1,3-Difluoro-5-pentylbenzene Chemical Properties

Density 

1.022

storage temp. 

2-8°C

1,3-Difluoro-5-pentylbenzene Usage And Synthesis

Uses

1,3-difluoro-5-pentylbenzene is a useful reactant for the preparation of a liquid crystal compound having high dielectric anisotropy.

Synthesis

Under nitrogen atmosphere, 1-bromo-3-fluorobenzene (262.5 g, 1.5 mol) was dissolved in anhydrous tetrahydrofuran (1 L) and added slowly and dropwise to magnesium flakes (36.5 g, 1.5 mol) while maintaining vigorous stirring. After refluxing the mixture for 1 h, a 1 mol/dm3 solution of Li?CuCl? catalyst in anhydrous tetrahydrofuran (45 mL, 3 mol%) was added. Subsequently, (S)-1-bromo-2-methylbutane (214.2 g, 1.58 mol) was slowly added dropwise to the mixture under reflux conditions with continuous stirring for 2 days. Upon completion of the reaction, the mixture was poured into 1500 mL of water and 100 mL of 10% hydrochloric acid. The crude product was extracted with pentane and the organic layer was washed with water (2 x 300 mL), separated and dried with magnesium sulfate and the solvent was evaporated. The product was purified by distillation under reduced pressure with a boiling point of 98-100 °C (28 mmHg) to give 205 g (83% yield) of the target compound, [α]D2? = +9.5° (c = 5.1; CHCl?). Mass spectra (EI) m/z: 166 (M?), 133, 110, 96. 1H NMR (CDCl?) δ 7.65-7.60 (m, 1H), 7.53 (t, J = 2.2, 3.1 Hz, 1H), 6.82-6.75 (m, 2H), 2.50 (d, J = 8.8 Hz, 2H), 1.60-1.58 (m, 1H ), 1.35-1.25 (m, 2H), 0.93 (t, J = 12.2 Hz, 3H), 0.86 (t, J = 11.4 Hz, 3H). 13C NMR (CDCl?) δ 11.65, 19.0, 29.4, 36.6, 42.3, 109.0, 115.5, 121.7, 124.9, 126.4, 128.9, 145.0, 161.4.

References

[1] Tetrahedron Letters, 2013, vol. 54, # 28, p. 3621 - 3623