1194-02-1Relevant articles and documents
Theoretical Design and Calculation of a Crown Ether Phase-Transfer-Catalyst Scaffold for Nucleophilic Fluorination Merging Two Catalytic Concepts
Carvalho, Nathália F.,Pliego, Josefredo R.
, p. 8455 - 8463 (2016)
Fluorinated organic molecules are playing an increased role in the area of pharmaceuticals and agrochemicals. This fact demands the development of efficient catalytic fluorination processes. In this paper, we have designed a new crown ether with four hydroxyl groups strategically positioned. The catalytic activity of this basic scaffold was investigated with high levels of electronic structure theory, such as the ONIOM approach combining MP4 and MP2 methods. On the basis of the calculations, this new structure is able to solubilize potassium fluoride in toluene solution much more efficiently than 18-crown-6 (18C6). In addition, the strong interaction of the new catalyst with the SN2 transition state leads to a very important catalytic effect, with a predicted free energy barrier of 23.3 kcal mol-1 for potassium fluoride plus ethyl bromide reaction model. Compared with experimental data and previous theoretical studies, this new catalyst is 104 times more efficient than 18C6 for nucleophilic fluorination of alkyl halides. The catalysis is predicted to be selective, leading to 97% of fluorination and only 3% of elimination. Catalytic fluorination of the aromatic ring has also been investigated, and although the catalyst is less efficient in this case, our analysis has indicated further development of this strategy can lead to more efficient catalysis.
Efficient synthesis of aryl fluorides
Anbarasan, Pazhamalai,Neumann, Helfried,Beller, Matthias
, p. 2219 - 2222 (2010)
Chemical Equation Presented Creating C-F bonds: A novel electrophilic fluorination of aryl and heteroaryl Crignard reagents has been discovered and was used for the efficient synthesis of various aryl fluoride derivatives (see picture; THF = tetrahydrofuran).
Copper-Mediated Oxidative Fluorination of Aryl Stannanes with Fluoride
Gamache, Raymond F.,Waldmann, Christopher,Murphy, Jennifer M.
, p. 4522 - 4525 (2016)
A regiospecific method for the oxidative fluorination of aryl stannanes using tetrabutylammonium triphenyldifluorosilicate (TBAT) and copper(II) triflate is described. This reaction is robust, uses readily available reagents, and proceeds via a stepwise protocol under mild conditions (60 °C, 3.2 h). Broad functional group tolerance, including arenes containing protic and nucleophilic groups, is demonstrated.
Fluorodediazoniation in ionic liquid solvents: New life for the Balz-Schiemann reaction
Laali, Kenneth K.,Gettwert, Volker J.
, p. 31 - 34 (2001)
Drawbacks associated with the classic Balz-Schiemann reaction are eliminated in a series of examples by conducting fluorodediazoniation in ionic liquid solvents, thus opening up a new horizon for a much in demand process.
Studying regioisomer formation in the pd-catalyzed fluorination of aryl triflates by deuterium labeling
Milner, Phillip J.,Kinzel, Tom,Zhang, Yong,Buchwald, Stephen L.
, p. 15757 - 15766 (2014)
Isotopic labeling has been used to determine that a portion of the desired product in the Pd-catalyzed fluorination of electron-rich, non-ortho-substituted aryl triflates results from direct C-F cross-coupling. In some cases, formation of a Pd-aryne intermediate is responsible for producing undesired regioisomers. The generation of the Pd-aryne intermediate occurs primarily via ortho-deprotonation of a L·Pd(Ar)OTf (L = biaryl monophosphine) species by CsF and thus competes directly with the transmetalation step of the catalytic cycle. Deuterium labeling studies were conducted with a variety of aryl triflates.
Fluorination of aryl boronic acids using acetyl hypofluorite made directly from diluted fluorine
Vints, Inna,Gatenyo, Julia,Rozen, Shlomo
, p. 11794 - 11797 (2013)
Aryl boronic acids or pinacol esters containing EDG were converted in good yields and fast reactions to the corresponding aryl fluorides using the readily obtainable solutions of AcOF. In reactions with aryl boronic acids containing EWG at the para position, there are two competing forces: one directing the fluorination to take place ortho to the boronic acid and the other, toward an ipso substitution. With EWG meta to the boronic acid, substitution ipso to the boron moiety takes place in good yields.
Aryl dechlorination and defluorination with an organic super-photoreductant
Glaser, Felix,Kerzig, Christoph,Larsen, Christopher B.,Wenger, Oliver S.
, p. 1035 - 1041 (2020)
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.
Method for pipeline continuous fluorination with fluorine salt as fluorine source
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Paragraph 0056-0061; 0094-0096, (2021/10/27)
The method comprises the following steps: dissolving a fluorine salt in an aqueous polar aprotic solvent as reaction liquid A, dissolving an aryl (heterocyclic) chloride in a polar aprotic solvent as reaction liquid B, and reacting a polar aprotic solvent in the reaction liquid A with a polar aprotic solvent of the reaction liquid B. The reaction medium consisting of the preheated reaction liquid A and the preheated reaction liquid B enters the reaction coil for a fluorination reaction, and the resulting product from the reaction coil is subjected to post-treatment to obtain the product. The method has the characteristics of no need of adding a phase transfer catalyst, continuous production, low production cost and the like.
A new reagent for efficient synthesis of nitriles from aldoximes using methoxymethyl bromide
ULUDAG, Nesimi,GIDEN, Ozge NUR
, p. 993 - 998 (2021/02/05)
This study outlines an efficient, high-yielding, and rapid method by which to access diverse nitriles from aldoximes with methoxymethyl bromide (MOM-Br) in THF. It represents the first application of MOM-Br as a deoximation reagent to synthesize nitriles. The reaction was performed at reflux to ensure excellent yield (79-96%) of the nitriles within 20-45 minutes. Furthermore, this method has been successfully applied to the synthesis of the synthesis precursor of aromatic, heteroaromatic, cyclic, and acyclic aliphatic.