To a suspension of 5-chloro-3-(3-chlorobenzyl)thiopbene-2-carboxylic acid from Example 1, Step 6 (230 mg, 0.801 mmol), 4-(1-azidoethyl)benzonitrile (146 mg, 0.848 mmol) [prepared according to Thompson et al. J. Org. Chem. 1993, 58, 5886, after reduction of commercially available 4-acetylbenzonitrile] and diphenyl diselenide (549 mg, 1.76 mmol) in acetonitrile at r.t. under N2 was added tributylphosphine (217 μL, 0.881 mmol, 1.1 eq) dropwise (suspension dissolved, slightly exothermic) and the mixture was stirred at r.t. for 6 h, quenched with saturated NaHCO3 and extracted with ether. The crude was purified by Combi Flash chromatography system (10-40% EtOAc/hexane) to give the desired product.
