The compound of example 220 (5 g, 0.0184 mol) was dissolved in carbon tetrachloride (125 mL). Benzoyl peroxide (250 mg) and NBS (3.6 g, 0.0202 mol) were added and the reaction mixture was refluxed at 80° C. The reaction mixture was cooled to room temperature and filtered through celite. The filtrate was concentrated to yield crude residue containing 85% mono bromo and 10% dibromo product and 5% starting material. The crude title compound obtained was used directly for preparation of compound of example 222.
