I. Dix, C. Doll, H. Hopf, P. G. Jones
FULL PAPER
(251.40): calcd. C 76.46, H 6.82, N 5.58; found C 76.46, H 6.76,
N 5.49.
(dd, J4-H/5-H ϭ 7.8, J4-H/6-H ϭ 1.8 Hz, 4-H, 1 H), 7.85Ϫ7.87 (m,
phenyl, 2 H), 8.57 (dd, J6-H/5-H ϭ 4.8, J6-H/4-H ϭ 1.8 Hz, 6-H, 1 H)
ppm. 13C NMR (100.6 MHz, CDCl3): δ ϭ 81.3 (ps-s, C-13), 82.9
(d, C-14), 116.8 (s, C-3), 121.3 (d), 127.9 (d), 128.9 (d), 129.2 (d),
138.9 (s), 141.9 (d), 148.9 (d), 160.2 (s, C-2) ppm. IR (KBr): ν˜ ϭ
3195 cmϪ1 (s), 3041 (w), 2100 (w), 1556 (w), 1426 (s), 802 (m), 744
(s), 696 (s). UV/Vis (CHCl3): λmax (lg ε) ϭ 236 nm (3.67), 242
(3.99), 262 (4.04), 282 (3.89), 310 (2.94), 314 (2.58), 320 (2.09). MS
(70 eV): m/z (%) ϭ 179 (100) [Mϩ], 178 (52). C13H9N (179.22):
calcd. C: 87.12, H 5.06, N 7.82; found C 86.79, H 5.15, N 7.63.
6,6Ј-Methanediylbis(pyrido[2,1-a]isoindole) (37): A solution of 26
(2.63 g, 10.5 mmol) in THF (100 mL) was treated under nitrogen
with a solution of TBAF·3H2O (1.18 g, 3.7 mmol) in water
(10 mL). After the mixture had been stirred for 1 d at room temp.,
the solvents were removed in vacuo and the remaining oil was dis-
solved in dichloromethane. The solution was washed carefully with
water, the organic phase was dried with sodium sulfate, and the
solvent was distilled off. The remaining solid (0.57 g) was extracted
with refluxing chloroform/petroleum ether, and the insoluble yel-
low solid was removed by filtration. An additional 0.17 g of the
yellow product crystallized from the mother liquor (total yield of
37: 0.74 g, 41%). Analytically pure material was obtained by recrys-
tallization from diethyl ether, yellow needles, m.p. 200 °C (de-
comp.). 1H NMR (400.1 MHz, CDCl3): δ ϭ 5.04 (s, 11-H, 2 H),
6.70Ϫ6.74 (m, 4 H), 7.15 (ddd, J1 ϭ 0.8, J2 ϭ 6.6, J3 ϭ 8.2 Hz, 2
H), 7.32 (ddd, J1 ϭ 0.9, J2 ϭ 6.6, J3 ϭ 8.5 Hz, 2 H), 7.51 (ps-d,
J ϭ 8.6 Hz, 2 H), 7.80Ϫ7.83 (m, 2 H), 8.03Ϫ8.06 (m, 2 H), 8.15
(ps-dt, J1 ϭ 0.9, J2 ϭ 8.3 Hz, 2 H) ppm. 13C NMR (100.6 MHz,
CDCl3): δ ϭ 21.2 (t, C-11), 106.9 (s), 112.6 (d), 115.5 (d), 116.0
(d), 116.4 (s), 118.2 (d), 118.6 (d), 119.8 (d), 120.3 (d), 124.7 (d),
125.7 (s), 126.2 (s) ppm. IR (KBr): ν˜ ϭ 3047 cmϪ1 (w), 1602 (s),
1446 (m), 1350 (m), 1308 (s), 1256 (m), 1211 (m), 1127 (m), 996
(m), 740 (s), 726 (s), 715 (s), 700 (s). UV/Vis (CHCl3): λmax (lg ε) ϭ
252 nm (4.84), 274 (4.44), 362 (4.32), 374 (4.36), 416 (3.60), 442
(3.52), 472 (3.35), 602 (3.45), 644 (4.04). MS (70 eV): m/z (%) ϭ
346 (100) [Mϩ], 345 (58), 180 (78). C25H18N2 (346.43): calcd. C
86.68, H 5.24, N 8.09; found C 86.70, H 5.24, N 7.97.
Pyrolysis of 4-(2-Ethynylphenyl)pyridine (10): A sample of 10
(0.072 g, 0.4 mmol) was pyrolyzed at 810 °C and 0.5 mbar (evap-
oration temperature 120 °C). HPLC/UV analysis of the pyrolysate
(0.050 g, mass recovery 69%) showed that benzo[f]isoquinoline (45)
was formed as the main product, together with five side products,
of which one was identified by spectral comparison as the benzo-
pentalene dimer 47 (see spectroscopic data below). By flash chroma-
tography (silica gel; diethyl ether) compound 45 (0.024 g, 33%), a
known compound,[29] was isolated. 1H NMR (400.1 MHz, CDCl3):
δ ϭ 7.71Ϫ7.75 (m, 2 H), 7.84 (AB-q, J ϭ 8.9 Hz, 8-H, 9-H, 2 H),
7.94Ϫ7.96 (m, 1 H), 8.44 (d, J ϭ 5.8 Hz, 1 H), 8.66Ϫ8.69 (m, 1
H), 8.76 (d, J ϭ 6.0 Hz, 1 H), 9.26 (s, 10-H, 1 H) ppm. 13C NMR
(100.6 MHz, CDCl3): δ ϭ 116.2 (d), 123.2 (d), 124.6 (d), 127.2 (d),
128.3 (s), 128.6 (d), 128.8 (d), 128.9 (d), 133.6 (s), 135.1 (s), 144.4
(d, C-2), 151.2 (d, C-10) ppm; the signal of one quaternary carbon
atom was not visible in the spectrum. IR (KBr): ν˜ ϭ 3389 cmϪ1
(w), 3289 (w), 3050 (w), 1620 (m), 1583 (m), 1519 (m), 1427 (m),
1394 (m), 1286 (m), 1251 (m), 1192 (m), 1106 (m), 1036 (m), 873
(m), 834 (s), 814 (s), 749 (s), 730 (s), 717 (s). UV/Vis (CHCl3): λmax
(lg ε) ϭ 234 nm (3.95), 238 (4.16), 248 (4.66), 252 (4.70), 272 (4.10),
280 (3.99), 294 (4.00), 320 (3.00), 334 (3.28), 350 (3.37). MS
(70 eV): m/z (%) ϭ 179 (100) [Mϩ], 178 (24), 152 (14), 151 (16).
3-Ethynyl-2-phenylpyridine (13)
a) 2-Chloro-3-[2-(trimethylsilyl)ethynyl]pyridine (40): Pd(PPh3)2-
Cl2 (0.065 g, 0.09 mmol), trimethylsilylethyne (0.5 mL), and a small
amount of CuI were added to a solution of 2-chloro-3-iodopyridine
[39, 0.44 g, 1.8 mmol, prepared from 2-chloropyridine (38) accord-
ing to ref.[27]] in triethylamine (20 mL), and the mixture was stirred
for 5 h at room temp. Petroleum ether was added, the solid material
was removed by filtration, and the solvent was removed in vacuo.
Flash chromatography (silica gel; pentane/diethyl ether, 10:1) pro-
vided the known[28] acetylene 40 (0.38 g, 99%). 1H NMR
(200.1 MHz, CDCl3): δ ϭ 0.09 (s, SiMe3, 9 H), 7.00 (dd, J5-H/6-H ϭ
4.8, J5-H/4-H ϭ 7.7 Hz, 5-H, 1 H), 7.60 (dd, J4-H/6-H ϭ 1.9, J4-H/5-H
ϭ 7.7 Hz, 4-H, 1 H), 8.13 (dd, J6-H/4-H ϭ 1.9, J6-H/5-H ϭ 4.8 Hz,
6-H, 1 H) ppm.
Pyrolysis of 3-(2-Ethynylphenyl)pyridine (11): A sample of 11
(0.484 g, 2.70 mmol) was pyrolyzed at 820 °C and 0.1 mbar (evap-
oration temperature 120 °C). The pyrolysate (0.380 g, mass recov-
ery 79%) was separated by flash chromatography (silica gel, diethyl
ether) to afford benzo[h]isoquinoline (52, 0.050 g, 10%)[30] and
benzo[f]quinoline (50, 0.060 g, 12%),[31] together with a yellow solid
1
(0.140 g), shown by H NMR analysis to be a mixture of isomers.
