The reaction of rifamycin S and the quinonic 3-(hydrazonomethyl)rifamycin derivatives with sodium sulfinates under neutral conditions were found to afford the hydroquinone-type 4-O-sulfonyl derivatives of rifamycin. 3-Amino-4-deoxo-4-iminorifamycin S also gave rise to the hydroquinone-type 4-deoxy-4-sulfonylamino derivatives of rifamycin when treated with sodium sulfinates. Under acidic conditions, rifamycin S and 3-bromorifamycin S produced the hydroquinone- and quinone-type 3-sulfonyl derivatives of rifamycin, respectively, by reactions with sodium sulfinates. Some of sodium salts of 4-O-sulfonylrifamycin SV derivatives afforded rifamycin S and sodium sulfinates and/or sodium sulfonates when heated in AcOEt.