Asymmetrical Acyclic Nitrones
2449
and 1 h for benzylamines. An equimolar amount of NaBH4 was added
portionwise and the reduction was completed within 1 h. The solvent was
evaporated, and the residue dissolved in hydrochloric acid and extracted
with ether (3 Â 15 mL). The water phase was basified with ammonia and
extracted with ether (4 Â 15 mL). The combined extracts were dried over
anhydrous Na2SO4 and filtered, and the solvent evaporated. The residue was
dissolved in MeOH (15 mL), and 35% H2O2 (40 mmol) and 5 mol %
Na2WO4 were added to the solution. The mixture was stirred at room tempera-
ture for 1 h and poured into water (25 mL), and then extracted with chloroform
(4 Â 15 mL). The combined extracts were dried (anhydrous Na2SO4) and
filtered, and the solvent evaporated. The residue was treated with ether to
give the crystalline nitrone after cooling in a refrigerator.
C-(3,4-Dimethoxyphenyl)-N-methyl-nitrone 3a. IR (KBr) nC55N
1
1594 cm21; H NMR (CDCl3) d 3.81 (3H, s), 3.86 (3H, s), 3.87 (3H, s),
6.84 (1H, d, J ¼ 8.3), 7.26 (1H, s), 7.40 (1H, d, J ¼ 8.3), 8.26 (1H, s).
13C NMR d 54.41; 56.31; 56.40; 109.39; 110.80; 111.27; 123.35; 127.21;
148.89; 151.21. Anal. calcd. for C10H13NO3 (195.22): C, 61.53; H, 6.71;
N, 7.18. Found: C, 60.83; H, 6.74; N, 6.84.
C-(2-Nitrophenyl)-N-methyl-nitrone 3b. IR (KBr) nC55N 1581 cm21
;
1H NMR (CDCl3) d 3.87 (3H, s), 7.45 (1H, t, J ¼ 7.6), 7.62 (1H, t,
J ¼ 7.6), 7.93 (2H, m), 9.05 (1H, d, J ¼ 7.9). Anal. calcd. for C8H8N2O3
(180.16): C, 53.33; H, 4.48; N, 15.55. Found: C, 53.46; H, 4.66; N, 15.02.
1
C-Phenyl-N-benzyl-nitrone 3c. IR (KBr) nC55N 1581 cm21; H NMR
(CDCl3) d 4.95 (2H, s), 7.30 (7H, m), 7.35 (2H, m), 8.12 (2H, m).
13C NMR d 71.67; 128.86; 129.01; 129.37; 129.62; 130.01; 130.84; 130.88;
133.71; 134.62. Anal. calcd. for C14H13NO (211.26): C, 79.59; H, 6.20;
N, 6.63. Found: C, 79.50; H, 6.36; N, 6.58.
C-(2-Nitrophenyl)-N-(2,3-dimethoxybenzyl)-nitrone 3d. IR (KBr)
1
nC55N 1576cm21; H NMR (CDCl3) d 3.79 (3H, s), 3.84 (3H, s), 5.08 (2H,
s), 6.90 (1H, m), 7.00 (2H, s), 7.40 (1H, t, J ¼ 7.5), 7.52 (1H, t, J ¼ 7.5),
7.91 (1H, t, J ¼ 8.0), 8.05 (1H, s), 9.08 (1H, d, J ¼ 8.0). 13C NMR d 56.26;
61.35; 67.26; 114.29; 123.42; 124.67; 125.27; 125.69; 126.66; 128.59;
129.75; 130.32; 133.68; 147.60; 148.27; 153.12. Anal. calcd. for C16H16N2O5
(316.31): C, 60.75; H, 5.10; N, 8.86. Found: C, 60.68; H, 5.26; N, 8.62.
C-(2-Nitrophenyl)-N-benzyl-nitrone 3e. IR (KBr) nC55N 1581 cm21
;
1H NMR (CDCl3) d 5.02 (2H, s), 7.34–7.43 (6H, m), 7.60 (1H, t, J ¼ 7.6),
7.94 (1H, d, J ¼ 7.9), 8.00 (1H, s), 9.05 (1H, d, J ¼ 7.9). 13C NMR
d 72.81; 124.78; 125.22; 128.61; 129.46; 129.63; 129.79; 130.50; 132.66;
133.01; 133.79; 147.55. Anal. calcd. for C14H12N2O3 (256.26): C, 65.62;
H, 4.72; N, 10.93. Found: C, 65.49; H, 4.86; N, 10.45.
C-(2,3-Dimethoxyphenyl)-N-benzyl-nitrone 3f. IR (KBr) nC55N
1
1581 cm21; H NMR (CDCl3) d 3.72 (3H, s), 3.80 (3H, s), 5.04 (2H, s),
6.95 (1H, m), 7.05 (1H, m), 7.31 (3H, m), 7.43 (2H, m), 7.76 (1H, s), 8.72
(1H, d, J ¼ 7.5). Anal. calcd. for C16H17NO3 (271.31): C, 70.83; H, 6.32;
N, 5.16. Found: C, 70.39; H, 6.52; N, 5.16.