Hydrogen sulfide was passed through a solution of methyl {5-[3-(4-cyano-2-propylphenoxy)propoxy]-1H-indol-1-yl}acetate (Example 51, 787 mg, 1.94 mmol) in DMF (15 mL) for 30 minutes at rt. Diethyl amine (0.3 mL, 2.90 mmol) was added, and the solution was heated to 70° C. for 3 h. The reaction mixture was cooled to rt, and the residual H2S was removed by passing argon through the reaction mixture for 30 minutes. The solvent was evaporated under reduced pressure and the residue was filtered through a plug of silica and washed with EtOAc. Concentration of solvent yielded a brown oil which was used in the next step without further purification. LC/MS m/z 441.2 (M+H)+; RT 3.35 min.
