4-amino-2-(2,6-dioxopiperidin-3-yl)-7-hydroxyisoindole-1,3-dione

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 2-(2,6-dioxopiperidin-3-yl)-7-hydroxy-1,3-dioxoisoindolin-4-ylcarbamate C3-4 (6.73 g, 17.2 mmol) in DCM (200 mL) was added TFA (20 mL) slowly. The mixture was stirred at room temperature overnight. Water (20 mL) was added to quench the reaction. The mixture was extracted with EA (100 mL×3). The combined organic layers were collected and dried over Na2SO4, filtered, and concentrated. The residue was purified by chromatography (silica gel, DCM:MeOH:PE) to give 4-amino-2-(2,6-dioxopiperidin-3-yl)-7-hydroxyisoindoline-1,3-dione 3 as a yellow solid (4.05 g, yield: 81%). 1H NMR (DMSOd6, 400 MHz) δ: 1.95-1.98 (m, 1H), 2.52-2.58 (m, 2H), 2.83-2.92 (m, 1H), 4.98 (dd, J=12.6, 5.4 Hz, 1H), 6.06 (s, 2H), 6.95 (d, J=8.8 Hz, 1H), 7.06 (d, J=9.2 Hz, 1H), 10.17 (s, 1H), 11.05 (s, 1H); MS (ESI+): m/z 290 (M+1); Elem. Anal. Calcd. for C13H11N3O5: C, 53.98; H, 3.83; N, 14.53. Found C, 53.96; H, 3.74; N, 14.45. to quench the reaction The mixture was extracted with EA (100 mL×3) The combined organic layers were collected dried over Na2SO4 filtered concentrated The residue was purified by chromatography (silica gel, DCM:MeOH:PE)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: deprotecting tert-butyl 2-(2,6-dioxopiperidin-3-yl)-7-hydroxy-1,3-dioxoisoindolin-4-ylcarbamate with trifluoroacetic acid to form 4-amino-2-(2,6-dioxopiperidin-3-yl)-7-hydroxyisoindoline-1,3-dione.