1640 J. Chin. Chem. Soc., Vol. 54, No. 6, 2007
Lai et al.
2a in about 50% yield.3a Recently, Greci and co-workers
further reported the isolation of unexpected by-product 2a
in 40% yield from the reaction of N,N-dimethyl-p-benzoyl-
aniline-iminium chloride with indole, but the reaction mech-
anism was not discussed.3b Owing to the potential applica-
bility, it is worthwhile to develop an alternative to prepare
these analogues. Now, we thus wish to report a convenient
method to prepare compounds 2 and 3 and the reaction
mechanism is proposed and investigated.
226.1106.
2b: red, m.p. 161-162 °C. 1H-NMR (CDCl3) d 1.21 (t,
12H, J = 6.9 Hz, 4 ´ CH3), 3.42 (q, 8H, J = 6.9 Hz, 4 ´
CH2), 6.65 (br t, 4H, J = 9.3 Hz, 4 ´ Ar-H), 8.11 (d, 2H, J =
9.0 Hz, 2 ´ Ar-H), 8.26 (d, 2H, J = 9.0 Hz, 2 ´ Ar-H). IR:
2961, 2910, 1593, 1543, 1517, 1452, 1403, 1374, 1357,
1269, 1238. HRMS for C20H28N4O: 340.2263; Found:
340.2263.
1
3a: yellow, m.p. 263-265 °C. H-NMR (CDCl3) d
1.21 (t, 6H, J = 7.2 Hz, 2 ´ CH3), 2.41 (q, 4H, J = 7.2 Hz, 2
´ CH2), 3.34 (brs., 8H, 4 ´ CH2), 3.67 (brs., 4H, 2 ´ CH2),
3.82 (brs., 4H, 2 ´ CH2), 6.92 (d, 2H, J = 9.0 Hz, 2 ´ Ar-H),
6.99 (d, 2H, J = 9.0 Hz, 2 ´ Ar-H), 8.18 (d, 2H, J = 9.0 Hz, 2
´ Ar-H), 8.26 (d, 2H, J = 9.0 Hz, 2 ´ Ar-H). IR: 2980, 2942,
2920, 2829, 1635, 1594, 1508, 1452, 1438, 1388, 1221,
1167. HRMS for C26H34N6O3: 478.2693; Found: 478.2692.
EXPERIMENTAL
Chemicals were commercially available and used
without further purification. The nitrosoanilines were com-
mercially available from Acros or prepared according to
literature processes.2d 1H-NMR spectra in CDCl3 were re-
corded on a Varian or Bruker 300 MHz NMR spectrometer.
High resolution mass spectra (HRMS) were obtained from
a VG-250 spectrometer (EI, 70 ev). FT-IR spectra [KBr,
cm-1] were obtained from a Perkin Elmer (RX-I) spectro-
photometer.
1
3b: yellow, m.p. 251-253 °C. H-NMR (CDCl3) d
0.90 (t, 6H, J = 7.2 Hz, 2 ´ CH3), 1.32-1.69 (m, 28H, 14 ´
CH2), 2.37 (t, 4H, J = 7.5 Hz, 2 ´ CH2), 3.32 (brs., 8H, 4 ´
CH2), 3.65 (brs., 4H, 2 ´ CH2), 3.80 (brs., 4H, 2 ´ CH2),
6.89-6.95 (m, 4H, 4 ´ Ar-H), 8.20 (d, 2H, J = 9.0 Hz, 2 ´
Ar-H), 8.26 (d, 2H, J = 9.0 Hz, 2 ´ Ar-H). IR: 2952, 2930,
2855, 2849, 1648, 1598, 1508, 1449, 1387, 1301, 1283,
1268. HRMS for C32H46N6O3: 562.3631; Found: 562.3630.
Preparation of azoxybenzene 2a (typical procedure)
N,N-Dimethylnitrosoaniline (5) (1.5 g, 10 mmol) was
added to methanol (38 mL) containing KOH (10 g). Ace-
tone (10 mL) was subsequently added and the solution was
heated under reflux for 2 h. The precipitated solid was fil-
tered off and purified by a flash column (eluent: CH2Cl2/
hexane = 1/1). Compound 2a was thus obtained in 60%
yield (0.85 g). Solvent was removed from the filtrate and
the residue was chromatographed on silica. Elution with
CH2Cl2 gave compound 4b in 5% yield (0.07 g), which was
characterized with an authentic sample. 2a: red, m.p. 252-
253 °C. 1H-NMR (CDCl3) d 3.05 (s, 12H, 4 ´ CH3), 6.69 (d,
2H, J = 9.3 Hz, 2 ´ Ar-H), 6.77 (d, 2H, J = 7.4 Hz, 2 ´
Ar-H), 8.17 (d, 2H, J = 9.3 Hz, 2 ´ Ar-H), 8.29 (d, 2H, J =
9.0 Hz, 2 ´ Ar-H). IR: 2912, 2815, 1600, 1512, 1433, 1366,
1230, 1159. HRMS for C16H20N4O: 284.1635; Found:
284.1637.
X-Ray Crystal Structure Analysis
Crystals of compound 3b were grown from dichloro-
methane-hexane (1:1) at room temperature. A single yel-
low crystal of suitable quality was mounted on a glass fiber
and used for measurement of precise cell constants and in-
tensity data collection. Diffraction measurement was made
on a Siemens SMART CCD diffractometer with graph-
ite-monochromated Mo-Ka radiation (l = 0.71073 Å), op-
erated at 293(2) K over the q range of 1.22-26.04°. No sig-
nificant decay was observed during the data collection.
2284 Reflections were observed with I ³ 2s(I) among the
32967 unique reflections, and 6027 reflections were used
in the refinement. Data were processed on a PC using the
SHELXTL software package.6 The structure of 3b was
solved using direct methods and refined by full-matrix least
square on F2 value. All non-hydrogen atoms were refined
anisotropically. The positions of hydrogen atoms were
identified by calculation, and their contributions in struc-
ture factors were included. The final indices were R1 =
0.0743, wR2 = 0.1706 with goodness-of-fit on F2 = 1.013.
Other data are described as follows: Formula C32H46N6O3;
formula weight 562.75; crystal size 0.51 ´ 0.36 ´ 0.11
Compounds 1a, 1b,2d 2b, 3a, 3b were prepared simi-
larly.
1a: yellow, m.p. 57-58 °C. 1H-NMR (CDCl3) d 2.36
(s, 3H, CH3), 2.51 (s, 3H, CH3), 7.21-7.39 (m, 4H, 4 ´
Ar-H), 7.66 (d, 2H, J = 7.5 Hz, 2 ´ Ar-H), 8.03 (d, 2H, J =
7.5 Hz, 2 ´ Ar-H). IR: 3027, 3025, 2920, 1485, 1452, 1379,
1328, 1157. HRMS for C14H14N2O: 226.1104; Found: