Methyl Thioglycolate → (3-Oxo-2-thiophen-2-ylmethyl-2,3-dihydro-1H-isoindol-1-ylsulfanyl)-acetic acid methyl ester

To a solution of 12 (500 mg, 2.04 mmol) in dichloromethane (15 mL) at room temperature was added methyl thioglycolate (204 μL, 2.24 mmol) and the resulting reaction mixture was stirred at room temperature for 18 hours in a sealed tube. The reaction mixture was poured onto saturated sodium bicarbonate and extracted with ethyl acetate (3×30 mL). The combined ethyl acetate extracts were dried over anhydrous sodium sulfate and concentrated in vacuo. Chromatography (SiO2, 5% EtOAc-Hexanes eluant) provided 650 mg of 13 as a white solid (679 mg theoretical, 96% yield).