https://doi.org/10.1351/goldbook.C01014
A form of
cycloaddition
across the terminal atoms of a fully conjugated system
with formation of two new σ-bonds to a single atom of the ('monocentric') reagent
. There is formal loss of one π-bond in the substrate and an increase in coordination number
of the relevant atom of the reagent
. An example is the addition
of sulfur dioxide to butadiene: The reverse of this type of reaction is designated 'cheletropic elimination
'.