Pyrrolidine, also known as tetrahydropyrrole, is a saturated five-membered heterocyclic ring, which is miscible with water. Pyrrolidine exists in many alkaloids and drug molecules, such as kappa opioids, antagonists of dopamine D4 receptors, and HIV reverse transcriptase inhibitors.
As the smallest nitrogen-containing unsaturated heterocyclic compound, 2H-azirine not only widely exists in natural products, but also is an important intermediate in organic synthesis. The 2H-azirine ring systems provide a versatile platform for the development of cascade sequences leading to densely functionalized heterocycles. The 2H-azirine ring can also be used as a dipolarophile.