W. R. Bowman et al. / Tetrahedron 63 (2007) 191–203
199
7.58 (1H, dd, J 1.5, 7.9) and 7.77–8.00 (5H, m); dC 14.2
(Me), 21.4 (Me), 60.6 (CH2), 120.7 (CH), 125.3 (CH),
125.8 (CH), 127.2 (CH), 127.3 (CH), 128.0 (C), 129.4
(CH), 130.7 (CH), 131.4 (C), 136.1 (C), 139.3 (CH), 142.6
(C), 166.0 (C) and 166.6 (C); m/z 309 (13%), 236 (3), 190
(16), 119 (100) and 91 (28).
(2H, m), 5.80 (1H, m, cyclohexenyl 2-H), 6.81–6.83 (1H,
m), 7.09–7.13 (1H, m), 7.19–7.23 (2H, m), 7.31–7.41 (3H,
m) and 7.62–7.63 (2H, m); dC 22.3 (CH2), 23.2 (CH2),
25.8 (CH2), 28.5 (Me), 28.7 (CH2), 119.4 (CH), 124.7
(CH), 127.1 (CH), 127.2 (CH), 128.2 (C), 128.9 (CH),
129.1 (CH), 129.3 (CH), 135.3 (C), 136.8 (C), 137.2 (CH),
148.2 (C) and 163.32 (C]N); m/z [(LSIMS) Found:
356.0907. C20H22NSe (M+H)+ requires 356.0912], 355
(79%), 314 (37), 260 (68), 232 (100) and 214 (50).
4.3.4. 3-[2-(Phenylacetylamino)phenyl]acrylic acid ethyl
ester 16c. General method for the synthesis of amides
using dicyclohexylcarbodiimide. Phenylacetic acid
(4.523 g, 33.26 mmol), dicyclohexylcarbodiimide (6.851 g,
33.26 mmol) and HOAT (0.334 g, 2.46 mmol) were added
to a solution of 3-(2-aminophenyl)acrylic acid ethyl ester
15 (R2¼CO2Et, R3¼H) (4.705 g, 24.63 mmol) in anhydrous
DCM (100 cm3). The reaction mixture was stirred for 36 h.
The crude mixture was then filtered and washed successively
with 2 M hydrochloric acid and saturated aqueous sodium
hydrogen carbonate solution. The combined organic frac-
tions were dried and concentrated under reduced pressure.
The crude product was purified by flash silica column chro-
matography to yield the ester 16c as a white solid (4.30 g,
56%), mp 117–118 ꢁC (Found: 309.1360. C19H19NO3 re-
quires 309.1364); nmax(thin film)/cmꢂ1 3263, 3027, 2978,
2929, 2853, 1713, 1661, 1634, 1579, 1527, 1454, 1316,
1260, 1177 and 972; dH(250 MHz, CDCl3) 1.34 (3H, t,
J 7.2, Me), 3.79 (2H, s, CH2Ph), 4.25 (2H, q, J 7.2,
CH2O), 6.25 (1H, d, J 15.9, CHCO2Et), 7.47–7.12 (8H,
m), 7.54 (1H, d, J 15.9, CH]CHCO2Et) and 7.75 (1H, d,
J 8.1); dC 14.3 (CH3), 44.5 (CH2), 60.6 (CH2), 121.0 (CH),
124.6 (CH), 125.8 (CH), 127.2 (CH), 127.5 (C), 127.8
(CH), 129.4 (CH), 129.5 (CH), 130.6 (CH), 134.2 (C),
135.5 (C), 138.9 (CH), 168.4 (C) and 169.6 (C); m/z 309
(M+, 23%), 268 (7), 240 (11), 191 (14), 146 (55), 118
(38), 91 (100) and 65 (13).
Compound 11m:33 nmax(neat)/cmꢂ1 3059, 2934, 2864, 1588,
1423, 763 and 746; dH(400 MHz, CDCl3) 1.87–1.93 (4H, m,
8,9-H), 2.62 (3H, s, CH3), 2.73–2.76 (2H, m, 7- or 10-H),
3.06–3.08 (2H, m, 7- or 10-H), 7.45 (1H, ddd, J 8.3, 6.9,
1.0, 2- or 3-H), 7.59 (1H, ddd, J 8.3, 6.9, 1.2, 2- or 3-H),
7.87 (1H, dd, J 8.3, 1.2, 1- or 4-H) and 7.98 (1H, dd, J 8.3,
1.0, 1- or 4-H); dC 22.0 (8,9-C), 22.5 (8,9-C), 23.3 (Me),
25.5 (7,10-C), 26.8 (7,10-C), 122.4 (CH), 125.4 (CH),
126.7 (C), 128.0 (CH), 128.0 (CH), 128.9 (C), 141.1 (C),
145.3 (C) and 158.6 (C); m/z (ESI) [Found: 198.1279.
C14H16N (M+H)+ requires 198.1277], 197 (100%), 182
(30), 169 (58) and 77 (20).
