5-Fluoro-1-naphthalenecarboxylic Acid, 1,1-DimethylethylEster (13). A stirred solution of 11 (0.42 g; 1.4 mmol) in THF (14 mL) was cooled to -78 °C under nitrogen. n-Butyllithium(1.6 M in hexanes, 1.1 mL, 1.8mmol) was added, and the resulting solution was stirred for 1.5 min, followed by addition of N-fluorobenzenesulfonimide (0.86 g; 2.7 mmol). After stirring for 30 min, the reaction was quenched with saturated aqueous ammonium chloride. The aqueous component was extracted with Et2O, and the combined organics were dried over magnesium sulfate and concentrated in vacuo. The crude product 12 was identified by 1H NMR as a 2/1 mixture of 5-F/5-H compounds. FSGC (toluene aseluent) resulted in 157 mg of 13 (46% yield).

 o-Bromobenzenediazoniumhexafluorophosphate. A solution of 95 mL of 12N hydrochloric acid in 650 ml of water is added with stirring to 60 g of o-bromoaniline(0.35 mole) in a 2-L, three-necked flask equipped with stirrer and thermometer. Solution is effected by heating the mixture on a steambath. A solution of 29 g(0.42 mole) of sodium nitrite in 75 ml of water is added with stirring while the mixture is maintained at −5 to −10 °C by means of a bath of ice and salt or of dry ice and acetone. At the end of the addition there is an excess of nitrous acid, which can be detected with starch iodide paper. Seventy-four milliliters (134 g, 0.60 mole) of 65% hexafluorophosphoric acid is added in one portion, with vigorous stirring, to the cold solution of the diazonium salt. Cooling and slow stirring are continued for an additional 30 minutes, and the precipitated diazonium hexafluorophosphate is then collected on a Büchnerfunnel. The diazonium salt is washed on the funnel with 300 ml of coldwater and with a solution of 80 ml of methanol in 320 ml of ether. The salt is partly dried by drawing air through the funnel for 2 hours. It is then transferred to a pile of several filterpapers, powdered with a spatula, and dried at about 25 °C for at least 12hours. The dried o-bromobenzenediazoniumhexafluorophosphate is cream-colored; weight 108–111 g. (94–97%);m.p. 151–156 °C.