Reaction Steps
Piperidine (0.96 mL, 9.7 mmol) was added to a suspension of 3,4-dimethoxybenzaldehyde (1.6 g, 9.7 mmol) and 2-[(carboxyacetyl)amino]benzoic acid (1.9 g, 8.6 mmol) in toluene (5.0 mL) and treated according to Procedure 2, acidifying with 1 M HCl. (E)-2-[[3-(3,4-Dimethoxyphenyl)-1-oxo-2-propenyl]amino]benzoic acid (tranilast) (2.1 g, 74%) was obtained as a yellow crystalline solid; mp 208-209° C., lit. [22] 206° C.; δH (500 MHz, DMSO-d6) 3.79 (s, 3H, OCH3), 3.82 (s, 3H, OCH3), 6.79 (d, J=15.5 Hz, 1H, CH═CHCO), 6.99 (d, J5′,6′=8.5 Hz, 1H, H5′), 7.16 (t, J3,4=J4,5=7.9 Hz, 1H, H4), 7.25 (d, J5′,6′=8.5 Hz, 1H, H6′), 7.38 (s, 1H, H2′), 7.56 (d, J=15.5 Hz, 1H, CH═CHCO), 7.61 (t, J4,5=J5,6=7.9 Hz, 1H, H5), 8.00 (d, J3,4=7.9 Hz, 1H, H3), 8.62 (d, J5,6=7.9 Hz, 1H, H6), 11.30 (s, 1H, NH), 13.61 (br s, 1H, CO2H).
