反应详情

To a solution of the title compound of Step D (3.0 g, 12 mmol) in dichloromethane (56 mL) cooled to 0° C. under a nitrogen atmosphere was added triphenylphosphine (3.72 g, 14 mmol) followed by carbon tetrabromide (5.9 g, 18 mmol). The mixture was allowed to warm to room temperature and was stirred for 2 h. The mixture was concentrated under reduced pressure and the residue was purified by flash chromatography (2:1 hexanes:ethyl acetate) to afford 3.19 g of the title compound of Step E as a light yellow powder. 1H NMR (CDCl3): δ 7.3-7.39 (m,3H), 4.35 (AB q,2H), 3.56 (s,3H), 2.16 (s,3H).

1. concentrationThe mixture was concentrated under reduced pressure
2. customthe residue was purified by flash chromatography (2:1 hexanes:ethyl acetate)