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Regiochemical Control in Intramolecular Cyclization of Methylene-Interrupted Epoxydiols

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journal contribution
posted on 17.07.2001, 00:00 by Radha S. Narayan, Meenakshi Sivakumar, Ezzeddine Bouhlel, Babak Borhan
Methylene-interrupted epoxydiols have multiple regiochemical routes for cyclization. The 5-exo process is the most prevalent under acidic conditions. However, the regioselectivity can be controlled by the appropriate choice of acid promoter and pendant groups adjacent to the epoxide. The 5-exo product is obtained exclusively without the presence of a carbocation-stabilizing pendant group. Alkenyl and thiophenyl groups adjacent to the epoxide alter the regioselectivity and enable access to the 5-endo tetrahydrofuran and 6-endo tetrahydropyran products.