反应详情

Trifluoroacetic acid (39.9 g, 0.35 mol) was added dropwise to a stirred, chilled (ice-methanol bath) mixture of 2-(4,6-difluoro-1-hydroxy-1-indanyl)acetic acid (11.3 g, 0.05 mol) in dichloromethane (250 mL). After 35 min. the mixture was concentrated in vacuo. Dichloromethane was added to the residue and the mixture was concentrated in vacuo. This procedure was repeated once more to give 6.4 g of crude (E)-2-(4,6-difluoro-1-indanylidene)acetic acid. Recrystallization of 0.9 g from acetone: water mixtures gave 0.15 g of (E)-2-(4,6-difluoro-1-indanylidene) acetic acid as a solid white: mp 238-239° C.; NMR (DMSO-d6): d 12.25 (br, 1H), 7.23-7.65 (m, 2H), 6.46 (t, 1H), 3.20-3.28, 2.97-3.20 (2m's, 4H); steady-state nOe: irradiation at 6.46 d, observed 21.6% nOe at 7.63 d.

1. temperaturechilled
2. concentrationAfter 35 min. the mixture was concentrated in vacuo
3. additionDichloromethane was added to the residue
4. concentrationthe mixture was concentrated in vacuo