Intramolecular ortho photocycloaddition of salicyclic acid derivatives: Multiple-step reaction cascades and their synthetic application
Final Report Abstract
The intramolecular photocycloaddition of olefins in 2-alk-4‘-enyloxy-substituted benzenes with an acceptor substituent in 1-position proceeds formally as a 1,2- addition at the aromatic core (ortho photocycloaddition). The primarily formed cyclobutanes are not stable, but rather deliver in an ensuing cascade reaction well defined, structurally complex products. Three classes of reactions were discovered and more closely studied. Upon long-wavelenth irradiation (wavelength λ ≥ 350 nm), the respective substituted indanones led to the formation of tetracyclic products which displayed the skeleton of protoilludane-type sesquiterpenes. At shorter wavelength, products with the core structure of prezizaene-type sesquiterpenes were obtained from the same substrates. Both cascade reactions were successfully implemented in the total synthesis of sesquiterpenes, most notably in the first completed syntheses of atlanticone C und agarozizanol B. A third cascade reaction was discovered for benzaldehyde-derived iminium ions leading for most substrates to substituted benzoxepanes. The reaction could be performed at λ = 366 nm or in the presence of thioxanthone as sensitizer with visible light (λ = 420 nm).
Publications
-
Photochemical Reaction Cascade from O-Pent-4-enyl-Substituted Salicylates to Complex Multifunctional Scaffolds. The Journal of Organic Chemistry, 83(6), 3069-3077.
Zech, Andreas & Bach, Thorsten
-
Concise Access to the Skeleton of Protoilludane Sesquiterpenes through a Photochemical Reaction Cascade: Total Synthesis of Atlanticone C. Angewandte Chemie International Edition, 58(41), 14629-14632.
Zech, Andreas; Jandl, Christian & Bach, Thorsten
-
Complex Carbocyclic Skeletons from Aryl Ketones through a Three‐Photon Cascade Reaction. Angewandte Chemie International Edition, 59(14), 5656-5659.
Næsborg, Line; Jandl, Christian; Zech, Andreas & Bach, Thorsten
-
Concise Total Synthesis of (+)-Atlanticone C. Synlett, 31(16), 1598-1602.
Bach, Thorsten; Proessdorf, Johanna; Zech, Andreas & Jandl, Christian
-
Concise Total Synthesis of Agarozizanol B via a Strained Photocascade Intermediate. Angewandte Chemie International Edition, 60(45), 24039-24042.
Rauscher, Niklas; Næsborg, Line; Jandl, Christian & Bach, Thorsten
-
Arene Activation through Iminium Ions: Product Diversity from Intramolecular Photocycloaddition Reactions. Angewandte Chemie International Edition, 61(40).
Proessdorf, Johanna; Jandl, Christian; Pickl, Thomas & Bach, Thorsten
-
The Awakening of a Sleeping Beauty: The ortho Photocycloaddition in the Total Synthesis of Protoilludane- and Prezizaene-Type Sesquiterpenes. Synlett, 34(12), 1343-1355.
Bach, Thorsten & Gilbert, Audrey
