Notizen/Notes Allenyl Enolates — A New Class of Chiral Ambident Nucleophiles, 2. Reaction with Iodine and Oxidizing Agents

The reaction of allenyl enolates, obtained by 1,6‐addition of lithium dimethylcuprate to 2‐en‐4‐ynoates 1a/b , with iodine is studied. Whereas the n ‐butyl‐substituted enyne 1a gives a mixture of vinyl iodide 2a (48%) and methylated allene 3a (7%), the tert ‐butyl‐substituted enyne 1b yields allene 3b (70%) exclusively. The products 2a and 3a are also obtained if Br 2 , O 2 , or CuCl 2 are used to trap the allenyl enolate derived from 1a and Me 2 CuLi · LiI. These findings are discussed with the assumption that iodo‐allene 5 and the iodo‐containing Gilman cuprate [Me 2 Cu(I)Li 2 ] 2 are acting as intermediates.