Studies on the Thermolysis of 2-(2-Hydroxy-2-arylethyl)pyrazines. An Example of a Retro-Ene-Type Reaction

Article abstract of DOI:10.1021/jo01294a016

Several substituted 2-(2-hydroxy-2-arylethyl)pyrazines (1-10) have been prepared and their thermolysis in diglyme and DMF studied.Each of these substrates decomposes to give the parent methylpyrazine and the corresponding aryl aldehyde.Kinetic, isotope effect, and solvent effect studies suggest a mechanism involving a nonpolar concerted six-membered-ring transition state.The degree of proton transfer in the transition state is discussed in detail.Methyl substituents on the pyrazine ring were found to strongly affect the reaction rate.This phenomenon is analyzed interms of the steric and electronic effects induced by the methyl substituents.