A 1,2- prototropy route and an iminium ion route to vinyl azomethine ylides are described. In both cases the vinyl azomethine ylides undergo 1,5-electrocyclisation to dihydropyrroles. In the former case the 1,5-electrocyclisation is solvent sensitive and competes with a prototropic process giving the imine of an α, β-unsaturated α-amino ester. The mechanism and solvent sensitivity are discussed. In