Malonic Acid → 4-Hydroxy-7-methyl-benzo[h]chromen-2-one

Participants

Reaction Conditions

Reaction Steps

The mixture of 5-methyl-1-naphthol (6) (1.0 g, 6.33 mmol), malonic acid (658 mg, 6.33 mmol), and PPA (10 g) was heated at 75° C. for 3 h. After the reaction, ice-water was added to the black residue. The solid was filtered, dissolved in 10% Na2CO3 solution, and stirred overnight. The basic solution was filtered, and the filtrate was acidified with 2 N HCl solution until the pH was about 4. The precipitate was then filtered and purified by silica gel chromatography to yield 7 (620 mg, 43%) as a yellow solid. mp 223-225° C.; 1H NMR (DMSO-d6) δ 2.69 (s, 3H), 5.70 (s, 1H), 7.57-7.61 (m, 2H), 7.86 (d, J=9.0 Hz, 1H), 7.92 (d, J=9.0 Hz, 1H), 8.23 (d, J=7.5 Hz, 1H), 12.8 (br s, 1H).

Provenance & Evidence