Construction of Fused Polyheterocycles through Sequential [4 + 2] and [3 + 2] Cycloadditions

A method
for Pd-catalyzed aerobic oxidative reaction of quinazolinones
and alkynes has been developed for sequential [4 + 2] and [3 + 2]
cycloadditions to assemble a novel fused-polycyclic system containing
tetrahydropyridine and dihydrofuran rings. The reaction process involves
C–H and N–H bond functionalization for the formation
of tetrahydropyridine and an oxygen radical cyclization for the dihydrofuran
ring. This atom- and step-economical synthesis is highly efficient
and has good substrate tolerance, which provides a new approach for
the construction of polycyclic molecules with potential pharmaceutical
interest.