Metal-mediated dearomatization leading to 2-azaspiro[4.5]decanes via tandem nucleophilic aromatic addition–Horner–Wadsworth–Emmons olefination–oxidative demetalation sequences

A ruthenium-mediated dearomatization sequence has been developed that delivers structurally intriguing azaspirolactam products in stereoselective fashion. Treatment of (η⁶-arene)Ru(cyclopentadienyl) complexes bearing N-benzyl-β-amido phosphonate side chains with excess NaH results in intramolecular nucleophilic aromatic addition to the ipso position of the coordinated arenes. Subsequent Horner–Wadsworth–Emmons (HWE) reaction with added aldehydes affords olefinated spirolactam cyclohexadienyl ruthenium complexes. Mild oxidation with CuCl₂ or CuBr₂ under CO effects removal and recovery of the CpRu(II) fragment. Substituents present on the cyclohexadienyl skeleton influence the outcome of demetalation and products obtained in this study include functionalized 2-azaspiro[4.5]decanes and tetrahydroisoquinolinones.