When the title compounds were heated in an evacuated reaction vessel, both transsulfonation and rearrangement occurred. At lower temperatures (80–120 °C) the corresponding phenylamidosulfates and sulfophenylamidosulfates (transsulfonation products) were the main products. Increasing temperature led to the formation of ring mono- and disulfonates (rearrangement products) at the expense of the transsulfonation products. The sulfonate group always migrated to the ortho and/or para position(s) to the amino group. In no case was any meta-product detected. There was no significant difference in the ease of transsulfonation among the anilinium salts studied except 2,6-dimethyl- and 2,4,6-trimethylanilinium salts. On the other hand, the ease of rearrangement and the orientation of ring sulfonation depended strongly on the structure of the substrate anilines. The thermal reactions of 2,4,6-trimethylanilinium butylamidosulfate produced (2,4,6-trimethylphenylimido)bis(sulfate) in addition to (2,4,6-trimethylphenylamido)sulfate. This is the first isolation of an arylimidobis(sulfate) from such reactions. Mechanisms of the transsulfonation and the rearrangement have been discussed.

Seven arylimidobis(sulfates), six of which are new compounds, have been prepared by the N-sulfonation of the corresponding primary aromatic amines with 2-methylpyridine-sulfur trioxide in 60–92% yields.

No abstract

The reaction between anilinotrimethylsilane (1) and a variety of sulfonating agents [SO3, ClSO3H, trimethylsilyl chlorosulfate (5), dioxane–sulfur trioxide complex, ethyl chlorosulfate (10)] has been studied. With SO3, 5, or a dioxane–sulfur trioxide complex a sulfur trioxide molecule was inserted selectively into the N–Si bond of 1 to yield trimethylsilyl phenylamidosulfate (2), which on treatment with acetic acid, trifluoroacetic acid, or methanol gave free phenylamidosulfuric acid (3). The reaction of 1 with ClSO3H afforded 3 directly, but the product was contaminated with slight amounts of anilinium hydrogensulfate and anilinium chloride. The reaction of 1 with 10 yielded a mixture containing dianilinium (4-sulfonatophenylamido)sulfate, 4-aminobenzenesulfonic acid, and ethyl phenylamidosulfate as major products (after desilylation). The reaction of 1 with 5 has been found to provide an improved method for preparing 3.

4-Methylanilinium butylamidosulfate, butylammonium (4-methylphenyl)amidosulfate, and 4-methylanilinium (4-methylphenyl)amidosulfate were heated separately under reduced pressure at different temperatures ranging from 80 to 180 °C. Butylammonium butylamidosulfate was heated with 4-methylaniline under atmospheric and reduced pressure. The product compositions were determined as functions of reaction time and temperature, and the components were separated and identified. At lower temperatures (4-methylphenyl)amidosulfate and 4-methylaniline-N,2-disulfonate were the major products, while at higher temperatures 4-methylaniine-2-sulfonate and 2,6-disulfonate were the major products. The ease of N–S bond cleavage of the amidosulfate salts (RNHSO3–R′NH3+) (1) depends largely on the basicity of both the parent amine (R′NH2) (2) and the salt-forming base (R′NH2) (3). The results suggest that the initial step of the transsulfonation involves the dissociation of 1 into 3 and the free acid followed by an equilibration between RNHSO3H and RNH2+SO3− (4). It is considered that 4 may be the sulfonating species and the free amines, 2 and 3, should be the receptors of a sulfonate group. In contrast to the widely accepted scheme (transsulfonation and subsequent intramolecular rearrangement), our results show that both the transsulfonation and the rearrangement process occur concurrently and the same type of mechanism (a bimolecular displacement, viz., B+ : SO3−+B′: \ightleftarrowsB+: +B+: SO3−) may be operative.