polycyclization

Polycyclization is a chemical reaction in which a single molecule undergoes a series of cyclization reactions to form a polycyclic compound. A polycyclic compound is a molecule that contains two or more fused or bridged rings. These reactions typically involve the formation of new carbon-carbon or carbon-heteroatom bonds, leading to the construction of complex molecular architectures.

The process of polycyclization can be initiated by various reactive intermediates, such as radicals, cations, or anions, or through concerted reaction mechanisms. The starting material is usually a linear or acyclic precursor containing multiple functional groups strategically positioned to enable sequential ring closures. The order in which the rings are formed can be critical and is often influenced by factors like steric hindrance, electronic effects, and reaction conditions.

Polycyclization reactions are of significant interest in organic synthesis, particularly in the total synthesis of natural products, many of which possess intricate polycyclic structures with important biological activities. Developing efficient and stereoselective polycyclization strategies is a key challenge and an active area of research. Methods for achieving polycyclization include transition-metal catalyzed reactions, radical cyclizations, and pericyclic reactions. The ability to construct complex polycyclic systems from simpler precursors allows for the exploration of novel chemical space and the development of new pharmaceuticals and materials.