Photoinduced Regioselective Decarbonylative and Decarboxylative C–O Bond Functionalizations: Approach toward Chemoselective Scissions of Isatoic Anhydride and Unraveling the Enroutes through Control Experiments and DFT Studies

Abstract

Distinctive, green, innovative, and well-organized photoinduced (metal-or photocatalyst-free) regioselective decarbonylative and decarboxylative C−O bond functionalization protocols to access aryl 2-aminobenzoates and 2-substituted benzoxazinone derivatives in excellent yields have been devised. These are achieved through the chemoselective scission of isatoic anhydride with ketones, diaryliodonium triflate, nitroalkene, phthalazinone, and phenol derivatives, which, in turn, served as the representative "electrophilic and nucleophilic" coupling partners. Control experiments and DFT calculations reveal that electrophilic radical-bearing coupling partners specifically follow the decarbonylation pathway, while nucleophilic radical-bearing conjugates facilitate the decarboxylation process. Thus, the devised methods represent the chemoselective fragmentation of isatoic anhydride, which occurs due to the electronic nature of the coupling partners. Again, the regioselective C−O/O−C bond formation is also a novel outcome of this methodology. We have also devised a green method for synthesizing 2-aminobenzoate-subtituted paracetamol through a decarboxylation route. A fluorescence quenching study indicates that phenyl 2-aminobenzoate specifically detects Fe(II) ions, exhibiting no reactivity toward various other metal ions. Additionally, transition-metal-catalyzed C−H bond functionalization of 2-substituted benzoxazinone with phenyl vinyl sulfone was performed at ease with significant yields, which appreciated the strategy developed by us.