2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 1H-Pyrrolo[2,3-b]pyridine-5-carboxylic acid

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Reaction Steps

A solution of crude acid 10 in CH2Cl2 (5 mL) was treated with DDQ in small portions until TLC analysis revealed no starting material left. The mixture was concentrated to afford a solid residue containing azaindole 11. The residue was dissolved in a 5% solution of HCl in MeOH (5 mL), and stirred at r.t. After 1.5 h the mixture was concentrated and diluted with CHCl3 and saturated brine. The mixture was basified with 50% NaOH solution to pH 11. The organic layer was discarded. The aqueous layer was neutralized with 6 M HCl and extracted with AcOEt (4×). The combined organic extracts were dried (MgSO4), filtered and concentrated. The residue was purified by PTLC using CH2Cl2:MeOH=9:1 as eluent to afford acid 12 (3.19 mg, 3% over 3 steps). 1H NMR (400 MHz; CD3OD) δ 6.58 (d, J=3.5 Hz, 1H), 7.42 (d, J=3.5 Hz, 1H), 8.58 (d, J=2.0 Hz, 1H), 8.85 (d, J=1.7 Hz, 1H).

Provenance & Evidence