Synthesis of Spirocyclohexadienones with Diverse Structural Types and Ring Sizes.

Dearomatization reactions represent one of the most straightforward and efficient approaches for transforming complex 3D molecules from planar aromatic systems. Over the past few decades, numerous synthetic methods have been established. However, current synthetic strategies remain confined to constructing only a single type of the common all-carbon, oxa-, or aza-spirocyclic frameworks, predominantly yielding thermodynamically and kinetically favored five- or six-membered rings and typically providing access to no more than three distinct ring sizes. Herein, we report an iodine-(III)-mediated dearomatization of phenol derivatives that enables the construction of three types of spirocycles as well as four distinct ring sizes of all-carbon spirocyclic compounds (three-, four-, five-, and six-membered rings). This strategy effectively controls chemo- and regioselectivity through the combined modulation of substrate structures, steric effects, and reaction conditions. Moreover, these diversely functionalized products can be readily transformed into fused bicyclic ring frameworks that show great potential for synthetic utility in organic synthesis.