Conclusion The MNDO reaction paths reported agree remarkably well with the observed and best theoretical estimates of the relative energies of the stable species and transition states for stepwise thermolyses of 1-3. Concerted paths are much higher in energy. The preferred reaction sequence for most trans-azoalkanes should involve the cis transition state.
[Hideg, Kalman; Lex, Laszlo Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1986 , p. 1431 - 1438]