The photochemical cyclodehydrogenation route to polycyclic azaarenes

Article abstract of DOI:10.1055/s-2007-983745

This paper reports an investigation of photochemical cyclodehydrogenation for the preparation of polycyclic azaarenes. Various naphthoquinolines and naphthoisoquinolines were obtained from 2-, 3-, and 4-[2-(1- and 2-naphthyl)vinyl]pyridine. 4-[2-(3-Phenanthryl)vinyl]pyridine gave pyreno[1,10-hij]isoquinoline. An efficient preparation of (2-arylvinyl)pyridines is described. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-983745

2164
PAPER
The Photochemical Cyclodehydrogenation Route to Polycyclic Azaarenes
Polycyclic
A
zaarene
s
b
i
y
Phot
c
ochemical
hCyclodehydr
a
ogenationR
e
oute l J. E. Hewlins,* Rhys Salter
School of Chemistry, Cardiff University, Park Place, Cardiff, CF10 3AT, UK
Fax +44(29)20874030; E-mail: Hewlins @cardiff.ac.uk
Received 12 April 2007
N
Abstract: This paper reports an investigation of photochemical cy-
clodehydrogenation for the preparation of polycyclic azaarenes.
Various naphthoquinolines and naphthoisoquinolines were ob-
tained from 2-, 3-, and 4-[2-(1- and 2-naphthyl)vinyl]pyridine. 4-[2-
(3-Phenanthryl)vinyl]pyridine gave pyreno[1,10-hij]isoquinoline.
An efficient preparation of (2-arylvinyl)pyridines is described.
N
1
2
N
N
N
Key words: polycycles, photochemistry, cyclizations, naphtho-
quinolines, naphthoisoquinolines
hν, air
+
4
5
3
The first paper of this series1 explained the need for gen-
eral and efficient preparative methods for polycyclic
azaarenes, and discussed one approach to such systems.
N
NH
H
H
H
hν
hν
O2
3
4
5
This paper describes the use of photochemical cyclodehy-
drogenation.
7
6
It is well known that (Z)-stilbene undergoes photocycliza-
tion followed by dehydrogenation in the presence of a
suitable oxidant (commonly air or iodine) to give phenan-
threne, and similar behavior is shown by aza-substituted
analogues.2 Since E/Z isomerism occurs photochemically,
it is possible in principle to use either isomer as starting
material. Loader and Timmons reported that (E)-2-
styrylpyridine and (E)-4-styrylpyridine led to ben-
zo[f]quinoline (1) and benzo[h]isoquinoline (2) respec-
tively, and (Z)-3-styrylpyridine (3) gave benzo[f]iso-
quinoline (4)3(Scheme 1). At about the same time, Galiaz-
zo et al. reported that (Z)-3-styrylpyridine also gave 5, in
lower yield.4 Derivatives of styrylpyridines also give sub-
stituted benzoquinolines and benzisoquinolines.4–7 Recent
work has shown that 4-styrylpyridine gives predominant-
ly benzo[h]isoquinoline (2) in Nafion-H+ resin at low oc-
cupancy, but that substituted cyclobutanes are dominant at
high occupancy.8 Other recent work showed that the prod-
uct isomer distribution from 3-styrylpyridine depends on
the degree of oxygenation.7 Photocyclization gives re-
versibly the intermediates 6 (by electrocyclization) and 7
(by electrocyclization and 1,7-H shift); isomer 6 can be
dehydrogenated by oxygen (to give 5) but its isomer 7 is
stable to oxygen and gives rise to 4 by a different process,
possibly involving disproportionation (Scheme 1).
Scheme 1 Photocyclodehydrogenation products of styryl-
pyridines3,4,7
ucts.10 The photophysics of (naphthylvinyl)pyridines has
been studied in detail,11–13 and it has been shown that 3-[2-
(1-naphthyl)vinyl]pyridine and 3-[2-(2-naphthyl)vi-
nyl]pyridine each give two photocyclodehydrogenation
products although full characterization data were not re-
ported.12 These observations are considered in more detail
below. Further examples of this approach to azaarenes in-
clude cyclization of the Schiff’s base derived from benzal-
dehyde and 2-naphthylamine,14 and the application to
form 4-aza[6]helicene,15 and several aza- and diaza[5]he-
licenes.16 In this paper, we report our investigations into
the scope and limitations of the photocyclodehydrogena-
tion of (2-arylvinyl)pyridines.
Aromatic aldehydes react with 2- and 4-picolines in hot
acetic anhydride to give (2-arylvinyl)pyridines.11,17 Ga-
liazzo et al.11 used this method to obtain n-[2-(m-naphth-
yl)vinyl]pyridines (m = 1,2; n = 2,4), for convenience
referred to below as ‘m,n-NVP’. We followed this proce-
dure using 2- and 4-picoline, reacting each with 1-naph-
thaldehyde in acetic anhydride under reflux. Two
products were obtained in each case, the isomeric pairs 8
and 9, and 16 and 17 (Figure 1), with the E-forms being
predominant. We obtained some improvement in yields
by use of the higher boiling propionic anhydride as sol-
vent and catalyst. When 2- and 4-picoline reacted similar-
ly with 2-naphthaldehyde, the E-isomers 10 and 18 were
obtained almost exclusively. Irradiation of these E-iso-
mers with long wavelength (365 nm) UV radiation in de-
aerated solutions in toluene gave good conversions to the
corresponding Z-isomers 11 and 19. The methyl group of
These processes have been applied to some more extend-
ed ring systems. Loader and Timmons reported reactions
of some styrylquinolines and styrylisoquinolines to give
tetracyclic products,9 and Aloisi et al. reported cyclization
of some (phenanthrylvinyl)pyridines to pentacyclic prod-
SYNTHESIS 2007, No. 14, pp 2164–2174
x
x.
x
x
.
2
0
0
7
Advanced online publication: 10.07.2007
DOI: 10.1055/s-2007-983745; Art ID: P04507SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Polycyclic Azaarenes by Photochemical Cyclodehydrogenation Route
2165
Li
3-picoline is less acidic than that of 2- or 4-picoline, but
the more reactive pyridine-3-acetic acid can be used for
the preparation of the corresponding 3-pyridine isomers.11
Treatment of 1- and 2-naphthaldehydes each with sodium
pyridine-3-acetate in hot acetic anhydride, followed by
decarboxylation, gave the isomeric pairs, 12/13 and 14/
15, in good yields.
O
OH
N
N
20
+
N
N
N
N
N
N
23
22
21
8 (E)-1,2-NVP
9 (Z)-1,2-NVP
16 (E)-1,4-NVP
17 (Z)-1,4-NVP
12 (E)-1,3-NVP
13 (Z)-1,3-NVP
pyridinyl
N
N
N
N
N
25
24
26 pyridin-2-yl
27 pyridin-3-yl
28 pyridin-4-yl
10 (E)-2,2-NVP
11 (Z)-2,2-NVP
14 (E)-2,3-NVP
15 (Z)-2,3-NVP
18 (E)-2,4-NVP
19 (Z)-2,4-NVP
Scheme 2 4-[2-(Naphthyl)propenyl]pyridines and [2-(3-phenan-
thryl)vinyl]pyridines
Figure 1 Isomers of n-[2-(m-naphthyl)vinyl]pyridine, ‘m,n-NVP’
However, the lithiated anions of 2-picoline and 4-picoline
reacted readily with phenanthrene-3-carbaldehyde, each
to give an alcohol which on dehydration gave a good yield
of the E-alkene 26 or 28 respectively. The same procedure
also worked for 3-picoline, so that the three isomeric al-
kenes were obtained exclusively as E-isomers 26–28.
As the yields obtained from the condensations between pi-
colines and naphthaldehydes were disappointing, espe-
cially in the 4-picoline cases, we subsequently sought an
alternative procedure. Reaction between 1-naphthalde-
hyde and the anion of 4-picoline, generated from butyl-
lithium, gave 1-(1-napththyl)-2-pyridin-4-ylethanol
which could be dehydrated by treatment with acid to give
(E)-1,4-NVP 16 in 66% overall yield in a short time. This
is a significant improvement.
Masetti et al. reported that photochemical irradiation of
(Z)-1,3-NVP 13 and (Z)-2,3-NVP 15 each gave two tetra-
cyclic products, though characterization data were not
given.12 We have examined the series of (naphthylvi-
nyl)pyridine isomers under a set of standard conditions.
The compound 1,4-NVP 16 was chosen as the model to
establish standard conditions, as this isomer can give only
one tetracyclic product. Various solvents have been used
in previous studies of photocyclodehydrogenation, in-
cluding cyclohexane,3,6,9 hexane,4,10 hexane–benzene,12
benzene,18 ethyl acetate,16 methanol,7 tert-butyl alcohol,6
and sulfuric acid;5,19 a major criterion being adequate sol-
ubility. For this study mixtures of toluene and hexane
were used. Dilute solutions are essential, to prevent near
complete absorption of radiation, and concentrations of
10–2 mol dm–3 were used. Polymeric material built up on
the vessel walls, causing further reduction in available ra-
diation. It was found convenient to use 10-hour irradiation
times, interrupted once to remove polymer. Air was bub-
bled through the solution for 30 minutes before and then
throughout the reaction time, and in one case iodine was
used as oxidant. Table 1 shows the yields of naphtho[1,2-
h]isoquinoline (32) obtained under a variety of conditions,
the optimum being formed in neat toluene without iodine.
