The 1,3-dipolar cycloaddition, also known as the Huisgen cycloaddition or Huisgen reaction,   is an organic chemical reaction belonging to the larger class of cycloadditions. It is the reaction between a 1,3-dipole and a dipolarophile, most of which are substituted alkenes, to form a five-membered ring. Rolf Huisgen first saw the prospects of varying the 1,3-dipole and its high value for synthesis of 5-membered heterocycles.
Classes of 1,3-dipoles
Huisgen and others investigated a range of 1,3-dipoles and dipolarophiles. These included:
- Azides and alkynes react in the Azide alkyne Huisgen cycloaddition.
- Diazo compounds are 1,3-dipoles in the Diazoalkane 1,3-dipolar cycloaddition.
- Nitrones react with alkenes to form isoxazolidines.
- Ozonolysis begins with a 1,3-dipolar cycloaddition of ozone. This is followed by a retro-1,3-dipolar cycloaddition and then a 1,3-dipolar cycloaddition of the fragments.
- Huisgen, Rolf (November 1963). "Kinetics and Mechanism of 1,3-Dipolar Cycloadditions". Angewandte Chemie International Edition. 2 (11): 633–645. doi:10.1002/anie.196306331.
- Huisgen, Rolf (October 1963). "1,3-Dipolar Cycloadditions. Past and Future". Angewandte Chemie International Edition. 2 (10): 565–598. doi:10.1002/anie.196305651.