Silver fluoride, reaction with 6-bromo

DL-Valiolamine (205) was synthesized from the exo-alkene (247) derived from 51 with silver fluoride in pyridine. Compound 247 was treated with a peroxy acid, to give a single spiro epoxide (248, 89%) which was cleaved by way of anchimeric reaction in the presence of acetate ion to give, after acetylation, the tetraacetate 249. The bromo group was directly displaced with azide ion, the product was hydrogenated, and the amine acety-lated, to give the penta-A, 0-acetyl derivative (250,50%). On the other hand. 

There was particular interest in the analogous reactions of 1-Oacetyl-2,3,5-tri-0-benzoyl-4-bromo-/ -D-ribose (37), because of the potential to prepare from it compounds related to nucleocidin, which is a 4 -fluoroaden-osine derivative having antitrypanosomal activity. With silver fluoride in acetonitrile, this bromide also reacted mainly with inversion of configuration, and gave the l-lyxo fluoride 140 (53% isolated yield), whereas, with silver tetrafluoroborate, much more of the more interesting 1-0-acetyl-2,3,4-tri-0-benzoyl-4-fluoro-/ -D-ribose (141) was obtained.38... 

Bromo-1,3,4-thiadiazoles can be transformed to the corresponding 2-fluoro compounds by treatment with silver fluoride, but the yield is low and the reaction attended with considerable decomposition. 

Fluorine can also be added to alkenes by reaction with a solution of anhydrous hydrogen fluoride in pyridine (Olah s reagent) containing either A-bromo- or Y-iodosuccinimide, or iodine or bromine and silver nitrate. The final addition of silver fluoride to the reaction mixture leads to the formation of vicinal difluorides 19 23133... 

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). ... 

Reaction of 6-deoxy-6-iodo or 6-bromo-6-deoxy carbohydrates with a hard base such as silver fluoride gives -elimination of the halide and the formation of a 5,6-ene for hexopyranosides [131] (reaction 4.141). Catalytic reduction of the unsaturated bond results in inversion of the configuration at C-5 and the formation of 6-deoxy-L-sugars [132] (reaction 4.141). Reduction of the unsaturated bond with hydrogen and Raney nickel, however, retains the configuration [132] (reaction 4.141). 

Silver(I) fluoride dispersed on the surface of finely powdered calcium fluoride shows improved fluoride nuclcophilicity for addition to alkenes in halofluorination reactions.56 For example, hex-1-ene with l,3-dibromo-5,5-dimethylhydantoin and silver(I) fluoride/calcium fluoride in dichloromethane at 20 C gives, within 1 hour, l-bromo-2-fluorohexanc in 90% yield while with silver(I) fluoride, under similar conditions, the yield is only 39%. 

Oxidation. Huoromethyl /7-tolyl sulfide, which can be oxidized to fluoromethyl /7-tolyl sulfoxide with (V-bromo-succinimide in methanol, is synthesized by the reaction of chloromethyl />-tolyl sulfide with potassium fluoride in the presence of 18-crown-6 (eq 11). Chloromethyl />-tolyl sulfoxide can be S3mthesized by a one-pot operation from methyl />-tolyl sulfide with silver(I) nitrate and sulfuryl chloride via the intermediacy of chloromethyl p-tolyl sulfide (eq 12). ... 

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