Fluorination of aromatic compounds with N-fluorobenzenesulfonimide under solvent-free conditions

Abstract

Reactions of N-fluorobenzenesulfonimide with methylbenzenes, phenols, and phenol ethers were studied under solvent-free conditions. The rate constant ratio for the reactions with mesitylene and durene indicates polar mechanism of the process. Solvent-free fluorination of aromatic compounds with N-fluorobenzenesulfonimide in some cases is more selective than reactions with other N-F reagents in a solvent.Fluorinated aromatic compounds are widely used as pesticides, medicinal agents, and various functional materials; therefore, development of ecologically friendly and selective fluorination procedures seems to be an important problem [1][2][3]. During the past two decades, N-F reagents [1-17] have been extensively used as source of fluorine in mild and selective fluorination of organic compounds. In particular, such reagent is N-fluorobenzenesulfonimide (NFSI) [2,4,[7][8][9][18][19][20][21][22][23][24]. It is nonhygroscopic, stable to storage, and convenient to handle with. N-Fluorobenzenesulfonimide is quite reactive, but at the same time it exhibits a moderate oxidative ability [2], which is important for fluorination of organic compounds with low oxidation potentials. N-Fluorobenzenesulfonimide is commonly used to effect fluorination of carbanions, enolates, and enol ethers in the synthesis of fluorinated intermediate products necessary for the manufacture of medicinal agents [7][8][9]. Direct fluorination of aromatic compounds with NFSI was performed less frequently than with other N-F reagents, e.g., 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts .The goal of the present work was to study the selectivity in fluorination of aromatic compounds, namely methyl-substituted benzenes, phenols, and phenol ethers, with NFSI in the absence of a solvent. The selectivity problem in electrophilic fluorination under these conditions remains poorly studied (cf. [22]).We have found that the yield of monofluoro derivatives in the fluorination of polymethylbenzenes

Solvent‐Free Fluorination of Electron‐Rich Aromatic Compounds with F‐TEDA‐BF4: Toward “Dry” Processes

“…Despite the rapidly growing interest in solvent‐free and mechanochemical organic syntheses in the last decade,, only limited data concerning solvent‐free aromatic fluorination has been reported to date , …”

“…As part of our ongoing efforts to develop environmentally benign methods for electrophilic aromatic fluorination,, , we began to investigate the solvent‐free fluorination of electron‐rich aromatic compounds with 1‐chloromethyl‐4‐fluoro‐1,4‐diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (F‐TEDA‐BF 4 , Selectfluor TM , 1 ).…”

Vitamin E-inspired multi-scale imaging agent

“…[23][24][25] Methods and Materials This strategy was adapted from previously reported methods. 36,37 Synthesis of F-Toc by nucleophilic fluorination…”

N-Fluorobenzenesulfonimide: a useful and versatile reagent for the direct fluorination and amination of (hetero)aromatic C–H bonds

“…Aer pioneering works by Kirk and colleagues on t BuLimediated regioselective C4-uorination of (5-methoxy-indol-3yl)-N,N-dimethylmethanamine with NFSI 28 and O'Neill's research group on catalyst-free C5-uorination of 6-methoxy-8nitroquinoline, 29 the rst general report of the transition-metalfree uorination of aromatic C-H bonds using NFSI as a uorinating reagent was published in 2009 by Andreev et al 30 They showed that in the absence of any catalyst or additive, the reaction of a variety of electron-rich arenes 11, including anisoles, phenols, toluenes, and naphthalenes with NFSI under solvent-free conditions furnished the mono-uorinatedproducts 12 in poor to good yields. However, the uorinations occurred not only on one C-H bond but resulted in mixtures of regioisometric mono-uorides in some case, e.g.…”