Hydrochloric Acid → 6-amino-2,3-dihydro-1H-indene-5-carboxylic acid

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Reaction Steps

30% Aqueous hydrogen peroxide solution (5.4 mL) was added to a solution of a mixture of 1,5,6,7-tetrahydrocyclopenta[f]indole-2,3-dione and 1,5,6,7-tetrahydrocyclopenta[e]indole-2,3-dione (3.9 g, 20.8 mmol) in 2 N sodium hydroxide (41 mL) over a period of 5 min. The mixture was then stirred at room temperature for 3 h. 1N HCl was added to adjust the pH to 5. The resulting mixture was extracted with EtOAc (3×). The combined organic layers were washed with brine, dried (Na2SO4) and concentrated in vacuo to afford 6-aminoindane-5-carboxylic acid. The solid was dissolved in EtOAc (4 mL) and ethanol (4 mL). To the solution above was added (trimethylsily)diazomethane (2 M in hexane) (18 mL, 36 mmol) at room temperature and The mixture was stirred for 16 h. The solvent was removed in vacuo. Flash chromatography of the residue (Si, hexanes/EtOAc) afforded methyl 6-aminoindane-5-carboxylate which contained about 10% methyl 5-aminoindane-4-carboxylate. LCMS calc.=192.1; found=192.2 (M+1)+. 1H NMR (500 MHz, CDCl3) δ 7.71 (s, 1H); 6.60 (s, 1H); 3.87 (s, 3H); 2.85-2.79 (m, 4H); 2.08-2.02 (m, 2H).

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