Recent Advances in the Generation of Onium Ylides for Sommelet–Hauser Rearrangements

Abstract The Sommelet–Hauser rearrangement of X-benzylic onium ylides (X = heteroatom) is an interesting transformation in organic synthesis. This rearrangement proceeds via dearomative [2,3]-sigmatropic rearrangement, followed by aromatization to form a carbon(sp2)–carbon(sp3) bond. Few advances were made in studies performed around 2000 on this rearrangement because of several competitive side reactions and structural limitations. However, studies performed in the last 15 years on the rearrangement have remarkably expanded the substrate scope and synthetic applications. In this review, the utility of the Sommelet–Hauser rearrangement and recent advances for the generation of onium ylides are described. 1 Introduction 2 Base-Induced Rearrangement 3 Transition-Metal-Catalyzed Rearrangement 4 Light-Mediated Rearrangement 5 Aryne-Induced Rearrangement 6 Conclusions and Outlook