In order to develop a general synthetic route to
N-substituted imidobissulfates, the reaction of di-
n-butyl-ammonium methylamidosulfate with a variety of sulfonating agents was investigated.
The sulfonating agents used in this study were sulfur trioxide as well as a number of sulfur trioxide complexes with Lewis bases,
i. e. 1, 4-dioxane,
N, N-dimethylformamide, pyridine, 2-picoline, 2, 6-lutidine, trimethylamine, and triethylamine.
Sulfonation of the methylamidosulfate with the tertiary amine-sulfur trioxide complexes gave directly methylimidobissulfate in excellent yields (90%). On the other hand, the use of sulfur trioxide as well as sulfur trioxide complex with 1, 4-dioxane or
N, N-dimethylformamide led to “methylamidodisulfate”, which afforded, on treatment with an appropriate base such as triethylamine, methylimidobissulfate in varying yields (1860%) depending upon the time of treatment. Mechanisms of the reaction are discussed.
Ten
N-substituted imidobissulfates, of which five are new compounds, were synthesized in 6490% yields by
N-sulfonation of the corresponding amidosulfates with 2-picoline-sulfur trioxide in 2-picoline as solvent at room temperature, and their infrared spectral data are also described.
This new reaction provides a general, high-yield method for the preparation of
N-substituted imidobissulfates, especially the secondary alkyl as well as cycloalkyl derivatives inaccessible by previously reported methods.
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