Ei Elimination: An Unprecedented Facet of Sulfone Chemistry

Thermolysis of methyl 3-phenylpropyl sulfone in the gas phase results in formation of allylbenzene. Activation parameters of Δ H ⧧ = 53.5 ± 1.0 kcal/mol and Δ S ⧧ = −0.7 ± 1.4 cal/(mol·K) were obtained over the range of 490−550 °C. Similar measurements with a deuterated analogue show a substantial isotope effect, and a lower activation enthalpy is observed for the formation of styrene from methyl 2-phenylethyl sulfone. Along with high-quality ab initio calculations of activation parameters and kinetic isotope effects, these results indicate that this is the first reported Ei reaction of a simple sulfone.