Benzal fluoride

Sulfur tetrafluoride [7783-60-0] SF, replaces halogen in haloalkanes, haloalkenes, and aryl chlorides, but is only effective (even at elevated temperatures) in the presence of a Lewis acid catalyst. The reagent is most often used in the replacement of carbonyl oxygen with fluorine (15,16). Aldehydes and ketones react readily, particularly if no alpha-hydrogen atoms are present (eg, benzal fluoride [455-31-2] from benzaldehyde), but acids, esters, acid chlorides, and anhydrides are very sluggish. However, these reactions can be catalyzed by Lewis acids (HP, BF, etc). 

Streitwieser, A. Mares, F. Acidity of hydrocarbons. XXIX. Kinetic acidities of benzal fluoride and 9-fluorofluorene. A pyramidal benzyl anion./. Am. Chem. Soc. 1968, 90, 2444—2445. 

Hydrofluoric acid and lead dioxide or nickel dioxide react with toluenes bearing electronegative substituents (nitro, cyano, carbo-ethoxy, etc.) to give the corresponding benzyl and/or benzal fluoride. 

Initial investigations in the Mannich-type reaction of silyl enolates with benzal-dehyde and aniline employed a series of bismuth(III) salts (Scheme 9, Table 10). These results were promising because the corresponding (l-amino ketone could be obtained in moderate to good yield with bismuth halides, except bismuth fluoride (Table 10, entries 1 1). Bismuth nitrate smoothly afforded the expected product (Table 10, entry 5). While bismuth acetate gave no conversion, bismuth trifluor-oacetate provided the product in only moderate yield (Table 10, entries 6 and 7). Phenyl bismuth ditriflate and diphenyl bismuth triflate appeared to be more efficient catalysts than all those previously tested (Table 10, entries 8 and 9). Bismuth(III) triflate led to the expected product in a good yield and in a short reaction time, without any difference between the anhydrous and the hydrated form (Table 10, entries 10 and 11). 

The reaction of the hydroxyallyl ylide Ph3As=CHCH=CHCH20H with benzal-dehyde takes place under phase-transfer conditions and gives a mixture of E and Z 3-hydroxyallyloxiranes it gives a higher yield in acetonitrile in the presence of potassium fluoride and aluminium oxide than in the presence of solid potassium hydroxide . ... 

The gas-phase reaction of benzotrichloride with hydrogen fluoride over a chromium trifluoride catalyst is claimed to give a 93% yield of benzotri-fluoride, and pentafluorobenzaldehyde reacts with sulphur tetrafluoride to give a-jtf-heptafluorotoluene, C,Fj-CFjH (see also Vol. 1, p. 208), a better route to which apparently involves the fluorination of 2,3,4,5,6-pentafiuoro-benzal chloride. Bromination of the heptafluoro-compound gives perfluoro-... 

Benzal chloride, -bromide, -iodide, -fluoride C6H5-CHX2... 

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