Tome, Augusto C.; Cavaleiro, Jose A. S.; Domingues, Fernando M. J., Phosphorus, Sulfur and Silicon and the Related Elements, 1993, vol. 79, # 1,4, p. 187 - 194
N-phenylmaleimides, o-, m- and p- substituted (1) reacted with excess chlorosulfonic acid to give the corresponding sulphonyl chlorides (2-5). These were condensed with amines and phenols to give derivatives (7-29) which underwent hydrolysis or ammonolysis to give respectively the sulfamoyl maleamic acids (31-34) and sulfamoyl maleamides (35-39).