation reactivities is lacking. This study presents a mechanistic degradation analysis of N,N,N-trimethylanilinium salts and highlights the implications for synthetic applications of this important class of salts. Kinetic degradation studies, in both solid and solution phases, have delivered insights into the physical and chemical parameters affecting anilinium salt stability. 1H NMR kinetic analysis of salt degradation has evidenced thermal degradation to methyl iodide and the parent aniline, consistent with a closed-shell SN2-centred degradative pathway, and methyl iodide being the key reactive species in applied methylation procedures. Furthermore, the effect of halide and non-nucleophilic counterions on salt degradation has been investigated, along with deuterium isotope and solvent effects. New mechanistic insights have enabled the investigation of the use of trimethylanilinium salts in O-methylation and in improved cross-coupling strategies. Finally, detailed computational studies have helped highlight limitations in the current state-of-the-art of solvation modelling of reaction in which the bulk medium undergoes experimentally observable changes over the reaction timecourse. This journal is
- Assante, Michele,Baillie, Sharon E.,Juba, Vanessa,Leach, Andrew G.,McKinney, David,Reid, Marc,Washington, Jack B.,Yan, Chunhui
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p. 6949 - 6963
(2021/06/02)
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- Preparation method of nitrogen-alkyl (deuterated alkyl) aromatic heterocycle and alkyl (deuterated alkyl) aryl ether compound
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The invention provides a method for preparing nitrogen-alkyl(deuterated alkyl)aromatic heterocycle and alkyl(deuterated alkyl)aryl ether compounds. The method adopted in the invention specifically comprises the following steps: firstly, adding an alkoxy base (MOR') or a combination reagent Q (comprising a base M'X, an alcohol C and a molecular sieve E) into a solvent B to be stirred; then, addingan aromatic compound D of nitrogen sulfonyl or oxygen sulfonyl into a mixture; separating and purifying after reaction to obtain nitrogen-alkyl(deuterated alkyl)aromatic heterocycle or alkyl(deuterated alkyl)aryl ether. The method can realize one-step conversion from an electron withdrawing benzenesulfonyl protecting group on a nitrogen or oxygen atom to an electron donating alkyl protecting group, avoids using highly toxic alkyl halide, and has advantages of being efficient, economical, environmentally friendly, mild in condition, good in substrate universality and high in yield; the prepareddeuterated compounds can be widely applied to the fields of pharmaceutical chemistry and organic chemistry synthesis.
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Paragraph 0066-0068
(2021/04/03)
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- Methylation with Dimethyl Carbonate/Dimethyl Sulfide Mixtures: An Integrated Process without Addition of Acid/Base and Formation of Residual Salts
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Dimethyl sulfide, a major byproduct of the Kraft pulping process, was used as an inexpensive and sustainable catalyst/co-reagent (methyl donor) for various methylations with dimethyl carbonate (as both reagent and solvent), which afforded excellent yields of O-methylated phenols and benzoic acids, and mono-C-methylated arylacetonitriles. Furthermore, these products could be isolated using a remarkably straightforward workup and purification procedure, realized by dimethyl sulfide‘s neutral and distillable nature and the absence of residual salts. The likely mechanisms of these methylations were elucidated using experimental and theoretical methods, which revealed that the key step involves the generation of a highly reactive trimethylsulfonium methylcarbonate intermediate. The phenol methylation process represents a rare example of a Williamson-type reaction that occurs without the addition of a Br?nsted base.
- Chan, Bun,Lui, Matthew Y.,Lui, Yuen Wai
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- Electrophotocatalytic SNAr Reactions of Unactivated Aryl Fluorides at Ambient Temperature and Without Base
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The electrophotocatalytic SNAr reaction of unactivated aryl fluorides at ambient temperature without strong base is demonstrated.
- Huang, He,Lambert, Tristan H.
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supporting information
p. 658 - 662
(2019/11/28)
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- Fluorinations of unsymmetrical diaryliodonium salts containing: Ortho -sidearms; Influence of sidearm on selectivity
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Activated aromatics were reacted with two different fluoroidoane reagents 1 and 2 in the presence of triflic acid to prepare only the para-substituted diaryliodonium salts. With fluoroiodane 1 the unsymmetrical diaryliodonium salts contained an ortho-propan-2-ol sidearm, whereas the alcohol sidearm was eliminated to form an ortho-styrene sidearm in the reaction with fluoroiodane 2. Only the diaryliodonium salts containing a styrene sidearm were fluorinated successfully to deliver para-fluorinated aromatics in good yields.
- Abudken, Ahmed M. H.,Hope, Eric G.,Singh, Kuldip,Stuart, Alison M.
