Theoretical calculations for the 1,4-hydrogen shift of 1-hydroxyallyl radicals leading to α-keto radicals; prediction of facilitation by 1-amino and 3-tin substituents

DFT calculations were carried out to elucidate the 1,4-hydrogen shift of 1-hydroxyallyl radicals to give α-keto radicals. The 1,4-H shift is predicted to be exothermic with large energy barriers. However, the energy barriers of 1,4-H shift were predicted to be lowered significantly by 1-amino and 3-tin substituents. The results agreed well with the experimental results shown by the stannylcarbonylation of alkynes in the presence of an amine, in which the 1,4-H shift of substituted 1-hydroxyallyl radicals has been proposed as a key step.