Reaction Steps
A solution of PBr3 in MeCN (1:10 v/v, 190 μL) was added over 20 min to a solution of 4 (185 mg, 0.6 mmol) in MeCN (25 mL) maintained at 0° C. under Ar. After addition of Et3N (80 μL), the mixture was stirred for a further one hour at 0° C. and then heated under reflux for 4 h. At this point, 6 (400 mg, 1.8 mmol) was added and the temperature was allowed to lower to ambient conditions. After 36 h, the solvent was evaporated under reduced pressure and the residue was purified by column chromatography [SiO2, hexane/CH2Cl2 (1:1 v/v)] to give 8a (135 mg, 51%) as an orange-red solid. HPLC [analytical, MeCN/H2O (90:10 v/v)]: RT=4.1 min, PA=1.6, APP=303.2±1.0 nm; mp=200° C.; FABMS: m/z=476 [M]+; 1H-NMR (400 MHz, chloroform-d): δ=0.85 (3H, s), 1.60 (3H, s), 4.57 (1H, d, 11 Hz), 4.67 (1H, d, 11 Hz), 6.75 (1H, d, 8 Hz), 6.90 (1H, t, 7 Hz), 6.97 (1H, d, 9 Hz), 7.16-7.19 (2H, m), 7.35-7.42 (3H, m), 7.64-7.73 (4H, m), 7.93 (2H, d, 9 Hz), 8.34 (2H, d, 9 Hz); 13C-NMR (100 MHz, chloroform-d): δ=22.9, 31.8, 41.2, 49.8, 104.8, 109.2, 118.7, 120.6, 120.7, 122.4, 122.6, 123.3, 124.3, 124.9, 127.8, 128.3, 128.7, 129.0, 137.0, 138.0, 146.6, 147.5, 148.4, 156.2, 157.9.
