Theory-guided discovery of unique chemical transformations of cyclopropenes.

[reaction: see text] Chiral 2-cyclopropenyl-4-tolyl sulfones, available by the [2 + 1]-cycloaddition of tosyldiazomethane to acetylenes under catalysis by the Rh(II) complex 1, provide a number of unusual transformations and useful chiral products. This chemistry is dominated by the unusual strain and reactivity of the cyclopropene ring system.