New functionalized alkenylmagnesium reagents bearing an oxygen function in the β-position. Preparation and reaction of 5-magnesiated-1,3-dioxin-4-one derivatives

5-Magnesiated-1,3-dioxin-4-ones have been prepared by performing a low temperature iodine–magnesium exchange reaction. These alkenylmagnesium reagents bearing an alkoxy function in the β-position react directly with aldehydes or with other electrophiles such as acid chlorides, allylic bromides, aryl and alkenyl iodides in the presence of a copper or palladium transition metal catalyst.