The following [3+2] cycloaddition was reported in Organic Letters, 2011, 402. Predict whether the reaction would be thermally or photochemically promoted. Justify your answer by showing overlap of the correct molecular orbitals. Assume the alkene is the electrophile.

Cycloaddition

A type of chemical reaction where two or more unsaturated molecules combine to form a cyclic adduct, important in the synthesis of heterocyclic compounds.

Organic Letters

A peer-reviewed scientific journal publishing original research articles in organic chemistry.

Molecular Orbitals

Orbitals that belong to a molecule as a whole, where electrons are considered to be delocalized over the entire molecule.