Reaction Steps
To a solution of 4-((1R,2S)-2-(tert-butyldimethylsilyloxy)-1-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)propylamino)benzo[b]thiophene-7-carbonitrile (355 mg, 0.69 mmol) in THF (33 mL) was added TBAF (0.70 mL, 0.70 mmol, 1 M solution in THF) at −50° C. After addition, the reaction mixture was stirred between −30° C. to −50° C. for 2 h, then quenched by adding saturated aqueous NH4Cl solution (10 mL) and extracted with EtOAc. The EtOAc extracts were washed with water, brine, dried over Na2SO4. The solvent was removed to provide a residue, which was subjected to flash chromatography purification to give the title compound 4-(1R,2S)-1-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-O-2-hydroxypropylamino)benzo[b]thiophene-7-carbonitrile (173 mg, 63%) and some dehydration product 4-(1-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)prop-1-enylamino)benzo[b]thiophene-7-carbonitrile (70 mg, 27%). Title compound: 1H NMR (400 MHz, Acetone-db, δ in ppm) 8.16 (d, J=8.8 Hz, 2H), 7.95 (d, J=8.8 Hz, 2H), 7.87 (d, J=5.7 Hz, 1H), 7.72 (d, J=5.7 Hz, 1H), 7.62 (d, J=8.2 Hz, 1H), 6.83 (d, J=8.2 Hz, 1H), 6.48 (d, J=8.6 Hz, 1H), 5.25 (dd, J=4.3, 8.6 Hz, 1H), 4.79 (b, 1H), 4.66 (m, 1H), 1.42 (d, J=6.3 Hz, 3H). Dehydration product: 1H NMR (400 MHz, Acetone-d6, 5 in ppm) 8.25 (d, J=8.2 Hz, 2H), 8.01 (d, J=8.2 Hz, 2H), 7.96 (d, J=5.5 Hz, 1H), 7.81 (d, J=5.5 Hz, 1H), 7.61 (d, J=8.2 Hz, 1H), 7.09 (q, J=7.0 Hz, 1H), 6.58 (d, J=8.2 Hz, 1H), 1.95 (d, J=7.0 Hz, 3H).
