ꢀ
S. Lesniak et al. / Tetrahedron 65 (2009) 10581–10589
10587
TFAext¼0 ppm):
d
ꢂ39.4 (m). Anal. Calcd for C11H9FN2O
Anal. Calcd for C9H8N2O (160.18): C, 67.49; H, 5.03; N, 17.49%.
Found: C, 67.74; H, 5.17; N, 12.33%.
(204.20): C, 64.70; H, 4.44; N, 13.72%. Found: C, 64.57; H, 4.57;
N, 13.58%.
4.3.6. (p-Tolyl)iminoacetonitrile 3b. Light yellow solid (hexane/
CH2Cl2 70:30), 56 mg (13%). Mp 66–68 ꢀC (hexane). Rf (hexane/
AcOEt, 3:1) 0.64. IR (KBr, cmꢂ1): 2229nCN, 1608nC]N, 1573, 1505,
4.2.4. cis-1-(p-Chlorophenyl)-4-cyano-3-methylazetidin-2-one
(4d). Yield 203 mg (46%), colourless solid. Mp 130–132 ꢀC (hexane/
CH2Cl2). IR (KBr, cmꢂ1): 2248nCN,1763nCO. 1H NMR (200 MHz, CDCl3,
1492, 1340, 1208, 1171, 823. 1H NMR (200 MHz, CDCl3, TMS)
d
2.39
(s, 3H), 7.14–7.28 (m, 4H), 7.54 (s, 1H). 13C NMR (50 MHz, CDCl3,
TMS)
TMS)
d
1.60 (d, J 7.5 Hz, 3H), 3.76 (dq, J 7.5, 5.6 Hz, 1H), 4.72 (d, J
11.38,
5.6 Hz, 1H), 7.36 (s, 4H). 13C NMR (50 MHz, CDCl3, TMS)
d
d
21.28, 115.48, 121.45, 130.31, 131.02, 140.87, 145.82. ESI(þ)-
44.72, 48.68, 114.53, 117.66, 129.63, 130.43, 134.86, 164.78. Anal.
Calcd for C11H9ClN2O (220.66): C, 59.88; H, 4.11; N, 12.70%. Found:
C, 59.74; H, 4.17; N, 12.58%.
MS (m/z): 145.0 [Mþ1]. Anal. Calcd for C9H8N2 (144.18): C, 74.98; H,
5.59; N, 19.43%. Found: C, 74.87; H, 5.63; N, 19.37%.
4.3.7. (p-Fluorophenyl)iminoacetonitrile 3c. Light yellow solid
(hexane/CH2Cl2 70:30), 53 mg (12%). Mp 73–76 ꢀC (hexane). Rf
4.3. Dehydrogenation of acetonitriles 1a–d with dimethyl
azodicaboxylate (DMAD)
(hexane/AcOEt, 3:1) 0.62. IR (KBr, cmꢂ1); 2230nCN, 1609nC]N
,
1597, 1578, 1503, 1486, 1330, 1235, 1161, 841, 782. 1H NMR
(200 MHz, CDCl3, TMS) 7.08–7.21 (m, 2H), 7.25–7.35 (m, 2H),
7.55 (s, 1H). 13C NMR (50 MHz, CDCl3, TMS)
115.20, 116.78 (d, J
23.1 Hz), 123.50 (d, J 8.9 Hz), 131.84 (d, J 2.2 Hz), 144.40 (d, J
3.2 Hz), 163.76 (d,
251.7 Hz). 19F NMR (188 MHz, CDCl3,
d
To a solution of 3 mmol of 1a–d in 1 mL of CH2Cl2, 0.632 g
(4.2 mmol) of DMAD was added. The mixture was stirred for 4 days
at rt. The solvent was removed in vacuum and products were
separated chromatographically (silica gel, hexane/CH2Cl2).
d
J
TFAext¼0 ppm):
d
ꢂ33.9 (m). ESI(þ)-MS (m/z): 149.0 [Mþ1]. Anal.
