Methanesulfonic Acid → Coumarin

Participants

Reaction Steps

To a mixture of 2,7-dihydroxynaphthalene (0.20 g, 1.3 mmol) and 1 (0.20 mg, 0.83 mmol) was added methanesulfonic acid (1.3 mL, 21 mmol) at 0° C. The clear brown solution gradually became dark orange within 4 h after which time the reaction mixture was diluted with cold (−30° C.) ethyl ether (10 mL), centrifuged (3000 rpm) at 4° C. for 20 minutes. After removing the ether by aspiration, the residual orange solid was dried under high vacuum, dissolved in H2O (3 mL), and purified by RP-HPLC using an appropriate linear gradient of acetonitrile containing 10% de-ionized water (A) and 0.1% (v/v) TFA/H2O (B) (3-50% A over 20 min. followed by a steep gradient to 100% A and equilibrium back to 3% A). The fractions containing the product were collected, concentrated, and lyophilized to give Mini401 as a white solid (5%). 1H NMR (DMSO-d6, 400 MHz): δ 10.21 (1H, s), 8.08 (1H, d, J=8.9 Hz), 7.94 (1H, d, J=8.8 Hz), 7.84 (3H, bs), 7.72 (1H, s), 7.33 (1H, d, J=8.8 Hz), 7.18 (1H, dd, J=8.8, 2.0 Hz), 6.44 (1H, s), 3.54 (2H, t, J=6.8 Hz), 3.32-3.29 (2H, m). 13C NMR (DMSO-d6, 75 MHz): δ 159.2, 157.6, 155.1, 153.0, 133.9, 131.5, 130.8, 125.3, 117.0, 115.2, 114.0, 111.9, 1079, 37.2, 33.9. LRMS (APCI+): Calc'd for C15H13NO3 255.1 m/z, measured 256.2 (MH+).

Provenance & Evidence