o-Quinodimethanes: Efficient Intermediates in Organic Synthesis.

The redox potentials of 25 cyclic nitroxides from four different structural classes (pyrrolidine, piperidine, isoindoline, and azaphenalene) were determined experimentally by cyclic voltammetry in acetonitrile, and also via high-level ab initio molecular orbital calculations. It is shown that the potentials are influenced by the type of ring system, ring substituents and/or groups surrounding the radical moiety. For the pyrrolidine, piperidine, and isoindolines there is excellent agreement (mean absolute deviation of 0.05 V) between the calculated and experimental oxidation potentials; for the azaphenalenes, however, there is an extraordinary discrepancy (mean absolute deviation of 0.60 V), implying that their one-electron oxidation might involve additional processes not considered in the theoretical calculations. This recently developed azaphenalene class of nitroxide represents a new variant of a nitroxide ring fused to an aromatic system and details of the synthesis of five derivatives involving differing aryl substitution are also presented.

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Experimental and theoretical studies of the redox potentials of cyclic nitroxides.

The background to the formation of the Commonwealth Scientific and Industrial Research Organization (CSIRO) polymer group is discussed. In particular, the challenges of working with high-conversion polymerization, as found in commercial systems, and the need to explain variations in polymer properties led to important advances in the theory of radical polymerization and control over both the initiation and termination steps. Studies on the fate of the macromonomer, formed in termination by disproportionation, led to an early form of addition/fragmentation now known as reversible addition–fragmentation chain transfer, whereas detailed studies on initiation pathways using nitroxide trapping led to nitroxide-mediated living radical polymerization. These studies contributed to the renaissance in free-radical polymerization studies. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5748–5764, 2005

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/pola.21067

Genesis of the CSIRO polymer group and the discovery and significance of nitroxide‐mediated living radical polymerization

Radical assembly: Halogen bonding has been observed for the first time between an isoindoline nitroxide and an iodoperfluorocarbon (see figure), which cocrystallize to form a discrete 2:1 supramolecular compound in which NO.I halogen bonding is the dominant intermolecular interaction. This illustrates the potential use of halogen bonding and isoindoline nitroxide tectons for the assembly of organic spin systems. The isoindoline nitroxide 1,1,3,3-tetramethylisoindolin-2-yloxyl (TMIO) and 1,4-diiodotetrafluorobenzene readily form a discrete 2:1 complex that shows evidence of relatively strong NO.I halogen bonding. This interaction was characterized in the solid state by single-crystal X-ray analysis, thermal analysis, and vibrational spectroscopy (IR and Raman), backed by density functional theory calculations. EPR spectroscopy performed on a solution of TMIO in pentafluoroiodobenzene, a halogen-bonding donor, indicates that halogen bonding induces an increase in electron density at the nitroxide nitrogen nucleus and an increase in the nitroxide rotational correlation time. Our findings demonstrate the potential of utilizing halogen-bonding interactions to promote the self-assembly of new isoindoline nitroxide tectons for the preparation of organic spin systems.

Halogen bonding between an isoindoline nitroxide and 1,4-diiodotetrafluorobenzene: new tools and tectons for self-assembling organic spin systems.

Reactions of methylcubane (1) with the tert-butoxyl radical (t-BuO•), with cytochrome P-450 enzymes, and with a methane monooxygenase (MMO) system have been studied. For the purpose of product char...

Regiochemical variations in reactions of methylcubane with tert-butoxyl radical, cytochrome p-450 enzymes, and a methane monooxygenase system

A versatile free-radical trapping agent, 1,1,3,3-tetramethylisoindolin-2-yloxyl, has been prepared from N-benzylphthalimide by reaction with 'methylmagnesium iodide' in refluxing toluene followed by hydrogenolysis and oxidation. The Grignard reaction gives 2-benzyl-1,1,3,3-tetramethylisoindoline along with a small proportion of an unexpected by-product, 2-benzyl-1-ethyl-1,3,3-trimethyliso-indoline.

PG Griffiths

Papers

Synthesis of the radical scavenger 1,1,3,3-Tetramethylisoindolin-2-yloxyl