The remaining NVP isomers were subjected to the same
We then examined two methylated cases. Loader and
Timmons had shown that several methylated styrylpy-
ridines undergo photocyclodehydrogenation to give meth-
ylated tricyclic products, though with much concomitant
polymerization,3 and other authors have successfully cy-
clized styrylpyridines with a variety of substituents.4–6
Developing the present new route to (naphthylvinyl)py-
ridines, we allowed 1-acetylnaphthalene to react with the
lithiated anion of 4-picoline to give the alcohol 20, which
was dehydrated by acid at room temperature to give a
mixture of the three alkenes 21–23. At higher tempera-
ture, only alkene isomers 22 and 23 were obtained. A sim-
ilar procedure starting from 2-acetylnaphthalene gave the
isomeric alkenes 24 and 25 (Scheme 2).
Aloisi et al. described the preparation and photochemistry
of several [(9-phenanthryl)vinyl]pyridines.10 We have
now prepared the corresponding isomers with substituents
at the 3-position of phenanthrene. When phenanthrene-3-
carbaldehyde and 4-picoline were heated in acetic anhy-
dride, the expected isomeric (E)- and (Z)-4-[2-(3-phenan-
thryl)vinyl]pyridines were obtained, but in poor yield.
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

2166
M. J. E. Hewlins, R. Salter
PAPER
Table 1 Photocyclodehydrogenation of 16 in 10–2 mol dm–3 solu-
tions
N
Solvent toluene–hexane Oxidant
Yield of 32 (%) after 10 h
hν, air
10
1:9
1:1
1:0
1:0
air
air
air
I2
28
44
55
50
33
N
N
+
hν, air
14
optimized conditions. Since all pairs of E-and Z-isomers
are interconverted under the irradiation, the E-isomers
were used as precursors.
34
35
(E)-1,2-NVP 8 gave naphtho[2,1-f]quinoline (29) (13%),
and (E)-1,3-NVP 12 gave naphtho[1,2-h]quinoline (30)
(4%) and naphtho[2,1-f]isoquinoline (31) (51%)
(Scheme 3). The isomeric products 29–31 were identified
by NMR spectra, and melting-points were in accord with
literature values from alternative preparations.20–22 (E)-
1,4-NVP 16 gave a 55% yield of naphtho[1,2-h]isoquino-
line (32), not previously described and identified from its
NMR spectrum.
N
hν, air
18
36
Scheme 4 Photocyclodehydrogenation of 2-napththyl compounds
N
N
hν, air
22
37
hν, air
8
29
N
N
hν, air
N
+
12
16
hν, air
31
30
25
38
Scheme 5 Methylated photocyclodehydrogenation products
N
hν, air
32
ground-state rotamer proportions correlate directly with
product yields12 which will depend on the initial electro-
cyclization and also on subsequent processes, for example
those studied by Lewis et al. for 3-styrylpyridine.7 Elec-
trocyclization in the stilbene series occurs in the first ex-
cited singlet state and depends on the sums of the free
valency indices at the linking positions.24 Bazzini et al.
have shown the value of ab initio calculations in related
systems.16 Without access to detailed calculations on the
present cases, some general observations can be made
about the results. Each of the 1,2- and 1,4-NVP isomers 8
and 16 could give only one azaarene, and this was ob-
served, with a particularly good yield from 16 where cy-
clization is between the naphthalene 2-position and
pyridine 3-position from either rotamer. Only one rotamer
of 8 could cyclize because of the nitrogen location, and a
poor yield was obtained. 1,3-NVP 12 gave the two prod-
ucts formally derived from the two rotamers around the C-
pyridine bond; the highest yield was 31, with cyclization
Scheme 3 Photocyclodehydrogenation of 1-napththyl compounds
The 2-naphthyl series behaved similarly. (E)-2,2-NVP 10
gave naphtho[1,2-f]quinoline (33) (10%), and (E)-2,3-
NVP 14 gave naphtho[2,1-h]quinoline (34) (2%) and
naphtho[1,2-f]isoquinoline (35) (28%), all previously pre-
pared by other routes.11,20,21,23 2,4-NVP 18 gave a 20%
yield of naphtho[2,1-h]isoquinoline (36), not previously
described (Scheme 4). All cases also gave insoluble poly-
meric material of unknown structure, in line with observa-
tions in previous related work,3,6,9 as well as a number of
by-products without the UV absorption indicative of tet-
racyclic aromatics.
Irradiation of the naphthylpropenylpyridines 22 and 25
proceeded similarly. Methyl derivatives 37 and 38 of the
expected tetracycles were obtained, but in lower yields
and were more difficult to purify (Scheme 5).
Each of the (naphthylvinyl)pyridines can exist as a num- to the pyridine 4-position rather than 2-position. This par-
ber of rotamers which could give rise to different cycliza- allels the tendency of 3-styrylpyridine to give predomi-
tion products, although it should not be expected that nantly benzo[h]isoquinoline (4) rather than the isomer
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

PAPER
Polycyclic Azaarenes by Photochemical Cyclodehydrogenation Route
2167
5.3,4,7 The 2-naphthyl series has additional possibilities be- appears to be disfavored, and ‘bent’ annulated products
cause cyclization could be to the naphthalene 1-position are formed rather than the ‘linear’ isomers, complementa-
forming ‘bent’ annulated products, or to the 3-position ry to a thermal route which appears to be controlled by
leading to ‘linear’ annulation. In practice, only the former steric considerations leading to ‘linear’ annulation.1 Some
was observed, and the results followed the pattern seen for of the azaarenes prepared have not to our knowledge been
the 1-naphthyl series, namely that cyclization of the 2,4- characterized previously and we have recorded 1H and 13C
NVP 18 was more effective than for 2,2-NVP 10, and the spectra for all under standard conditions as reference in-
2,3-NVP gave predominantly 35, cyclized on to the pyri- formation, with assignments established by 2D methods
dine 4-position rather than the 2-position. Cyclization ad- and NOE where appropriate.
jacent to the nitrogen atom appears to be generally
disfavored.
The efficient preparation of (2-arylvinyl)pyridines from
methylated starting materials is expected to be generally
Irradiation of the 2- and 3-pyridine isomers of (E)-[2-(3- applicable to other compounds. It may be advantageous
phenanthryl)vinyl]pyridine 26 and 27 in toluene or ben- over the Wittig reaction used by others16,18 as that requires
zene as for the naphthyl compounds gave complete con- a halomethyl starting material.
version to polymeric material of unknown structure.
Noting that some arylvinylpyrenes cyclize in presence of
Caution: Where information is available, aza-arenes in general are
less potent as mutagens and carcinogens than the isosteric parent
iodine, but not oxygen,25 an attempt was made with the
present phenanthryl compounds 26 and 27, but no penta-
cyclic product was identified. The analogous 4-pyridine
compound 28 behaved quite differently, rapidly giving
new UV absorption which was not as expected for the
aza[5]helicene 39 (Scheme 6). The product was character-
ized as the fully dehydrogenated pyreno[1,10,9-hij]iso-
quinoline (40), presumably derived from an initial
azahelicene which then undergoes a subsequent cycliza-
tion despite the final bond formation adjacent to nitrogen.
An easy formation of 39 would accord with the observa-
tions in the naphthalene series where cyclization of the 4-
pyridine compounds is relatively easy. Since our work
was competed, Bazzini et al. have reported formation of
40 from 7-[2-(2-naphthyl)vinyl]isoquinoline, though sev-
eral other isomers of this gave the expected azaheli-
cenes.16 The same authors have very recently reported the
cyclization of 3-[(2-(3-phenanthryl)vinyl]pyridine using
benzene as solvent,18 so our failure with this may be due
to interfering reactions involving the toluene solvent.
carbocycles. Nevertheless, precautions should be taken with these
compounds. The experiments described were carried out on small
scales in a well ventilated fume cupboard and all residues and waste
disposed of as potentially hazardous material. Benzene was used in
some cases where toluene failed, requiring appropriate precautions
for use and disposal.
Melting points were determined on a Reichert hot stage apparatus.
IR spectra were recorded in Nujol mulls on a PerkinElmer 1600
FTIR spectrometer. UV spectra were determined in Analar (AR)
EtOH on a PerkinElmer Lambda 2 spectrophotometer. Microanaly-
ses were performed on a PerkinElmer 240C Elemental Analyzer.
Mass spectra at low resolution were measured with a Varian CH5-
D or a Fisons VG Platform II spectrometer using electron impact
ionization. Accurate mass values were determined by the EPSRC
Mass spectrometry service (Swansea) on a VG ZAB spectrometer.
