Nitric Acid → 2-Bromo-5-nitrothiophene

Nitric acid (24.00 g, 1.42 sp gr, 0.381 mol) in acetic anhydride (50 ml) at 0° C. was added dropwise to a cooled (0° C.) rapidly stirred solution of the compound of step 5.1 (24.77 g, 0.152 mol) in acetic anhydride (50 ml). At the end of the addition the stirring was continued for 0.5 hr and the mixture was refrigerated overnight. The mixture was poured into ice water (400 ml) and the precipitate was filtered off, dissolved in ether (2×200 ml), and washed with water until free of acid. The solvent was removed in vacuo and the residue was purified by column chromatography [silica gel/petroleum fraction (bp 40°-60° C.), dichloromethane, 5:1] and was recrystallised from ethanol/dimethoxyethane, 100:1 to give a pale yellow solid which was dried in vacuo (P2O5) to give 66% yield of 20.89 g.

1. additionAt the end of the addition the stirring
2. waitthe mixture was refrigerated overnight
3. filtrationthe precipitate was filtered off
4. dissolutiondissolved in ether (2×200 ml)
5. washwashed with water until free of acid
6. customThe solvent was removed in vacuo
7. customthe residue was purified by column chromatography [silica gel/petroleum fraction (bp 40°-60° C.), dichloromethane, 5:1]
8. customwas recrystallised from ethanol/dimethoxyethane, 100:1
9. customto give a pale yellow solid which
10. dry with materialwas dried in vacuo (P2O5)
11. customto give 66% yield of 20.89 g

ORD record

ord-ec004479039c4b0987215662dbf4638b

Source dataset

uspto-grants-1998_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05820781