cycloaddition 1,3-dipolar cycloaddition A ring formation reaction where a 1,3-dipolar compound reacts with an alkene or alkyne to form a five-membered ring compound. Huisgen cycloaddition Huisgen reaction Huisgen's 1,3-dipolar cycloaddition RXNO RXNO:0000018 https://www.wikidata.org/wiki/Q902907