Synthesis of New 3,4-Disubstituted 2,5-Dihydro-1H-pyrrol-1-yloxyl Spin-Label Reagents via Allylic Rearrangements

3-Substituted 4-Bromo-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-yloxyl Radicals as Versatile Synthons for Synthesis of New Paramagnetic Heterocycles

“…8 This technique requires the design of lipophilic or hydrophilic spin labels for site and function directed labelling of biomolecules. Introduction of a second arm into the 2,5-dihydropyrrole ring was achieved by Michael reaction 9 or Claisen rearrangement 10 or Grignard reaction. 11 The spin labels which proved to be the most useful protein reagents were those in which reactivity of the thiol specific arm was increased by an allylic double bond.…”

Reaction of β‐Bromo‐β,γ‐unsaturated Pyrroline Nitroxide Aldehydes and Nitriles with AromaticN,S‐Binucleophiles

“…We proposed that a diamagnetic derivative of aldehyde 1 and nitrile 4 should be used in these reactions in such forms, which prevent the oxidation of aromatic thiols, because the formed aromatic disulfides cannot react further as S ‐nucleophiles. Therefore, compounds 1 and 4 were first converted to the O ‐acetyl derivatives 5 and 6 by a previously reported methodology , through the reduction to the corresponding hydroxylamine with ascorbic acid, followed by treatment with acetyl chloride in the presence of Et 3 N in chloroform (Scheme ).…”

Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates

“…The 1 H-NMR spectra were recorded with a Bruker Avance 3 Ascend 500 system (Bruker BioSpin Corp., Karslruhe, Germany) operated at 500 MHz, and the 13 C-NMR spectra were obtained at 125 MHz and 31 P-NMR 202 MHz in CDCl 3 or DMSO-d 6 at 298 K. The "in situ" reduction of the nitroxides was achieved by addition of five equivalents of hydrazobenzene ((PhNH) 2 /radical). The O-acetyl derivative of compound 22 for NMR measurement was prepared as described previously [49]. The EPR (electron paramagnetic resonance) spectra were recorded on MiniScope MS 200 (Magnettech GMBH, Berlin, Germany) instrument in CHCl 3 solution, and the concentrations were 1.0 × 10 −4 M. All radicals gave a 3-line spectra characteristic of monoradicals, a N = 14.4-15.6 G, radical concentration was > 98% in each case and referred for TEMPO (1-oxyl-2,2,6,6-tetramethylpiperidine.…”