1-(4-Fluorophenyl)-2-nitrobutane C10H12FNO2
-2-nitrobutan01.png)
Procedure: 0.1 mol (19.52 g) 1-(4-Fluorophenyl)-2-nitrobut-1-en is dissolved in approximately 70 ml of toluene(1). 0.21 mol (7.94 g) sodium borohydride is dissolved in approximately 100 ml of water, which has been mixed with a few flakes or solution of NaOH/KOH, and added to a 500-ml three-neck round-bottom flask equipped with a dropping funnel for the toluene solution, an air or Dimroth condenser, a strong stirrer, and sufficient cooling (20 °C) provided by a water bath. To the sodium borohydride solution, 1-2 ml of Aliquat 336(2) (= Adogen 464 = trioctylmethylammonium chloride) is added. Under vigorous stirring, the toluene solution is added from the dropping funnel at a rate of about 1 drop/sec. The reaction can run independently overnight. After the addition is complete, the mixture is stirred for several hours until no further reaction is detectable by TLC or visually. Any unreacted NaBH4 is carefully hydrolyzed with 50% acetic acid, releasing the nitroalkane from the nitronate salt under sufficient cooling and vigorous stirring(3), the toluene phase is separated and extracted with 3x 50 ml toluene. The extracts are washed with water and possibly NaHCO3 solution, dried, the toluene is evaporated, and the residue, preferably with little coloration(4), is distilled in vacuum. The nitroalkane is obtained as a colorless oil. The yield is 85-98%.
Notes: The procedure is highly scalable when using a mechanical stirrer.
(1) The use of other, water-immiscible and hydrolysis-stable solvents is of course possible.
(2) The use of other phase transfer catalysts is possible, but in individual cases, an adjustment of the reaction conditions may be necessary, as the extraction constants of quaternary ammonium compounds vary.
(3) Maintain stoichiometry to prevent the precipitation of interfering boric acid, which makes work-up particularly difficult for larger batches.
(4) Non-reduced nitroalkene decomposes during distillation with gas evolution and formation of products with similar boiling points to the main product, so for maximum purity, a large excess of reducing agent and long reaction time are essential.
Source: modified version of a procedure from The Hive, experimentally verified by the author
Delivered by: hefefurz (see post in the LambdaForum)
Last update: 01/06/2009
Other names: 1-Fluoro-4-(2-nitrobutyl)benzene; 1-(4-Fluorophenyl)-2-nitrobutane