28 g (114 mmol) of 2-borono-5-ethoxycarbonylindole, 12 g (113 mmol) of sodium carbonate and 17.2 g of 2,4-(113 mmol) dichloropyrimidine were initially charged in 412 ml of ethanol. The clear solution was freed of oxygen by vigorous stirring and passing argon through (20 minutes). At RT, 2.67 g of tetrakis(triphenylphosphine)palladium(0) were added. The mixture was heated to from 65° C. to 70° C. for 2 hours (h). Subsequently, 112 ml of water and 112 ml of 30% hydrochloric acid were added and the mixture was cooled to 0° C. After filtration and drying under reduced pressure, 37.3 g (93% of theory) of ethyl 2-(2-chloropyrimidin-4-yl)-1H-indole-5-carboxylate were obtained (HPLC >96%).
