rearrangementbased

Rearrangement-based is a descriptor used in chemistry to categorize reactions and strategies that rely on rearrangements of a molecule's carbon skeleton. In these processes, bond migrations, skeletal shifts, or ring contractions and expansions reorganize connectivity to produce the product, often with little or no change in oxidation state. The approach contrasts with stepwise functional-group interconversions and can enable rapid construction of complex frameworks from simpler precursors. Mechanistically, rearrangement-based transformations can proceed through carbocation rearrangements, sigmatropic and pericyclic rearrangements, or radical and metal-catalyzed pathways. They can be concerted or stepwise, and are frequently driven by factors such as strain relief, aromatic stabilization, or the formation of stronger bonds.

Common examples span several classes of reorganizations. Carbocation rearrangements include Wagner-Meerwein and pinacol rearrangements; sigmatropic rearrangements encompass Claisen, Cope, and other [3,3]-rearrangements; ring-contracting or expanding sequences also fall into this category. More recently, rearrangement cascades and skeletal editing strategies have highlighted the use of sequential or tandem rearrangements to build complexity in a single operation.

Applications of rearrangement-based methods appear in natural product total synthesis, medicinal chemistry, and the design of cascade or domino reactions that construct multiple bonds and rings efficiently. These approaches can offer strategic advantages such as rapid skeleton remodeling, access to otherwise challenging motifs, and streamlined synthetic sequences, though they may require careful control of selectivity and reaction conditions.