Intramolecular Photoreactions of (5S)-5-Oxymethyl-2(5H)-furanones as a Tool for the Stereoselective Generation of Diverse Polycyclic Scaffolds.
The photoactivated evolution of a series of enantiomerically pure 5-oxymethyl-2(5H)-furanones has been investigated. The observed intramolecular photoreactions have proven to be a straightforward entry to diverse and stereochemically rich fragment-molecules, most of which contain the privileged tetrahydropyran (THP) scaffold. The formation of the THP involves a 1,5-hydrogen atom transfer process, leading to a diradical intermediate that recombines to form a new σ C-C bond. These reactions take place under both sensitized and nonsensitized conditions, and they are highly stereoselective. When the substrate contains an allyl residue, the intramolecular [2 + 2] cycloaddition leading to cyclobutanes competes advantageously. When the substrate contains a THP residue, the cyclization involves the concomitant formation of [6,6]-spiroketals with nonanomeric relationships.
Departament de Química and ‡Servei de RMN, Universitat Autònoma de Barcelona , 08193 Bellaterra, Spain.
Guillaume
G
Lejeune
Departament de Química and ‡Servei de RMN, Universitat Autònoma de Barcelona , 08193 Bellaterra, Spain.
Josep
J
Font
Departament de Química and ‡Servei de RMN, Universitat Autònoma de Barcelona , 08193 Bellaterra, Spain.
Teodor
T
Parella
Departament de Química and ‡Servei de RMN, Universitat Autònoma de Barcelona , 08193 Bellaterra, Spain.
Ramon
R
Alibés
Departament de Química and ‡Servei de RMN, Universitat Autònoma de Barcelona , 08193 Bellaterra, Spain.
Marta
M
Figueredo