Calcd for C8H5FN2 (148.14): C, 64.86; H, 3.40; N, 18.91%. Found: C,
64.77; H, 3.29; N, 18.93%.
4.3.1. 2-(p-Methoxyphenyl)iminomalononitrile 2a. Yellow solid
(hexane/CH2Cl2 80:20), 57 mg (20% from 2:1 stoichiometry). After
recrystallisation from hexane mp 95–97 ꢀC, lit.29 mp 97 ꢀC. Rf
4.3.8. (p-Chlorophenyl)iminoacetonitrile 3d. Light yellow solid
(hexane/CH2Cl2 70:30), 44 mg (9%). Mp 62–64 ꢀC (hexane). Rf
(hexane/AcOEt, 3:1) 0.66. IR (KBr, cmꢂ1): 2231nCN, 1605nC]N, 1580,
(hexane/AcOEt, 4:1) 0.54. IR (KBr, cmꢂ1): 2228nCN
,
2211nCN
1605nC]N, 1507, 1265, 1169, 1160, 1026, 845. 1H NMR (200 MHz,
CDCl3, TMS)
3.92 (s, 3H), 6.96–7.08 (m, 2H), 7.72–7.82 (m, 2H). 13
,
d
C
1572, 1481, 1330, 1093, 832. 1H NMR (200 MHz, CDCl3, TMS)
d
7.18–
7.27 (m, 2H), 7.38–7.46 (m, 2H), 7.55 (s, 1H). 13C NMR (50 MHz,
CDCl3, TMS)
NMR (50 MHz, CDCl3, TMS)
128.09, 138.98, 164.86.
d 56.08, 110.65, 113.54, 114.78, 115.42,
d
114.98, 122.63, 129.87, 132.67, 136.03, 146.59. ESI(þ)-
MS (m/z): 164.0 [Mþ1]. Anal. Calcd for C8H5ClN2 (164.60): C, 58.38;
4.3.2. 2-(p-Tolyl)iminomalononitrile 2b. Light yellow solid (hexane/
CH2Cl2 80:20), 56 mg (22% from 2:1 stoichiometry). Mp 92–93 ꢀC
(hexane), lit.30 98–100 ꢀC. Rf (hexane/AcOEt, 4:1) 0.72. IR (KBr,
cmꢂ1): 2236nCN, 2219nCN, 1605nC]N, 1530, 1215, 1173, 1154, 818. 1H
H, 3.06; N, 17.02%. Found: C, 58.31; H, 3.01; N, 17.11%.
4.4. Preparative flash vacuum thermolysis
NMR (200 MHz, CDCl3, TMS)
d
2.46 (s, 3H), 7.30–7.38 (m, 2H), 7.47–
The FVT was carried out in a 30ꢁ2.5 cm electrically heated
horizontal quartz tube packed with quartz rings, at 1.5ꢁ10ꢂ3 Torr.
All precursors 4a–d or 7a (1 mmol) were slowly sublimed from
a flask held at 50–60 ꢀC into the thermolysis tube preheated to
720 ꢀC for 4–d or 600 ꢀC for 7a. The products were collected in
a CO2/acetone trap. After thermolysis, the whole system was
brought to atmospheric pressure, allowing a slow warming up to rt,
and the products were dissolved either in CDCl3 for 1H NMR
measurement or in Et2O for their separation with the use of pre-
parative TLC (SiO2, hexane/AcOEt 2:1).
