To a solution of ethyl 4-[[4-(4-ethylphenyl)-2,2-dimethyl-(2H)-thiochromen-6-yl]-ethynyl]-benzoate (940.0 mg, 2.08 mmol) in 10.0 mL THF and 5.0 mL ethanol (EtOH) was added NaOH (416.0 mg, 10.4 mmol, 5.2 mL of a 2M aqueous solution). The resulting solution was stirred overnight at room temperature. The reaction mixture was acidified with 10% aqueous HCl and extracted with EtOAc. The combined organic layers were washed with H2O, saturated aqueous NaCl, and dried (Na2SO4) before removing the solvent under reduced pressure. The residual solid was recrystallized from CH3CN to give 786.0 mg (89%) of 4[[4-(4-ethylphenyl)-2,2-dimethyl-(2H)-thiochromen-6-yl]-ethynyl]-benzoic acid as a colorless solid. 1H NMR (300 MHz, d6-acetone) δ: 8.01 (2H, d, J=8.3 Hz), 7.60 (2H, d, J=8.5 Hz), 7.42 (2H, m), 7.29 (2H, m), 7.22 (3H, m), 5.94 (1H, s), 2.69 (2H, q, J=7.7 Hz), 1.47 (6H, s), 1.25 (3H, t, J=7.7 Hz). This compound, the final desired product, was termed Compound 1.
