The regioselectivity of acid-catalyzed epoxide ring-opening depends on carbocation stability
The regioselectivity of acid-catalyzed epoxide ring-opening reactions and rearrangements is predominantly governed by the stability of the developing carbocation intermediate at the more substituted carbon.
The claim addresses a fundamental chemical principle: in acid-catalyzed epoxide ring-opening, protonation (or Lewis acid coordination) weakens a C-O bond, leading to significant carbocation character at the more substituted carbon, which dictates the regiochemical outcome. Paper [7] directly supports this by stating that acid-catalyzed epoxide rearrangements are dominated by carbocation stability, and Paper [6] supports the standard regioselective ring-opening behavior favoring more-substituted positions. The other papers are either about biocatalytic, photocatalytic, or transition-metal processes that do not discuss acid-catalyzed carbocation-driven epoxide ring-opening.
Brotons G, García-Martínez P, Bernardo O, López LA. Lewis Acid-Catalyzed Alkylation of Azulene Derivatives with Epoxides and Oxetanes: A Regioselective Approach to Functionalized Azulene Alcohols.. 2025. https://doi.org/10.1021/acs.orglett.5c02648
Paper [6] notes that Lewis acid-catalyzed ring-opening of epoxides proceeds with high regioselectivity favoring nucleophilic attack at the more substituted position, consistent with carbocation stability in unsymmetrical systems.
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Funk B, Yasuda M, West JG. Radical Rearrangement of Terminal Epoxides to Methyl Ketones via Cobalt Photocatalysis.. 2026. https://doi.org/10.1021/acs.orglett.6c01341
Paper [7] explicitly states that the acid-catalyzed Meinwald rearrangement of epoxides is dominated by carbocation stability in determining regioselectivity.
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