Ammonium Hydroxide → 1-ethyl-4-chloro-6-bromo-1H-pyrazolo[3,4-b]quinoline

Participants

Reaction Steps

A mixture of N- (1-ethylpyrazol-5-yl)-3-bromoanthranilic acid and N-(1-ethylpyrazol-5-yl)-5-bromoanthranilic acid (34.8 g, 0.11 mol) and POCl3 (100 mL) was heated at reflux for 8 hours. The reaction mixture was cooled to room temperature and then was poured into ice-water and neutralized with concentrated NH4OH. The mixture was extracted with CH2Cl2 and the CH2Cl2 layer was dried over MgSO4 and evaporated to dryness. The residue was purified by column chromatography on silica gel eluting with CH2Cl2 /ether (9/1) to afford 2.7 g of 1-ethyl-4-chloro-8-bromo-1H-pyrazolo[3,4-b]quinoline (labelled as Example 44 (b)) and 22.5 g (64%) of 1-ethyl-4-chloro-6-bromo-1H-pyrazolo[3,4-b]quinoline (labelled as Example 44 (c)).

Provenance & Evidence