Oxidative ring closure of alkyl-substituted 2-hydroxyacetophenone trifluoromethanesulfonate esters (triflates) occurs upon exposure to base in anaerobic DMF at 20-90 degrees 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.
Ketones
Ketones Q 0350Unexpected Migration and Oxidative Cyclization of Substituted 2-Acetophenone Triflates under Basic Conditions: Synthetic and Mechanistic Insights. -Treatment of unsubstituted and monosubstituted 2-acetophenone triflates with bases at 0-20°C leads to migrated products of type (IV) via hypervalent sulfur intermediates. At high temperature, they are transformed to benzofuran-3-ones. Starting from disubstituted 2-acetophenone triflates benzofuran-3-ones are directly obtained. -(COE*, J. W.; BIANCO, K. E.; BOSCOE, B. P.; BROOKS, P. R.; COX, E. D.; VETELINO, M. G.; J. Org. Chem. 68 (2003) 26, 9964-9970; Pfizer Global Res. Dev., Pfizer Inc., Groton, CT 06340, USA; Eng.) -Jannicke 21-062
This viewpoint provides a brief overview of the procedures for initiating post-grant proceedings before the United States Patent Trial and Appeal Board, including a discussion of why companies are now commonly electing to use those proceedings, both as part of an overall litigation strategy and outside of the litigation context.
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