Arylations silver® fluoride

Treatment of aryl tellurium trichlorides with silver fluoride, potassium bromide, or potassium iodide causes chlorine to be exchanged for other halogens (see p. 320). The reaction of 4-ethoxyphenyl tellurium trichloride with silver acetate gave a compound of indefinite composition6. 

METHYL SULFOXIDE (67-68-5) CjHjOS (CHjIjSO Combustible liquid [explosion limits in air (vol %) 2.6 to 63.0 flashpoint 203°F/95°C oc autoignition temp 419°F/215°C Fire Rating 2]. Violent or explosive reaction with strong oxidizers, acryl halides, aryl halides and related compounds, alkali metals p-bromobenzoyl acetanilide, boron compounds, especially hydrides iodine pentafluoride, magnesium perchlorate, methyl bromide, perchloric acid, periodic acid, silver fluoride, sodium... 

Fluorinations with Silver Fluoride. Reaction of AgF with alkyl and aryl halides often results in the formation of the corresponding fluorides usually under mild conditions. With gemi-nal dihalides, this conversion has been shown to involve a carbo-nium ion intermediate (eq 1). Chloro quinones react with AgF under high pressure and temperature conditions to give partial conversion to the fluoro quinone (eq 2). Cis- and trans-2,3-difluoro-2,3-dihydrobenzofuran can be similarly obtained by the reaction of AgF with trans-2,3-dibromo-2,3-dihydrobenzofuran (eq 3). Bromoadamantanes and l-bromobicyclo[3.3.1]nonan-3-one undergo fluorination with AgF to yield bridgehead fluorine derivatives (eq 4). 

Other Reactions with AgF. Treatment of vicinal di-bromo steroids with aqueous AgF results in the formation of epoxides.The AgF-initiated methanolysis of 2,2-dibromo-1,3-dimethylcyclopropanecarboxylic acid has also been studied in detail. Thiophilic heavy metal salts such as AgF have been used for ring opening of penicillin derivatives (eq 14), although other catalysts such as silver(I) oxide are better. Treatment of ( )-aryl- and -alkenylpentafluorosilicates with silver fluoride affords symmetrical ( , )-1,3-dienes in high yields (eq 15). ... 

In addition to arylboronic acids, arylboronates have also been successfully used in fluorination reactions (Scheme 7.56) [93]. These boron compounds are attractive substrates since they are typically more robust than other boron species and can often be stored for long periods of time. The catalyst system for this reaction was a copper(I) triflate species along with 2 equiv of silver fluoride. While several sources of electrophilic fluorine generated the aryl fluorides, N-fluoro-2,4,6-trimethylpyridinium hexafluorophosphate was the most effective. The chemistry displayed broad functional group tolerance with the lowest yields obtained with heteroarylboronates. The authors were also able to devise a one-pot borylation-fluorination reaction starting from the parent arene. The arene was converted into an arylboronate through an iridium-catalyzed borylation reaction in the first step of the reaction, while fluorination was achieved during the second step. This is particularly attractive since it facilitates the conversion of unfunctionalized substrates into aryl fluorides. 

The formation of aryl fluorides from aryl iodides has been achieved using silver fluoride and a cationic copper reagent. The reaction is likely to involve oxidative addition of the aryl iodide to the copper to give an aryl copper(III) iodide, followed by trans-metalation of silver fluoride forming an aryl copper(III) fluoride, (12). The product is formed after reductive elimination. There has been a theoretical study, using DPT, of the gas-phase fluorodenitration of nitrobenzene. ... 

A recently discovered variant of the Wallach technique is the silver ion cata lyzed fluorination of aryl diazo sulfides in hydrogen fluonde-pyridine-toluene solvent [57] (equation 12) Electron withdrawing substituents such as acetyl give higher yields of aryl fluoride (71%) than electron donating groups (butyl 39%, methoxy, 2-14%), reductive dediazoniation competes with fluorination... 

In general, the syntheses of these complexes are achieved through (i) nucleophilic addition/substitution reactions of silver(i) fluoride or (ii) transmetallation reactions with other metal alkyl, alkenyl, and aryl complexes. 

Aromatic fiuorination by the silver ion-promoted decomposition of aryl-diazo sulfides is similar to the Balz-Schiemann process. It provides efficient utilization of stoichiometric levels of fluoride ion, but has yet to be used for heterocyclic synthesis (91JOC4993). 

A more general synthetic procedure to prepare aryltrifluoro-l -sulfanes. e.g. 4, is the fluorination of an aryl disulfide, e.g. 3, with silver(ll) fluoride, although the cost of the silver(II) fluoride precludes large-scale synthesis.80... 

In 2005 and 2006, Mori et al. reported the arylation of heterocycles with aryl iodides using palladium dichloride complexes as catalysts and silver nitrate or fluoride as activators (Scheme 10.50). The best coupling conditions were obtained with a combination of silver nitrate and potassium fluoride.82... 

Friedel-Crafts alkylation has been used in an important synthesis of aryl C-glycosides, which are potent anti-tumor agents, from glycosyl fluorides (equation 99)65 661. The reaction takes place rapidly in dichloromethane, at room temperature using a novel zirconium complex and silver perchlorate combination catalyst. A similar alkylation has been performed by replacing the aromatic compound with either a silyl enol ether or an allylic compound using silver triflate as the catalyst662,663. 

Table 5 shows fluorination yields in the silver(I) ion promoted decomposition of several aryl diazo sulfides using excess, stoichiometric, and substoichiometrie levels of fluoride. ... 

Table 5. Silver I) Ion Promoted Acid Decomposition of Aryl Diazo Sulfides 2 to Aryl Fluorides ...

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