In hydrogen fluonde

Fluorodediazoniation of alkyl carbamates in hydrogen fluonde/pyndine (70/30) represents a novel route to alkyl fluoroformates [6, 9] (equation 4)... 

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... 

Halofluonnation of a-diazoacetophenone by N halosuccmimides in hydrogen fluonde-pyndine provides good yields of a-fluoro-a-haloacetopheiiones [6] (equation 24)... 

The hydrofluonnation of alkenes also occurs in the gas phase, generally at somewhat higher temperatures [J]. Huoroethane is obtained m yields as high as 98% at 100 to 160 C by reaction in the presence of minor amounts of higher ot-olefms [6], and 2-fluoropropane is prepared in greater than 90% yield at <.80 "C from hydrogen fluonde and propene in the presence of activated carbon [7]... 

Lead tetrafluoride, generated in situ from lead dioxide and hydrogen fluonde, can replace benzylic hydrogen by fluonne [3] Under sirmlar conditions phenol is simultaneously oxidized to 4,4-difluoro-2,5-cyclohexadienone [4 (equations 3 and 4)... 

The tnmethylsilyl enol ether of 1 mdanone (3 2 mmol) in 2 mL of methylene chlonde is added to a mixture of xenon difluonde (4 mmol) and a catalytic amount of pyndimum poly (hydrogen fluonde) m 5 mL of methylene chlonde The mixture IS stured at 0 C for 2 h and poured into dilute sodium bicarbonate solution, tlie organic layer is separated and dned After concentration and column chromatogra phy (silica gel, hexanes), 2-fluoro-1 -mdanone (mp, 59 C) is obtamed in 87% yield... 

Anhydrous hydrogen fluonde, potassium fluonde, and sodium fluonde have all been used to promote the chlorine-fluonne exchangein tetmchloropyrukizine All three fliionne sources replace the chlonne in position 3 first Both sodium and potassium... 

Although both cuprous and cupric fluorides have been studied in the past, an active fluorine donor can be formed from cupric oxide and hydrogen fluonde. This donor, in combination with 2,2 -bipyridine, effectively displaces the halogen of... 

Pentafluorophenol is oxidized to different products depending on oxidation agents and reaction condibons The mtermediate is usually pentafluorophenoxy radical, which attacks the aromabc nng to give dimenc and tnmenc products Electrochemical oxidation of pentafluorophenol m hydrogen fluonde solvent and in the presence of a strong Lewis base or acid leads to a different rabo of products [61] (equation 55)... 

Trifluoromethyl groups are very resistant to hydrolysis, unless they are allylic or benzylic, or vicinal to a carbon linked to hydrogen. In the last case, elimination of hydrogen fluonde leads to the formation of a difluoromethylene group which is key to additional reactions... 

Difluorododecane is unaffected by sodium methoxide in methanol, but its treatment with potassium tert-butoxide in tetrahydrofuran eliminates hydrogen fluonde stereospecifically rneso and dl compounds give, respectively, ( )- and (2) 6 fluoro 6 dodecene [12] (equation 11)... 

Preferential elimination of hydrogen fluonde from vicinal halofluoro compounds occurs also in the cyclohexane series [55 56, 57], acenaphthene series [55], and benzodihydrofuran series [59 60] Here, the strength of the base and the stereochemistry play important roles... 

In l-chloro-2-fluoroacenaphthene [58] and in 2,3-dihalo-2,3-dihydrobenzofuran [59, 60], potassium t rt-butoxide eliminates hydrogen fluonde in preference to hydrogen chloride. trares-2-Chloro-3-fluoro-2,3-dihydrobenzofuran loses hydrogen fluoride quantitatively on treatment with sodamide in tert-butyl alcohol [60] (equation 29). 

Anhydrous hydrogen fluonde is a superior reagent for various cyclizations It converts aryl-substituted diethyl arylmalonates into tetralones in good yields [5] (equation 6)... 

---