PAPER
Polycyclic Azaarenes by Photochemical Cyclodehydrogenation Route
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1H NMR (CDCl3): d = 8.63 (d, J = 8 Hz, 1 H, H-5¢), 8.58 (br s, 1 H,
H-4¢), 8.40 (d, J = 2 Hz, 1 H, H-2¢¢), 8.38 (dd, J = 5, 2 Hz, 1 H, H-
6¢¢), 7.88 (dd, J = 8, 1 Hz, 1 H, H-8¢), 7.85 (d, J = 8 Hz, 1 H, H-1¢),
7.72 (app s, 2 H, H-9¢,10¢), 7.64 (td, J = 8, 1 Hz, 1 H, H-6¢), 7.59 (td,
J = 8, 1 Hz, 1 H, H-7¢), 7.51 (dd, J = 8, 2 Hz, 1 H, H-2¢), 7.45 (dt,
J = 8, 2 Hz, 1 H, H-4¢¢), 7.13 (dd, J = 8, 5 Hz, 1 H, H-5¢¢), 5.11 (dd,
J = 7.2, 5.8 Hz, 1 H, CHCH2), 3.11 (AB of ABX, 2 H, CHCH2),
3.03 (br s, 1 H, OH).
1H NMR (CDCl3): d = 8.60 (dt, J = 5, 2 Hz, 1 H, H-6), 7.78 (dd,
J = 8, 2 Hz, 1 H, H-8¢¢), 7.76 (br s, 1 H, H-1¢¢), 7.72 (dd, J = 8, 2 Hz,
1 H, H-5¢¢), 7.67 (d, J = 9 Hz, 1H, H-4¢¢), 7.47–7.42 (m, 2 H, H-
6¢¢,7¢), 7.39 (td, J = 8, 2 Hz, 1 H, H-4), 7.33 (dd, J = 9, 2 Hz, 1 H,
H-3¢¢), 7.17 (d, J = 8 Hz, 1 H, H-3), 7.08 (ddd, J = 8, 5, 1 Hz, 1 H,
H-5), 6.99 (d, J = 12 Hz, 1 H, H-2¢), 6.78 (d, J = 12 Hz, 1 H, H-1¢).
MS (EI): m/z (%) = 232 (14, [M + 1]+), 231, 230, 115, 78, 51 (100).
Anal. Calcd for C17H13N: C, 88.28; H, 5.67; N, 6.06. Found: C,
88.25; H, 5.60; N, 6.31.
MS (EI): m/z (%) = 299 (11, [M]+), 280, 207, 177, 93 (100), 65.
b) This alcohol (1.50 g, 0.005 mol) was dehydrated by treatment
with acid for 12 h at r.t. followed by wet flash column chromatog-
raphy (PE–EtOAc) to give 27; yellow oily solid; yield: 0.82 g
(58%); one spot Rf = 0.39 (EtOAc–PE, 1:1).
1H NMR (CDCl3): d = 8.81 (d, J = 2 Hz, 1 H, H-2), 8.74 (d, J = 8
Hz, 1 H, H-5¢¢), 8.73 (br s, 1 H, H-4¢¢), 8.52 (dd, J = 5, 1.5 Hz, 1 H,
H-6), 7.92 (dd, J = 8, 2 Hz, 1 H, H-4), 7.90 (dd, J = 8, 1 Hz, 1 H,
H-8¢¢), 7.89 (d, J = 8 Hz, 1 H, H-1¢¢), 7.84 (dd, J = 8, 2 Hz, 1 H, H-
2¢¢), 7.74 (app s, 2 H, H-9¢¢,10¢¢), 7.69 (td, J = 8, 1 Hz, 1 H, H-6¢¢),
7.62 (td, J = 8, 1 Hz, 1 H, H-7¢¢), 7.44 (d, J = 16 Hz, 1 H, H-2¢), 7.33
(dd, J = 8, 5 Hz, 1 H, H-5¢), 7.27 (d, J = 16 Hz, 1 H, H-1¢).
(Z)-4-[2-(2-Naphthyl)vinylpyridine (19)
From 18. Chromatography gave 19 (188 mg, 63%) as a colorless oil
followed by unchanged starting material. Distillation (bp 190 °C/
0.6 mm Hg) gave pure 19.
1H NMR (CDCl3): d = 8.45 (d, J = 5 Hz, 2 H, H-2,6), 7.79 (dd,
J = 8, 2 Hz, 1 H, H-8¢¢), 7.72 (dd, J = 8, 2 Hz, 1 H, H-5¢¢), 7.70 (s, 1
H, H-1¢¢), 7.68 (d, J = 9 Hz, 1 H, H-4¢¢), 7.49–7.43 (m, 2 H, H-
6¢¢,7¢¢), 7.23 (dd, J = 9, 2 Hz, 1 H, H-3¢¢), 7.14 (d, J = 5 Hz, 2 H, H-
3,5), 6.95 (d, J = 12 Hz, 1 H, H-2¢), 6.58 (d, J = 12 Hz, 1 H, H-1¢).
MS (EI): m/z (%) = 231 (32, [M+]), 230, 114, 99, 63 (100), 51.
MS (EI): m/z (%) = 282 (8, [M + 1]+), 281, 280 (100), 278, 202, 140,
79.
HRMS (EI): m/z [M]+ calcd for C21H15N: 281.1204; found:
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.21; H, 5.90; N, 6.01.
281.1204.
Photocyclodehydrogenation; General Procedure E
A soln of the arylvinylpyridine (231 mg, 1.0 mmol) in toluene (100
mL), aerated by bubbling air for 30 min before and throughout the
reaction, was irradiated (l = 366 nm) at 19 °C for 10 h, with one in-
terruption to remove polymer from the vessel wall. The resulting
soln was filtered and the filtrate evaporated to leave a brown oily
solid which was purified by wet-flash column chromatography elut-
ing with mixtures of PE and EtOAc.
(E)-4-[2-(3-Phenanthryl)vinyl]pyridine (28)
a) From 4-picoline (1.27 mL, 0.013 mol) and phenanthrene-3-car-
baldehyde (2.68 g, 0.013 mol). Removal of the solvent afforded
crude 1-(3-phenanthryl)-2-pyridin-4-ylethanol; yellow oil: yield:
3.80 g (98%).
IR (Nujol): 3285 (OH), 1605 (CN) cm–1.
1H NMR (CDCl3): d = 8.65 (d, J = 8 Hz, 1 H, H-5¢), 8.61 (br s, 1 H,
H-4¢), 8.42 (d, J = 6 Hz, 2 H, H-2¢¢,6¢¢), 7.89 (dd, J = 8, 1.5 Hz, 1 H,
H-8¢), 7.86 (d, J = 8 Hz, 1 H, H-1¢), 7.74 (app s, 2 H, H-9¢,10¢), 7.65
(td, J = 8, 1.5 Hz, 1 H, H-6¢), 7.61 (td, J = 8, 1.5 Hz, 1 H, H-7¢), 7.54
(dd, J = 8, 1.5 Hz, 1 H, H-2¢), 7.13 (d, J = 6 Hz, 2 H, H-3¢¢,5¢¢), 5.19
(dd, J = 7.6, 5.4 Hz, 1 H, CHCH2), 3.14 (AB of ABX system, 2 H,
CHCH2).
Photocyclization of (E)-1,2-NVP (8); Naphtho[2,1-f]quinoline
(29)
Chromatography gave three unidentified by-products, followed by
naphtho[2,1-f]quinoline (29); crude yield: 31 mg (13%); pure as
light yellow crystals (toluene); mp 225–227 °C (Lit.21 mp 226–
227 °C).