NMR spectra were recorded at 20 °C on Bruker WM360 and
AMX360 instruments at 360 MHz for 1H and 90 MHz for 13C (with
Waltz-16 1H decoupling or by DEPT-135), using sample concentra-
tions of approximately 0.06 M. Chemical shifts are quoted relative
to TMS (d = 0). Correlations were determined from COSY-45,
HETCOR and HMQC using 256 sets of 1024 data points. Nuclear
Overhauser enhancements (NOE) were determined by the differ-
ence method using 12 repetitions of 8 ‘irradiated’ and 8 ‘blank’
pulses, the summed FIDs subtracted and Fourier-transformed after
line-broadening of 1 Hz. Bruker DISNMR and UXNMR software
was used throughout. TLC was carried out on Merck silica gel 60
F
254. Flash chromatography was carried out using Fisons matrix sil-
ica gel 60, 35–70 micron.
N
39
PE refers to petroleum ether of boiling range 40–60 °C. Et2O was
dried over sodium wire. Toluene was dried by azeotropic distilla-
tion. N2 was passed through CaCl2 and silica gel. 1-Naphthalde-
hyde, 2-naphthaldehyde, 1-acetylnaphthalene, and pyridine-3-
acetic acid were commercially available (Aldrich). Phenanthrene-3-
carbaldehyde was prepared as previously described.1
hν, air
28
N
40
Photoreactions were carried out in a Photophysics RQ400 immer-
sion-well reactor model 3140, using UV radiation (l = 365–366
nm) from a Photophysics 400 W medium pressure mercury lamp
with a borosilicate filter. The Pyrex vessel was water-cooled, and
Scheme 6 Photocyclodehydrogenation of 28
This work has confirmed that photocyclodehydrogenation equipped with gas inlet and outlet.
can lead to a range of naphthoquinolines and naphthoiso-
2-(2-Arylvinyl)pyridines and 4-(2-Arylvinyl)pyridines; General
quinolines. Yields are generally acceptable, though limit-
ed by concomitant polymerization, and quantities are
limited by the nature of the photochemistry. The method
generally gives better yields of fused isoquinolines than
quinolines. Closure on to a position adjacent to nitrogen
Procedure A
The following procedure was modified from literature,11 and shows
typical quantities.
The naphthaldehyde (7.80 g, 0.05 mol) and 2- or 4-picoline (4.65 g,
0.05 mol) were refluxed in propionic anhydride (45.5 g, 0.35 mol)
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

2168
M. J. E. Hewlins, R. Salter
PAPER
for 48 h. The black mixture was quenched with H2O (90 mL) and
neutralized with NaOH soln. The tar-like mixture was extracted
with CHCl3 (3 × 50 mL), the extract washed with aq sat. soln of
NaHSO3 (2 × 150 mL), dried (K2CO3), the solvent removed by
evaporation, and the black crude product purified as detailed below.
1H NMR (CDCl3): d = 8.32 (d, J = 5 Hz, 2 H, H-2,6), 8.01 (dd,
J = 8, 2 Hz, 1 H, H-8¢¢), 7.89 (dd, J = 8, 1 Hz, 1 H, H-5¢¢), 7.82 (d,
J = 8 Hz, 1 H, H-4¢¢), 7.52 (m, 2 H, H-6¢¢,7¢¢), 7.35 (t, J = 8 Hz, 1 H,
H-3¢¢), 7.29 (dd, J = 8, 2 Hz, 1 H, H-2¢¢), 7.29 (d, J = 12 Hz, 1 H, H-
2¢), 6.92 (d, J = 5 Hz, 2 H, H-3,5), 6.77 (d, J = 12 Hz, 1 H, H-1¢).
MS (EI): m/z (%) = 231 (27, [M+]), 152, 115 (100), 101, 88, 75.
(E)- and (Z)-2-[2-(1-Naphthyl)vinyl]pyridines (8 and 9)
From 1-naphthaldehyde and 2-picoline. Distillation (bp 128–
184 °C/0.02 mm Hg) and dry flash column chromatography (PE–
EtOAc) gave 8 and 9.
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.28; H, 5.76; N, 6.13.
(ii) (E)-4-[2-(1-Naphthyl)vinyl]pyridine (16)
Crude solid; yield: 6.42 g (28%); off-white crystals (toluene–PE,
(i) (E)-2-[2-(1-Naphthyl)vinyl]pyridine (8)
Off-white solid; yield: 3.23 g (28%); mp 38–40 °C (Lit.11 mp 39–
40 °C).
1H NMR (CDCl3): d = 8.68 (dt, J = 5, 1 Hz, 1 H, H-6), 8.43 (d,
J = 16 Hz, 1 H, H-2¢), 8.32 (d, J = 8 Hz, 1 H, H-8¢¢), 7.87 (dd,
J = 7.5, 2 Hz, 1 H, H-5¢¢), 7.84–7.82 (2 d, each J = 8 Hz, each 1 H,
H-2¢¢,4¢¢), 7.71 (td, J = 8, 2 Hz, 1 H, H-4), 7.58–7.47 (m, 4 H, H-
3,3¢¢,6¢¢,7¢¢), 7.24 (d, J = 16 Hz, 1 H, H-1¢), 7.20 (dd, J = 8, 5 Hz, 1
H, H-5).
1:1); mp 83–84 °C (Lit.11 mp 82–83 °C).
1H NMR (CDCl3): d = 8.62 (d, J = 5 Hz, 2 H, H-2,6), 8.18 (dd,
J = 8, 1 Hz, 1 H, H-8¢¢), 8.09 (d, J = 16 Hz, 1 H, H-2¢), 7.88 (dd,
J = 8, 1 Hz, 1 H, H-5¢¢), 7.85 (d, J = 8 Hz, 1 H, H-4¢¢), 7.76 (d, J = 8
Hz, 1 H, H-2¢¢), 7.57 (td, J = 8, 1 Hz, 1 H, H-7¢¢), 7.52 (td, J = 8, 1
Hz, 1 H, H-6¢¢), 7.50 (t, J = 8 Hz, 1 H, H-3¢¢), 7.43 (d, J = 5 Hz, 2 H,
H-3,5), 7.06 (d, J = 16 Hz, 1 H, H-1¢).
MS (EI): m/z (%) = 232 (44, [M + 1]+), 231, 230 (100), 202, 153,
101, 88.
MS (EI): m/z (%) = 232 (10, [M + 1]+), 231, 230 (100), 229, 152,
115, 78.
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.42; H, 5.84; N, 6.16.
Anal. Calcd for C17H13N: C, 88.28; H, 5.67; N, 6.06. Found: C,
88.09; H, 5.49; N, 5.78.
(E)-4-[2-(2-Naphthyl)vinyl]pyridine (18)
From 2-naphthaldehyde (15.6 g, 0.1 mol) and 4-picoline (9.5 g, 0.1
mol) in Ac2O (72 g, 0.7 mol). Distillation (bp 200–210 °C/0.01 mm
Hg) gave a yellow solid consisting of 18 (8.90 g, 39%) with a trace
of its Z-isomer 19. Recrystallization (toluene–PE, 1:1) gave pure
18; light yellow solid; mp 164–166 °C (Lit.11 mp 158–160 °C).
1H NMR (CDCl3): d = 8.60 (d, J = 6 Hz, 2 H, H-2,6), 7.91 (s, 1 H,
H-1¢¢), 7.86–7.82 (m, 3 H, H-4¢¢,5¢¢,8¢¢), 7.75 (dd, J = 9, 2 Hz, 1 H,
H-3¢¢), 7.52–7.46 (m, 2 H, H-6¢¢,7¢¢), 7.47 (d, J = 16 Hz, 1 H, H-2¢),
7.41 (d, J = 6 Hz, 2 H, H-3,5), 7.14 (d, J = 16 Hz, 1 H, H-1¢¢).
(ii) (Z)-2-[2-(1-Naphthyl)vinyl]pyridine (9)
Colorless oil; yield: 0.17 g (1%).
1H NMR (CDCl3): d = 8.54 (d, J = 5 Hz, 1 H, H-6), 8.06 (dd, J = 8,
1 Hz, 1 H, H-8¢¢), 7.87 (dd, J = 8, 1 Hz, 1 H, H-5¢¢), 7.79 (dd, J = 8,
3 Hz, 1 H, H-4¢¢), 7.49 (m, 2 H, H-6¢¢,7¢¢), 7.35 (t, J = 8 Hz, 1 H, H-
3¢¢), 7.35 (d, J = 8 Hz, 1 H, H-2¢¢), 7.30 (d, J = 12 Hz, 1 H, H-2¢),
7.18 (td, J = 8, 1 Hz, 1 H, H-4), 6.99 (d, J = 12 Hz, 1 H, H-1¢), 6.97
(dd, J = 8, 5 Hz, 1 H, H-5), 6.79 (d, J = 8 Hz, 1 H, H-3).
MS (EI): m/z (%) = 232 (25, [M + 1]+), 231, 230 (100), 202, 152,
115, 78.
MS (EI): m/z (%) = 232 (44, [M + 1]+), 231, 230, 202, 101, 63, 51
(100).
