Benzyl Bromide → 1H-Indole-2,3-dione, 5-methyl-1-(phenylmethyl)-

Participants

Reaction Conditions

Reaction Steps

To a mixture of 5-methylisatin (8.05 g, 50 mmol) and K2CO3 (8.16 g, 60 mmol) in DMF (100 mL) was added BnBr (6.5 mL, 55 mmol) dropwise over 2 min. After addition, the resulting mixture was heated in an oil bath at 75° C. for 1.5 h. After cooling to rt, the reaction mixture was poured onto ice/cold water (250 mL), rinsed with H2O (50 mL) and stirred for 5 min. The resulting precipitates were collected by suction filtration and air dried to give 1-benzyl-5-methylisatin as dark red solid. MS ESI 252.0 [M+H]+, calcd for [C16H13NO2+H]+ 252.1. 1-Benzyl-5-methylisatin was suspended in DMSO (100 mL) and cooled to 0° C. Hydrazine hydrate (5 mL) was added dropwise over 5 min. After addition, the resulting clear red solution was heated at 120° C. for 2 h then 140° C. for 5 h. After cooling to rt, it was poured into a 1 L Erlenmeyer flask, rinsed with H2O (50 mL) and ice was added until a total volume about 300 mL. 2 M HCl (50 mL) was added and the mixture was extracted with EtOAc (200 mL×2, then 100 mL), and the organic layer was dried (Na2SO4). Removal of solvents followed by drying under high vacuum for 2 days gave the title compound as a dark red solid (12.53 g, quantitative yield over 2 steps, contained some DMSO residue). 1H NMR (400 MHz, CDCl3) δ 7.35-7.29 (m, 5H), 7.09 (s, 1H), 6.97 (d, J=7.6 Hz, 1H), 6.61 (d, J=8.0 Hz, 1H), 4.91 (s, 2H), 3.60 (s, 2H), 2.31 (s, 3H); MS ESI 238.0 [M+H]+, calcd for [C16H15NO+H]+ 238.1.

Provenance & Evidence