Water → Pyrrole-2,5-dicarboxylic acid

Temperature

70 °C

Pyrrole-2,5-dicarbaldehyde (0.21 g, 1.71 mmol) was dissolved in 35 ml of hot water and placed in a hot water bath (95–100° C.). A solution of KMnO4 (0.788 g, 5.13 mmol) in 10 ml of water was added dropwise in a period of 5 min. The reaction mixture was stirred at 95–100° C. for 1 h, and was then cooled to 70° C. The brown precipitates (MnO2) were filtered off and washed with water. The filtrate was acidified at 0° C. with 5 M HCl to pH 2, evaporated to dryness, and dried under high vacuum. The product was dissolved in 80 ml of anhydrous EtOH and the solution was filtered through a funnel. The filtrate was evaporated to give a brown solid (0.25 g), which was used in next reaction without further purification. ESI MS: 154.00 (M−H+). 1H NMR (DMSO-d6) δ 12.68 (br. S), 12.17 (s), 6.72 (s).

1. customplaced in a hot water bath
2. custom(95–100° C.)
3. customThe brown precipitates (MnO2)
4. filtrationwere filtered off
5. washwashed with water
6. customwas acidified at 0° C. with 5 M HCl to pH 2
7. customevaporated to dryness
8. customdried under high vacuum
9. dissolutionThe product was dissolved in 80 ml of anhydrous EtOH
10. filtrationthe solution was filtered through a funnel
11. customThe filtrate was evaporated

ORD record

ord-bad78fd0b1884fa19653c251280576cc

Source dataset

uspto-grants-2006_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07064218B2