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p. 6140 - 6146
(2020/10/30)
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- Discovery and characterization of an acridine radical photoreductant
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Photoinduced electron transfer (PET) is a phenomenon whereby the absorption of light by a chemical species provides an energetic driving force for an electron-transfer reaction1–4. This mechanism is relevant in many areas of chemistry, including the study of natural and artificial photosynthesis, photovoltaics and photosensitive materials. In recent years, research in the area of photoredox catalysis has enabled the use of PET for the catalytic generation of both neutral and charged organic free-radical species. These technologies have enabled previously inaccessible chemical transformations and have been widely used in both academic and industrial settings. Such reactions are often catalysed by visible-light-absorbing organic molecules or transition-metal complexes of ruthenium, iridium, chromium or copper5,6. Although various closed-shell organic molecules have been shown to behave as competent electron-transfer catalysts in photoredox reactions, there are only limited reports of PET reactions involving neutral organic radicals as excited-state donors or acceptors. This is unsurprising because the lifetimes of doublet excited states of neutral organic radicals are typically several orders of magnitude shorter than the singlet lifetimes of known transition-metal photoredox catalysts7–11. Here we document the discovery, characterization and reactivity of a neutral acridine radical with a maximum excited-state oxidation potential of ?3.36 volts versus a saturated calomel electrode, which is similarly reducing to elemental lithium, making this radical one of the most potent chemical reductants reported12. Spectroscopic, computational and chemical studies indicate that the formation of a twisted intramolecular charge-transfer species enables the population of higher-energy doublet excited states, leading to the observed potent photoreducing behaviour. We demonstrate that this catalytically generated PET catalyst facilitates several chemical reactions that typically require alkali metal reductants and can be used in other organic transformations that require dissolving metal reductants.
- MacKenzie, Ian A.,Wang, Leifeng,Onuska, Nicholas P. R.,Williams, Olivia F.,Begam, Khadiza,Moran, Andrew M.,Dunietz, Barry D.,Nicewicz, David A.
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- Aryl dechlorination and defluorination with an organic super-photoreductant
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Direct excitation of the commercially available super-electron donor tetrakis(dimethylamino)ethylene (TDAE) with light-emitting diodes at 440 or 390 nm provides a stoichiometric reductant that is able to reduce aryl chlorides and fluorides. The method is very simple and requires only TDAE, substrate, and solvent at room temperature. The photoactive excited state of TDAE has a lifetime of 17.3 ns in cyclohexane at room temperature and an oxidation potential of ca. -3.4 V vs. SCE. This makes TDAE one of the strongest photoreductants able to operate on the basis of single excitation with visible photons. Direct substrate activation occurs in benzene, but acetone is reduced by photoexcited TDAE and substrate reduction takes place by a previously unexplored solvent radical anion mechanism. Our work shows that solvent can have a leveling effect on the photochemically available redox power, reminiscent of the pH-leveling effect that solvent has in acid-base chemistry.
- Glaser, Felix,Kerzig, Christoph,Larsen, Christopher B.,Wenger, Oliver S.
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p. 1035 - 1041
(2020/08/28)
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- Fluorination of arylboronic esters enabled by bismuth redox catalysis
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Bismuth catalysis has traditionally relied on the Lewis acidic properties of the element in a fixed oxidation state. In this paper, we report a series of bismuth complexes that can undergo oxidative addition, reductive elimination, and transmetallation in a manner akin to transition metals. Rational ligand optimization featuring a sulfoximine moiety produced an active catalyst for the fluorination of aryl boronic esters through a bismuth (III)/bismuth (V) redox cycle. Crystallographic characterization of the different bismuth species involved, together with a mechanistic investigation of the carbonfluorine bond-forming event, identified the crucial features that were combined to implement the full catalytic cycle.
- Planas, Oriol,Wang, Feng,Leutzsch, Markus,Cornella, Josep
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p. 313 - 317
(2020/01/28)
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- Radical Carbofluorination of Alkenes with Arylhydrazines and Selectfluor: Additives, Mechanistic Pathways, and Polar Effects
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Radical carbofluorination reactions starting from arylhydrazines and nonactivated alkenes, in which the C?F bond is formed through the use of Selectfluor, can be improved through the addition of anisole. Because direct trapping products could be detected only in trace amounts, anisole does primarily act as a reversible scavenger for the highly reactive ammonium radical dication released from Selectfluor in the C?F bond-forming step. As shown for three diverse substitution patterns, the main role of anisole is to prevent, or at least reduce, the undesired addition of the ammonium radical dication to the alkene, which in turn leads to an unfavorable consumption of the arylhydrazine-derived precursors required for carbofluorination. Moreover, besides the remarkable polar effects in radical trapping, this study shows that the Selectfluor-derived nitrogen-centered radical dication may add directly to alkenes, which has not been described so far.
- Pirzer, Anna S.,Alvarez, Eva-Maria,Friedrich, Heike,Heinrich, Markus R.
