RING EXPANSION BY DUSHYANT KUMAR

Ring expansions are valuable because they allow access to larger systems that are difficult to synthesize through a single cyclization due to the slow rate of formation (seven member and larger rings). Classifying ring expansions by the mechanism of expansion and the atom(s) added allows one to see the similarities between different expansions methods and different incorporated atoms. The broadest classification comes by the mechanism of expansion. The rings can be expanded by attack of the ring onto an outside group already appended to the ring (a migration/insertion), opening of a bicycle to a single larger ring, or coupling a ring closing with an expansion.These expansions can be further broken down by what type of atom they incorporate (a carbon or a heteroatom) into the expanded ring.