Year-end Sale % OFF 
Abstract
Four different chiral 1,3-cyclohexadienes were synthesized and investigated in photooxygenations with singlet oxygen. A strong influence of substituents at the double bond was observed for the mode selectivity of the reactions. Phenyl and alkyl groups afford mixtures of ene and (4 + 2) products, whereas a trimethylsilyl group yields exclusively hydroperoxides, presumably due to a large group effect. Additionally, the same diastereoselectivity for both reaction modes gives evidence for common perepoxide intermediates. Finally, the photooxygenation of a methylensulfonyl substituted 1,3-cyclohexadiene proceeds with very high diastereoselectivity, which can be explained by an intramolecular hydrogen bridge, shielding one face of the compound.
Highlights
Singlet oxygen (1O2) represents a powerful and atom-economic oxidant, which has found numerous applications in organic synthesis.[1]
During our work on synthetic applications of singlet oxygen,[8] we found excellent regioand high diastereoselectivities in the photooxygenation of 1,4-cyclohexadienes 1, which are available by Birch reduction, to afford hydroperoxides 2 (Scheme 1)
For the convenient synthesis of cyclohexadienes, we developed a new cobalt-catalyzed DielsAlder methodology, starting from a boron-functionalized 1,3-diene 3 and various alkynes 4.9 Very recently, we succeeded in a one-pot combination of this reaction with an allylboration in the presence of aldehydes 5, which afforded the desired 1,3-cyclohexadienes 6 from three simple precursors in moderate to good yields (Scheme 2)
Summary
Singlet oxygen (1O2) represents a powerful and atom-economic oxidant, which has found numerous applications in organic synthesis.[1]. Complete conversion was achieved after 10 min in deuterochloroform as solvent and the product ratios were directly determined from the 1H NMR spectra (500 MHz) of the crude reaction mixture. The photooxygenations afforded hydroperoxides 7 and endoperoxides 8 in various ratios and the labile products were directly isolated by column chromatography in high yields and in analytically pure form (Table 1).
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
