Ring-expanding and Ring-opening Transformations of Benzofurans and Indoles with Introducing Heteroatoms

Skeletal transformations of heteroaromatic compounds while cleaving their endocyclic bonds have been emerging as new synthetic tools in modern organic chemistry. Especially, endocyclic insertion of a heteroatom into a heteroaromatic core is a game-changing approach to exotic classes of heterocyclic compounds. In this Highlight Review is summarized recent progress of ring-expanding and ring-opening reactions of benzofurans and indoles.