In organic chemistry, a variety of synthetic procures are particularly useful in closing carbocyclic and other rings; these are termed ring-closing reactions. Examples include:
* alkyne trimerisation;
* the Bergman cyclization of an enediyne;
* the Diels–Alder, between a conjugated diene and a substituted alkene, and other cycloaddition reactions;
* the Nazarov cyclization reaction, originally being the cyclization of a divinyl ketone;
* various radical cyclizations;
* ring-closing metathesis reactions, which also can be used to accomplish a specific type of polymerization;
* the Ruzicka large ring synthesis, in which two carboxyl groups combine to form a carbonyl group with loss of  and ;
* the Wenker synthesis converting a beta amino alcohol to an aziridine
* other reactions, such as an amino group reacting with a hydroxy group, as in the biosynthesis of solanine