Complexity‐Building Exhaustive Dearomatization of Benzenoid Aromatics within an ESIPT‐Initiated Three‐Step Photochemical Cascade.

Source abstract

Abstract Dearomative cycloadditions offer rapid access to complex 3D molecular architectures, commonly via a sp 2 ‐to‐sp 3 rehybridization of two atoms of an aromatic ring. Here we report that the 6e π‐system of a benzenoid aromatic pendant could be exhaustively depleted within a single photochemical cascade. An implementation of this approach involves the initial dearomative [4+2] cycloaddition of the Excited State Intramolecular Proton Transfer (ESIPT)‐generated azaxylylene, followed by two consecutive [2+2] cycloadditions of auxiliary π moieties strategically positioned in the photoprecursor. Such photochemical cascade fully dearomatizes the benzenoid aromatic ring, saturating all six sp 2 atoms to yield a complex sp 3 ‐rich scaffold with high control of its 3D molecular shape, rendering it a robust platform for rapid systematic mapping of underexplored chemical space. Significant growth of molecular complexity—starting with a modular synthesis of photoprecursors from readily available building blocks—is quantified by Böttcher score calculations.