Exploiting phosphonate chemistry in metal-mediated dearomatization: stereoselective construction of functionalized spirolactams from arene ruthenium complexes.

Arene ruthenium complexes possessing beta-amido phosphonate side chains participate in intramolecular spirocyclization reactions to deliver stable cyclohexadienyl ruthenium adducts. Spirocyclization is accomplished via a tandem two-step sequence that involves stereoselective nucleophilic aromatic addition to the ipso position of the coordinated arene, followed by intermolecular Horner-Wadsworth-Emmons olefination. The resulting eta5-cyclohexadienyl complexes can then be diastereoselectively converted to metal-free azaspiro[4.

Functionalized spiro- and fused-ring heterocycles via oxidative demetalation of cyclohexadienyl ruthenium complexes.

Electron-rich alkoxy- and chloro-substituted azaspirocyclic cyclohexadienyl Ru(II) complexes have been converted to either azaspiro[4.5]decane derivatives or functionalized tetrahydroisoquinolines by treatment with suitable oxidizing agents. Copper(II) chloride was found to provide demetalated products in high yield relative to the other oxidants examined (FeCl(3), DDQ, CAN, [Cp(2)Fe][PF(6)], phenyliodine diacetate, IBX).

Oxidative demetalation of cyclohexadienyl ruthenium(II) complexes: a net Ru-mediated dearomatization.

[reaction: see text] An experimentally simple method for the demetalation of spirocyclic cyclohexadienylruthenium(II) complexes has been developed. Treatment of an alkoxy-substituted cyclohexadienyl complex with CuCl(2) affords either azaspiro[4.5]decane derivatives or heavily functionalized tetrahydroisoquinolines.