Comparison of the Ease of Thermolysis of Ortho-Substituted Phenyl Azides Having α,β or β,γ Imine Functions

Article abstract of DOI:10.1021/jo00212a012

o-Azidobenzaldehyde benzylimine (7) thermolyzes 34 times faster than phenyl azide and 1.6 times faster than p-chlorobenzaldehyde o-azidoanil (8), whereas benzaldehyde (o-azidobenzyl)imine (9) and acetophenone (o-azidobenzyl)imines (10a-e) show little or no rate enhancement over phenyl azide.An electrocyclic mechanism can account for the rates of 7 and 8 relative to each other but not of 8 relative to phenyl azide; 9 and 10a-e appear to thermolyze by nitrene formation, even though a mechanism through intramolecular cycloaddition may in principle be available.A mechanism based on electrostatic effects in a dipolar transition state can corr elate the effects of different types of α,β-unsaturated ortho substituents.