4.4. Radical cyclisation reactions for the synthesis of
indoles and quinolines
4.4.1. [2-(p-Tolyl)-1H-indol-3-yl]acetic acid ethyl ester
10a. General method for the radical cyclisation of imido-
yl selanides using syringe pump addition of Bu3SnH.
3-{2-[(Phenylselanyl-p-tolyl-methylene)-amino]-phenyl}-
acrylic acid ethyl ester 5a (0.469 g, 1.05 mmol) was dis-
solved in anhydrous toluene (100 cm3). The reaction
mixture was deoxygenated and heated to reflux. A solution
of Bu3SnH (0.61 cm3, 2.31 mmol, 2.2 equiv) in toluene
(20 cm3) was added via a syringe pump over 5 h and
AIBN (0.164 g, 1.05 mmol) was added over 5 h as five equal
aliquots. The reaction mixture was cooled and the solvent
removed under reduced pressure. The crude mixture was
purified by flash silica column chromatography using an
eluent system of light petroleum and EtOAc to yield the
indole 10a as a pale yellow oil (0.293 g, 95%) (Found:
293.1419. C19H19NO2 requires 293.1415); nmax(thin film)/
cmꢂ1 3373, 3053, 3024, 2976, 2921, 2869, 1718, 1506,
1457, 1342, 1306, 1176, 1029 and 822; dH(250 MHz,
CDCl3) 1.23 (3H, t, J 7.1, CH3), 2.38 (3H, s, CH3), 3.80
(2H, s, CH2CO2Et), 4.14 (2H, q, J 7.1 CH2O), 7.12–7.30
(5H, m), 7.49–7.52 (2H, m), 7.64–7.66 (1H, m) and 8.18
(1H, br s, NH); dC 14.2 (CH3), 21.2 (CH3), 31.2 (CH2),
60.8 (CH2), 105.3 (C), 110.8 (CH), 119.2 (CH), 119.9
(CH), 122.3 (CH), 128.1 (CH), 129.1 (C), 129.5 (C), 129.6
(CH), 135.7 (C), 136.3 (C), 137.9 (C) and 172.3 (C]O);
m/z 292 (M+, 40%), 269 (20), 220 (100), 204 (22), 177 (5),
155 (4) and 91 (4).
4.3.5. 3-{2-[(Phenylselanyl-p-tolylmethylene)amino]phe-
nyl}acrylic acid ethyl ester 5a. The general procedure for
the synthesis of imidoyl selanides was used. Yellow oil
(64%) [HRMS (FAB) Found: 450.0968. C25H24NO2Se
(M++H) requires 450.0972]; nmax(thin film)/cmꢂ1 3056,
2976, 1707, 1628, 1592, 1474, 1314, 1267, 1172, 1092
and 910; dH(250 MHz, CDCl3) 1.32 (3H, t, J 7.2, Me),
2.29 (3H, s, Me), 4.26 (2H, q, J 7.2, CH2O), 6.38 (1H, d,
J 16.0, CHCO2Et), 6.89 (1H, d, J 8.0), 7.53–7.01 (10H,
m), 7.59 (2H, d, J 8.0) and 7.86 (1H, d, J 16.0,
CH]CHCO2Et); dC 14.3 (CH3), 21.3 (CH3), 60.2 (CH2),
118.7 (CH), 119.8 (CH), 124.6 (C), 124.7 (CH), 127.2
(CH), 127.7 (CH), 128.7 (CH), 128.8 (CH), 128.9 (C),
129.1 (CH), 130.5 (CH), 135.2 (CH), 135.5 (C), 140.7 (C),
140.8 (CH), 150.3 (C), 165.2 (C) and 167.0 (C); m/z
(FAB) 450 (M++H, 10%), 366 (4), 292 (42), 248 (42), 220
(90), 128 (19), 119 (100), 91 (25), 77 (15) and 65 (5).
4.3.6. (Z)-Phenyl N-2-cyclohexenylphenylethaneselenoi-
midate 5m. The general method for the synthesis of imidoyl
selanides was used and yielded after purification the imidoyl
selanide 5m (27%) as a yellow oil and 6-methyl-7,8,9,10-tet-
rahydrophenanthridine 11m (55%) as colourless crystals,
mp 84–86 ꢁC.
4.4.2. Cyclisation of (Z)-phenyl 4-methyl-N-[(2-penten-1-
yl)phenyl]benzoselenoimidate 5e. The general method for
the radical cyclisation of imidoyl selanides using syringe
pump addition of the imidoyl selanide 5e gave a crude mix-
ture, which was analysed by 1H NMR spectroscopy as
10e:11e:2-(p-tolyl)quinoline, 1:4:3, along with other minor
unknown products. 3-Propyl-2-(p-tolyl) quinoline 11e
(39%), the indole 10e (10%) and 2-(p-tolyl) quinoline
(6%) were isolated using column chromatography.
Compound 5m: nmax(neat)/cmꢂ1 3055, 2925, 2853, 2831,
1644, 1117, 740 and 692; dH(400 MHz, CDCl3) 1.64–1.76
(4H, m), 2.14 (3H, s, Me), 2.14–2.21 (2H, m), 2.32–2.36