h⁶-Arene ruthenium complexes possessing N-benzyl acrylamides are converted into ruthenium-coordinated azaspirocyclic cyclohexadienyl complexes. The spriro cyclization is achieved by the intramolecular nucleophilic addition of the zwitterionic intermediate generated by the conjugated addition of phosphine to the a,b-unsaturated acrylamide moiety, thus resembling the MBH reaction.