Cesium carbonate → Ethyl-6-methoxy-8-(4-Methyl-piperazin-1-yl)-4-oxo-4H-chromene-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

Ethyl 8-bromo-4-oxo-4H-chromene-2-carboxylate (9.2 g, 28.1 mmol), as prepared in Example 2c above, was azeotroped with anhydrous toluene then the white solid was dissolved in 300 ml anhydrous toluene in a 500 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 (4.0 ml, 35.1 mmol), 2,2′-bis (diphenylphosphino)-1,1′-binaphthyl (1.05 g, 1.69 mmol,), tris(dibenzylideneacetone) dipalladium (0) (0.50 g, 0.56 mmol) then cesium carbonate (12.8 g, 39.3 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) (0.10 g, 0.11 mmol) and 2,2′-bis (diphenylphosphino)-1,1′-binaphthyl (0.20 g, 0.32 mmol,) was added and the reaction was stirred at 80° C. for another 55 h at which time the conversion was essentially complete.

Provenance & Evidence