Diastereoselective Umpolung cyclisation of ketones promoted by hypervalent iodine

Umpolung reactivity facilitated by hypervalent iodine has emerged as an appealing method for the efficient α-functionalization of ketones. However, skeletal reorganisation or migration reactions remain comparatively underexplored, primarily due to the challenging taming of transient carbocationic intermediates. In this study, we introduce a method for the functionalisation of ketones, employing a 6<i>-endo-trig</i> cyclisation initiated by Umpolung of silyl enol ethers, resulting in the diastereoselective formation of <i>cis</i>-substituted cyclohexanes. Additional investigations, both experimental and computational, give insight into the mechanistic intricacies of this process, and shed light on an unconventional iodine(iii)-reactivation mechanism.