[NH:1]1[C:5]2=[N:6][CH:7]=[CH:8][CH:9]=[C:4]2[CH:3]=[C:2]1[CH:10]=[O:11].[H-].[Na+].FC(F)(F)S(O[CH2:20][C:21]([F:24])([F:23])[F:22])(=O)=O>CN(C)C=O>[F:22][C:21]([F:24])([F:23])[CH2:20][N:1]1[C:5]2=[N:6][CH:7]=[CH:8][CH:9]=[C:4]2[CH:3]=[C:2]1[CH:10]=[O:11]1H-Pyrrolo[2,3-b]pyridine-2-carbaldehyde (1.8 g, 12.32 mmol) was added to a solution of sodium hydride (0.54 g, 13.55 mmol) in N,N-dimethylformamide (50 mL) at rt under nitrogen. The reaction mixture was allowed to stir for 1 h before the reaction mixture was cooled to 0° C. and 2,2,2-trifluoroethyl trifluoromethanesulfonate (2.04 ml, 14.78 mmol available, for example, from Sigma Aldrich) was added dropwise. The reaction mixture was stirred for 1 h at 0° C. and for 14 h at rt under nitrogen. The reaction was quenched by addition of water (150 mL). After addition of Et2O (150 mL), the layers were separated. The aqueous layer was further extracted with Et2O (3×150 mL) and the combined organic layers were washed with H2O. The combined water layers were extracted with Et2O (150 mL). The organic layers collected were combined, dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was loaded in dichloromethane on two 100 g SNAP silica cartridge and purified by SP4, eluting with 0-30% ethyl acetate/cyclohexane gradient. The appropriate fractions were combined and evaporated under reduced pressure to give the required product 1-(2,2,2-trifluoroethyl)-1H-pyrrolo[2,3-b]pyridine-2-carbaldehyde (2.6 g, 11.39 mmol, 93% yield) as a white solid.
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