The conversion of allenes to strained three-membered heterocycles

This article reviews methods for converting allenes to strained, three-membered methylene heterocycles, and also covers the reactivity of these products. Specifically, the synthesis and reactivity of methylene aziridines, allene oxides/spirodiepoxides, methylene silacyclopropanes, methylene phosphiranes, and methylene thiiranes are described, including applications to the synthesis of complex molecules. Due to the primary focus on heterocyclic motifs, the all-carbon analogue of these species (methylene cyclopropane) is only briefly discussed.