title: N-Oxide as an Intramolecular Oxidant in the Baeyer-Villiger Oxidation: Synthesis of 2-Alkyl-2H-indazol-3-yl Benzoates and 2-Alkyl-1,2-dihydro-3H-indazol-3-ones.
abstract: In this study, we describe the intramolecular Baeyer-Villiger oxidation of ketones to esters using N-oxide. 2-Nitro-N-alkyl-N-(2-oxo-2-phenylethyl)benzenesulfonamide compounds are known to undergo base-mediated C-arylation followed by N-N bond formation, producing unstable five-membered ring intermediates that spontaneously dehydrate to indazole oxides. We identified the reaction conditions under which the cyclic intermediate undergoes acid-mediated intramolecular Baeyer-Villiger oxidation of the ketone in which N-oxide serves as the intramolecular oxidizing agent. The solid-phase synthesis plays a critical role in the successful transformation, allowing rapid access to the unstable but Baeyer-Villiger oxidation-prone intermediate. This synthetic route provides practical access to 2-alkyl-2H-indazol-3-yl benzoates and 2-alkyl-1,2-dihydro-3H-indazol-3-ones, which are known privileged structures possessing remarkable diverse pharmacologically relevant activities.
authors.affiliation: Department of Organic Chemistry, Faculty of Science, Palacký University , 17. listopadu 12, 771 46 Olomouc, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Schütznerová
authors.affiliation: Department of Organic Chemistry, Faculty of Science, Palacký University , 17. listopadu 12, 771 46 Olomouc, Czech Republic.|Department of Chemistry and Biochemistry, 251 Nieuwland Science Center, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Viktor
authors.initials: V
authors.lastname: Krchňák