Role of curvature in acridone for 1O2 oxidation of a natural product homoallylic alcohol: A novel iso ‐hydroperoxide intermediate

Strategies for improving1O2 oxidation paths to dihydrobenzofurans are needed. A density functional theory study provides evidence that acridone curvature and phenol O –H···π bonding facilitate1O2 oxidation of a prenyl side group to reach a dihydrobenzofuran. Mechanistic insight is provided for aniso-hydroperoxide intermediate preceding the dihydrobenzofuran. Notably, our evidence for theiso-hydroperoxide intermediate is reminiscent of otheriso species, such as oxywater andiso-iodoform in fields outside biosynthetic and1O2 chemistry. AbstractA density functional theoretical (DFT) study is presented, implicating a1O2 oxidation process to reach a dihydrobenzofuran from the reaction of the natural homoallylic alcohol, glycocitrine. Our results predict an interconversion between glycocitrine and aniso-hydroperoxide intermediate [R(H)O+–O−] that provides a key path in the chemistry which then follows. Formations of allylic hydroperoxides are unlikely from a1O2‘ene’ reaction. Instead, the dihydrobenzofuran arises by1O2 oxidation facilitated by a 16 ° curvature of the glycocitrine ring imposed by a pyramidalN-methyl group. This curvature facilitates the formation of theiso-hydroperoxide, which is analogous to theiso species CH2I+–I− and CHI2+–I− formed by UV photolysis of CH2I2 and CHI3. Theiso-hydroperoxide is also structurally reminiscent of carbonyl oxides (R2C=O+–O−) formed in the reaction of carbenes and oxygen. Our DFT results point to intermolecular ...
Source: Photochemistry and Photobiology - Category: Science Authors: Tags: RESEARCH ARTICLE Source Type: research