5-amino-1-phenyl-1H-pyrazole-3,4-dicarboxylic acid diethyl ester → 6-(4-bromo-phenyl)-5-(4-chloro-phenyl)-4-oxo-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidine-3-carboxylic acid

6-(4-Bromo-phenyl)-5-(4-chloro-phenyl)-4-oxo-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidine-3-carboxylic acid is prepared from 5-amino-1-phenyl-1H-pyrazole-3,4-dicarboxylic acid diethyl ester and 4-bromo-N-(4-chloro-phenyl)-benzimidoyl chloride by following a similar procedure as described in example 2 except that the reaction mixture is heated at 170° C. in a microwave for 45 min instead of 20 min. the crude product is purified by preparative LC/MS to yield 6-(4-bromo-phenyl)-5-(4-chloro-phenyl)-4-oxo-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidine-3-carboxylic acid as the major product and 6-(4 bromo-phenyl)-5-(4-chloro-phenyl)-4-oxo-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidine-3-carboxylic acid ethyl ester (example 341) as by product. Example 340: HPLC-MS calculated C24H14BrClN4O3 (M+1+): 520.0. Found: 520.0. Example 341: 1H NMR (CDCl3) δ (ppm) 8.10(d, 2H), 7.50(t, 2H), 7.41(m, 3H), 7.34 (d, 2H), 7.20(d, 2H), 7.09 (d, 2H), 4.52(q, 2H), 1.45(t, 3H). HPLC-MS calculated C26H18BrClN4O3 (M+1+): 549.0. Found: 549.0.