The traditional thermal Mannich reaction is unsuitable for preparing polymerizable N-methylene amino substituted acrylamides and methacrylamides. Herein we provide a facile multi-gram high yield synthesis of these monomeric precursors to stimuli-responsive polymers by the addition of acrylamides and methacrylamides onto in situ generated or freshly isolated methylene Schiff base (iminium) salts. The X-ray crystal structure of the hydrated iminium salt, 1-(hydroxymethyl)azocan-1-ium chloride and monomer·HCl salt (N-[(azocan-1-yl)methyl]prop-2-enamide hydrochloride) is described.