My PhD dissertation - Institut Fresnel

101
4 The Preparation and Racemate Resolution of
Biphenyls and Biphenylbisphosphines
4.1 Preparation of 6,6’-Dibromobiphenyl-2,2’-diol and
Derivatives Thereof
1,3-Dibromo-2-iodobenzene (29): Butyllithium (1.0 mol) in hexane (0.50 L) was added to a
solution of diisopropylamine (0.15 L, 0.11 kg, 1.1 mol) in tetrahydrofuran (2.0 L) at 0 °C. The
solution was then cooled to -75 °C and 1,3-dibromobenzene (0.12 L, 0.24 kg, 1.0 mol) was
added dropwise over 90 min, so that temperature stayed below -70 °C. The slightly yellow
suspension was stirred for 2 h before a solution of iodine (0.25 kg, 1.0 mol) in tetrahydrofuran
(0.40 L) was added all at once. The reaction mixture was allowed to warm up to 25 °C and a
saturated aqueous sodium sulfite solution (0.20 L) was added. The volatiles were removed
under reduced pressure and the aqueous phase was extracted with ethyl acetate (2 × 0.25 L)
and washed with 1.0 M hydrochloric acid (0.10 L; 0.10 mol) to afford a slightly yellow solid
which was recrystallized from ethanol to give colorless prisms; m.p. 99 - 101 °C; yield:
0.35 kg (96%).
1 H NMR: δ = 7.56 (d, J = 8.0 Hz, 2 H), 7.06 (t, J = 8.0 Hz, 1 H) ppm.
13 C NMR: δ = 131.2, 131.0, 130.2, 109.2 ppm.
C6H3Br2I (361.8) calcd. C 19.92% H 0.84%
found C 19.97% H 0.80%.
2,2’,6,6’-Tetrabromobiphenyl (30): Butyllithium (0.75 mol) in hexane (0.49 L) was added
dropwise over 2 h to a solution of 1,3-dibromo-2-iodobenzene (29; 0.27 kg, 0.75 mol) in
diethyl ether (1.4 L) at -75 °C. Copper(II) bromide (0.17 kg, 0.75 mol) was then added all at
once and the black slurry was kept at the same temperature for 45 min before nitrobenzene
(77 mL, 93 g, 0.75 mol) was added. At 25 °C, a 12% ammonium hydroxide solution (0.40 L)