Ruthenium-Catalyzed Selective Oxidation Of N-Boc Indoles

The heterocyclic compounds containing nitrogen atoms are important skeleton structure of pharmaceuticals, natural products and pesticides. Indole, quinoline, pyrrole, pyridine and other aromatic heterocyclic compounds, as cheap and readily available chemicals, can be functionalized by oxidation or reduction reactions and were used for the organic synthesis. Transition metal-catalyzed reduction and oxidation of aromatic or heteroaromatic compounds have become feasible methods for the transformation of aromatic compounds. In this thesis, ruthenium-catalyzed selective oxidation of N-Boc indoles has been achieved.In this work, Ru-catalyzed oxidative dearomatization of N-Boc indoles 1 was achieved by using sodium periodate (NaI04) as the oxidant for the synthesis of 2-substituted-3-oxoindoline 2. The oxidation reaction of tert- Butyl 2-methyl-1H-indole-1-carboxylate was chosen as a model reaction to optimize the reaction conditions such as oxidant, solvent, temperature and catalyst screening. It was found that the best result was obtained under the following conditions:tert-Butyl 1H-indole-l-carboxylate/sodium periodate= 1/1.5 (the molar ratio of material) and 6.0 mol% ruthenium trichloride in CH3CN at 70 ℃. The desired product was isolated in 92% yield. This novel method for the synthesis of 2-substituted-3-oxoindolines has many advantages such as mild reaction conditions and high selectivity.