Anal. Calcd for C17H13N: C, 88.28; H, 5.67; N, 6.06. Found: C,
87.99; H, 5.97; N, 6.31.
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.13; H, 5.83; N, 6.02.
(E)-2-[2-(2-Naphthyl)vinyl]pyridine (10)
(Z)- and (E)-4-[2-(3-Phenanthryl)vinyl]pyridine (28)
From 2-naphthaldehyde (9.90 g, 0.063 mol) and 2-picoline (5.90 g,
0.063 mol) in propionic anhydride (57 g, 0.441 mol). Distillation
(bp 119–210 °C/0.001 mm Hg) followed by dry flash column chro-
matography (PE–EtOAc) gave 2-naphthaldehyde followed by 10;
crude yield: 4.35 g (30%); pure as off-white crystals (toluene–PE,
1:3); mp 127–128 °C (Lit.11 mp 123–124 °C).
1H NMR (CDCl3): d = 8.64 (dd, J = 5, 2 Hz, 1 H, H-6), 7.95 (br s, 1
H, H-1¢¢), 7.87– 7.78 (m, 4 H, H-3¢¢,4¢¢,5¢¢,8¢¢), 7.80 (d, J = 16 Hz, 1
H, H-2¢), 7.69 (td, J = 8, 2 Hz, 1 H, H-4), 7.48 (m, 2 H, H-6¢¢,7¢¢),
7.44 (d, J = 8 Hz, 1 H, H-3), 7.17 (d, J = 16 Hz, 1 H, H-1¢), 7.17
(ddd, J = 8, 5,1 Hz, 1 H, H-5).
From phenanthrene-3-carbaldehyde (2.32 g, 0.0113 mol) and 4-pi-
coline (1.05 g, 0.0113 mol) in Ac2O (8.04 g, 0.079 mol). Distillation
(bp 240 °C/0.1 mm Hg), followed by dry flash column chromato-
graphy (PE–EtOAc) separated the E- and Z-products.
(i) (Z)-4-[2-(3-Phenanthryl)vinyl]pyridine
Oily solid; yield: 0.04 g (1%).
1H NMR (CDCl3): d = 8.58 (br s, 1 H, H-4¢¢), 8.47 (br s, 2 H, H-2,6),
8.41 (dd, J = 7, 2 Hz, 1 H, H-5¢¢), 7.86 (dd, J = 7, 2 Hz, 1 H, H-8¢¢),
7.74 (d, J = 8 Hz, 1 H, H-1¢¢), 7.71 (AB system, J = 5 Hz, 2 H, H-
9¢¢,10¢¢), 7.63–7.56 (m, 2 H, H-6¢¢,7¢¢), 7.42 (dd, J = 8, 1 Hz, 1 H, H-
2¢¢), 7.20 (d, J = 5.5 Hz, 2 H, H-3,5), 7.04 (d, J = 12 Hz, 1 H, H-2¢),
6.63 (d, J = 12 Hz, 1 H, H-1¢).
MS (EI): m/z (%) = 232 (12, [M + 1]+), 231, 230 (100), 79, 78, 52,
51.
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.12; H, 5.88; N, 5.88.
(ii) (E)-4-[2-(3-Phenanthryl)vinyl]pyridine (28)
Yellow solid; yield: 0.42 g (13%); mp 138–141 °C.
(E)- and (Z)-4-[2-(1-Naphthyl)vinyl]pyridines (16 and 17)
From 1-naphthaldehyde (15.6 g, 0.1 mol) and 4-picoline (9.5 g, 0.1
mol) in Ac2O (72 g, 0.7 mol). Distillation (bp 180–238 °C/0.08 mm
Hg) followed by column chromatography (PE–EtOAc) gave 16 and
17.
1H NMR (CDCl3): d = 8.74 (br s, 1 H, H-4¢¢), 8.73 (d, J = 8 Hz, 1
H, H-5¢¢), 8.61 (d, J = 6 Hz, 2 H, H-2,6), 7.90 (dd, J = 8, 1 Hz, 1 H,
H-8¢¢), 7.89 (d, J = 8 Hz, 1 H, H-1¢¢), 7.83 (dd, J = 8, 2 Hz, 1 H, H-
2¢¢), 7.74 (AB system, J = 5 Hz, 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¢¢), 7.56 (d, J = 16 Hz,
1 H, H-2¢¢), 7.43 (d, J = 6 Hz, 2 H, H-3,5), 7.19 (d, J = 16 Hz, 1 H,
H-1¢¢).
(i) (Z)-4-[2-(1-Naphthyl)vinyl]pyridine (17)
Colorless oil; yield: 2.80 g (12%).
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

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Polycyclic Azaarenes by Photochemical Cyclodehydrogenation Route
2169
3-(2-Arylvinyl)pyridines; General Procedure B
MS (EI): m/z (%) = 232 (26, [M + 1]+), 231, 114, 100, 75, 62, 51
(100).
This procedure was modified from the literature.11
Sodium pyridine-3-acetate (4.15 g, 0.026 mol) and the naphthalde-
hyde (4.10 g, 0.026 mol) were heated under reflux in Ac2O (19.5 g,
0.184 mol) for 24 h. The black tar-like mixture was poured into H2O
(50 mL) and the two immiscible phases left for 72 h. The H2O-im-
miscible material was refluxed in NaOH soln (3 M, 50 mL) for 2 h,
cooled, neutralized with HCl (3 M) and the resulting brown solid
was collected by filtration and dried (P2O5). This crude substituted
acrylic acid was added in small portions to a preheated (230 °C)
suspension of copper chromite (1 g) in quinoline (50 mL) maintain-
ing the temperature above 225 °C. The mixture was refluxed for a
further 2 h, and then distilled under reduced pressure.
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.10; H, 5.60; N, 6.23.
(ii) (E)-3-[2-(2-Naphthyl)vinyl]pyridine (14)
White solid; crude yield: 0.48 g (7%); white crystals (toluene–PE,
1:2); mp 114–116 °C (Lit.11 mp 118–119 °C).
1H NMR (CDCl3): d = 8.79 (br s, 1 H, H-2), 8.52 (d, J = 5 Hz, 1 H,
H-6), 7.90–7.81 (m, 4 H, H-4,4¢¢,5¢¢,8¢¢), 7.84 (br s, 1 H, H-1¢¢), 7.74
(dd, J = 8, 1 Hz, 1 H, H-3¢¢), 7.52–7.45 (m, 2 H, H-6¢¢,7¢¢), 7.33 (d,
J = 16 Hz, 1 H, H-2¢), 7.31 (dd, J = 8, 5 Hz, 1 H, H-5), 7.19 (d,
J = 16 Hz, 1 H, H-1¢).
MS (EI): m/z (%) = 232 (22, [M + 1]+), 231, 230, 114, 100, 87, 75
(100), 62.
(E)- and (Z)-3-[2-(1-Naphthyl)vinyl]pyridines (12 and 13)
From sodium pyridine-3-acetate (4.15 g, 0.026 mol) and 1-naph-
thaldehyde (4.10 g, 0.026 mol) in Ac2O (19.5 g, 0.184 mol). Distil-
lation gave 1-naphthaldehyde, followed by quinoline, then a
fraction (bp 160–190 °C/0.005 mm Hg) which was separated by
column chromatography (PE–EtOAc).
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.42; H, 5.62; N, 6.22.
(2-Arylvinyl)pyridines via Alcohols; General Procedure C
a) n-BuLi in hexane (2.5 M, 5.72 mL, 0.0143 mol) was added to a
stirred soln of freshly distilled diisopropylamine (1.70 mL, 0.013
mol) in anhyd THF (20 mL) at –5 °C under N2. After 30 min, the
soln was cooled to –78 °C and picoline (1.27 mL, 0.013 mol) was
added. The orange soln was warmed to –5 °C, maintained at this
temperature for 30 min, cooled to –78 °C and the aldehyde or ke-
tone (2.03 g, 0.013 mol) added. The mixture was warmed to r.t.,
stirred for 30 min, cooled to –5 °C and quenched with a 20% molar
excess of NH4Cl, resulting in two yellow layers. The THF layer was
separated and the solvent evaporated. The aqueous layer was ex-
tracted with CHCl3 (2 × 20 mL) and the combined extracts added to
the residue from the THF layer and the solvent removed. The result-
ing oil was dissolved in hot CHCl3 (20 mL) and the alcohol left to
crystallize overnight.
(i) (Z)-3-[2-(1-Naphthyl)vinyl]pyridine (13)
Colorless oil; yield: 1.04 g (17%).
1H NMR (CDCl3): d = 8.38 (d, J = 2 Hz, 1 H, H-2), 8.32 (dd, J = 5,
2 Hz, 1 H, H-6), 8.04 (dd, J = 8, 1 Hz, 1 H, H-8¢¢), 7.89 (dd, J = 8,
1 Hz, 1 H, H-5¢¢), 7.80 (d, J = 8 Hz, 1 H, H-4¢¢), 7.50 (m, 2 H, H-
6¢¢,7¢¢), 7.36 (t, J = 8 Hz, 1 H, H-3¢¢), 7.31 (dd, J = 8, 1 Hz, 1 H, H-
2¢¢), 7.25 (dt, J = 8, 2 Hz, 1 H, H-4), 7.21 (d, J = 12 Hz, 1 H, H-2¢),
6.94 (dd, J = 8, 5 Hz, 1 H, H-5), 6.82 (d, J = 12 Hz, 1 H, H-1¢).
MS (EI): m/z (%) = 232 (45, [M + 1]+), 231, 230, 99 (100), 75, 62,
51.
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.44; H, 5.88; N, 6.31.
b) This alcohol (0.008 mol) was added to a soln of concd H2SO4 (10
mL) in glacial AcOH (40 mL) and stirred for 12 h at r.t., or for 3 h
at reflux. The resulting yellow soln was poured into H2O (200 mL),
neutralized with NaOH soln and extracted into CHCl3 (3 × 100
mL). The combined extracts were dried (K2CO3), filtered, and the
solvent removed to leave a yellow oily-solid which was purified by
wet-flash column chromatography eluting with mixtures of PE and
EtOAc.
(ii) (E)-3-[2-(1-Naphthyl)vinyl]pyridine (12)
Colorless oil; yield: 1.52 g (25%).
1H NMR (CDCl3): d = 8.77 (d, J = 2 Hz, 1 H, H-2), 8.49 (dd, J = 5,
2 Hz, 1 H, H-6), 8.16 (br d, J = ca. 9 Hz, 1 H, H-8¢¢), 7.89 (d, J = 16
Hz, 1 H, H-2¢), 7.84 (dd, J = 8, 2 Hz, 1 H, H-4), 7.84 (dd, J = 8, 2
Hz, 1 H, H-5¢¢), 7.80 (d, J = 8 Hz, 1 H, H-2¢¢), 7.71 (d, J = 8 Hz, 1
H, H-4¢¢), 7.52 (td, J = 8, 2 Hz, 1 H, H-7¢¢), 7.51 (td, J = 8, 2 Hz, 1
H, H-6¢¢), 7.46 (t, J = 8 Hz, 1 H, H-3¢¢), 7.26 (dd, J = 8, 5 Hz, 1 H,
H-5), 7.05 (d, J = 16 Hz, 1 H, H-1¢).
(E)-4-[2-(1-Naphthyl)vinyl]pyridine (16)
a) From 4-picoline and 1-naphthaldehyde. The intermediate white
solid was filtered off and washed (PE), affording 1-(1-naphthyl)-2-
pyridin-4-ylethanol; colorless crystals; yield: 2.57 g (79%); mp
167–169 °C.
MS (EI): m/z (%) = 232 (18, [M + 1]+), 231, 230 (100), 115, 102,
101, 88.
Anal. Calcd for C17H13N: C, 88.28; H, 5.66; N, 6.06. Found: C,
88.04; H, 5.62; N, 5.94.
IR (Nujol): 3186 (OH), 1610 (CN) cm–1.
(E)- and (Z)-3-[2-(2-Naphthyl)vinyl]pyridines (14 and 15)
From sodium pyridine-3-acetate (4.92 g, 0.031 mol) and 2-naph-
thaldehyde (4.84 g, 0.031 mol) in Ac2O (22.13 g, 0.217 mol). Dis-
tillation gave quinoline, followed by 2-naphthaldehyde, then a
fraction (bp 110–180 °C/0.005 mm Hg) which was separated by
column chromatography (EtOAc–PE).
1H NMR (CDCl3): d = 8.45 (d, J = 6 Hz, 2 H, H-2¢¢,6¢¢), 8.12 (d,
J = 8 Hz, 1 H, H-8¢), 7.91 (dd, J = 8, 1 Hz, 1 H, H-5¢), 7.81 (d, J = 8
Hz, 1 H, H-2¢), 7.62 (d, J = 8 Hz, 1 H, H-4¢), 7.53 (2 td, J = 8, 1 Hz,
2 H, H-6¢,7¢), 7.47 (t, J = 8 Hz, 1 H, H-3¢), 7.17 (d, J = 6 Hz, 2 H,
H-3¢¢,5¢¢), 5.72 (dd, J = 8.5, 3.9 Hz, 1 H, CHCH2), 3.24 and 3.12
(AB of ABX system, JAB = 13.6, JAX = 3.9, JBX = 8.5 Hz, 2 H,
CHCH2).
(i) (Z)-3-[2-(2-Naphthyl)vinyl]pyridine (15)
Colorless oil; yield: 1.60 g (22%).
MS (EI): m/z (%) = 250 (5, [M + 1]+), 249, 157, 129, 128, 127, 93
(100).
1H NMR (CDCl3): d = 8.52 (d, J = 2 Hz, 1 H, H-2), 8.42 (dd, J = 5,
2 Hz, 1 H, H-6), 7.78 (dd, J = 8, 2 Hz, 1 H, H-8¢¢), 7.71 (dd, J = 8,
2 Hz, 1 H, H-5¢¢), 7.71 (br s, 1 H, H-1¢¢), 7.68 (d, J = 8 Hz, 1 H, H-
4¢¢), 7.53 (dt, J = 8, 1 Hz, 1 H, H-4), 7.47–7.42 (m, 2 H, H-6¢¢,7¢¢),
7.29 (dd, J = 8, 1 Hz, 1 H, H-3¢¢), 7.09 (dd, J = 8, 5 Hz, 1 H, H-5),
6.91 (d, J = 12 Hz, 1 H, H-2¢), 6.63 (d, J = 12 Hz, 1 H, H-1¢).
Anal. Calcd for C17H15NO: C, 81.89; H, 6.07; N, 5.62. Found: C,
81.70; H, 5.82; N, 5.51.
b) Dehydration of this alcohol (2 g, 0.008 mol) at r.t. gave exclu-
sively 16 as an off-white solid (1.54 g, 83%), identical to the mate-
rial prepared by the previous procedure.
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

2170
M. J. E. Hewlins, R. Salter
PAPER
(Z)- and (E)-4-[2-(1-Naphthyl)prop-1-en-1-yl]pyridine (22 and
23)
a) From 1-acetylnaphthalene (2.21 g, 1.98 mL, 0.013 mol) and 4-pi-
coline (1.27 mL, 0.013 mol). The intermediate white solid was fil-
tered off and washed with cold Et2O (2 × 5 mL), affording 2-(1-
naphthyl)-1-pyridin-4-ylpropan-2-ol (20); white solid; yield: 2.91 g
(91%); mp 165–167 °C.
1H NMR (CDCl3): d = 8.27 (br s, 2 H, H-2,6), 7.83 (m, 1 H, H-8¢¢),
7.77 (d, J = 9 Hz, 1 H, H-4¢¢), 7.76 (m, 1 H, H-5¢¢), 7.67 (br s, 1 H,
H-1¢¢), 7.50–7.46 (m, 2 H, H-6¢¢, 7¢¢), 7.24 (dd, J = 9, 2 Hz, 1 H, H-
3¢¢), 6.82 (d, J = 5.5 Hz, 2 H, H-3,5), 6.48 (d, J = 1.2 Hz, 1 H, H-
1¢), 2.33 (d, J = 1.2 Hz, 3 H, CH3).
MS (EI): m/z (%) = 246 (30, [M + 1]+), 245 (100), 244, 230, 128,
115.
IR (Nujol): 3226 (OH), 1603 (CN) cm–1.
UV (EtOH): lmax (e) = 302 (7550), 267 (15650), 223 nm (52020).
1H NMR (CDCl3): d = 8.89 (d, J = 9 Hz, 1 H, H-2¢¢), 8.33 (d, J = 6
Hz, 2 H, H-2¢,6¢), 7.91 (dd, J = 8, 2 Hz, 1 H, H-8¢¢), 7.79 (dd, J = 7,
2 Hz, 1 H, H-5¢¢), 7.57 (td, J = 8, 2 Hz, 1 H, H-6¢¢), 7.52 (td, J = 8,
2 Hz, 1 H, H-7¢¢), 7.36–7.30 (m, 2 H, H-3¢¢,4¢¢), 6.81 (d, J = 6 Hz, 2
H, H-3¢,5¢), 3.52 (d, J = 13 Hz, 1 H, CHAHB), 3.40 (d, J = 13 Hz, 1
H, CHAHB), 2.43 (s, 1 H, OH), 1.79 (s, 3 H, CH3).
Anal. Calcd for C18H15N: C, 88.13; H, 6.16; N, 5.71. Found: C,
87.91; H, 6.26; N, 5.60.
(ii) (E)-4-[2-(2-Naphthyl)prop-1-en-1-yl]pyridine (25)
Crude white solid; yield: 0.77 g (41%); pure as white crystals (tolu-
ene–PE, 1:3); mp 132–134 °C.
1H NMR (CDCl3): d = 8.62 (d, J = 6 Hz, 2 H, H-2,6), 7.95 (d, J = 2
Hz, 1 H, H-1¢¢), 7.89–7.84 (m, 3 H, H-4¢¢,5¢¢,8¢¢), 7.61 (dd, J = 9, 2
Hz, 1 H, H-3¢¢), 7.50 (m, 2 H, H-6¢¢, 7¢¢), 7.30 (d, J = 6 Hz, 2 H, H-
3,5), 6.88 (s, 1 H, H-1¢), 2.42 (s, 3 H, CH3).
MS (EI): m/z (%) = 263 (4, [M+]), 171, 127, 93, 65, 43 (100).
Anal. Calcd for C18H17NO: C, 82.09; H, 6.51; N, 5.32. Found: C,
81.76; H, 6.60; N, 5.30.
b) The alcohol 20 (2.10 g, 0.008 mol) was dehydrated by treatment
with acid for 3 h at reflux and the product was purified by chroma-
tography.
MS (EI): m/z (%) = 246 (22, [M + 1]+), 245 (100), 244, 230, 128,51.
UV (EtOH) : lmax (e) = 305 (20450), 276 (24490), 246 (13530), 227
nm (27430).
(i) (Z)-4-[2-(1-Naphthyl)prop-1-en-1-yl]pyridine (22)
Colorless solid; yield: 0.32 g (16%); mp 56.5–58 °C.
Anal. Calcd for C18H15N: C, 88.13; H, 6.16; N, 5.71. Found: C,
88.33; H, 6.02; N, 5.55.
1H NMR (CDCl3): d = 8.16 (d, J = 6 Hz, 2 H, H-2,6), 7.89 (dd,
J = 8, 1 Hz, 1 H, H-5¢¢), 7.83 (2 dd superimposed, each J = 8, 1 Hz,
each 1 H, H-4¢¢,8¢¢), 7.49 (td, J = 8, 1 Hz, 1 H, H-6¢¢), 7.46 (t obsc,
1 H, H-3¢¢), 7.42 (td, J = 8, 1 Hz, 1 H, H-7¢¢), 7.22 (dd, J = 7, 1 Hz,
1 H, H-2¢¢), 6.66 (d, J = 1.5 Hz, 1 H, H-1¢), 6.60 (d, J = 6 Hz, 2 H,
H-3,5), 2.33 (d, J = 1.5 Hz, 3 H, CH3).
(E)-2-[2-(3-Phenanthryl)vinyl]pyridine (26)
a) From 2-picoline (1.27 mL, 0.013 mol) and phenanthrene-3-car-
baldehyde (2.68 g, 0.013 mol). Removal of the solvent afforded al-
most pure 1-(3-phenanthryl)-2-pyridin-2-ylethanol; viscous yellow
oil; yield: 3.84 g (99%).
1H NMR (CDCl3): d = 8.75 (s, 1 H, H-4¢), 8.72 (d, J = 8 Hz, 1 H, H-
5¢), 8.58 (d, J = 5 Hz, 1 H, H-6¢¢), 7.88 (dd, J = 8, 1 Hz, 1 H, H-8¢¢),
7.87 (d, J = 8 Hz, 1 H, H-1¢), 7.72 (app s, 2 H, H-9¢, 10¢), 7.65 (dd,
J = 8, 1 Hz, 1 H, H-2¢), 7.65–7.55 (m, 3 H, H-6¢,7¢,4¢), 7.19 (dd,
J = 7, 5 Hz, 1 H, H-5¢¢), 7.13 (d, J = 7 Hz, 1 H, H-3¢¢), 5.99 (br s, 1
H, OH), 5.45 (dd, J = 7.5, 4.6 Hz, 1 H, CHCH2), 3.27 (AB of ABX
system, 2 H, CHCH2).
MS (EI): m/z (%) = 246 (30, [M + 1]+), 245 (100), 230, 152, 63, 51.
UV (EtOH): lmax (e) = 314 (1150), 295 (5870), 283 (9170), 272
(11920), 259 (14670), 223 nm (64190).
Anal. Calcd for C18H15N: C, 88.13; H, 6.16; N, 5.71. Found: C,
87.96; H, 6.34; N, 5.55.
(ii) This was followed by a mixture of 22 and the E-isomer 23
(0.87g, 45%) but a pure sample of 23 could not be obtained due to
very similar Rf values.
MS (EI): m/z (%) = 300 (35, [M + 1]+), 299, 178, 93 (100), 80, 65.
b) This alcohol (1.90 g, 0.0064 mol) was dehydrated by treatment
with acid at r.t. for 12 h to give exclusively 26; crude yellow solid;
yield: 1.13 g (63%); pure as bright yellow crystals (benzene, HAZ-
ARD); mp 118–120 °C.
1H NMR (CDCl3): d = 8.82 (s, 1 H, H-4¢¢), 8.72 (d, J = 8 Hz, 1 H,
H-5¢¢), 8.65 (dd, J = 5, 1 Hz, 1 H, H-6), 7.92 (d, J = 16 Hz, 1 H, H-
2¢¢), 7.89 (dd, J = 8, 1 Hz, 1 H, H-8¢¢), 7.88 (m, 2 H, H-1¢¢,2¢¢), 7.73
(app s, 2 H, H-9¢¢,10¢¢), 7.69 (td, J = 8, 2 Hz, 1 H, H-4), 7.68 (td,
J = 8, 1 Hz, 1 H, H-6¢¢), 7.61 (td, J = 8, 1 Hz, 1 H, H-7¢¢), 7.46 (d,
J = 8 Hz, 1 H, H-3), 7.37 (d, J = 16 Hz, 1 H, H-1¢), 7.18 (ddd, J = 8,
5, 1 Hz, 1 H, H-5).
(Z)- and (E)-4-[2-(2-Naphthyl)prop-1-en-1-yl]pyridine (24 and
25)
a) From 2-acetylnaphthalene (2.21 g, 0.013 mol) and 4-picoline
(1.27 mL, 0.013 mol). The intermediate white solid was filtered off
and washed with cold Et2O (2 × 5 mL) to give 2-(2-naphthyl)-1-py-
ridin-4-ylpropan-2-ol; white solid; yield: 2.10 g (61%); mp 161–
163 °C.
IR (Nujol): 3159 (OH), 1606 (CN) cm–1.
1H NMR (CDCl3): d = 8.35 (d, J = 6 Hz, 2 H, H-2¢,6¢), 7.82 (m, 2 H,
H-8¢¢ and ArH), 7.79–7.77 (m, 2 H, H-1¢¢ and ArH), 7.52 (dd, J = 9,
2 Hz, 1 H, H-3¢¢), 7.49–7.46 (m, 2 H, H-6¢¢, 7¢¢), 6.91 (d, J = 6 Hz,
2 H, H-3¢,5¢), 3.20 (d, J = 13.1 Hz, 1 H, CHAHB), 3.11 (d, J = 13.1
Hz, 1 H, CHAHB), 2.29 (br s, 1 H, OH), 1.68 (s, 3 H, CH3).
MS (EI): m/z (%) = 282 (21, [M + 1]+), 281, 280 (100), 140, 79, 78,
52.
UV (EtOH) : lmax (e) = 367 (12670), 350 (30920), 338 (38340), 269
(31430), 249 (33240), 241 (25340), 221 (13940), 203 nm (24840).
MS (EI): m/z (%) = 264 (50, [M + 1]+), 263, 171, 127, 93, 43 (100).
Anal. Calcd for C18H17NO: C, 82.10; H, 6.51; N, 5.32. Found: C,
82.29; H, 6.79; N, 5.23.
Anal. Calcd for C21H15N: C, 89.65; H, 5.37; N, 4.98. Found: C,
89.77; H, 5.42; N, 4.78.
b) This alcohol (2.0 g, 0.0076 mol) was dehydrated by treatment
with acid for 3 h at reflux. Chromatography gave 24 and 25.
(E)-3-[2-(3-Phenanthryl)vinyl]pyridine (27)
a) From 3-picoline (1.27 mL, 0.013 mol) and phenanthrene-3-car-
baldehyde (2.68 g, 0.013 mol). Removal of the solvent followed by
wet flash column chromatography (EtOAc–PE afforded 1-(3-
phenanthryl)-2-pyridin-3-ylethanol: yellow solid; yield: 1.90 g
(49%).
(i) (Z)-4-[2-(2-Naphthyl)prop-1-en-1-yl]pyridine (24)
Crude white solid; yield: 0.18 g (10%); pure as white crystals (tolu-
ene–hexane); mp 93–95 °C.
IR (Nujol): 3272 (OH), 1602 (CN) cm–1.
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

PAPER
Polycyclic Azaarenes by Photochemical Cyclodehydrogenation Route
2171
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),
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M. J. E. Hewlins, R. Salter
PAPER
8.08 (d, J = 9.0 Hz, 1 H, H-6), 8.03 (dd, J = 7.4, 1.4 Hz, 1 H, H-7),
7.92 (d, J = 9.0 Hz, 1 H, H-12), 7.72 (td, J = 7.4, 1.4 Hz, 1 H, H-9),
7.67 (td, J = 7.4, 1.4 Hz, 1 H, H-8), 7.55 (dd, J = 8.1, 4.3 Hz, 1 H,
H-2); NOE 8.25 → 7.92 (6%) and 7.55 (5%).
