Modular and selective synthesis of pyrazolo-azepino-centred polycyclic aromatic and non-aromatic architectures

Abstract

The pyrazolo-azepino-centred polyheterocyclic fused system is a privileged scaffold, but it lacks an effective synthetic approach, with modular synthesis being even more scarce. Accordingly, we herein report a highly efficient I₂-DMSO-mediated one-pot, four-component protocol to construct this fascinating scaffold. This system provides an unprecedented temperature-controlled highly selective formation of aromatics and non-aromatics, affording planar and non-planar tetracyclic architectures that can be interconverted surprisingly by simple methods. Mechanistically, a cooperative aza-[4 + 3] cycloaddition is responsible for the skeleton construction process, while the endogenous oxidant I₂ is responsible for the subsequential aromatization stage.