Treatment of 4‐hydroxy‐N‐methylisoquinolinium iodide with triethylamine in tetrahydrofuran or acetonitrile forms 2‐methyl‐4‐oxidoisoquinolinium (2) in situ. Once formed, 2 can be trapped with dipolarophiles possessing varying degrees of activation to form the 5H‐benzocyclohepten‐5,8‐imine ring system. Various 2‐D nmr experiments were used in the identification of the stereochemical and regiochemical assignments for the ring system.