Photooxygenation of oxygen‐substituted naphthalenes†. (13th July 2017)

• Record Type: Journal Article
• Authors: Bauch, Marcel; Krtitschka, Angela; Linker, Torsten
• Other Names: Ihmels Heiko guestEditor.; Linker Torsten guestEditor.; Trofimov Aleksei guestEditor.
• Is Part Of: Journal of physical organic chemistry. Volume 30:Number 9(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-07-13
• Subjects: kinetics -- labile peroxides -- low‐temperature experiments -- naphthalenes -- singlet oxygen; Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.3734
• Languages: English
• ISSNs: 0894-3230

Abstract

Abstract: The reaction of oxygen‐substituted naphthalenes with singlet oxygen ( 1 O2 ) has been investigated, and labile endoperoxides have been isolated and characterized at –78°C for the first time. Low‐temperature kinetics by UV spectroscopy revealed that alkoxy and silyloxy substituents remarkably increase the rate of photooxygenations compared to 1, 4‐dimethylnaphthalene, whereas acyloxy‐substituted acenes are inert towards 1 O2 . The reactivities nicely correlate with HOMO energies and free activation energies, which we determined by density functional theory calculations. The lability of the isolated endoperoxides is due to their very fast back reaction to the corresponding naphthalenes even at –20°C under release of 1 O2, making them to superior sources of this reactive species under very mild conditions. Finally, a carbohydrate‐substituted naphthalene has been synthesized, which reacts reversibly with 1 O2 and might be applied for enantioselective oxidations in future work. Abstract : Various naphthalenes1 are smoothly photooxygenated to afford endoperoxides2 quantitatively. Important is the low temperature of –78°C and the proper solvent to handle and isolate such labile species. Reactivities nicely correlate with the HOMO energies of naphthalenes1 . The endoperoxides2 reconvert quantitatively to the parent naphthalenes1 under release of singlet oxygen even at –20°C, making them to superior organic sources of this reactive species under very mild conditions.