J. Spura et al. / C. R. Chimie xxx (xxxx) xxx
3
SCE (saturated calomel electrode) [17]), are given against
SCE.
recrystallized from hexane providing 0.19 g (71%) of pure
1b as a yellow solid. M.p. 91e92 ꢃC.
DFT calculations (geometry optimization and frequency
analysis) were performed using Gaussian 03W (release
B.01) program [18] at the B3LYP/Lanl2DZ//HF/6-31G level.
Solvation in CH3CN was accounted for using the Tomasi
PCM method [19]. All stationary points were found to be
stable global minima as attested by the absence of negative
vibration frequencies in harmonic frequency analysis. A
scaling factor of 0.98 was applied to B3LYP/Lanl2DZ-
calculated IR frequencies [20].
1H NMR spectrum (300 MHz, CDCl3),
d, ppm (J, Hz): 0.31
(s, 9H, SieCH3); 6.78e6.82 (m, 1H); 6.87e6.94 (m, 2H);
7.02e7.13 (m, 2H); 7.16e7.17 (d, 1H); 8.78 (s, 1H); 0.95 (s,
1H, OH). 13C NMR spectrum (75 MHz, CDCl3), , ppm: 13C
d
NMR (75 MHz, CDCl3),
d
, ppm: ꢀ1.77; 115.08; 115.67;
115.73; 119.94; 121.71; 128.67; 135.77; 145.77; 152.34;
156.12; 165.58. 29Si NMR (80 MHz, CDCl3),
d
, ppm: ꢀ9.55.
MS (EI, 70 eV), m/z (Irel, %): 259 [M]þ (58); 231 (100); 216
(24); 186 (21); 150 (18); 73 (34); 28 (17). Anal. Calcd
(C14H17NO2Si), %: C 64.82; H 6.60; N 5.40. Found, %: C 64.70;
H 6.60; N 5.33.
1H and 13C NMR spectra were recorded on a Varian-300
spectrometer (300 and 75 MHz, respectively) in CDCl3, with
TMS as the internal standard for 1H and 29Si nuclei and
2-[(5-Trimethylgermyl-2-furyl)methyleneamino]-
phenol (1c) was prepared similarly to 1b, reacting 5-
trimethylgermyl-furan-2-carbaldehyde (0.49 g, 2.3 mmol)
with a suspension of 2-aminophenol (0.22 g, 2.3 mmol) in
ethanol (10 mL). After stirring the mixture at room tem-
perature for 4.5 h, the solvent was evaporated and the
residue dissolved in diethyl ether to be dried on MgSO4. The
crude product obtained after evaporation of ether was
recrystallized from hexane affording 0.15 g (66%) of pure 1c
using the residual solvent proton signal (77.05 ppm) for 13
C
nuclei. Elemental analyses were performed on a CARLO
ERBA EA-1108 elemental analyzer. Thin-layer chromatog-
raphy (TLC) was carried out on Merck silica gel 60 F254
plates. The mass-spectra were recorded under electron
impact conditions on
a GC-MS Agilent Technologies
7890 GC system with 5975C EI/CI MSD (70 eV) and a
capillary column HP-5.
ꢃ
For X-ray analysis, diffraction data were collected at
as a light yellow solid. M.p. 94e96 C.
ꢀ100 ꢃC on a Bruker-Nonius Kappa CCD diffractometer
1H NMR (300 MHz, CDCl3),
d, ppm (J, Hz): 0.48 (s, 9H,
using graphite monochromatic Mo K
a
radiation (
l
¼
Ge-CH3); 6.67e6.68 (d, 1H, J¼3.3 Hz, H-3); 6.86e6.90 (m,
0.71073 Å). The crystal structures of 2b and 2c were solved
by direct methods and refined by full-matrix least squares.
All non-hydrogen atoms were refined in anisotropic
approximation. For further details, see crystallographic
data for 2b and 2c deposited at the Cambridge Crystallo-
graphic Data Centre as Supplementary Publication
Numbers CCDC 1870490 (for 2b) and CCDC 1870491 (for
2c). Copies of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK.
1H), 6.98e7.02 (m, 2H); 7.14e7.23 (m, 2H); 7.33 (ps, 1H,
CeOH); 8.51 (s, 1H). 13C NMR (75 MHz, CDCl3),
d, ppm:
ꢀ1.88; 114.97; 115.56; 116.09; 119.97; 120.25; 128.59;
135.81; 144.91; 152.34; 155.96; 165.60. MS (EI, 70 eV), m/z (
Irel, %): 305 [M]þ (23); 277 (31); 186 (100); 158 (22); 119
(14); 28 (55). Anal. Calcd (C14H17GeNO2), %: C 55.32; H 5.64;
N 4.61. Found, %: C 55.54; H 5.66; N 4.47.
