Syntheses and Reactions of Fluorine-containing Pyrazolium Aminimine

Abstract

The reaction of perfluoro(2-methy1-2-pentene) [1] with 1, 1-dimethylhydrazine (DMH)was studied and a series of fluorine-containing pyrazolium aminimines and pyrazoles were prepared. Substituted compound [2] was first given by nucleophilic attack of DMH on [1] followed by proton shift. By debydrofluorination, compound [2] was changed in to a diene intermediate [3] and cyclized to pyrazolium aminimine [4], or condensed to a ketenimine intermediate [3] after changing into [3] and then cyclized to [6], a dimethylhydrazono derivative of [4]. Compound [6] was also obtained by treating [4] with DMI 1, but the reaction rate was small. When [2] was treated with primary amin es, imine derivatives of [4] were obtained as well. By heating, aminimine [4] and [6] which are stabilized with perfluoroalkyl group, were converted to pyrazole [8] and [10], respectively, and were also easily transmuted to pyrazole [8] or [11], and [12], the hydrochloride of [10], respectively, by bubbling hydrogen chloride gas at room temperature. Aminimine [4] was readily hydrolyzed by moisture in the air or the solution, and was changed into aminimine [13] having carbonyl group. Compound [13] was so stable that it did not changed even if heated to 200°C or exposed to hydrogen chloride.