Formally Stereoretentive S1 Reactions of Homoallylic Tertiary Alcohols Via Nonclassical Carbocation.

We present a stereoretentive nucleophilic substitution of homoallylic tertiary alcohols via the formation of a nonclassical cyclopropyl carbinyl (CPC) carbocation intermediate. This strategy enables the creation of highly congested tertiary centers with preserved stereocontrol, addressing the typical challenges of carbocation instability and reactivity in S1 mechanisms. The stabilization of the CPC intermediate is crucial for achieving precise regio- and stereoselectivity, significantly enhancing the utility of S1-type mechanisms in complex molecule synthesis.