Hydromagnesiation of 1-Arylallenes with Magnesium Hydride toward Cinnamylmagnesium Reagents.

We herein report that magnesium hydride, generated via solvothermal treatment of magnesium iodide with sodium hydride in tetrahydrofuran, is capable of promoting the hydromagnesiation of 1-arylallenes. The resulting cinnamylmagnesium species could be functionalized by the subsequent treatment with aldehydes or ketones in the presence of zinc chloride to form various homoallylic alcohols in a diastereoselective manner via a 6-membered ring chair-like transition state.