[1,3]-Sigmatropic Rearrangements of Divinylcyclopropane Derivatives and Hetero Analogs in Competition with Cope-Type Rearrangements- A DFT Study

摘要

Two possible types of competing [1,3] rearrangements of divinylcyclopropane derivatives and of the hetero-analogous compounds vinylcyclopropanecarbaldehyde and vinylcyclopropanecarbthioaldehyde to five-membered ring compounds have been investigated theoretically by (U)DFT (Becke3LYP/6-31G) methodology. Although both of the rearrangement pathways correspond to a reaction of the monosubstituted cyclopropane substructure, i.e. a reaction of vinylcyclo-propane or of cyclopropanecarb(thio)aldehyde, new features in the reactivity are seen due to the combination of two substituents. Reaction parameters such as reaction and activation energies of the [1,3]-sigmeatropic rearrangements have been calculated and compared. Substituent effects of hydroxy and formyl (donor and acceptor) groups in specific positions have also been considered. On the basis of these calculations, the [1,3] rearrangement of vinylcyclopro-panecarbaldehydes to dihydrofurans can be expected to be kinetically favored over their conversion to cyclopentenes, while formation of the latter should be favored thermodynamically. This prediction is borne out by the experimental findings. Depending on the substitution pattern, the [1,3]-sigmatropic rearrangement of vinylcyclo-propanecarbaldehydes may compete with the [3,3]-sigmatropic rearrangement. For the other investigated structures, the [1,3] rearrangement is strongly disfavored.