A synthetic route
to liphagal, a natural PI3Kα inhibitor
isolated from Aka coralliphaga, was
established. The present route features an organic redox process where
an alkynylquinone undergoes reductive cyclization in the presence
of a hydroquinone derivative such as hydroxyquinol (1,2,4-benzenetriol)
and catalytic PdCl2 to provide a substituted benzofuran
suitable for accessing the natural product. The benzofuran formation
takes place via the redox transformation between the alkynylquinone
and the electron-rich hydroquinones followed by the concomitant Pd(II)-catalyzed
oxycyclization of the resultant alkynylhydroquinone.