Unexpected Migration and Oxidative Cyclization of Substituted 2-Acetophenone Triflates under Basic Conditions: Synthetic and Mechanistic Insights
journal contributionposted on 26.12.2003, 00:00 by Jotham W. Coe, Krista E. Bianco, Brian P. Boscoe, Paige R. Brooks, Eric D. Cox, Michael G. Vetelino
Oxidative ring closure of alkyl-substituted 2-hydroxyacetophenone trifluoromethanesulfonate esters (triflates) occurs upon exposure to base in anaerobic DMF at 20−90 °C. Alkyl substitution is required for ring closure. A migrated enol triflate product forms at lower temperature in high yield via migration of the trifluoromethanesulfonate in the unsubstituted and monoalkyl-substituted cases. The alkyl-substituted enol triflates also enter into the benzofuran-3-one ring-forming process under thermal cyclization conditions. Potential mechanistic pathways are evaluated.