Gas-Phase Pyrolysis of 2,3-Dihydro-1,4-diazepines: Involvement of the Saturated Portion of the Ring in Chemical Reactions and Novel cis-trans Isomerization of a Fused Ring System. -The observed cis-trans isomerization of fused diazepine systems (I), ( III) is explained mechanistically by sequential 1,5-hydrogen shift (no yields given). -(ELLIS, M. J.; LLOYD, D.; MCNAB, H.; WALKER, M. J.; J. Chem. Soc., Chem.