Peroxide oxidation of an isatin; 2-Amino-4-bromo-benzoic acid
SyntheticPage 466
DOI:
10.1039/SP466
Submitted Sep 03, 2010, published Sep 16, 2010
Christopher Cooksey (
rsc@chriscooksey.demon.co.uk)
A contribution from
R J H Clark Group, UCL
Chemicals Used
6-Bromoisatin page 464
NaOH
H2O2
Procedure
6-Bromoisatin (4.8 g, 21 mmol) was dissolved in NaOH solution (2.4 g in 60 cm3) by warming to 50 °C. H2O2 (100 vol, 5.5 cm3, about 48 mmol) was added dropwise (exothermic reaction) so that the temperature was maintained between 50 °C and 51 °C. After cooling, the mixture was acidified with HCl (4M) to pH 3 to give a white paste which was filtered and washed with water (30 cm3). The yield was 3.97 g (87%)
Author's Comments
On the same scale and 5x the scale, lower yields (79%) were obtained.
940 mg of the product was recrystallised from aqueous ethanol (50 cm3, 1:1) to give long (>1 cm) colourless needles (789 mg), m.p. 227.2 °C (lit: m.p. 230 °C).
The literature yield was 99%; 26 analogous anthranilic acids were described.
Data
δH (dmso-d6) 12.5brs (1H), 7.57d (1H, 8.5), 6.96d (1H, 2.0), 6.62dd (1H, 8.5, 2.0), 5.3brs (2H)
Lead Reference
Holt SJ, Sadler PW, Proc Roy Soc Lond B, 1958, 148(933), 481-494
PMID: 13542639
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Keywords: anthranilic acid, carboxylic acids, isatin, oxidation
