To trifluoro-methane sulfonic acid 3-cyano-6,6-dimethyl-11-oxo-6,11-dihydro-5H-benzo[b]carbazol-8-yl ester (Compound B1, 7.80 g, 18.0 mmol), 4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-3,6-dihydro-2H-pyridine-1-carboxylic acid tert-butyl ester (6.11 g, 19.8 mmol, 1.1 eq.), Pd(PPh3)2Cl2 (630 mg, 0.898 mmol, 0.05 eq.), and sodium carbonate (5.71 g, 53.9 mmol, 3.0 eq.), DME (125 ml) and water (25 ml) were added. The mixture was subjected to reduced pressure under ultrasonication treatment, followed by filling with nitrogen. This procedure was repeated five times to remove air. After further stirring at 80° C. for 2 hours under nitrogen atmosphere, the mixture was cooled to room temperature, added with water (250 ml), and further stirred for 30 minutes. The precipitates were filtered and washed with water (50 ml). They were further washed with CH3CN (50 ml) to obtain the target compound as a crude product (gray powder, 7.54 g, 90%).
