A method for the photoinduced evolution of atomic oxygen from pyridazine N-oxides was developed. This underexplored oxygen allotrope mediates arene C–H oxidation within complex, polyfunctional molecules. A water-soluble pyridazine N-oxide was also developed and shown to promote photoinduced DNA cleavage in aqueous solution. Taken together, these studies highlight the utility of pyridazine N-oxides as photoactivatable O­(3P) precursors for applications in organic synthesis and chemical biology.

A new polyene cyclization strategy exploiting β-ionyl derivatives was developed. Photoinduced deconjugation of the extended π-system within these chromophores unveils a contrathermodynamic polyene that engages in a Heck bicyclization to afford [4.4.1]-propellanes. This cascade improves upon the limited regioselectivity achieved using existing biomimetic tactics and tolerates both electron-rich and electron-deficient (hetero)­aryl groups. The utility of this approach was demonstrated with the diverted total synthesis of taxodione and salviasperanol, two isomeric abietane diterpenes that were previously inaccessible along the same synthetic pathway.

No abstract

A versatile polyene cyclization strategy was developed that exploits conjugated -ionyl derivatives. Photomediated disruption of the extended -system within these chromophores unveils a contra-thermodynamic polyene that engages in a Heck-type cyclization to afford [4.4.1]-propellanes. The connectivity of overbred polycycles generated from this process is controlled by the position of the requisite C–Br bond. Thus, compared to conventional biomimetic polyene cyclization, this approach allows for complete control of regiochemistry and facilitates incorporation of both electron-rich and electron-deficient (hetero)aryl groups. This strategy was successfully applied to the total synthesis of taxodione and salviasperanol, two isomeric abietane-type diterpenes that previously could not be prepared along the same synthetic pathway.

A versatile polyene cyclization strategy was developed that exploits conjugated -ionyl derivatives. Photomediated disruption of the extended -system within these chromophores unveils a contra-thermodynamic polyene that engages in a Heck-type cyclization to afford [4.4.1]-propellanes. The connectivity of overbred polycycles generated from this process is controlled by the position of the requisite C–Br bond. Thus, compared to conventional biomimetic polyene cyclization, this approach allows for complete control of regiochemistry and facilitates incorporation of both electron-rich and electron-deficient (hetero)aryl groups. This strategy was successfully applied to the total synthesis of taxodione and salviasperanol, two isomeric abietane-type diterpenes that previously could not be prepared along the same synthetic pathway.