To a solution of 1,4-diethoxy-2,3-naphthalenedicarboxylic acid (0.75 g, 2.5 mmol, 1.1 eqs) in glacial acetic acid (5 ml) was added 4-amino-benzylsulfonamide (0.43 g, 2.3 mmol). The reaction mixture was heated at 120° C. for 18 h. The reaction mixture was allowed to cool to ambient temperature and then poured into water (5 ml). The precipitate was filtered off, triturated with ethyl acetate/40:60 petroleum ether and then dried in vacuo to give the title compound as a beige solid (790 mg, 69%). δH [2H6]—DMSO 1.48 (6H, t); 4.40 (2H, s); 4.52 (4H, q); 7.00 (2H, s); 7.51 (2H, d, 8.5Hz); 7.56 (2H, d, 8.5 Hz); 7.89 (2H, m); 8.43 (2H, m)
