352-33-0Relevant articles and documents
Photocatalytic monofluorination of benzene by fluoride via photoinduced electron transfer with 3-cyano-1-methylquinolinium
Ohkubo, Kei,Fujimoto, Atsushi,Fukuzumi, Shunichi
, p. 10719 - 10725 (2013)
The photocatalytic fluorination of benzene occurs under photoirradiation of an oxygen-saturated acetonitrile (MeCN) of the 3-cyano-1-methylquinolinium ion (QuCN+) containing benzene and tetraethylammonium fluoride tetrahydrofluoride (TEAF·4HF) with a xenon lamp (500 W) attached to a colored-glass filter (λ + and benzene exhibited absorption bands due to QuCN ? (λmax = 500 nm) and the benzene dimer radical cation (λmax = 900 nm), which were generated by photoinduced electron transfer from benzene to the singlet excited state of QuCN+. The decay rate of the transient absorption band due to the benzene dimer radical cation was accelerated by the addition of TEAF·4HF. The observed rate constant increased with increasing concentration of TEAF·4HF. The rate constant of the electrophilic addition of fluoride to the benzene radical cation was determined to be 9.4 × 109 M-1 s-1. Thus, the photocatalytic reaction is initiated by intermolecular photoinduced electron transfer from benzene to the single excited state of QuCN+. The benzene radical cation formed by photoinduced electron transfer reacts with the fluoride anion to yield the F-adducted radical. However, QuCN? can reduce O2 to O2?-, and this is followed by the protonation of O2?- to afford HO2?. The hydrogen abstraction of HO2? from the F-adduct radical affords fluorobenzene and H2O2 as the final products.
Fluorination of arylboronic esters enabled by bismuth redox catalysis
Planas, Oriol,Wang, Feng,Leutzsch, Markus,Cornella, Josep
, p. 313 - 317 (2020/01/28)
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.
Palladium-catalysed electrophilic aromatic C-H fluorination
Yamamoto, Kumiko,Li, Jiakun,Garber, Jeffrey A. O.,Rolfes, Julian D.,Boursalian, Gregory B.,Borghs, Jannik C.,Genicot, Christophe,Jacq, Jér?me,Van Gastel, Maurice,Neese, Frank,Ritter, Tobias
, p. 511 - 514 (2018/03/02)
Aryl fluorides are widely used in the pharmaceutical and agrochemical industries, and recent advances have enabled their synthesis through the conversion of various functional groups. However, there is a lack of general methods for direct aromatic carbon-hydrogen (C-H) fluorination. Conventional methods require the use of either strong fluorinating reagents, which are often unselective and difficult to handle, such as elemental fluorine, or less reactive reagents that attack only the most activated arenes, which reduces the substrate scope. A method for the direct fluorination of aromatic C-H bonds could facilitate access to fluorinated derivatives of functional molecules that would otherwise be difficult to produce. For example, drug candidates with improved properties, such as increased metabolic stability or better blood-brain-barrier penetration, may become available. Here we describe an approach to catalysis and the resulting development of an undirected, palladium-catalysed method for aromatic C-H fluorination using mild electrophilic fluorinating reagents. The reaction involves a mode of catalysis that is unusual in aromatic C-H functionalization because no organometallic intermediate is formed; instead, a reactive transition-metal-fluoride electrophile is generated catalytically for the fluorination of arenes that do not otherwise react with mild fluorinating reagents. The scope and functional-group tolerance of this reaction could provide access to functional fluorinated molecules in pharmaceutical and agrochemical development that would otherwise not be readily accessible.
