Reaction Steps
Sodium hydroxide (5.0 M, 27 ml, 135 mmol) was added to a suspension of 7-hydroxy-3,4-dihydro-4-methylcoumarin (Compound of formula B1) (8.0 g, 45 mmol) in water (40 ml) at room temperature and the resulting solution stirred for 20 min. At this time, TLC (4% methanol:chloroform) showed the clean formation of product at the expense of starting material. The solution was cooled to 5° C. and carefully acidified with concentrated HCl to pH less than about 1, keeping the temperature at less than about 15° C. throughout the addition. The solution was extracted with ethyl ether (4×100 ml), the organic layers washed with saturated NaCl (4×50 ml), combined, dried (Na2SO4), filtered and the solvent removed to give a pale orange oil. Further purification by filtering through a short pad of silica gel and eluting with ethyl acetate afforded pure product as a white solid (8.3 g, 94%): m.p. 92-94° C.; 1H NMR (DMSO-d6) d 1.13 (d, JJ=7.0, 3H), 2.33 (dd, JJ=15.0, 8.9, 1H), 2.52 (dd, JJ=15.5, 7.3, 1H), 3.32 (m, 1H), 6.16 (dd, JJ=8.2, 2.4, 1H), 6.28 (d, JJ=2.4, 1H), 6.84 (d, JJ=8.2, 1H), 9.08 (s, 1H), 9.59 (s, 1H), 11.87 (s, 1H); 13C NMR (DMSO-d6) d 20.39, 28.97, 41.0, 102.58, 106.01, 122.55, 127.27, 155.19, 156.18, 173.74; m/z (EI; TMS derivatized; M+) 412; IR (neat; cm−1) 3360.1, 2974.1, 2935.1, 2876.4, 1748.0, 1713.8, 1625.9, 1606.3, 1518.4, 1459.8, 1381.6, 1347.4, 1283.9, 1254.6, 1239.9, 1156.9, 1117.8, 1025.0, 981.0, 937.1, 849.1, 810.1.
