Acylierung von Heterocyclen mit Kohlensäurederivaten. IV. Umsetzung von Benzoxazolin 2‐thion mit Arylcyanaten. Kinetik und Mechanismus

Acylation of Heterocycles with Carbonic Acid Derivatives. IV. Reaction of Benzoxazolin-2-thione with Aryl Cyanates. Kinetics and Mechanism The arylcyanate benzoxazoline-2-thione (1) reaction in the presence and absence of the tertiary amines yields 1-aryloxyiminocarbonylbenzoxazoline-2-thione (2) and 2-thiocyanatobenzoxazole (4). A mechanism is proposed based on the influences of the reactants concentration, the concentration and basicity of tertiary amines, the solvent-water concentration, the arylcyanate substituents electronic effects on the reaction rate and the apparent activation parameters. This mechanism consists in the nucleophilic attack of the benzoxazoline-2-thione S-atom on the cyanate, followed by rearrangement through a four-center transition state.