Allylic Rearrangements. XVIII. Coupling Reactions of Butenylmagnesium Bromide

Abstract

In connection with our work on the nature of the butenyl Grigiiard reagent it was desirable to study the coupling reactions of butenylmagnesium bromide. Henne, Chanan and Turk have coupled butenyl chlorides in the presence of magnesium while Lespieau and Heitzmann have reported similar experiments with crotyl bromide, but the results of these investigators are not in agreement. Furthermore, it is not clear whether or not the butenyl Grignard reagent is truly involved under conditions where the organometallic compound couples as rapidly as it forms. Indeed, valuable information might be expected from a comparison of the products resulting from the rapid coupling of two halide molecules with magnesium and from the coupling of a preparation of the Grignard reagent with a suitable halide. We have, therefore, made a study of the coupling reactions of butenylmagnesium bromide. After the completion of this work a paper by Levy and Cope appeared describing a number of similar experiments but without comment as to the significance of the results.