Nucleophilic Aromatic Substitution. Part XV. Phase-Transfer Catalysis of Sulfodechlorination and Identification of a Primary Product of Sulfite Ion with 1-Chloro-2,4-dinitrobenzene

Article abstract of DOI:10.1002/hlca.19820650108

With conventional phase-transfer catalysis using quaternary ammonium salts, yields of 2,4-dinitrobenzenesulfonic acid (2) in the sulfodechlorination of 1-chloro-2,4-dinitrobenzene (1) with sulfite ions are no better than those obtained with the classical method in aqueous ethanol (80-82percent).Yields up to 97percent and a very pure product are obtained, however, by using protonated tertiary amines as catalysts.The optimum chain-lenght of the amine is found with tributylamine.On mixing solutions of the reagents and catalysts a strong bluish-red colour develops immediately, but dis appears within ca. 1 h.Comparison of the NMR. spectrum of this primary product with model adducts of sulfite ions and di- and trinitrobenzene derivatives demonstrates that the primary addition of the nucleophile to 1-chloro-2,4-dinitrobenzene does not take place at C(1), but at C(5).It is shown that the increments calculated for a C_(sp3₎-SO3^- group and for the 1,3-dinitro- and 1,3,5-trinitropentadienyl ring moieties can be employed for the approximate calculation of 1H-chemical shifts using Clerc and Pretschs's modification of the Shoolery rules.