2-[(5-Triethylsilyl-2-furyl)methyleneamino]-phenol
(1d) was prepared similarly to 1b from 5-triethylsilylfuran-
2-carbaldehyde (0.43 g, 2.0 mmol), with stirring for 4.5 h.
The recrystallization of the crude product from hexane
gave pure 1d as a brown solid (0.42 g, 69%). M.p. 49e51 ꢃC.
For the following syntheses, the hetaryl-substituted 2-
carbaldehydes have been prepared according to the
Dubac procedure [21] treating furan- and thio-
phenecarbaldehyde with lithium morpholide (aldehyde
protection) and s-BuLi and then with the corresponding
Alk3MCl (M ¼ Si, Ge).
1H NMR (400 MHz, CDCl3,
d, ppm): 0.80e0.89 (m, 6H,
SieCH2), 1.00e1.01 (m, 9H, SieCH2CH3), 6.86e6.91 (m, 1H),
6.98e7.0 (m, 1H), 7.14e7.18 (m, 2H), 7.65e7.28 (m, 2H),
7.55e7.56 (d, 2H), 8.79 (s, 1H). 13C NMR (75 MHz, CDCl3,
d,
2-[2-Furylmethyleneamino]-phenol (1a) [22].
A
ppm): 4.20; 7.26; 114.96; 115.68; 119.99; 128.65; 133.24;
mixture of furan-2-carbaldehyde (0.25 g, 2.3 mmol), 2-
aminophenol (0.22 g, 2.3 mmol), and benzene (2 mL) was
refluxed for 4 h. The reaction was monitored by TLC using
petroleum ether (PE)/Et2O, 10:0.1. After cooling down, the
solvent was evaporated and the residue was dissolved in
diethyl ether and dried over MgSO4. The obtained crude
product was recrystallized from hexane affording 0.32 g
(74%) of pure 1a as a brown solid. M.p. 62e63 ꢃC (lit. m.p.
68 ꢃC [23]; melting with decomposition at 160e175 ꢃC was
reported earlier [24]).
135.21; 135.28; 144.23; 147.29; 149.29; 152.24. 29Si NMR
(80 MHz, CDCl3, d, ppm): 0.98. MS, m/z (I, %): 317 (100), 288
(45), 260 (74), 232 (45), 170 (69), 116 (36), 28(87). Anal.
Calcd (C17H23NO2Si), %: C 67.73; H 7.69; N 4.64. Found, %: C
67.46; H 7.69; N 4.57.
2-[(5-Triethylgermyl-2-furyl)methyleneamino]
phenol (1e) was synthesized similarly to 1b, using 5-
triethylgermylfuran-2-carbaldehyde (0.59 g, 2.3 mmol)
and a prolonged (12 h) stirring. Pure 1e crystallized from
hexane as a yellow solid (0.19 g, 66%). M.p. 64e65 ꢃC.
2-[(5-Trimethylsilyl-2-furyl)methyleneamino]-
1H NMR (400 MHz, CDCl3,
d, ppm): 1.06e1.16 (m, 15H,
phenol
(1b).
5-Trimethylsilyl-furan-2-carbaldehyde
SieCH2CH3); 6.83e6.93 (m, 3H); 7.11e7.17 (m, 1H);
7.21e7.23 (m, 1H); 7.38e7.41 (m, 1H); 7.84 (s, 1H); 8.69 (s,
(0.39 g, 2.3 mmol) was added to a suspension of 2-
aminophenol (0.22 g, 2.3 mmol) in ethanol (10 mL) and
the resulting solution was stirred for 14 h at room tem-
perature. The reaction was monitored by TLC (PE/Et2O,
10:0.1). After evaporation of ethanol, the residue was dis-
solved in diethyl ether (ca. 10 mL) and dried over MgSO4.
After evaporation of ether, the crude product was
1H). 13C NMR (75 MHz, CDCl3,
d, ppm): 4.44; 8.84; 114.88;
115.45; 115.72; 119.94; 121.41; 128.54; 135.71; 135.73;
144.80; 152.36; 156.16. MS, m/z (I, %): 347 (19), 318 (37),
290 (24), 260 (19), 186 (100), 131 (16), 28(89). Anal. Calcd
(C17H23GeNO2), %: C 59.01; H 6.70; N 4.04. Found, %: C
59.13; H 6.71; N 3.97.
Please cite this article as: J. Spura et al., Novel R3M (M ¼ Si, Ge) substituted furan and thiophene-derived aldimines: Synthesis,