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.
Effects based upon kinds of methylenating agent, solvent and base used, were remarkably observed in methylenation of catechol (1a), pyrogallol (1b), 1, 2-dihydroxy-3-methoxy-(1c) and 1, 2-dihydroxy-4, 5-dimethoxybenzenes (1d), 2, 3-dihydroxy-4-methoxy-(1e), 3, 4-dihydroxy-(1f) and 3, 4-dihydroxy-5-methoxybenzaldehydes (1g) and 3, 4-dihydroxy-5-bromobenzaldehyde (1h), on this heterogeneous reaction system. In addition to these effects, however, there was remarkable fluctuation in yields dependent on reaction operation, but itwas elucidated that the methylenedioxy derivatives were obtained in good yields from inexpensive methylene dichloride and the above aromatic compounds in a short period, when concentrations of (1a1h) have been regulated below 1 M in the reaction system according to a procedure devised by the present authors.