Use of fluoride ion as a reagent in acetylene- and allene-forming eliminations

Abstract

The use of fluoride ion as a reagent for promoting elimination from halogenoethylenes has been investigated. Tetraethylammonium fluoride in acetonitrile and potassium fluoride in various solvents are good dehydrohalogenating reagents for systems (I)–(IV) in which the leaving groups are anti-related. Acetylenes can be obtained in good yields without any substitution or post-addition reactions. Elimination from the 2-halogeno-1-p-nitrophenylpropenes (VI) and (VII) leads to p-nitrophenylallene in good yields, thus indicating the potential usefulness of fluoride ion for obtaining this type of sensitive compound. The effect of dicyclohexyl-18-crown-6-ether in the reaction mixture has been briefly explored.