Photostimulated Intreamolecular SRN1 Reactions with Nitrogen Nucleophilles: Synthesis of fused Azaheterocycles

VICTORIA A. VAILLARD; MARÍA E. BUDÉN; SANDRA E. MARTÍN; ROBERTO A. ROSSI

Santiago de Compostela, España

Conferencia; 19th IUPAC Conference on Physical Organic Chemistry; 2008

PHOTOSTIMULATED INTRAMOLECULAR SRN1 REACTIONS WITH NITROGEN NUCLEOPHILES: SYNTHESIS OF FUSED AZAHETEROCYCLES Victoria A. Vaillard, María E. Budén, Sandra E. Martín, and Roberto A. Rossi Victoria A. Vaillard, María E. Budén, Sandra E. Martín, and Roberto A. Rossi INFIQC, Dpto. de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina. rossi@fcq.unc.edu.ar INFIQC, Dpto. de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina. rossi@fcq.unc.edu.ar The radical nucleophilic substitution, or SRN1 reaction, is a chain process through which an aromatic nucleophilic substitution is achieved. The initiation step is an electron transfer (ET) from suitable donors to the substrate to afford a radical anion. In some systems, the ET step is spontaneous; however, in others light can initiate the reaction.1 Several nucleophiles such as carbanions and heteroatom anions can be used for SRN1 reactions to form new C?C or C-heteroatom bonds in good yields. An exception to this is the intermolecular reaction of aromatic amide ions with aromatic substrates. In these cases, not only C?N bond formation was achieved, but also C?C bond formation was observed. For instance, 2-naphthylamide ions reacts under irradiation with ArI and 1-aryl 2-naphthylamines were formed regioselectively in 45?63% yields, with 3?6% of N-arylation.2 When a substrate has both, the leaving group and the nucleophilic center, the intramolecular reaction affords a cyclic product.1 In the present work, we will report the intramolecular arylation of aromatic amide ions such as 1 with a pendant aryl moiety with a suitable leaving group, to obtain fused azaheterocycles 2 or 3. Product 2 by spontaneous oxidation affords 4.3  To extend the applications of this methodology, we have studied nucleophiles derived from pyrrole or similar heterocycles. When the nitrogen has acidic N-H bond, the anions 5 are formed. If these substrates contain an aryl moiety with a suitable leaving group bonded with different bridges Z, the fused azaheterocycles 6 are formed in good yields by the SRN1 mechanism.   To extend the applications of this methodology, we have studied nucleophiles derived from pyrrole or similar heterocycles. When the nitrogen has acidic N-H bond, the anions 5 are formed. If these substrates contain an aryl moiety with a suitable leaving group bonded with different bridges Z, the fused azaheterocycles 6 are formed in good yields by the SRN1 mechanism.  We will discuss the scope and limitation of these novel ring closure reactions to synthesize fused azaheterocycles. We will discuss the scope and limitation of these novel ring closure reactions to synthesize fused azaheterocycles. 1. Rossi, R. A.; Pierini, A. B.; Peñéñory, A. B. Chem.Rev. 2003, 103, 71-167. 1. Rossi, R. A.; Pierini, A. B.; Peñéñory, A. B. Chem.Rev. 2003, 103, 71-167. 2. Pierini, A. B.; Baumgartner, M. T.; Rossi, R. A. Tetrahedron Lett. 1987, 28, 4653-4656. 3. Budén, M. E.; Rossi, R. A. Tetrahedron Lett. 2007, 48, 8739-8742.