Orbital-Overlap Control in the Solid-State Reactivity of β-Azido-Propiophenones: Selective Formation of <i>cis</i>-Azo-Dimers

Solid-state photolysis of 1a,b yields selectively cis-3a,b. X-ray analysis of 1a,b reveals the molecules adopt an extended structure and as such the crystal packing arrangement consists of planar, π-stacked molecules. The shortest intermolecular distance between adjacent N-atoms is ∼3.76 Å and would lead to formation of trans-3a,b, whereas cis-3a,b is formed by dimerization between N-atoms that are ∼3.9 Å apart. We propose that the molecular orbital alignment of the adjacent nitrenes controls the solid-state reactivity.