Abstract:
Small carbo- and heterocycles have become versatile building blocks owing to their intrinsic ring strain
and ease of synthesis. However, the traditional approaches of heterocycle synthesis involved the
combination of one strained-carbocycle or heterocycle with one unsaturated molecule. On the
contrary, there is an exciting possibility of combining two different strained rings to furnish varieties of
heterocycles, where one of the strained rings can act as a valuable alternative to the unsaturated
molecule. These strategies are also useful to access multi-functionalized rings. Despite these distinctive
synthetic benefits, this chemistry has not drawn considerable attention of the community. In this
minireview, we explicitly choose this topic to reveal the unexplored possibilities with these different
strained rings. This minireview provides comprehensive details with the mechanistic rationale about the
reactivity of these pairs of small rings when they are allowed to react together in the presence of
different Lewis acids. Subsequently, it will also open a new avenue for heterocycle synthesis
