Kabachnik–Fields reactions with stable nitroxide free radicals

Abstract

This paper is dedicated to Professor György Keglevich on the occasion of his 65 th birthday

Synthesis of 3,4-Disubstituted Pyrroline Nitroxides Containing Diphenylphosphane or Diphenylphosphane Oxide Substituents

“…cend 500 system operated at 500 MHz, and 13 C NMR spectra were obtained at 125 MHz, 31 P NMR 202 MHz in CDCl 3 or DMSO-d 6 at 298 K. The paramagnetic compounds were reduced to N-hydroxylamines with hydrazobenzene (DPPH, 5 equiv)/radicals in situ in the NMR tube. All monoradicals gave a triplet line at aN = 14.5 G. IR spectra were recorded with a Bruker Alpha FT-IR instrument with ATR support (diamond plate).…”

“…1 H NMR (500 MHz, CDCl 3 + (PhNH) 2 ):  = 7.41-7.40 (m, 7 H,), 3.51 (t, J = 6.5 Hz, 2 H), 1.49 (s, 6 H), 1.37-1.30 (m, 34 H), 0.99 (t, J = 6.5 Hz, 3 H); 3 H arom are overlapped with diphenylhydrazine signals. 13…”

“…Organophosphorus compounds are a crucial molecular class in synthetic chemistry because of their applicability as building blocks in ligands of catalysts. In recent years, our laboratory successfully investigated reactions on stable free nitroxide radicals (Arbuzov, 12 Kabachnik-Fields, 13 McCormac, 14 and phospha-Brook rearrangement 15 ), which yield-ed new paramagnetic organophosphorus compounds. In continuation of our research on pyrroline nitroxides diversely substituted with diphenylphosphane, 14 diphenylphosphane oxide, 14 or phosphonate ester, 12 we evaluated 3,4-disubstituted phosphorus-containing pyrroline nitroxide free radicals.…”

“…13 C NMR (125 MHz, CDCl3 ):  = 139.0 (d, J = 7 Hz, 1 C), 137.6 (d, J = 25 Hz, 1 C), 134.1 (d, J = 19.0 Hz, 2 C), 133.4 (4 C), 128.6 (2 C), 128.4 (d, J = 7.0 Hz, 4 C), 73.9 (d, J = 17 Hz, 1 C), 71.9 (d, J = 2.0 Hz, 1 C), 65.2 (1 C), 29.8 (2 C), 22.7 (2 C).…”

“…13 C NMR (125 MHz, DMSO-d 6 + (PhNH) 2 ):  = 166.5 (d, J = 4 Hz, 1 C), 151.6 (d, J = 5.5 Hz, 1 C), 137.5 (d, J = 98 Hz, 1 C), 132.8 (d, J = 104 Hz, 2 C), 132.1 (d, J = 10 Hz, 4 C), 131 (d, J = 10 Hz, 2 C), 128.7 (d, J = 12 Hz, 4 C), 72.4 (d, J = 10 Hz, 1 C), 70.3 (d, J = 10 Hz, 1 C), 25.5 (2 C), 24.8 (2 C). 31 P NMR (202 MHz, DMSO-d 6 + (PhNH) 2 ):  = 23.27.…”