1H NMR (CDCl3): d = 9.09 (br d, J = ca. 8.6 Hz, 1 H, H-4), 9.04
(dd, J = 4.3, 1.6 Hz, 1 H, H-2), 8.98 (d, J = 9.3 Hz, 1 H, H-11), 8.80
(br d, J = 8.3 Hz, 1 H, H-10), 8.64 (d, J = 9.0 Hz, 1 H, H-5), 8.28
(d, J = 9.3 Hz, 1 H, H-12), 8.07 (d, J = 9.0 Hz, 1 H, H-6), 8.02 (dd,
J = 7.9, 1.4 Hz, 1 H, H-7), 7.76 (td, J = 7.9,1.4 Hz, 1 H, H-9), 7.68
(td, J = 7.9, 1.4 Hz, 1 H, H-8), 7.64 (dd, J = 8.5, 4.3 Hz, 1 H, H-3);
NOE 8.64 → 9.09 (18%) and 8.07 (7%).
MS (EI): m/z (%) = 300 (5, [M + 1]+), 299, 179, 178, 93 (100), 65.
b) This alcohol (3.50 g, 0.012 mol) was dehydrated by treatment
with acid at r.t. for 12 h to give after wet flash column chromatog-
raphy (PE–EtOAc) exclusively 28; light-yellow solid; yield: 2.24 g
(68%); recrystallized as light-yellow powder (benzene, HAZARD);
mp 141.5–142.5 °C.
13C NMR (CDCl3): d = 149.6 (C-2), 147.5 (C-12a), 132.35, 131.6
(C-4), 130.3, 128.6 (C-7), 128.2 (C-6), 128.0 (C-12), 127.8, 127.2
(C-9), 126.9 (C-8), 125.6, 125.3 (C-11), 123.2 (C-10), 121.4 (C-3),
120.5 (C-5).
NMR as reported for 28 under General Procedure A.
MS (EI): m/z (%) = 282 (22, [M + 1]+), 281 (100), 280, 140, 126, 51.
UV (EtOH): lmax (e) = 368 (6860), 351 (28590), 339 (35030), 281
(28370), 273 (30740), 250 (41900), 242 (32220), 204 nm (48210).
MS (EI): m/z (%) = 230 (21, [M + 1]+), 229 (100), 228, 101, 100, 88.
Anal. Calcd for C21H15N: C, 89.65; H, 5.37; N, 4.98. Found: C,
89.98; H, 5.42; N, 4.89.
Anal. Calcd for C17H11N: C, 89.06; H, 4.84; N, 6.11. Found: C,
89.26; H, 4.77; N, 6.04.
Isomerization of E- to Z-Isomer; General Procedure D
Photocyclization of (E)-1,3-NVP (12)
Chromatography gave five components. The first unidentified ma-
terial was followed by:
A soln of E-isomer 10 or 18 (300 mg) in toluene (110 mL), deaerat-
ed by bubbling N2 through for 30 min before and throughout the re-
action, was irradiated (l = 366 nm) at 19 °C for 1 h. Solvent was
removed in vacuo and the resultant yellow oil purified by wet-flash
column chromatography eluting with mixtures of PE and EtOAc.
(i) Naphtho[1,2-h]quinoline (30)
White solid; yield: 9 mg (4%); mp 113–115 °C (Lit.12 mp 118–
119 °C).
(Z)-2-[2-(2-Naphthyl)vinyl]pyridine (11)11
From 10. Chromatography gave unchanged E-isomer 10 followed
by a fraction which was distilled (bp 250 °C/0.5 mm Hg) to give 11;
colorless oil; yield: 70%.
1H NMR (CDCl3): d = 9.37 (d, J = 9.0 Hz, 1 H, H-5), 9.07 (dd,
J = 4.3, 1.7 Hz, 1 H, H-3), 8.76 (br d, J = ca. 8.1 Hz, 1 H, H-10),
8.75 (d, J = 9.0 Hz, 1 H, H-11), 8.25 (dd, J = 8.1, 1.7 Hz, 1 H, H-1),
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York