Stereoselective Synthesis of the Core Structures of Pyrrocidines and Wortmannines through the Excited-State Nazarov Reactions

The
reaction conditions and scope of the excited-state Nazarov
reaction of dicyclicvinyl ketones were studied. The stereochemistry
of this electrocyclization is consistent with the mechanism of the
pericyclic reaction and Woodward–Hoffmann rule. UV-light-promoted
excited-state Nazarov reactions gave hydrofluorenones bearing a syn–cis configuration via a disrotatory cyclization.
The core tricyclic hydrofluorenones of pyrrocidines and wortmannines
were constructed via the excited-state Nazarov reactions, which demonstrated
their synthetic potential in complex natural product total synthesis.