Cesium carbonate → Ethyl-8-(4-Methyl-piperazin-1-yl)-4-oxo-4H-chromene-2-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

Ethyl 8-bromo-4-oxo-4H-chromene-2-carboxylate as prepared in Reference Example 1c (Davies, Stephen et al., J. Chem. Soc. Perkin Trans I p 2597, 1987) (3.0 g, 10.1 mmol) was azeotroped with anhydrous toluene then the white solid was dissolved in 100 mL anhydrous toluene and transferred to the reaction vessel. The mixture was subjected to vacuum/argon (×2) and the following were added in order (positive argon pressure): N-methylpiperazine (1.3 ml, 11.1 mmol), 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (0.75 g, 1.2 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.48 g, 0.5 mmol) then cesium carbonate (4.6 g, 14.1 mmol). The mixture was again subjected to vacuum/argon and was heated at 80° C. overnight.

Provenance & Evidence