Studies of Reactions of Amines with Sulfur Trioxide. VI. Thermal Reactions of Anilinium, Dimethylanilinium, and Trimethylanilinium Salts of Butylamidosulfuric Acid

Abstract

Abstract 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.