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supporting information
p. 2786 - 2792
(2019/02/03)
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- Detosylative (Deutero)alkylation of Indoles and Phenols with (Deutero)alkoxides
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An efficient strategy for N/O-(deutero)alkylation of indoles and phenols with alkoxides/alcohols as the alkylation reagents is described. The consecutive detosylation/alkylation transformations feature mild reaction conditions, high ipso-selectivity, and good functional group tolerance (>50 examples). A one-pot selective N-alkylation of unprotected indoles with alcohols and TsCl is also realized. The application of this method is demonstrated by the introduction of isotope-labeled (CD3 and 13CH3) groups using the readily accessible labeled alcohols and the synthesis of pharmaceuticals.
- Zhu, Ming-Hui,Yu, Cheng-Long,Feng, Ya-Lan,Usman, Muhammad,Zhong, Dayou,Wang, Xin,Nesnas, Nasri,Liu, Wen-Bo
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supporting information
p. 7073 - 7077
(2019/09/30)
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- Efficient and selective hydrogenation of C-O bonds with a simple sodium formate catalyzed by nickel
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A Ni-catalyzed hydrogenation of C-O compounds with sodium formate is developed. Various esters, i.e. aryl, alkenyl, benzyl pivalates, and even the aryl ethers, were efficiently reduced with a loading of nickel catalysts down to 0.5 mol%. Reactive functional groups such as C-C double bonds, carbonyl, CN, MeS and halogen groups are tolerable. This reaction can be used for the modification of complex molecules and carried out at a large scale.
- Xi, Xiaoxiang,Chen, Tieqiao,Zhang, Ji-Shu,Han, Li-Biao
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p. 1521 - 1524
(2018/02/19)
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- Decarbonylation of Aromatic Aldehydes and Dehalogenation of Aryl Halides Using Maghemite-Supported Palladium Catalyst
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A facile decarbonylation reaction of a variety of aromatic and heteroaromatic aldehydes using maghemite-supported palladium catalyst has been developed. The magnetic properties of catalyst facilitated an easy and efficient recovery of the catalyst from the reaction mixture using an external magnet. It was found that the catalyst could be reused up to four consecutive catalytic runs without a significant change in activity. In addition, the catalyst was also very effective in the dehalogenation of aryl halides. This is the first report on efficient utilization of directly immobilized Pd on maghemite in decarbonylation and dehalogenation reactions.
- Ajda?i?, Vladimir,Nikoli?, Andrea,Simi?, Stefan,Manojlovi?, Dragan,Stojanovi?, Zoran,Nikodinovic-Runic, Jasmina,Opsenica, Igor M.
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p. 119 - 126
(2017/12/27)
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- METHOD FOR AROMATIC FLUORINATION
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Disclosed is a fluorination method comprising providing an aryl fluorosuifonate and a fluorinating reagent to a reaction mixture; and reacting the aryl fluorosuifonate and the fluorinating reagent to provide a fluorinated aryl species. Also disclosed is a fluorination method comprising providing, a salt comprising a cation and an aryloxyiate, and SO2F2 to a reaction mixture; reacting the SO2F2 and the ammonium salt to provide a fluorinated aryl species. Further disclosed a fluorination method comprising providing a compound having the structure Ar-OH to a reaction mixture; where A is an aryl or heteroaryl; providing SO2F2 to the reaction mixture; providing a fluorinating reagent to the reaction mixture; reacting the SO2F2, the fluorinating reagent and the compound having the structure Ar-OH to provide a fluorinated aryl species having the structure Ar-F.
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Paragraph 0047-0049
(2017/12/18)
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- Nucleophilic deoxyfluorination of phenols via aryl fluorosulfonate intermediates
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This report describes a method for the deoxyfluorination of phenols with sulfuryl fluoride (SO2F2) and tetramethylammonium fluoride (NMe4F) via aryl fluorosulfonate (ArOFs) intermediates. We first demonstrate that the reaction of ArOFs with NMe4F proceeds under mild conditions (often at room temperature) to afford a broad range of electronically diverse and functional group-rich aryl fluoride products. This transformation was then translated to a one-pot conversion of phenols to aryl fluorides using the combination of SO2F2 and NMe4F. Ab initio calculations suggest that carbon-fluorine bond formation proceeds via a concerted transition state rather than a discrete Meisenheimer intermediate.
- Schimler, Sydonie D.,Cismesia, Megan A.,Hanley, Patrick S.,Froese, Robert D.J.,Jansma, Matthew J.,Bland, Douglas C.,Sanford, Melanie S.
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supporting information
p. 1452 - 1455
(2017/02/10)
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- Copper-Mediated Radiofluorination of Arylstannanes with [18F]KF
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A copper-mediated nucleophilic radiofluorination of aryl- and vinylstannanes with [18F]KF is described. This method is fast, uses commercially available reagents, and is compatible with both electron-rich and electron-deficient arene substrates. This method has been applied to the manual synthesis of a variety of clinically relevant radiotracers including protected [18F]F-phenylalanine and [18F]F-DOPA. In addition, an automated synthesis of [18F]MPPF is demonstrated that delivers a clinically validated dose of 200 ± 20 mCi with a high specific activity of 2400 ± 900 Ci/mmol.
