Abstract
It is shown that SN 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-1Himidazol-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 buten3-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) isoxazol5-yl)vinyl-, 1-(pyrrolidin-1-yl)but-3-ynyl-substituted nitronyl nitroxide and a diradical – 2,2′((1E,7E)-octa-1,7-dien-3,5-diyne-1,8-diyl)bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3oxide-1-oxyl). The new nitroxides were characterized by X-ray single crystal data, ESR and static magnetic susceptibility measurements.
Highlights
The increasing application of polyfunctional nitronyl nitroxides (NNs)[1] in the field of molecular magnetism stimulates the development of the chemistry of these compounds.[2]
We found that interaction of highly electrophilic derivatives of 1,2,4-triazine
In this work convergent schemes of nitroxide synthesis based on SNH reactions of 4,4,5,5tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl lithium salt with activated azines, 3,6diaryl-1,2,4-triazines and pyridazine-N-oxide are suggested
Summary
The increasing application of polyfunctional nitronyl nitroxides (NNs)[1] in the field of molecular magnetism stimulates the development of the chemistry of these compounds.[2]. An important parameter for the crystal structure of nitroxides is the intermolecular distance between the paramagnetic centers, the oxygens in the N–O groups. The dominant structure comes from two equivalent imidazoline nitrogen (the modeling invariably produced equal values for two independently varied couplings), one proton and one nitrogen with rather large couplings, a standard set of 12 methyl protons, and two slightly different protons, most likely methylene ones (it is their “difference” that produces the specific look of the spectrum).
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