A degassed mixture of the product of Step 3 (2.7 g, 12 mmol), the product of Step 2 (2.5 g, 12 mmol) and potassium carbonate (13.2 g, 96 mmol) in ethylene glycol dimethyl ether (70 ml) and water (30 ml) was treated with triphenylphosphine (314 mg, 1.2 mmol) and palladium acetate (135 mg, 0.6 mmol), then heated under reflux for 1 hour. After cooling to room temperature, the mixture was filtered through filter aid and the filtrate diluted with water and ethyl acetate. The organic phase was separated, washed with water and brine, dried, concentrated in vacuo and the residue purified by silica gel chromatography to give the title compound (2.9 g, 74%); MS(ES+) m/e 305 [M+H]+.