- Makaravage, Katarina J.,Brooks, Allen F.,Mossine, Andrew V.,Sanford, Melanie S.,Scott, Peter J. H.
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supporting information
p. 5440 - 5443
(2016/11/04)
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- Synthesis and characterization of a novel N-F reagent derived from the ethano-Tr?ger's base: 1JFN coupling constants as a signature for the N-F bond
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Methylation of 2,8-dimethyl-6H,12H-5,11-ethanodibenzo[b,f][1,5]-diazocine (ethano-Tr?ger's base) with methyl iodide followed by ion metathesis and fluorination with N-fluoro-2,3,4,5,6-pentachloropyridinium triflate affords a new electrophilic N-F reagent, that is more reactive than Selectfluor. 2D 19F-15N HMQC experiments provide 1JNF coupling constants which are diagnostic for the N-F functional group.
- Pereira, Raul,Wolstenhulme, Jamie,Sandford, Graham,Claridge, Timothy D. W.,Gouverneur, Véronique,Cvengro?, Ján
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supporting information
p. 1606 - 1609
(2016/01/30)
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- Palladium-Catalyzed, Site-Selective Direct Allylation of Aryl C-H Bonds by Silver-Mediated C-H Activation: A Synthetic and Mechanistic Investigation
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We describe a method for the site-selective construction of a C(aryl)-C(sp3) bond by the palladium-catalyzed direct allylation of arenes with allylic pivalates in the presence of AgOPiv to afford the linear (E)-allylated arene with excellent regioselectivity; this reaction occurs with arenes that have not undergone site-selective and stereoselective direct allylation previously, such as monofluorobenzenes and non-fluorinated arenes. Mechanistic studies indicate that AgOPiv ligated by a phosphine reacts with the arene to form an arylsilver(I) species, presumably through a concerted metalation-deprotonation pathway. The activated aryl moiety is then transferred to an allylpalladium(II) intermediate formed by oxidative addition of the allylic pivalate to the Pd(0) complex. Subsequent reductive elimination furnishes the allyl-aryl coupled product. The aforementioned proposed intermediates, including an arylsilver complex, have been isolated, structurally characterized, and determined to be chemically and kinetically competent to undergo the proposed elementary steps of the catalytic cycle.
- Lee, Sarah Yunmi,Hartwig, John F.
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supporting information
p. 15278 - 15284
(2016/12/06)
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- Design and synthesis of new potassium channel activators derived from the ring opening of diazoxide: Study of their vasodilatory effect, stimulation of elastin synthesis and inhibitory effect on insulin release
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Benzenesulfonylureas and benzenesulfonylthioureas, as well as benzenecarbonylureas and benzenecarbonylthioureas, were prepared and evaluated as myorelaxants on 30 mM KCl-precontracted rat aortic rings. The most active compounds were further examined as stimulators of elastin synthesis by vascular smooth muscle cells and as inhibitors of insulin release from pancreaticβ-cells. The drugs were also characterized for their effects on glycaemia in rats. Benzenesulfonylureas and benzenesulfonylthioureas did not display any myorelaxant activity on precontracted rat aortic rings. Such an effect could be attributed to their ionization at physiological pH. By contrast, almost all benzenecarbonylureas and benzenecarbonylthioureas displayed a myorelaxant activity, in particular the benzenecarbonylureas with an oxybenzyl group linked to the ortho position of the phenyl ring. The vasodilatory activity of the most active compounds was reduced when measured in the presence of 80 mM KCl or in the presence of 30 mM KCl and 10 μM glibenclamide. Such results suggested the involvement, at least in part, of KATP channels. Preservation of a vasodilatory activity in rat aortic rings without endothelium indicated that the site of action of such molecules was located on the vascular smooth muscle cells and not on the endothelial cells. Some of the most active compounds also stimulated elastin synthesis by vascular smooth muscle cells. Lastly, most of the active vasorelaxant drugs, except 15k and 15t at high concentrations, did not exhibit marked inhibitory effects on the insulin releasing process and on glycaemia, suggesting a relative tissue selectivity of some of these compounds for the vascular smooth muscle.
- Bouider, Nafila,Fhayli, Wassim,Ghandour, Zeinab,Boyer, Marjorie,Harrouche, Kamel,Florence, Xavier,Pirotte, Bernard,Lebrun, Philippe,Faury, Gilles,Khelili, Smail
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p. 1735 - 1746
(2015/03/30)
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- RADIOIODINATED COMPOUNDS
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This disclosure relates to reagents and methods useful in the synthesis of aryl iodines, for example, in the preparation of iodine labeled radiotracers. The reagents and methods provided herein may be used to access a broad range of compounds, including aromatic compounds, heteroaromatic compounds, amino acids, nucleotides, and synthetic compounds.
