Direct ring fluorination of aryl oxygen compounds with xenon difluoride

Abstract

age [BFg • 0Et2-(CH3C0)20, -10°, three products in 70%], bromination (1 equiv of NBS, 98%), and dehydrobromination (LiCl-DMF, 130°, 77%) gave the tropone 13.9 3-Isopropylcyclohepta-2,6-dienone, one of the ether cleavage products, was also converted to 13 by treatment with DDQ-p-TsOH (benzene, 100°) in 80% yield. The tropone 13 was transformed to the tropolone 14 by the usual procedure (NH2NH2 • H2O at 25°and then 2 N KOH at 80°, 100%).10 The product was identical in all respects with the naturally occurring material.11 2-Isopropyltropone ( 16) has been prepared from 15 (derived from l,l,3,3-tetrabromo-4-methylpentan-2-one and furan) by sequential treatments with H2 over 10% Pd/C in C2H5OH (96%), BBrs in CH2CI2 at -78-25°( giving 6bromo-2-isopropylcyclohept-2-enone as major product in 70%), 1 equiv of Br2 in CCI4 (100%), and LiCl in DMF at 150°( 20%). The tropone 16 can be converted to a-thujaplicin ( 17) by the known method.12,13

Facile preparations of 4-fluororesorcinol

“…It is normally achieved by performing the Balz-Schiemann reaction (4,5) or via electrophilic fluorination with reagents such as trifluoromethyl hypofluorite (6), acetyl hypofluorite (7), or xenon difluoride (8).…”

Chemistry of xenon derivatives. Synthesis and chemical properties

“…Thus the reaction of XeF 2 with anisole and 1,2-dimethoxybenzene gives 4-fluoroanisole and 4-fluoro-1,2-dimethoxybenzene (yields 72% and 37%, respectively). 198 The reaction of phenol with XeF 2 in CH 2 Cl 2 yields a mixture or isomeric fluorophenols (47%); 198 in water, phenol is oxidised into p-benzoquinone. 63,199,200 Hydroquinone and 4-tert-butylcatechol are oxidised by XeF 2 into benzoquinone derivatives, 201 whereas catechol affords 4-fluorocatechol in 38% yield.…”

“…63,199,200 Hydroquinone and 4-tert-butylcatechol are oxidised by XeF 2 into benzoquinone derivatives, 201 whereas catechol affords 4-fluorocatechol in 38% yield. 198 The initially proposed structure of the reaction product of pentafluorophenol with XeF 2 (C 6 F 5 OOC 6 F 5 ) 202 was later refuted; 203 it was shown that this reaction yielded perfluoro-4-phenoxycyclohexa-2,5-dienone and perfluorocyclohexa-2,5-dienone. The reaction of (perfluoroaryl)trimethylsilanes (Ar F = C 6 F 5 , 4-CF 3 C 6 H 4 , 4-C 5 F 4 N) with XeF 2 results in desilylation and formation of perfluorobiaryls.…”

“…As mentioned above, the reaction of phenol with XeF 2 is nonselective. 198 4-Fluorophenol was obtained from 2,6-di-tert-butylphenol in high yield using a two-step synthesis, viz., fluorination by XeF 2 at low temperatures and subsequent treatment of the monofluoride 84 with AlCl 3 resulting in the elimination of…”

Fluorination of 2H-Indazoles Using N-Fluorobenzenesulfonimide

“…Moreover, constructions of C– 18 F bond are also desirable because 18 F is widely used as the radiotracer for positron emission tomography (PET) imaging . Therefore, tremendous efforts have been devoted for development of strategies for C–F bond formation using various nucleophilic, electrophilic, and radical fluorinating agents such as tetrabutylammoniumfluoride (TBAF), N -fluoropyridinium triflate, XeF 2 , Selectfluor, N -fluorobenzenesulfonimide (NFSI) etc. Sun’s and Li’s group reported fluorination of N -heterocycles such as imidazo­[1,2- a ]­pyridines and 8-aminoquinolines using selectfluor and NFSI respectively as fluorine source (Scheme a and b). , Among the fluorinating agents, NFSI has attracted much interest because it is a nonhygroscopic, stable crystalline solid that is easy to handle and commercially available.…”