Photoinduced Regioselective\nDecarbonylative and Decarboxylative\nC–O Bond Functionalizations: Approach toward Chemoselective\nScissions of Isatoic Anhydride and Unraveling the Enroutes through\nControl Experiments and DFT Studies

Distinctive, green, innovative, and well-organized photoinduced\n(metal- or photocatalyst-free) regioselective decarbonylative and\ndecarboxylative C–O bond functionalization protocols to access\naryl 2-aminobenzoates and 2-substituted benzoxazinone derivatives\nin excellent yields have been devised. These are achieved through\nthe chemoselective scission of isatoic anhydride with ketones, diaryliodonium\ntriflate, nitroalkene, phthalazinone, and phenol derivatives, which,\nin turn, served as the representative “electrophilic and nucleophilic”\ncoupling partners. Control experiments and DFT calculations reveal\nthat electrophilic radical-bearing coupling partners specifically\nfollow the decarbonylation pathway, while nucleophilic radical-bearing\nconjugates facilitate the decarboxylation process. Thus, the devised\nmethods represent the chemoselective fragmentation of isatoic anhydride,\nwhich occurs due to the electronic nature of the coupling partners.\nAgain, the regioselective C–O/O–C bond formation is\nalso a novel outcome of this methodology. We have also devised a green\nmethod for synthesizing 2-aminobenzoate-subtituted paracetamol through\na decarboxylation route. A fluorescence quenching study indicates\nthat phenyl 2-aminobenzoate specifically detects Fe(II) ions, exhibiting\nno reactivity toward various other metal ions. Additionally, transition-metal-catalyzed\nC–H bond functionalization of 2-substituted benzoxazinone with\nphenyl vinyl sulfone was performed at ease with significant yields,\nwhich appreciated the strategy developed by us.