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Page/Page column 49
(2015/12/08)
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- A Fluorinated Ligand Enables Room-Temperature and Regioselective Pd-Catalyzed Fluorination of Aryl Triflates and Bromides
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A new biaryl monophosphine ligand (AlPhos, L1) allows for the room-temperature Pd-catalyzed fluorination of a variety of activated (hetero)aryl triflates. Furthermore, aryl triflates and bromides that are prone to give mixtures of regioisomeric aryl fluorides with Pd-catalysis can now be converted to the desired aryl fluorides with high regioselectivity. Analysis of the solid-state structures of several Pd(II) complexes, as well as density functional theory (DFT) calculations, shed light on the origin of the enhanced reactivity observed with L1.
- Sather, Aaron C.,Lee, Hong Geun,De La Rosa, Valentina Y.,Yang, Yang,Müller, Peter,Buchwald, Stephen L.
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supporting information
p. 13433 - 13438
(2015/11/09)
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- Synthesis of aryl fluorides from potassium aryltrifluoroborates and selectfluor mediated by iron(III) chloride
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The synthesis of fluorinated arenes by the iron-mediated fluorination of potassium aryltrifluoroborates with Selectfluor and potassium fluoride is described. The fluorination reaction uses commercially available reagents and without requiring the addition
- Dubbaka, Srinivas Reddy,Gadde, Satyanarayana,Narreddula, Venkateswara Reddy
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p. 854 - 860
(2015/03/14)
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- PhenoFluorMix: Practical chemoselective deoxyfluorination of phenols
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A practical deoxyfluorination with novel deoxyfluorinating reagent PhenoFluorMix, a mixture of N,N'-1,3-bis(2,6-diisopropylphenyl)chloroimidazolium chloride and CsF, is presented. PhenoFluorMix overcomes the challenges associated with hydrolysis of PhenoFluor. PhenoFluorMix does not hydrolyze, is readily available on decagram scale, and is storable in air. In this paper, we demonstrate the practicality of the reagent and exhibit the deoxyfluorination of a variety of phenols and heterocycles.
- Fujimoto, Teppei,Ritter, Tobias
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supporting information
p. 544 - 547
(2015/03/05)
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- FLUORINATION OF ORGANIC COMPOUNDS
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Methods for fluorinating organic compounds utilizing a novel organic reagent are described herein. The invention further discloses the utility of this reagent for incorporation of the 18 F isotope into hydroxyl group -containing organic molecules for PET imaging studies. Preparation of the reagents is described along with isolable intermediate structures from reaction of the reagent with a hydroxyl group-containing organic molecule.
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- Silver-mediated fluorination of potassium aryltrifluoroborates with Selectfluor Dedicated to Professor Andrea Vasella on the occasion of his 71st birthday
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A simple and practical procedure for the silver-mediated fluorination of aryl- and heteroaryltrifluoroborates with electrophilic fluorine from Selectfluor and LiOH·H2O is presented. The reaction procedure is simple and easy to set up, the process produces fluorinated arenes and heteroarenes in good to excellent yields and a wide range of electronically and structurally diverse substrates are tolerated.
- Dubbaka, Srinivas Reddy,Narreddula, Venkateswara Reddy,Gadde, Satyanarayana,Mathew, Thresen
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p. 9676 - 9681
(2015/01/08)
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- Pd-catalyzed nucleophilic fluorination of aryl bromides
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On the basis of mechanism-driven reaction design, a Pd-catalyzed nucleophilic fluorination of aryl bromides and iodides has been developed. The method exhibits a broad substrate scope, especially with respect to nitrogen-containing heteroaryl bromides, and proceeds with minimal formation of the corresponding reduction products. A facilitated ligand modification process was shown to be critical to the success of the reaction.
- Lee, Hong Geun,Milner, Phillip J.,Buchwald, Stephen L.
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supporting information
p. 3792 - 3795
(2014/04/03)
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- FLUORINATION OF ARYL COMPOUNDS
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The invention provides compositions and methods of using the compositions in fluorinating aryl precursors containing a leaving group replaceable by a fluorine atom. The compositions include a metal ion source, a electrophilic fluorine source, a base, and a compound, which is an aryl precursor of the aryl fluoride, and which has a leaving group replaceable by the fluorine atom. Exemplary methods of the invention make use of such compositions and methods to prepare an aryl fluoride compound. In an exemplary embodiment, the electrophilic fluorine source is a source of 18F.
