Generation Of N-centered Radicals Research Articles

Recent Advances in Copper-Catalyzed C-N Bond Formation Involving N-Centered Radicals.

C-N bonds are pervasive throughout organic-based materials, natural products, pharmaceutical compounds, and agricultural chemicals. Considering the widespread importance of C-N bonds, the development of greener and more convenient ways to form C-N bonds, especially in late-stage synthesis, has become one of the hottest research goals in synthetic chemistry. Copper-catalyzed radical reactions involving N-centered radicals have emerged as a sustainable and promising approach to build C-N bonds. As a chemically popular and diverse radical species, N-centered radicals have been used for all kinds of reactions for C-N bond formation by taking advantage of their inherently incredible reactive flexibility. Copper is also the most abundant and economic catalyst with the most relevant activity for facilitating the synthesis of valuable compounds. Therefore, the aim of the present Review was to illustrate recent and significant advances in C-N bond formation methods and to understand the unique advantages of copper catalysis in the generation of N-centered radicals since 2016. To provide an ease of understanding for the readers, this Review was organized based on the types of nitrogen sources (amines, amides, sulfonamides, oximes, hydrazones, azides, and tert-butyl nitrite).

Photo- and Radiation-Chemical Generation and Thermodynamic Properties of the Aminium and Aminyl Radicals Derived fromN-Phenylglycine and (N-Chloro,N-phenyl)glycine in Aqueous Solution: Evidence for a New Photoionization Mechanism for Aromatic Amines

The generation of N-centered radicals (aminium and aminyl radicals) by photoionization and by pulse-radiolytic one-electron oxidation of N-phenylglycine (1), or by laser flash photolysis or reductive dechlorination of (Nchloro,N-phenyl)glycine (2) has been studied in order to model photodamage to amino acids and proteins, as well as degradation of nitrogen-containing drinking-water pollutants. The aminium radical .‡(H-N-phenyl)glycine (1.‡), a gdistonic radical zwitterion, was found as a product of photoionization (FPI(1)ˆ 0.34, 0.22, 0.30, and 0.01 at 193, 248, 266, and 308 nm) or chemical one-electron oxidation of 1. The aminyl radical .(N-phenyl)glycine (1(NyH) .), a g-distonic radical anion, is a product of reductive dehalogenation of 2, or of Nchloro photohomolysis, for which the upper limits of FNCl(2) at 193, 248, 266, or 308 nm excitation are 0.61, 0.43, 0.60, and 0.38, or of deprotonation of 1.‡ (pKa(1 .‡)ˆ 7.35 0.15). The reduction potential E8(1.‡/1) at pH 6 is 0.89 0.02 V versus a normal hydrogen electrode (NHE). The quantum yields of 193, 248, 266, or 308 nm photoionization of 2 are FPI(2)ˆ 0.29, 0.10, 0.08, and 0.01. For 1, an additional process leading to 1.‡ and H . takes place that is identified in terms of water-assisted ionization for which the quantum yields FWA(1) at 193, 248, 266, or 308 nm are 0.37, 0.26, 0.50, and 0.01, respectively. A full thermodynamic description of the system is given, including the different possible acid ± base forms, their redox potentials, and bond dissociation energies.