7.55 (m, 2H). 13C NMR (50 MHz, CDCl3, TMS)
112.79, 123.95, 130.67, 143.32, 145.06.
d 21.80, 107.92, 109.59,
4.3.3. 2-(p-Fluorophenyl)iminomalononitrile 2c. Light yellow solid
(hexane/CH2Cl2 80:20), 31 mg (12% from 2:1 stoichiometry). Mp
93.5–94.5 ꢀC (hexane). Rf (hexane/AcOEt, 4:1) 0.71. IR (KBr, cmꢂ1):
2238nCN, 2226nCN, 1602nC]N, 1587, 1541, 1499, 1243, 1161, 851. 1H
NMR (200 MHz, CDCl3, TMS)
13C NMR (50 MHz, CDCl3, TMS)
(d, J 1.1 Hz) 117.41, (d, J 23.4 Hz), 126.43 (d, J 9.5 Hz), 141.68 (d, J
3.3 Hz), 165.30 (d,
258.5 Hz). 19F NMR (188 MHz, CDCl3,
d
7.20–7.32 (m, 2H), 7.61–7.70 (m, 2H).
d
108.94 (d, J 3.0 Hz), 109.26, 112.47
All products 3a–d obtained in this way had spectroscopic data
identical with those prepared by dehydrogenation of amines 1a–d.
The yields of separated compounds: 3a 40 mg (25%), 3b 44 mg
(30%), 3c 48 mg (33%), 3d 50 mg (30%), 3a (from 7a) 40 mg (25%).
J
TFAext¼0 ppm): ꢂ27.4 (m). ESI(ꢂ)-MS (m/z): 173.0 [M]. Anal. Calcd
d
for C9H4FN2 (173.15): C, 62.43; H, 2.33; N, 24.27%. Found: C, 62.51;
H, 2.24; N, 24.29%.
4.5. Flash vacuum thermolysis in tandem with UV-
photoelectron spectroscopy
4.3.4. 2-(p-Chlorophenyl)iminomalononitrile 2d. Light yellow solid
(hexane/CH2Cl2 80:20), 22 mg (8% from 2:1 stoichiometry). Mp
132–134 ꢀC (hexane), lit.30 136–138 ꢀC. Rf (hexane/AcOEt, 4:1) 0.72.
IR (KBr, cmꢂ1): 2238nCN, 2222nCN, 1594nC]N, 1544, 1533, 1473, 1208,
The PE spectra were recorded on a home-built, three-part
spectrometer equipped with a main body device (Meca2000), He–I
radiation source (Focus) and a spherical analyser (Omicron). The
spectrometer is operating at constant analyser energy mode and is
monitored by the microcomputer supplemented with a digital-
analogue converter. Spectral results of the single scans are built
with 2048 points and are accurate within 0.05 eV. They are cali-
brated against the autoionisation of xenon at 12.13 and 13.45 eV,
and nitrogen at 15.59 eV and 16.98 eV. Sample manipulations were
carried out in a thermolysis oven attached directly to an inlet
probe; a distance between the oven exit and the ionisation head
does not exceed 1 cm. Precursors 4a and 4d were slowly vaporised
under low pressure (10ꢂ7 Torr in the ionisation chamber) directly in
1163, 1092, 1011, 839, 818. 1H NMR (200 MHz, CDCl3, TMS)
d
7.45–
7.58 (m, 4H). 13C NMR (50 MHz, CDCl3, TMS)
124.66, 130.41, 139.42, 143.80.
d 108.97, 110.19, 112.31,
4.3.5. (p-Methoxyphenyl)iminoacetonitrile 3a. Light yellow solid
(hexane/CH2Cl2 70:30), 98 mg (20%). Mp 55–57 ꢀC (hexane). Rf
(hexane/AcOEt, 3:1) 0.48. IR (KBr, cmꢂ1): 2223nCN, 1608nC]N, 1562,
1505, 1457, 1432, 1298, 1258, 1177, 1164, 1020, 831. 1H NMR
(200 MHz, CDCl3, TMS)
(m, 2H), 7.54 (s, 1H). 13C NMR (50 MHz, CDCl3, TMS)
114.79,123.54,128.53,141.06,161.64. ESI(þ)-MS (m/z): 161.0 [Mþ1].
d
3.85 (s, 3H), 6.90–7.00 (m, 2H), 7.28–7.37
d
55.63, 114.49,