In the neat flow vacuum pyrolysis of 2-methoxy-2-(o-N,N+dimethylaminomethyl)phenyl-3-trimethylsilyl-5,5-dime-thyl-2-silahexane (4) at $600^{circ}C$ and its static thermolysis at $350^{circ}C23-benzo-5-aza-1-silacyclohexane$, (5) has been obtained in97% and 46％ y ields, respectively. Product 5 might have been formed via an intramolecular rearrangement invoIving a zwitterionic species generated from the pentacoordinated silene Si-atom. From trapping experiments with an excess of MeOH, we have obtained 2-(o-N,N-dimethylaminomethyl)phenyl-5,5-dimethyl-2-trimethylsiloxy-2-silahexane (6) and 2-(o-N,N-dimethylaminomethyl)phenyl-2-methoxy-5,5-dime-thyl-2-silahexane (7) formed via an intermolecular protodesilylation reaction rather than through trapped prod-ucts of the silene.