[Cl:1][C:2]1[N:3]=[CH:4][C:5]2[CH:10]=[C:9]([CH:11](OCC)[O:12]CC)[N:8]([CH:18]3[CH2:22][CH2:21][CH2:20][CH2:19]3)[C:6]=2[N:7]=1.Cl.[OH-].[Na+].C([O-])(O)=O.[Na+]>O1CCOCC1>[Cl:1][C:2]1[N:3]=[CH:4][C:5]2[CH:10]=[C:9]([CH:11]=[O:12])[N:8]([CH:18]3[CH2:19][CH2:20][CH2:21][CH2:22]3)[C:6]=2[N:7]=1To a stirred solution of 2-chloro-7-cyclopentyl-6-diethoxymethyl-7H-pyrrolo[2,3-d]pyrimidine (6.29 g, 19.5 mmol) in 1,4-dioxane (68 mL) is added conc. HCl (19 mL) at room temperature. The reaction mixture is stirred for 30 minutes, then neutralized with 2N NaOH aqueous solution and saturated NaHCO3 aqueous solution. The mixture extracted into EtOAc (×3), combined organic extracts are dried (MgSO4), filtered and concentrated to give 6 g of the crude 2-chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carbaldehyde as a beige solid. To a stirred suspension of the crude 2-chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carbaldehyde in MeCN (125 mL) and H2O (125 mL) is added H2N—SO3H (6.62 g, 58.5 mmol) at room temperature. The reaction mixture is stirred for 3 hours before the pH is made >10 with 2N NaOH aqueous solution and the reaction stirred for 1 hour. The mixture extracted into dichloromethane (×3), combined organic extracts are dried (MgSO4), filtered and concentrated. The residue is purified by SiO2 chromatography, eluting with a gradient of 5% EtOAc/petrol to 20% EtOAc/petrol providing 4.00 g of 2-chloro-7-cyclopentyl-7H-pyrrolo[2,3-d]pyrimidine-6-carbonitrile as a white solid, 83% yield.
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