Methanol → Methyl 3-bromocinnamate, predominantly trans

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Reaction Steps

A solution of trans-3-(3-bromophenyl)-2-propenoic acid (0.405 mol) in methanol (300 ml) was treated with conc. sulfuric acid (6.0 ml) and heated under reflux for 10 h. The cooled mixture was filtered to afford the title compound (46.14 g, 47%) as brilliant white crystals, m.p. 53-55° C. (Found: C, 50.10; H, 3.58; Br; 33.21. C10H9BrO2 requires C, 49.82; H, 3.76; Br, 33.14%); νmax (nujol)/cm−1 1730.5, 1715.0, 1644; δH (270 MHz) 3.81 (3H, s, OCH3); 6.43 (1H, d, 2-H, 3J2,3=16.2 Hz); 7.25 (1H, t, 5′-H, Jo=7.8 Hz); 7.43 (1H, dt, 4′-H, Jo=7.9, Jm=1.0 Hz); 7.50 (1H, dt, 6′-H, Jo=7.9, Jm=1.0 Hz); 7.60 (1H, d, 3-H, 3J3,2=16.2 Hz); 7.66 (1H, t, 2′-H, Jm=1.7 Hz). δc (67.8 MHz) 51.8 (OCH3); 123.0 (3′-C); 133.0 (4′-C); 136.4 (1′-C); 143.1 (3-C); 166.9 (CO2Me). Remaining signals lie in the range 119.3-130.7 ppm; m/z 242.0, 240.0 (46.67, 47.64, M+), 211.0, 209.0 (72.69, 74.00), 182.9, 180.9 (15.67, 16.83), 161.0 (4.19), 130.0 (9.44), 102.1 (100).

Provenance & Evidence