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Paragraph 00117; 00118-00121
(2014/07/22)
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- Copper-catalyzed [18F]fluorination of (Mesityl)(aryl)iodonium salts
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A practical, rapid, and highly regioselective Cu-catalyzed radiofluorination of (mesityl)(aryl)iodonium salts is described. This protocol utilizes [18F]KF to access 18F-labeled electron-rich, -neutral, and -deficient aryl fluorides under a single set of mild conditions. This methodology is applied to the synthesis of protected versions of two important radiotracers: 4-[18F]fluorophenylalanine and 6-[ 18F]fluoroDOPA.
- Ichiishi, Naoko,Brooks, Allen F.,Topczewski, Joseph J.,Rodnick, Melissa E.,Sanford, Melanie S.,Scott, Peter J.H.
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supporting information
p. 3224 - 3227
(2014/07/08)
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- Continuous flow reactor for Balz-Schiemann reaction: A new procedure for the preparation of aromatic fluorides
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A facile and highly efficient procedure for the preparation of aromatic fluorides by Balz-Schiemann reaction via two continuous flow reactors has been set up. The continuous diazotization reactor was run at about 25 °C with residence times of 10-20 s, and the continuous fluorodediazoniation reactor was performed with a residence time of 1 min in high yields. The reaction times can be greatly reduced by increasing temperature and thereby taking advantage of superior mass and heat transfer of a continuous flow system.
- Yu, Zhi-Qun,Lv, Yan-Wen,Yu, Chuan-Ming,Su, Wei-Ke
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p. 1261 - 1263
(2013/03/14)
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- Synthesis of functionalized aryl fluorides using organolithium reagents in flow microreactors
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Flow on: Flow microreactors enable the generation of aryl lithium compounds and subsequent electrophilic fluorination with NFSI and N-fluorosultam. The reaction can be successfully accomplished to synthesize various aryl fluorides involving an electron-withdrawing, an electron-donating, and a sterically hindered functional group in good yields. Copyright
- Nagaki, Aiichiro,Uesugi, Yuki,Kim, Heejin,Yoshida, Jun-Ichi
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supporting information
p. 705 - 708
(2013/05/08)
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- Mild copper-mediated fluorination of aryl stannanes and aryl trifluoroborates
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This communication describes a mild copper-mediated fluorination of aryl stannanes and aryl trifluoroborates with N-fluoro-2,4,6-trimethylpyridinium triflate. This protocol demonstrates broad substrate scope and functional group tolerance, and does not require the use of any noble metal additives. The reaction is proposed to proceed via an arylcopper(III) fluoride intermediate.
- Ye, Yingda,Sanford, Melanie S.
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supporting information
p. 4648 - 4651
(2013/05/09)
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- Fluorination of 4-alkyl-substituted phenols and aromatic ethers with fluoroxy and N-F reagents: Cesium fluoroxysulfate and N-fluoro-1,4-diazonia- bicyclo[2.2.2]octane dication salts case Dedicated to Prof. Dr. Boris ?emva in honor to his great contribution to fluorine chemistry.
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4-Alkyl-substituted phenols and aromatic ethers were comparatively fluorinated with electrophilic fluorinating reagents such as cesium fluoroxysulfate (CFS), Selectfluor F-TEDA-BF4, and Accufluor NFTh in MeCN or MeOH. Reactions resulted in the formation of three types of products: 2-fluoro-4-alkyl-substituted corresponding compounds (5) as a result of ortho fluorination process, 4-alkyl-4-fluoro-cyclohexa-2,5- dienone compounds (6), resulting after an addition-elimination process, and 4-fluorosubstituted corresponding compounds (7) derived from ipso attack and release of the 4-alkyl group. The distribution of products depends on the bulkiness of alkyl groups at both positions and reaction media. The reaction in methanol proved more selective toward the formation of 2-fluoro derivatives. Tyramin and l-tyrozine were transformed with NFTh reagent in methanol to their fluorophenyl-substituted derivatives in good yield.
- Pravst, Igor,Stavber, Stojan
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p. 276 - 282
(2014/01/06)
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- Cu-catalyzed fluorination of diaryliodonium salts with KF
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A mild Cu-catalyzed nucleophilic fluorination of unsymmetrical diaryliodonium salts with KF is described. This protocol preferentially fluorinates the smaller aromatic ligand on iodine(III). The reaction exhibits a broad substrate scope and proceeds with high chemoselectivity and functional group tolerance. DFT calculations implicate a CuI/CuIII catalytic cycle.
- Ichiishi, Naoko,Canty, Allan J.,Yates, Brian F.,Sanford, Melanie S.
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supporting information
p. 5134 - 5137
(2013/10/22)
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- Copper-mediated fluorination of arylboronate esters. Identification of a Copper(III) fluoride complex
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A method for the direct conversion of arylboronate esters to aryl fluorides under mild conditions with readily available reagents is reported. Tandem reactions have also been developed for the fluorination of arenes and aryl bromides through arylboronate ester intermediates. Mechanistic studies suggest that this fluorination reaction occurs through facile oxidation of Cu(I) to Cu(III), followed by rate-limiting transmetalation of a bound arylboronate to Cu(III). Fast C-F reductive elimination is proposed to occur from an aryl-copper(III)-fluoride complex. Cu(III) intermediates have been generated independently and identified by NMR spectroscopy and ESI-MS.
