Density functional study of 1,3-hydrogen shifts in 2,4-pyronone

Density functional calculations have been performed to study 1,3 hydrogen shifts in 2,4-pyronone. In pyronone, two 1,3-hydrogen shift reaction paths are possible. Path I leads to the formation of 4-hydroxy-α-pyrone and Path II gives 2-hydroxy-γ-pyrone. Diketo form is found to be the most stable form followed by 4-hydroxy-α-pyrone and 2-hydroxy-γ-pyrone. Activation energy for Path I is lower than that for Path II. Both the reactions are predicted to be endothermic. Inclusion of electron correlation lowers the energy barrier and makes the reaction less endothermic. Variation of descriptors like chemical hardness and electrophilicity along the two different pathways has also been investigated. Effect of solvent on barrier heights has also been examined. Effect of different substituents (fluoro, methyl and phenyl) at position 6 of pyronone has also been studied.