Methanol → 3,5-Diamino-2-methylbenzoic acid

To the stirred suspension of commercial 3,4-diaminobenzoic acid (10.3 g) in methanol (150 ml) conc. sulphuric acid (5 ml) was added cautiously. The mixture was stirred under reflux for 3 h. About half of the solvent is removed by distillation and dichloromethane (150 ml) is added. The organic layer was poured in ice water (300 ml) and with vigorous stirring the pH was adjusted to 11 with 10M NaOH. The organic layer was separated and the aqueous layer extracted with dichloromethane (150 ml). The combined organic layers were dried over sodium sulfate and concentrated. The residue was purified by fractional crystallisation from dichloromethane to give methyl 3,4-diaminobenzoate (7.05 g) as beige coloured solid.

1. additionwas added cautiously
2. temperatureunder reflux for 3 h
3. customAbout half of the solvent is removed by distillation and dichloromethane (150 ml)
4. additionis added
5. additionThe organic layer was poured in ice water (300 ml)
6. stirringwith vigorous stirring the pH
7. customThe organic layer was separated
8. extractionthe aqueous layer extracted with dichloromethane (150 ml)
9. dry with materialThe combined organic layers were dried over sodium sulfate
10. concentrationconcentrated
11. customThe residue was purified by fractional crystallisation from dichloromethane

ORD record

ord-b7c5f20697a549eeb96209813ccb8ca4

Source dataset

uspto-grants-2014_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08912186B2