- Fier, Patrick S.,Luo, Jingwei,Hartwig, John F.
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supporting information
p. 2552 - 2559
(2013/03/29)
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- Methylation using dimethylcarbonate catalysed by ionic liquids under continuous flow conditions
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The ionic liquid, tributylmethylammonium methylcarbonate, has been employed as a catalytic base for clean N-methylation of indole with dimethylcarbonate. The reaction conditions were optimised under microwave heating to give 100% conversion and 100% selectivity to N-methylindole, and subsequently transferred to a high temperature/high pressure (285 °C/150 bar) continuous flow process using a short (3 min) residence time and 2 mol% of the catalyst to efficiently methylate a variety of different amines, phenols, thiophenols and carboxylic acid substrates. The extremely short residence times, versatility, and high selectivity have significant implications for the synthesis of a wide range of pharmaceutical intermediates, as high product throughputs can be obtained via this scalable continuous flow protocol. It has also been shown that the ionic liquid can be generated in situ from tributylamine, which has the net effect of transforming an ineffective stoichiometric base into a highly efficient catalyst for this broad class of reactions.
- Glasnov, Toma N.,Kappe, C. Oliver,Holbrey, John D.,Seddon, Kenneth R.,Yan, Ting
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p. 3071 - 3076,6
(2020/09/16)
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- Direct trifluoro-methoxylation of aromatics with perfluoro-methyl- hypofluorite
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The reactivity of CF3OF (FTM) has been widely studied especially in halogenated olefinic systems and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is well documented. On the other hand, the chemical behavior of the perfluoro-methyl-hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. In this work the reactivity of CF3OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group (via radical mechanism) or the fluorine atom (via electrophilic addition) by varying the reaction conditions has been explored. In particular we have observed that the trifluoro-methoxy free radical substitution can be the main synthetic pathway if the reaction is promoted by an independent and steady source of CF3O radical.
- Venturini, Francesco,Navarrini, Walter,Famulari, Antonino,Sansotera, Maurizio,Dardani, Patrizia,Tortelli, Vito
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experimental part
p. 43 - 48
(2012/08/14)
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- FLUORINATION OF ORGANIC COMPOUNDS
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Methods for fluorinating organic compounds are described herein.
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Page/Page column 22-23
(2012/11/06)
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- Ipso-Fluorination of aryltrimethylsilanes using xenon difluoride
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Reaction of aryltrimethylsilanes with xenon difluoride in C 6F6/Pyrex at room temperature gives aryl fluorides in good yield. The reaction is inhibited when acetonitrile is used as solvent but proceeds well in CFCl3/Pyrex or CH 2Cl2/Pyrex. Pyrex appears to be a very effective heterogeneous catalyst for this ipso-fluorination. The reaction does not proceed in PTFE, quartz, soda glass or glassy-carbon flasks or Pyrex flasks pre-rinsed with 2 M NaOH. Aryltrimethylstannanes and arylboronic acids and their esters do not undergo ipso-fluorination under similar conditions. Plausible mechanisms involving electrophilic addition of polarised xenon difluoride [FXeδ+?F→Pyrex δ-] followed by ligand coupling are discussed.
- Lothian, Aileen P.,Ramsden, Christopher A.,Shaw, Maxine M.,Smith, Rachel G.
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experimental part
p. 2788 - 2793
(2011/05/02)
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- On the reactivity of imidazole carbamates and ureas and their use as esterification and amidation reagents
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The optimization, substrate scope, and mechanism of esterification and amidation of carboxylic acids mediated by imidazole-based reagents are discussed. The innate reactivity of carbonylimidazole reagents with a range of nucleophiles is also explored. New reagents developed for the synthesis of α,β-unsaturated esters are described, as are reagents for the preparation of tertiary amides directly from carboxylic acids.
- Heller, Stephen T.,Sarpong, Richmond
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experimental part
p. 8851 - 8859
(2011/12/02)
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- Deoxyfluorination of phenols
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An operationally simple ipso fluorination of phenols with a new deoxyfluorination reagent is presented.
- Tang, Pingping,Wang, Weike,Ritter, Tobias
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supporting information; experimental part
p. 11482 - 11484
(2011/10/02)
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- Iodonium Cyclophanes for SECURE Arene Functionalization
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This disclosure relates to compounds, reagents, and methods useful in the synthesis of aryl fluorides, for example, in the preparation of 18F labeled radiotracers. For example, this disclosure provides universal “locked” aryl substituents that result in StereoElectronic Control of Unidirectional Reductive Elimination (SECURE) from diaryliodonium salts. The reagents and methods provided herein may be used to access a broad range of compounds, including aromatic compounds, heteroaromatic compounds, amino acids, nucleotides, and synthetic compounds.
