Electrophilic Cyclization

Electrophilic cyclization reaction has been demonstrated as an efficient tool in the synthesis of a great variety of heterocyclic compounds in many different ring sizes. The rings can be constructed through endo or exo cyclization modes, depending on the different substrates and electrophiles employed. Numerous electrophiles, such as halonium ions (I⁺, Br⁺, Cl⁺, F⁺), Se, S, Hg, Au, Ag, and Pt could successfully promote the electrophilic cyclizations. These electrophilic cyclization reactions could proceed under relatively mild conditions and tolerate all kinds of functional groups. Most of these methodologies proceed stereo- and regioselectively in excellent yields. In recent years, electrophilic cyclizations have been widely used in the synthesis of pharmaceuticals and natural products. A large number of publications in this field are present. Focusing on the applications of electrophilic cyclization in organic synthesis, the literatures after 1991 are summarized in this chapter, and they are sorted by different electrophiles.