Although this last product could be purified by recrystallization
(petroleum ether, dichloromethane) and high-vacuum sublimation,
NMR analysis showed that it still consisted of two isomers. Its
spectroscopic data[21,22] showed it to be benzopentalene dimer (47).
Spectroscopic data: 52: 1H NMR (400.1 MHz, CDCl3): δ ϭ
7.63Ϫ7.75 (m, 4 H), 7.90Ϫ7.93 (m, 2 H), 8.70 (d, J2-H/3-H ϭ 5.2 Hz,
2-H, 1 H), 8.77 (d, J9-H/8-H ϭ 8.3 Hz, 9-H, 1 H), 10.03 (s, 10-H, 1
H) ppm. 13C NMR (100.6 MHz, CDCl3): δ ϭ 121.2 (d), 121.9 (d),
b) 3-Ethynyl-2-phenylpyridine (13): A solution of phenylmagnesium
bromide in THF (22 mL) was prepared from bromobenzene (3.6 g,
22.9 mmol) and magnesium turnings (0.55 g, 22.6 mmol). Com-
pound 40 (2.37 g, 11.3 mmol) and Ni(dppp)Cl2 (0.233 g, 124.8 (d), 125.3 (d), 127.4 (d), 128.9 (d), 129.3 (s), 131.7 (d), 132.1
0.43 mmol) were added to this solution. The mixture was heated
under reflux for 5 h and stirred for 3 d at room temp. For workup,
saturated ammonium chloride solution was added, followed by ex-
traction with diethyl ether. The organic phase was dried (sodium
sulfate) and the solvent was removed in vacuo. The obtained 41
was purified by flash chromatography (silica gel; dichloromethane).
It was dissolved in THF (17 mL), and a solution of TBAF in THF
(1.1 , 3 mL) and water (2 mL) were added. The mixture was
stirred at room temp. overnight and extracted carefully with dichlo-
romethane. After drying (sodium sulfate) and solvent evaporation,
flash chromatography (silica gel; dichloromethane) yielded 13
(s), 135.9 (s), 144.9 (d), 146.6 (d) ppm; the signal of one quaternary
carbon atom was not visible in the spectrum. IR (film): ν˜ ϭ 3060
cmϪ1 (m), 3037 (m), 2957 (w), 2934 (w), 1610 (s), 1596 (m), 1565
(w), 1501 (w), 1449 (m), 1440 (m), 1422 (m), 1406 (m), 1240 (s),
996 (m), 869 (m), 844 (s), 809 (w), 748 (s), 714 (m). MS (70 eV):
m/z (%) ϭ 179 (100) [Mϩ], 178 (18), 152 (10), 151 (12). 50: 1H
NMR (400.1 MHz, CDCl3): δ ϭ 7.51 (dd, J3-H/2-H ϭ 4.4, J3-H/2-H
ϭ 8.4 Hz, 3-H, 1 H), 7.60Ϫ7.68 (m, 2 H), 7.89Ϫ7.91 (m, 1 H),
3
3
7.95 (d, J ϭ 9.2 Hz, 9-H or 10-H, 1 H), 7.99 (d, J ϭ 9.3 Hz, 9-
H or 10-H, 1 H), 8.56 (ps-d, 3J ϭ 8.0 Hz, 5-H, 1 H), 8.89 (dd,
J
J
4-H/2-H ϭ 1.7, J4-H/3-H ϭ 8.4 Hz, 4-H, 1 H), 8.94 (dd, J2-H/4-H ϭ 1.6,
2-H/3-H ϭ 4.4 Hz, 2-H, 1 H) ppm. 13C NMR (100.6 MHz, CDCl3):
(0.49 g, 24%) as
(400.1 MHz, CDCl3): δ ϭ 3.15 (s, 14-H, 1 H), 7.13 (dd, J5-H/6-H
4.8, J5-H/4-H ϭ 7.8 Hz, 5-H, 1 H), 7.34Ϫ7.40 (m, phenyl, 3 H), 7.82 128.7 (d), 129.6 (s), 130.7 (d), 130.9 (d), 131.6 (s), 148.1 (s, C-10a),
a
colorless solid, m.p. 72 °C. 1H NMR
ϭ
δ ϭ 121.2 (d), 122.5 (d), 125.4 (s), 127.1 (d), 127.3 (d), 128.1 (d),
2554
Eur. J. Org. Chem. 2002, 2547Ϫ2556