Vinylallenes—V(xf2): Reaction des magnesiens vinylalleniques avec les cetones et aldehydes conjugues et transposition d'oxy-cope de certains alcools en resultant

Vinylallenic Grignard reagents prepared from 5-halogeno alk-3-ene-1-ynes react with acyclic conjugated aldehydes and ketones leading exclusively to 4-ethynyl hexa 1,5-diene 3-ols 5; with cyclohexénone and other ketones having more extended conjugation, the same alcohol 5 is still the major product but isomeric ketones and alcohols are also obtained resulting from the intervention of the two other nucleophilic sites of the reagent. The alcohols 5 are easily isomerised to δ-ethylenic ξ-acetylenic aldehydes and ketones 6 by reflux of their solution in diglyme or by fast distillation through a column heated at 350°.