4-Hydroxyphthalic acid → 5-Hydroxyisoindoline-1,3-dione

Participants

Reaction Conditions

Reaction Steps

To a mixture of ammonium carbonate (5.28 g, 54.9 mmol) in conc. AcOH (25 mL) was slowly added 4-hydroxyphthalic acid (5.0 g, 27.45 mmol). The resulting mixture was heated at 120° C. for 45 min., then the clear, bright yellow mixture was heated at 160° C. for 2 h. The resulting mixture was maintained at 160° C. and was concentrated to approximately 15 mL, then was cooled to room temp. and adjusted pH 10 with a 1N NaOH solution. This mixture was cooled to 0° C. and slowly acidified to pH 5 using a 1N HCl solution. The resultant precipitate was collected by filtration and dried under reduced pressure to yield 5-hydroxyisoindoline-1,3-dione as a pale yellow powder as product (3.24 g, 72%): 1H NMR (DMSO-d6) δ 7.00-7.03 (m, 2H), 7.56 (d, J=9.3 Hz, 1H).

Provenance & Evidence