New approach to synthesis of nitronyl and imino nitroxides based on SNH methodology

Abstract

Dedicated to Professor Usein M. Dzhemilev on the occasion of his 65 th birthday AbstractIt is shown that S N H approach opens new possibilities in the synthesis of polyfunctional nitronyl and imino nitroxides. It is found that the interaction of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl lithium salt Li1 with 3,6-diaryl-1,2,4-triazines leads to formation of the corresponding triazines bearing nitronyl nitroxide or imino nitroxide substituent at position 5 of the heterocycle. The reaction of Li1 with pyridazine-N-oxide gives rise to nitroxide with buten-3-ynyl substituent 5. Spin-labeled 5 could be readily transformed by the use of 1,3-dipolar and nucleophilic addition reactions, as well as oxidative coupling, that gives a large group of new paramagnets: 2-(1H-pyrazol-5-yl)vinyl-, 2-ethynylcyclopropyl-, 2-(3-(ethoxycarbonyl) isoxazol-5-yl)vinyl-, 1-(pyrrolidin-1-yl)but-3-ynyl-substituted nitronyl nitroxide and a diradical -2,2′-

Synthesis and Thin Films of Thermally Robust Quartet (S = 3/2) Ground State Triradical

“…(Nitronyl nitroxide-2-ido)­(triphenylphosphine)­gold­(I) ( 4 ) is synthesized by the reaction of nitronyl nitroxide ( 7 ) and Au I (PPh 3 )Cl with NaOH in methanol/dichloromethane. ,, After purification by chromatography (deactivated Al 2 O 3 ), the spin concentration of 4 is up to 99%. Di-iodo-Blatter radical 5 and its monoiodo analogue 6 are prepared according to previous literature. , …”

Substitution of a Fluorine Atom in Perfluorobenzonitrile by a Lithiated Nitronyl Nitroxide

“…4,4,5,5-Tetramethyl-4,5-dihydro-1 H -imidazol-3-oxide-1-oxyl was synthesized as reported elsewhere . THF was freshly distilled over benzophenone sodium ketyl.…”

“…4,4,5,5-Tetramethyl-4,5dihydro-1H-imidazol-3-oxide-1-oxyl was synthesized as reported elsewhere. 8 THF was freshly distilled over benzophenone sodium ketyl. Other chemicals were of the highest purity commercially available and were used as received.…”

“…Thus, we recently developed a new method for producing nitronyl nitroxides that involves nucleophilic substitution of a hydrogen atom (S N H) in a series of azines and their N -oxides by the action of a paramagnetic lithium derivative ( 1-Li ) of radical 1 . This approach paved the way for the synthesis of previously inaccessible mono- and diradicals as well as their heterospin complexes with a new type of structural organization. − In addition to these results, the S N Ar substitution of fluorine in electron-deficient polyfluorinated aromatics (nitrobenzene, pyridine, and phthalo- and benzonitrile) by means of a paramagnetic O-nucleophilethe alkoxide anion generated from the 4-hydroxy-2,2,6,6-tetramethylpiperidine oxide (TEMPOL)has been reported as a facile route to the polynitroxides showing strong electron exchange between nitroxide groups . With the aim to develop new methods for nitronyl nitroxide modification based on S N Ar-type substitution, we tested whether it is possible to use 1-Li as a C-nucleophile to replace a fluorine atom in polyfluorinated benzonitriles.…”

Heterocyclic and Open-Chain Carboranes via Transition-Metal-Free C–H Functionalization of Mono- and Diazine-N-oxides

“…It has been revealed that this reaction is accompanied by opening of the diazine ring, thus leading to the formation of butenynyl-substituted carborane 4g . It should be mentioned that some data on the synthesis of vinyl acetylene-containing compounds through organometal-induced destruction of pyridazine- N -oxide are available in the literature . The dihydro compound 3g -OLi, derived from the addition of nucleophilic agent 2 to azine- N -oxide 1g , in the cyclic 3g -OLi-A and open-chain 3g- OLi-B forms can be regarded as the most reasonable reaction intermediate .…”