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TCI Practical Example: Fluorination of an Alcohol Using DAST

We are proud to present the deoxofluorination of 4-nitrobenzyl alcohol by using DAST.

Used Chemicals

• 4-Nitrobenzyl Alcohol [N0180]
• (Diethylamino)sulfur Trifluoride (= DAST) [D1868]
• Dichloromethane

Procedure

To a solution of 4-nitrobenzyl alcohol (153 mg, 1.0 mmol) in dichloromethane (2.8 mL) was added DAST (144 µL, 1.1 mmol) dropwise and the mixture was stirred at room temperature for 1 hour. Ice water (3 mL) and dichloromethane (10 mL) was added to the reaction mixture. The reaction mixture was extracted with dichloromethane (5 mL x 3) and the organic layer was dried over sodium sulfate and filtered. The solvent was removed under reduced pressure and the residue was purified by column chromatography (ethyl acetate:hexane = 1:99 - 20:80 on silica gel) twice, then was further purified by column chromatography (dichloromethane:hexane = 1:99 - 20:80 on silica gel) to give 4-nitrobenzyl fluoride as a pale yellow solid (111 mg, 72%).

Experimenter’s Comments

The reaction mixture was monitored by TLC (ethyl acetate:hexane = 1:4, Rf = 0.50).
Since toxic hydrogen fluoride would be produced from DAST and moisture in the air, this work was done in a fume hood using appropriate protective equipment.

Analytical Data

4-Nitrobenzyl Fluoride

¹H NMR (270 MHz, CDCl₃); δ 8.27 (d, J = 7.8 Hz, 1H), 7.54 (d, J = 7.6 Hz, 1H), 5.51 (d, J = 46.7 Hz, 1H).

Lead Reference

• 4-NITROBENZYL FLUORIDE
  • W. J. Middleton, E. M. Bingham, Org. Synth. 1977, 57, 72.