aziridines

Aziridines are a class of nitrogen-containing heterocycles consisting of a saturated, three-membered ring in which one atom is nitrogen. The parent compound, aziridine, has two carbon atoms and one nitrogen in the ring. Substituents on nitrogen or carbon give a range of N-substituted and C-substituted aziridines, which are widely exploited in synthesis.

The three-membered ring imposes significant angle strain, making aziridines highly reactive toward ring-opening. This reactivity is modulated by substituents on nitrogen (for example tosyl, nosyl, or carbamates) that stabilize intermediates and influence selectivity. N-Substituted aziridines are common because they improve stability and steer reactivity in downstream transformations.

Synthesis of aziridines typically involves aziridination of alkenes by nitrene transfer from precursors such as N-tosyl or N-nosyl imino reagents under copper, rhodium, or other metal catalysis. Alternative routes include intramolecular cyclization of beta-haloamines or amino alcohols, and other cyclization strategies from suitable precursors. These methods allow control over regio- and stereochemistry in many cases.

Reactions of aziridines commonly begin with nucleophilic ring-opening, producing beta-amino, beta-hydroxy, or related derivatives. Nucleophiles such as amines, alcohols, thiols, or organometallic reagents can open the ring, with stereochemical and regioselectivity guided by substitution and catalysts. Enantioselective aziridination and ring-opening strategies enable access to chiral amines and diamines.

Applications of aziridines include serving as versatile building blocks in organic synthesis, enabling access to beta-amino compounds, 1,2-diamines, and various natural products. Chiral aziridines are especially valuable for enantioselective syntheses and pharmaceutical development. Handling aziridines requires appropriate safety precautions due to their ring strain and reactivity.