LETTER
Synthesis of a-Nitroamines
2507
counter electrode was a cylindrical platinum spiral. Anodic and
cathodic compartments were separated by a G3-glass diaphragm
fitted with an agar gel (methyl cellulose 0.5% vol. dissolved in 1 M
TEAP/DMF solution).
Acknowledgment
We acknowledge financial support by the MIUR ‘La metodologia
elettrochimica in chimica organica: un’opportunità per sintesi pulite
ed efficienti’ (PRIN 2004).
General Procedure for the Solvent-Free Aza-Henry Reaction
A nitroalkane (1.0 mL) was added to the cathodic compartment of
the electrochemical cell. No supporting electrolyte was added to the
cathodic compartment. The electrolysis was carried out under
galvanostatic control (J = 40 mA·cm–2), under an inert atmosphere
(Ar), until the necessary amount of current quantity (0.1 F mol–1 re-
lated to the imine) was passed. At the end of the electrolysis, the
imine (0.2 mmol) was added and the resulting mixture was stirred
for 5 min at r.t. The reaction was practically immediate [TLC mon-
itored CHCl3–MeOH (9:1) for P,P-diphenyl-N-arylmethylene
phosphinic amides and Et2O–hexanes (4:6) for N-arylmethylene-
sulfonamides] and afforded the crude nitroamine adduct which was
purified by simple evaporation of the residual nitroalkane and, if
necessary, filtration through a pad of silica gel. All the known
isolated nitroamines gave spectral data in accordance with those
reported in the literature.17c,19
References
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4-Methyl-N-[2-nitro-1-(4-nitrophenyl)ethyl]benzenesulfon-
amide (2e)
Mp 136–137 °C. 1H NMR (200 MHz, CDCl3): d = 7.98 (d, J = 8.7
Hz, 2 H), 7.55–7.30 (m, 4 H), 7.22 (d, J = 7.7 Hz, 1 H), 7.06 (d,
J = 8.7 Hz, 2 H), 5.25–5.10 (m, 1 H), 4.90–4.55 (m, 3 H), 2.27 (s, 3
H). 13C NMR (50.3 MHz, CDCl3): d = 148.4, 144.1, 142.8, 136.8,
129.7, 127.9, 127.0, 124.0, 78.3, 54.9, 21.4.
4-Methyl-N-{2-nitro-1-[4-(trifluoromethyl)phenyl]ethyl}ben-
zenesulfonamide (2f)
1
Mp 122–124 °C. H NMR (200 MHz, acetone-d6): d = 7.60–7.40
(m, 7 H), 7.20–7.05 (d, J = 8.1 Hz, 2 H), 5.53–5.25 (m, 1 H), 5.00–
4.85 (m, 2 H), 2.30 (s, 3 H). 13C NMR (50.3 MHz, acetone-d6):
d = 144.7, 142.4, 139.7, 130.8, 129.6, 129.0, 128.4, 126.9, 126.8,
122.7, 117.7, 78.3, 57.2, 21.3.
4-Methyl-N-(2-methyl-2-nitro-1-phenylpropyl)benzenesulfon-
amide (3a)
Mp 129–131 °C. 1H NMR (200 MHz, CDCl3): d = 7.83 (d, J = 7.9
Hz, 1 H), 7.49 (d, J = 7.9 Hz, 2 H), 7.40–7.25 (m, 1 H), 7.20–6.80
(m, 5 H), 5.80–5.70 (m, 1 H), 5.15 (br s, 1 H), 4.70–4.55 (m, 1 H),
2.33 (s, 3 H), 0.91 (t, 3 H). 13C NMR (50.3 MHz, acetone-d6):
d = 143.5, 139.5, 137.2, 129.9, 129.4, 128.4, 127.7, 94.4, 61.5, 25.4,
21.3, 10.3.
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N-[1-(4-Methoxyphenyl)-2-nitroethyl]-P,P-diphenylphos-
phinic Amide (3c)
Mp 163–164 °C. 1H NMR (200 MHz, CDCl3): d = 7.90–7.70 (m, 4
H), 7.60–7.30 (m, 6 H), 7.20 (d, J = 8.7 Hz, 2 H), 6.84 (d, J = 8.7
Hz, 2 H), 5.00–4.65 (m, 3 H), 4.35–4.15 (m, 1 H), 3.77 (s, 3 H). 13
NMR (50.3 MHz, CDCl3): d = 159.7, 132.5, 132.3, 132.2, 131.9,
131.7, 130.1, 130.0, 128.8, 128.5, 127.7, 114.4, 80.9, 80.8, 55.3,
53.0.
C
4-Methyl-N-(2-methyl-2-nitro-1-phenylpropyl)benzenesulfon-
amide (4a)
Mp 134–135 °C. 1H NMR (200 MHz, CDCl3): d = 7.83 (d, J = 8.3
Hz, 2 H), 7.60–6.80 (m, 7 H), 6.20 (d, J = 10.4 Hz, 1 H), 4.96 (br s,
1 H), 2.27 (s, 3 H), 1.64 (s, 3 H), 1.54 (s, 3 H). 13C NMR (50.3 MHz,
CDCl3): d = 143.2, 136.9, 134.6, 129.2, 128.4, 127.8, 126.7, 90.6,
64.0, 25.0, 23.0, 22.3.
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Franchini, M.; Fochi, M.; Ricci, A. J. Org. Chem. 2004, 69,
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Synlett 2007, No. 16, 2505–2508 © Thieme Stuttgart · New York