Preparation and reactions of 2-chlorotetrafluoro-cyclobutenyl copper reagent

Abstract

1-Chloro-2-iodotetrafluorocyclobutene reacted with activated zinc powder in DMF solvent at room temperature to give 2-chloro-tetrafluorocyclobutenyl zinc reagent. Treatment of this organozinc reagent with cuprous bromide at room temperature for one hour provided a simple route to the 1-chloro-tetrafluorocyclobutenyl copper reagent in excellent yield. 1-chlorotetrafluorocyclobutenyl copper reagent exhibited excellent stability at room temperature in the absence of oxygen and/or moisture. Alkylation reactions of this organocopper reagent were performed, and the reaction of this organocopper reagent with acyl halides gave acylated polyfluorocyclobutenes, which have not been reported in the literature. 2-Chlorotetrafluorocyclobutenyl zinc reagent were also prepared from 1-chloro-2-iodotetrafluorocyclobutene with acid washed zinc powder in excellent yield in glyme solvent such as triglyme or monoglyme. The acylation reaction of the zinc reagent with acyl chlorides in glyme solvent using cuprous bromide as a catalyst occurred and gave much higher yields of acylated derivatives compared with that of pregenerated copper reagent in DMF solvent. Nucleophilic reactions of the synthesized 1-acetyl-2-chlorotetrafluorocyclobutene with alkoxide, amine, and Grignard reagent were carried out. Potassium ethoxide and diethylamine racted rapidly with 1-acetyl-2-chlorotetrafluorocyclobutene and gave only monosubstituted product at beta-position in good yield. With methyl-magnesium iodide, the tertiary alcohol was the only isolated product.