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Page/Page column 27-28
(2011/08/08)
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- Unprecedented directing group ability of cyclophanes in arene fluorinations with diaryliodonium salts
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For the first time it is shown that exceptionally electron-rich arene rings can be fluorinated exclusively during the reductive elimination reactions of diaryliodonium fluorides. The 5-methoxy[2.2]paracyclophan-4-yl directing group simultaneously reduces unproductive aryne chemistry and eliminates ligand exchange reactions by a combination of steric and electronic effects. Use of the cyclophane directing group permits an unprecedented degree of control in fluorination reactions of diaryliodonium salts.
- Graskemper, Joseph W.,Wang, Bijia,Qin, Linlin,Neumann, Kiel D.,Dimagno, Stephen G.
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p. 3158 - 3161
(2011/08/06)
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- Silver-mediated fluorination of aryl silanes
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A regiospecific silver-mediated fluorination of aryl silanes is reported. The reaction is operationally simple, and employs Ag2O as readily available, inexpensive silver source, which can be recovered.
- Tang, Pingping,Ritter, Tobias
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supporting information; experimental part
p. 4449 - 4454
(2011/08/03)
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- Microwave-assisted methylation of phenols with DMF-DMA
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We evaluated the potential of N,N-dimethylformamide dimethylacetal (DMF-DMA) as a methylating agent for a library of para-substituted phenols under microwave irradiation. The rate of reaction was dictated by the electronic nature of the para-substituent. With an electron-withdrawing group the reaction was completed within 30 min. For electron-donating groups, the reaction times were 60 min. Esterification and enamino-ketone formation was also observed with carboxylic acid and ketone functional groups, respectively.
- Belov, Pavel,Campanella, Veronica L.,Smith, Alison W.,Priefer, Ronny
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experimental part
p. 2776 - 2779
(2011/06/19)
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- Evidence for in situ catalyst modification during the Pd-catalyzed conversion of aryl triflates to aryl fluorides
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A mechanistic investigation of the Pd-catalyzed conversion of aryl triflates to fluorides is presented. Studies reveal that C-F reductive elimination from a LPdII(aryl)F complex (L = t-BuBrettPhos or RockPhos) does not occur when the aryl group is electron rich. Evidence is presented that a modified phosphine, generated in situ, serves as the actual supporting ligand during catalysis with such substrates. A preliminary study of the reactivity of a LPdII(aryl)F complex based on this modified ligand is reported.
- Maimone, Thomas J.,Milner, Phillip J.,Kinzel, Tom,Zhang, Yong,Takase, Michael K.,Buchwald, Stephen L.
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supporting information; experimental part
p. 18106 - 18109
(2012/01/02)
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- Silver-catalyzed late-stage fluorination
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Carbon-fluorine bond formation by transition metal catalysis is difficult, and only a few methods for the synthesis of aryl fluorides have been developed. All reported transition-metal-catalyzed fluorination reactions for the synthesis of functionalized arenes are based on palladium. Here we present silver catalysis for carbon-fluorine bond formation. Our report is the first example of the use of the transition metal silver to form carbon-heteroatom bonds by cross-coupling catalysis. The functional group tolerance and substrate scope presented here have not been demonstrated for any other fluorination reaction to date.
- Tang, Pingping,Furuya, Takeru,Ritter, Tobias
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supporting information; experimental part
p. 12150 - 12154
(2010/10/04)
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- FLUORINATION OF ORGANIC COMPOUNDS
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Methods for fluorinating organic compounds are described herein.
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Page/Page column 63; 91; 104
(2010/07/10)
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- NO-CARRIER-ADDED NUCLEOPHILIC [F-18] FLUORINATION OF AROMATIC COMPOUNDS
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Phenyliodonium ylide derivatives substituted with electron donating as well as electron withdrawing groups on the aromatic ring are shown for use as precursors in aromatic nucleophilic substitution reactions. The iodonium ylide group is substituted by nucleophiles such as halide ions to provide the corresponding haloaryl derivatives. No- carrier-added [F-18]fluoride ion exclusively substitutes the iodonium ylide moiety in these derivatives and provides high specific activity F- 18 labeled fluoro derivatives. Protected L-dopa-6-iodonium ylide derivative have been synthesized as a precursors for the preparation of no-carrier-added 6-[F- 18]fluoro-L-dopa. The iodonium ylide group in this L-dopa.derivative is nucleophilically substituted by no-carrier-added [F-18]fluoride ion to provide a [F-18]fluoro intermediates which upon acid hydrolysis yielded 6-[F- 18]fluoro-L-dopa.
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Page/Page column 11-12
(2010/11/03)
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