Isatin → 3-hydroxy-3-(5-hydroxy-2-methyl-1,3-benzothiazol-6-yl)-1,3-dihydro-2H-indol-2-one

Participants

Reaction Steps

To a cooled (0° C.) solution of 2-methylbenzo[d]thiazol-5-ol (4.0 g, 24.0 mmol) in anhydrous tetrahydrofuran (50 mL) was added isopropylmagnesium chloride (2 M solution in tetrahydrofuran, 12.0 mL, 24.0 mmol). The resultant suspension was stirred at 0° C. for 0.5 h and isatin (3.1 g, 21.2 mmol) was added in one portion. The reaction mixture was stirred at ambient temperature for 48 h and was diluted with a saturated aqueous solution of ammonium chloride (80 mL) and ethyl acetate (200 mL). The phases were separated and the aqueous phase was extracted with ethyl acetate (3×50 mL). The combined organic solution was washed with brine (50 mL), dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The crude product was triturated with boiling ethyl acetate (10 mL), filtered and dried in vacuo to afford 3-hydroxy-3-(5-hydroxy-2-methyl-1,3-benzothiazol-6-yl)-1,3-dihydro-2H-indol-2-one (4.11 g, 62%) as an off-white microcrystalline solid: 1H NMR (300 MHz, DMSO-d6) δ10.34 (s, 1H), 10.02 (br s, 1H), 8.85 (br s, 1H), 7.78 (d, J=8.6 Hz, 1H), 7.18-7.10 (m, 1H), 7.01-6.74 (m, 4H), 2.77 (br s, 3H); MS (ES+) m/z 313.1 (M+1).

Provenance & Evidence