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
'.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1094 [Terms] [Paper]