To a solution of 2-(4-bromophenyl)-4-(1-methylpiperidin-4-yloxy)-9,10-dihydro-4H-3,10a-diaza-benzo[f]azulene (example 81A) (140 mg, 0.31 mmole) in CH2Cl2 (7 mL) cooled at 0° C. is added N-chlorosuccinimide (41 mg, 0.31 mmole). The reaction mixture is stirred at 0° C. for 1 h then is allowed to reach room temperature. Another portion of N-chlorosuccinimide (60 mg) is added. After 1 hour at room temperature, AcOEt is added and the reaction mixture is basified to pH 10 with 1N NaOH solution. The organic phase is washed with water, dried over magnesium sulphate, filtered and the solvent is removed under reduced pressure. The residue is purified by silica gel chromatography using (CH2Cl2:MeOH) with a gradient from (100:0) to (90:10) to give 2-(4-bromophenyl)-1-chloro-4-(1-methylpiperidin-4-yloxy)-9,10-dihydro-4H-3,10a-diaza-benzo[f]azulene melting at 169° C.
