Ethyl 5-methyl-8-chloro-4-oxo-4H-chromene-2-carboxylate (1.0 g, 3.6 mmol) as prepared in Reference Example 6c above, was azeotroped with anhydrous toluene then the white solid was dissolved in 100 ml anhydrous toluene in a 250 mL single-neck round bottom flask. The mixture was degassed by alternating argon sparge and vacuum (3×), and the following were added in order: N-methylpiperazine (0.6 ml, 5.37 mmol), (2′-dicyclohexylphosphanyl-biphenyl-2-yl)dimethyl-amine (JACS 1998, 120, p 9722) (40 mg, 0.1 mmol), tris(dibenzylideneacetone)dipalladium(0) (66 mg, 0.072 mmol) then cesium carbonate (1.6 g, 5.37 mmol). The mixture was again degassed via alternating argon sparge and vacuum and was heated at 80° C. for 17 h. Additional tris(dibenzylideneacetone)dipalladium(0) (66 mg, 0.072 mmol) and (2′-dicyclopentylphosphanyl-biphenyl-2-yl)-dimethyl-amine (40 g, 0.1 mmol) were added and the reaction was stirred at 80° C. for another four days at which time the conversion was still only about 50% complete by HPLC. Tetrahydrofuran (100 mL) was added, and the combined mixture was filtered, concentrated under vacuum and purified by chromatography on silica eluted with 2.5% methanol in chloroform. The desired fractions were concentrated under vacuum to yield a yellow powder (250 mg=21%).