13C NMR (CDCl3): d = 149.3 (C-3), 146.2 (C-4a), 135.8 (C-1),
133.1, 130.3, 130.0, 129.75, 128.8 (C-7), 127.7 (C-6), 126.8 (C-8),
126.6 (C-9), 126.45, 125.8 (C-12), 123.1 (C-10), 122.3 (C-5), 122.1
(C-11), 121.6 (C-2).
Naphtho[1,2-f]quinoline (33)
Off-white solid; yield: 24 mg (10%); mp 104–107 °C (Lit.21,23mp
106–107 °C); one spot Rf = 0.49 (EtOAc–PE, 1:1).
1H NMR (CDCl3): d = 9.40 (br d, J = ca. 8.6 Hz, 1 H, H-1), 9.00
(dd, J = 4.2, 1.6 Hz, 1 H, H-3), 8.93 (br d, J = ca. 8.3 Hz, 1 H, H-
12), 8.17 (d, J = 8.7 Hz, 1 H, H-5), 8.08 (d, J = 8.7 Hz, 1 H, H-6),
8.06 (dd, J = 7.7, 1.7 Hz, 1 H, H-9), 7.96 (d, J = 8.5 Hz, 1 H, H-8),
7.87 (d, J = 8.5 Hz, 1 H, H-7), 7.72 (td, J = 7.7, 1.7 Hz, 1 H, H-11),
7.66 (td, J = 7.7, 1.7 Hz, 1 H, H-10), 7.58 (dd, J = 8.6, 4.2 Hz, 1 H,
H-2).
13C NMR (CDCl3): d = 148.9 (C-3), 148.8 (C-4a), 135.6 (C-1),
133.5, 130.85, 130.7 (C-6), 130.0, 128.8 (C-9), 128.6 (C-5), 128.25
(C-8), 127.3 (C-12), 126.8, 126.6 (C-11 and C-7 superimposed),
126.3 (C-10), 125.4, 120.35 (C-2).
MS (EI): m/z (%) = 230 (21, [M + 1]+), 229 (100), 228, 200, 114,
100.
UV (EtOH): lmax (e) = 361 (2510), 343 (2510), 296 (18460), 265
(67350), 235 (18070), 215 nm (28900).
Anal. Calcd for C17H11N: C, 89.05; H, 4.84; N, 6.11. Found: C,
89.09; H, 4.45; N, 5.71.
MS (EI): m/z (%) = 230 (47, [M + 1]+), 229 (100), 228, 201, 114,
100.
(ii) Two further by-products, followed by:
HRMS (EI): m/z [M]+ calcd for C17H11N: 229.0891; found:
229.0891.
Naphtho[2,1-f]isoquinoline (31)
Crude yield: 120 mg (51%); sublimed (160 °C/0.03 mm Hg) as a
pure white solid; mp 238–240 °C (Lit.22 mp 224–226 °C).
Photocyclization of (E)-2,3-NVP (14)
Chromatography gave five components.
1H NMR (CDCl3): d = 9.36 (s, 1 H, H-1), 8.83 (d, J = 9.1 Hz, 1 H,
H-11), 8.80 (br d, J = ca. 8 Hz, 1 H, H-10), 8.78 (d, J = 5.9 Hz, 1 H,
H-3), 8.64 (d, J = 9.0 Hz, 1 H, H-5), 8.49 (d, J = 5.9 Hz, 1 H, H-4),
8.09 (d, J = 9.1 Hz, 1 H, H-12), 8.06 (d, J = 9.0 Hz, 1 H, H-6), 8.03
(dd, J = 7.8, 1.5 Hz, 1 H, H-7), 7.76 (td, J = 7.8, 1.5 Hz, 1 H, H-9),
7.71 (td, J = 7.8, 1.5 Hz, 1 H, H-8); NOE 9.36 → 8.09 (8%).
13C NMR (CDCl3): d = 152.1 (C-1), 144.7 (C-3), 134.5, 133.0,
130.6, 130.1, 128.7 (C-7), 128.1 (C-6), 127.3 (C-8), 127.1 (C-9),
126.5, 125.5 (C-12), 123.4 (C-10), 122.7 (C-11), 120.7 (C-5), 116.3
(C-4).
(i) Naphtho[2,1-h]quinoline (34)
White solid; yield: 4 mg (2%); mp 89–94 °C (Lit.20 mp 95–96 °C);
one spot Rf = 0.80 (EtOAc–PE, 1:3).
1H NMR (CDCl3): d = 11.21 (br d, J = ca. 8.9 Hz, 1 H, H-12), 9.21
(dd, J = 4.2, 2.0 Hz, 1 H, H-2), 8.28 (dd, J = 8.1, 1.9 Hz, 1 H, H-4),
8.02 (d, J = 8.6 Hz, 1 H, H-8), 8.01 (dd, J = 7.8, 1.2 Hz, 1 H, H-9),
7.94 (d, J = 8.5 Hz, 1 H, H-6), 7.88 (d, J = 8.6 Hz, 1 H, H-7), 7.85
(d, J = 8.5 Hz, 1 H, H-5), 7.83 (td, J = 7.8, 1.2 Hz, 1 H, H-11), 7.67
(td, J = 7.8, 1.2 Hz, 1 H, H-10), 7.55 (dd, J = 8.1, 4.2 Hz, 1 H, H-
3); NOE 8.28 → 7.85 (4%) and 7.55 (3%).
MS (EI): m/z (%) = 230 (20, [M + 1]+), 229 (100), 228, 200, 114,
100, 57.
13C NMR (CDCl3): d = 148.4 (C-12c), 148.3 (C-2), 136.4 (C-4),
133.9, 133.6, 131.7, 130.7 (C-12), 129.8 (C-8), 128.6 (C-6), 126.85
(C-7), 128.4 (C-9), 127.8, 127.3 (C-11), 126.55 (C-5), 126.4, 126.2
(C-10), 120.5 (C-3).
MS (EI): m/z (%) = 230 (71, [M + 1]+), 229 (100), 228, 114, 100,
83, 74, 50.
Anal. Calcd for C17H11N: C, 89.06; H, 4.84; N, 6.11. Found: C,
89.16; H, 5.11; N, 6.58.
Photocyclization of (E)-1,4-NVP (16); Naphtho[1,2-h]isoquino-
line (32)
Chromatography gave a small amount of the Z-isomer 17 followed
by 32; crude yield: 126 mg (55%); sublimed (160 °C/0.03 mm Hg)
as a pure white solid; mp 193–195 °C.
1H NMR (CDCl3): d = 10.13 (s, 1 H, H-4), 8.87 (d, J = 9.1, 1 H, H-
11), 8.76 (d, J = 9.1 Hz, 1 H, H-5), 8.72 (br d, J = ca. 8.4 Hz, 1 H,
H-10), 8.71 (d, J = 5.4 Hz, 1 H, H-2), 8.06 (d, J = 9.1 Hz, 1 H, H-
6), 8.00 (dd, J = 7.8, 1.2 Hz, 1 H, H-7), 7.91 (d, J = 9.1 Hz, 1 H, H-
12), 7.77 (d, J = 5.4 Hz, 1 H, H-1), 7.73 (td, J = 7.8, 1.2 Hz, 1 H, H-
9), 7.66 (td, J = 7.8, 1.2 Hz, 1 H, H-8); NOE 10.13 → 8.76 (23%).
13C NMR (CDCl3): d = 147.6 (C-4), 144.3 (C-2), 135.4, 132.3,
130.2, 128.8 (C-6), 128.7 (C-7), 128.6, 127.7, 127.1 (C-9), 126.8
(C-8), 125.8 (C-11), 125.2, 125.2 (C-12), 122.8 (C-10), 120.8 (C-1),
119.9 (C-5).
HRMS (EI): m/z [M]+ calcd for C17H11N: 229.0891; found:
229.0891.
(ii) three by-products, followed by:
Naphtho[1,2-f]isoquinoline (35)
Colorless crystals; yield: 65 mg (28%); mp 82–84 °C (Lit.12 mp 79–
80 °C); one spot Rf = 0.32 (EtOAc–PE, 1:1).
1H NMR (CDCl3): d = 9.38 (s, 1 H, H-4), 9.08 (br d, J = ca. 8.4 Hz,
1 H, H-12), 8.91 (br d, J = ca. 6.1 Hz, 1 H, H-1), 8.74 (d, J = 6.1 Hz,
1 H, H-2), 8.05 (dd, J = 7.8, 1.3 Hz, 1 H, H-9), 8.00 (d, J = 8.5 Hz,
1 H, H-8), 7.98 (d, J = 8.5 Hz, 1 H, H-5), 7.93 (d, J = 8.5 Hz, 1 H,
H-6), 7.84 (d, J = 8.5 Hz, 1 H, H-7), 7.74 (td, J = 7.8, 1.3 Hz, 1 H,
H-11), 7.67 (td, J = 7.8, 1.3 Hz, 1 H, H-10); NOE 9.38 → 7.98 (7%).
