Balz-Schiemann加成

来源：智能 2024年12月10日 12:16

tion 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 filter papers, powdered with a spatula, and dried at about 25°/1 mm. for at least 12 hours. The dried o-bromobenzenediazonium hexafluorophosphate is cream-colored; weight 108–111 g. (94–97%); m.p. 151–156° (dec.).

B. 1-Bromo-2-fluorobenzene. Caution! This step should be carried out in a hood because the PF5 evolved on thermal decomposition of the diazonium salt is poisonous. The apparatus consists of a 1-L, three-necked, round-bottomed flask equipped with a thermometer, a condenser, a magnetic stirrer (optional), and a 250-mL Erlenmeyer flask that is attached by means of a short rubber Gooch connecting tube. The dry powdered hexafluorophosphate salt is placed in the Erlenmeyer flask, and 300 mL of hey mineral oil is placed in the round-bottomed flask. The mineral oil is heated to 165–170° by means of an oil bath or electric heating mantle and maintained at this temperature while the salt is added rapidly in portions over a period of 30 minutes. The flask is cooled rapidly to room temperature, the side flask is removed, and 400 mL of 10% aqueous sodium carbonate is added slowly through the condenser. The mixture is steam-distilled until no more oil is visible in the distillate.

The oil, which is heier than water, is separated, and the aqueous layer is extracted with three 50-mL portions of methylene chloride. The oil and extracts are combined, dried over anhydrous sodium sulfate, and distilled from a Claisen flask with an indented neck. Colorless 1-bromo-2-fluorobenzene is collected at 58–59°/17 mm. or 156–157°/760 mm.; weight 45–47 g. (73–75% based on o-bromoaniline); nD25 1.5320–1.5325.

In a 100-mL PFA made reactor equipped with a reflux condenser, 4-aminopyridine (470 mg, 5mmol) was added to HF/Pyridine (70% HF, 10 mL) at 0oC. The mixture was allowed to stand at room temperature until 4-aminopyridine was completely dissolved. After cooling down to –78oC, NaNO2 (380 mg, 5.5 mmol) was added to a solution of 4-aminopyridine in HF, the stirred solution was allowed to stand at 0oC for 30 min and then stand at 60oC for 15-30 min. By quenching the resultant solution with ice water, followed by the neutralization with cold saturated NaHCO3, the resulting mixture was extracted with CH2C12, the combined organic phase was dried over MgSO4, and evaporated under reduced pressure to give the crude product, which was distilled to give the desired product (460 mg, 95%).

Günther Schiemann生于德国的布雷斯劳，1925年授予弗罗兹瓦夫大学的学位，并转任系主任。1950年转任伊斯坦布尔大学的建筑工程学院主席，在那里他着重科学研究氯矿物学。