To 0.51 g (1.6 mmol) of 2-bromo-7-methylamino-thioxanthen-9-one (14) and 10 mL of triethylamine in 15 mL of anhyd CH2Cl2 was added 0.61 g (2.1 mmol) of 3-chloro-2-chlorocarbonyl-benzo[b]thiophene-6-carboxylic acid methyl ester (12) dissolved in 10 mL of anhyd CH2Cl2 at 5-8° C. in an ice bath. A catalytic amount of DMAP was added. The reaction mixture was warmed at room temperature and stirred for 48 h under N2. The reaction mixture was filtered to remove triethylamine hydrochloride salt, the filtrate was washed three times with aq saturated NaHCO3, H2O, three times with aq. 2N HCl to remove unreacted amines, H2O, brine, dried over Na2SO4, and concentrated in vacuo to give crude ester 10. The crude ester 10 was chromatographed on silica gel, eluting with 20% ethyl acetate in hexane to give 0.55 g (60% yield) of NMR pure 10 (LG−=Cl−) as a brown powder, mp 237-239° C. Found: C, 52.09; H, 2.64; N, 2.47%; calcd for C25H15NO4S2ClBr: C, 52.40; H, 2.62; N, 2.44%; 1H-NMR (400 MHz, CDCl3): 3.61 (3H, s), 3.92 (3H, s), 7.35-7.54 (3H, m), 7.66-7.80 (2H, m), 8.02 (1H, d, J=8.2 Hz), 8.40 (1H, s), 8.51 (1H, s), 8.69 (1H, s); 13C-NMR (100 MHz, CDCl3): 38.3, 52.6, 120.8, 120.9, 122.8, 124.9, 126.3, 127.3, 127.4, 127.8, 128.6, 129.6, 130.0, 131.0, 132.7, 134.1, 135.8, 136.1, 137.6, 138.7, 141.4, 162.5, 166.5, 178.1.
