Three-Membered Rings with Two Hetero Atoms

Three-membered rings with one heteroatom are of great interest, both scientifically and technically. They are energy-rich compounds comparable with cyclopropane because of their ring strain. The unfavorable ring-strain energy is usually not apparent in the rate of formation of three-membered rings. The formation of three-membered rings is easier than the closure of open chains to larger rings. Many syntheses of three-membered ring systems occur under surprisingly mild conditions; hence, three-membered rings with two heteroatoms could also be formed. Nitrones, hydrazones, and aliphatic diazo compounds are all formulated with three-membered rings. Many three-membered rings with two heteroatoms have been synthesized. Their formation occurs surprisingly smoothly with an ease comparable to that of the three-membered rings with one hetero atom. The classes of compounds discussed are oxaziranes, diaziridines, and diazirines. The preparation, proof of structure, properties, and reactions of these compounds are described in this chapter.