Diisopropylethylamine → 6-chloro-4'-(3-chlorophenyl)-2'-(5-fluoro-2-methylphenyl)-1'-methyl spiro[3H-indole-3,3'-piperidine]-2,6'(1H)-dione

To a solution of racemic (2′R,3R,4′S)-6-chloro-4′-(3-chlorophenyl)-2′-(5-fluoro-2-methylphenyl)-2,3-dihydro-1′-methyl-2,6′-dioxospiro[indole-3,3′-piperidine]-1-ethanol (0.09 g, 0.175 mmol) prepared in example 56b in methanol (10 mL) was added N,N′-diisopropylethylamine (2 mL, 11.1 mmol) and the crude was refluxed for 1 h. The reaction mixture was concentrated and the residue was partitioned between ethyl acetate and water. The organic layer was separated, and concentrated. The residue was purified by chromatography (EtOAc:CH2Cl2=1:2) to give racemic (2′R,3R,4′S)-6-chloro-4′-(3-chlorophenyl)-2′-(5-fluoro-2-methylphenyl)-1′-methylspiro[3H-indole-3,3′-piperidine]-2,6′(1H)-dione as a white solid (Yield 0.06 g, 70.6%).