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.

摘要: 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 undergo base-mediated C-arylation followed by N–N bond formation, producing unstable five-membered ring intermediates that spontaneously dehydrate indazole oxides. We identified reaction conditions under which cyclic intermediate undergoes acid-mediated ketone in N-oxide serves as oxidizing agent. The solid-phase synthesis plays a critical role successful transformation, allowing rapid access but oxidation-prone intermediate. This synthetic route provides practical 2-alkyl-2H-indazol-3-yl benzoates and 2-alkyl-1,2-dihydro-3H-indazol-3-ones, privileged structures possessing remarkable diverse pharmacologically relevant activities.