Trifluoroacetic acid methylene chloride → 2-(3-(2-bromobenzoyl)thioureido)-5,5-dimethyl-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylic acid

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Reaction Steps

A solution of 40% v/v TFA/DCM (13.4 mL) was added to tert-butyl 2-(3-(2-bromobenzoyl)thioureido)-5,5-dimethyl-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylate (0.25 g, 0.48 mmol) and the mixture was stirred at room temperature for 1 h. The volatiles were removed at 30° C. and the material was purified by reverse-phase chromatography (10-100% MeCN/water). 2-(3-(2-Bromobenzoyl)thioureido)-5,5-dimethyl-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylic acid (0.16 g, 0.33 mmol, 69% yield) was isolated as a pale, yellow solid. 1H NMR (400 MHz, DMSO) δ 14.70 (s, 1H), 13.48 (s, 1H), 12.21 (s, 1H), 7.72 (apparent dd, J=7.8, 1.2 Hz, 1H), 7.62 (apparent dd, J=7.4, 1.8 Hz, 1H), 7.53-7.42 (m, 2H), 4.66 (s, 2H), 2.75 (s, 2H), 1.23 (s, 6H). 13C NMR (101 MHz, DMSO) δ 174.29, 167.42, 165.95, 147.16, 137.00, 133.01, 132.56, 129.70, 129.60, 128.04, 124.63, 119.33, 116.98, 70.62, 59.29, 37.74, 26.65. LCMS retention time: 3.193 min; LCMS purity at 214 nm=98%. HRMS m/z calculated for C18H18BrN2O4S2 [M++1]: 468.9886. found 468.9860. Melting point 188.4° C., decomposition.

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