6-(2-Haloethyl)-2,2-dimethyl-4H-1,3-dioxins: versatile haloethyl vinyl ketone equivalents for carbocycle construction

6-(2-Iodoethyl)-2,2-dimethyl-4H-1,3-dioxin has been prepared in five steps from ethyl acetoacetate. A variety of enolates were then alkylated with this iodide. The resulting 6-alkyl-4H-1,3-dioxins were either subjected to further transformations and/or heated (or subjected to a Lewis acid) to effect facile retrocycloaddition reactions. The resulting enones were found to smoothly participate in conjugate addition or olefin metathesis reactions to provide various carbocyclic ring systems. Collectively, these examples document the synthetic equivalency of dioxin 2 with iodoethyl vinyl ketone and, moreover, delineate a strategy for accomplishing the sequential reactions with nucleophiles at the β′, followed by the β electrophilic sites.