title: Design concept for α-hydrogen-substituted nitroxides.
abstract: Stable nitroxides (nitroxyl radicals) have many essential and unique applications in chemistry, biology and medicine. However, the factors influencing their stability are still under investigation, and this hinders the design and development of new nitroxides. Nitroxides with tertiary alkyl groups are generally stable but obviously highly encumbered. In contrast, α-hydrogen-substituted nitroxides are generally inherently unstable and rapidly decompose. Herein, a novel, concept for the design of stable cyclic α-hydrogen nitroxides is described, and a proof-of-concept in the form of the facile synthesis and characterization of two diverse series of stable α-hydrogen nitroxides is presented. The stability of these unique α-hydrogen nitroxides is attributed to a combination of steric and stereoelectronic effects by which disproportionation is kinetically precluded. These stabilizing effects are achieved by the use of a nitroxide co-planar substituent in the γ-position of the backbone of the nitroxide. This premise is supported by a computational study, which provides insight into the disproportionation pathways of α-hydrogen nitroxides.
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors: Michal
authors: M
authors: Amar
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors: Sukanta
authors: S
authors: Bar
authors: Department of Chemical Research Support, Weizmann Institute of Science, 76100 Rehovot, Israel.
authors: Mark A
authors: MA
authors: Iron
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors: Hila
authors: H
authors: Toledo
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors: Boris
authors: B
authors: Tumanskii
authors: Department of Chemical Research Support, Weizmann Institute of Science, 76100 Rehovot, Israel.
authors: Linda J W
authors: LJ
authors: Shimon
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors: Mark
authors: M
authors: Botoshansky
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors: Natalia
authors: N
authors: Fridman
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors: Alex M
authors: AM
authors: Szpilman