Transfer of sulphonic acid groups from N-alkylsulphamic acids: a new and simple sulphonation procedure

N-n-Butyl- and -cyclohexyl-sulphamic acids reacted (at temperatures of 150–195°) with aniline, NN-dimethyl-aniline, and anisole to yield the corresponding p-substituted benzenesulphonic acids (as either the n-butylammonium or cyclohexylammonium salts) in excellent (≥90%) yields. When the sulphamic acids were replaced by the corresponding ammonium sulphamates (including a secondary sulphamate salt, morpholinium morpholine-N-sulphonate), the salts proved substantially less reactive as sulphonating agents, and they failed, for example, to sulphonate anisole. These sulphamic acid reactions constitute the first use of such substituted sulphamic acids in sulphonation procedures.