Synthesis and Reactivity of a Stable Prototropic Isomer of 2-Acetyl-3-methylpyrrole

4-isocyanobut-1-ene reacts rapidly with acetyl bromide to afford an unstable imidoyl bromide adduct. Subsequent in situ cyclization under Heck conditions generates a stable prototropic isomer of 2-acetyl-3-methyl pyrrole. The reactivity of this molecule towards acid, base and oxidants is explored and its conversion to ∝-methylidene γ-lactam is demonstrated. In protonated form, its acetylated vinyl imine functions as a reactive dienophile in Diels-Alder reactions.