13C NMR (CDCl3): d = 152.2 (C-4), 144.1 (C-2), 134.1, 133.4,
133.4, 130.3, 129.7 (C-8), 128.9 (C-9), 128.5 (C-6), 128.2, 127.1
(C-12), 126.95 (C-11), 126.7 (C-7), 126.45 (C-10), 126.00 (C-5),
125.45, 120.5 (C-1).
MS (EI): m/z (%) = 230 (40, [M + 1]+, 229 (100), 228, 200, 114,
100.
UV (EtOH): lmax (e) = 359 (4000), 350 (3180), 342 (5180), 321
(9000), 286 (14990), 264 (72720), 256 (54980), 239 (25630), 220
nm (24990).
MS (EI): m/z (%) = 230 (21, [M + 1]+), 229 (100), 228, 200, 100,
87, 74, 63.
Anal. Calcd for C17H11N: C, 89.06; H, 4.84; N, 6.11. Found: C,
89.20; H, 4.70; N, 6.17.
HRMS (EI): m/z [M]+ calcd for C17H11N: 229.0891; found:
229.0891.
Photocyclization of (E)-2,2-NVP (10)
Chromatography gave three unidentified by-products followed by:
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

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Polycyclic Azaarenes by Photochemical Cyclodehydrogenation Route
2173
Photocyclization of (E)-2,4-NVP (18); Naphtho[2,1-h]isoquino-
line (36)
H-4), 7.70 (s, 1 H, H-5), 7.69 (td, J = 7.7, 1.4 Hz, 1 H, H-10), 2.87
(s, 3 H, CH3); NOE 2.87 → 7.70 (3%) and 8.08 (5%).
Chromatography gave two by-products followed by 36; light-yel-
low crystals; yield: 45 mg (20%); mp 85–87 °C; one spot Rf = 0.46
(EtOAc–PE, 1:1).
1H NMR (CDCl3): d = 10.41 (s, 1 H, H-1), 9.09 (br d, J = ca. 8.4 Hz,
1 H, H-12), 8.70 (d, J = 5.5 Hz, 1 H, H-3), 8.06 (dd, J = 7.5, 1.3 Hz,
1 H, H-9), 8.04 (d, J = 8.5 Hz, 1 H, H-6), 7.97 (d, J = 8.5 Hz, 1 H,
H-8), 7.85 (2 d, each J = 8.5 Hz, 2 H, H-5,7), 7.83 (d, J = 5.5 Hz, 1
H, H-4), 7.76 (td, J = 7.5, 1.3 Hz, 1 H, H-11), 7.69 (td, J = 7.5, 1.3
Hz, 1 H, H-10).
13C NMR (CDCl3): d = 150.8 (C-1), 143.6 (C-3), 137.7, 136.4,
133.3, 131.1, 129.4, 128.6 (C-12), 128.4 (C-9), 128.1 (C-8), 127.1,
126.7 (C-11), 126.6 (C-10), 125.4 (C-5), 124.7, 122.2 (C-7), 120.0
(C-4), 20.7 (CH3).
MS (EI): m/z (%) = 244 (56, [M + 1]+), 243 (100), 228, 215, 121,
114.
HRMS (EI): m/z [M]+ calcd for C18H13N: 243.1048; found:
243.1048.
13C NMR (CDCl3): d = 150.7 (C-1), 143.4 (C-3), 136.6, 133.75,
131.5 (C-6), 131.4, 129.3, 128.7 (C-9), 128.4 (C-8), 128.1 (C-12),
126.95 (C-11), 126.8, 126.7 (C-10), 126.5 and 125.4 (C-5 and C-7),
125.5, 120.9 (C-4).
MS (EI): m/z (%) = 230 (30, [M + 1]+), 229 (100), 227, 200, 114,
100.
UV (EtOH): lmax (e) = 376 (1150), 356 (1250), 318 (8250), 294
(23690), 283 (38050), 250 (14600), 220 nm (34910).
The next component eluted was unreacted starting material fol-
lowed by polymeric ‘baseline’ material.
Attempted Photocyclizations of (E)-2- and (E)-3-[2-(3-Phenan-
thryl)vinyl]pyridines (26 and 27)
HRMS (EI): m/z [M]+ calcd for C17H11N: 229.0891; found:
229.0891.
From 26 or 27 (281 mg, 1.0 mmol) in toluene (450 mL) irradiating
for 18 h. The solvent was removed from the yellow soln affording a
brown oily solid for which TLC revealed one ‘baseline spot’ of high
molecular weight, and which gave an envelope of broadened signals
in the 1H NMR spectrum. Similar results were found with I2 in place
of aeration.
UV (EtOH): lmax (e) = 375 (1320), 356 (1800), 316 (11380), 294
(33100), 280 (49990), 242 (22030), 216 (42500), 201 nm (32650).
Photocyclization of (Z)-4-[2-(1-Naphthyl)prop-1-en-1-yl]pyri-
dine (22); 11-Methylnaphtho[1,2-h]isoquinoline (37)
From 22 (245 mg, 1 mmol) in anhyd toluene (250 mL) irradiating
for 24 h. Chromatography gave two minor by-products, followed by
starting material and its E-isomer, and then 37; cream-colored waxy
solid; yield: 25 mg (10%); one spot Rf = 0.32 (EtOAc–PE, 1:1). Re-
peated attempts at purification by column chromatography did not
give a sharp-melting-point material.
1H NMR (CDCl3): d = 10.07 (s, 1 H, H-4), 8.91 (m, 1 H, H-10), 8.78
(d, J = 9.0 Hz, 1 H, H-5), 8.66 (d, J = 5.5 Hz, 1 H, H-2), 8.04 (d,
J = 9.0 Hz, 1 H, H-6), 8.02 (m, 1 H, H-7), 7.75 (s, 1 H, H-12), 7.68
(d, J = 5.5 Hz, 1 H, H-1), 7.67–7.65 (m, 2 H, H-8 and H-9), 3.22 (s,
3 H, CH3).
13C NMR (CDCl3): d = 147.3 (C-4), 143.7 (C-2), 138.9, 134.8,
133.5, 131.3, 129.45, 129.1 and 128.8 (C-6 and C-7), 128.3 (C-12),
128.2, 127.4 (C-10), 126.3 and 125.9 (C-8 and C-9), 124.5, 120.4
(C-5), 119.9 (C-1), 28.0 (CH3).
MS (EI): m/z (%) = 244 (25, [M + 1]+), 243 (100), 242, 241, 213,
189, 121.
Photocyclization of (E)-4-[2-(3-Phenanthryl)vinyl]pyridine
(28); Pyreno[1,10,9-hij]isoquinoline (40)
From 28 (253 mg, 0.9 mmol) in toluene (450 mL) irradiating for 2
h. The yellow precipitate was filtered off, the filtrate evaporated and
the resulting brown oily solid was purified by wet flash column
chromatography (PE–EtOAc) to give the photocyclized product 40
as a bright yellow solid followed by starting material, its Z-isomer,
and ‘baseline’ polymeric material; yellow needles (toluene); yield:
110 mg (44%); mp 291–292 °C; one spot Rf = 0.79 (EtOAc–PE,
1:1).
1H NMR (CDCl3): d = 9.50 (d, J = 7.8 Hz, 1 H, H-8), 9.08 (d,
J = 5.3 Hz, 1 H, H-6), 8.25 (dd, J = 7.7, 1.0 Hz, 1 H, H-10), 8.16 and
8.18 (AB system, J = 8.3 Hz, 2 H, H-1,2), 8.11 (d, J = 8.8 Hz, 1 H,
H-3), 8.05 (t, J = 7.8 Hz, 1 H, H-9), 8.03 and 7.98 (2d, J = 8.8 Hz,
2 H, H-11,12), 7.85 (d, J = 8.8 Hz, 1 H, H-4), 7.85 (d, J = 5.3 Hz, 1
H, H-5); NOE 7.85 → 8.11 (2%) and 9.08 (4%).
13C NMR (CDCl3): d = 149.1 (C-7a), 145.3 (C-6), 136.2, 131.5 (C-
3), 131.2, 130.45, 130.1, 128.5 (C-10), 128.1 and 126.7 (C-12 and
C-11), 126.5 (C-9), 126.0, 125.85 (C-1 and C-2), 124.8 (C-4), 123.6
(C-8), 122.95, 122.35, 120.2, 118.8 (C-5).
HRMS (EI): m/z [M]+ calcd for C18H13N: 243.1048; found:
243.1048.
MS (EI): m/z (%) = 278 (36, [M + 1]+), 277, 248, 83, 71, 69, 57
(100).
UV (EtOH): lmax (e) = 365 (100), 347 (470), 326 (1130), 267
(27270), 260 (22290), 221 nm (12110).
HRMS (EI): m/z [M]+ calcd for C21H11N: 277.0891; found:
277.0891.
Photocyclization of (E)-4-[2-(2-Naphthyl)prop-1-en-1-yl]pyri-
dine (25); 6-Methylnaphtho[2,1-h]isoquinoline (38)
From 25 (245 mg, 1.0 mmol) in anhyd benzene (HAZARD, 110
mL) irradiating for 48 h. Chromatography gave first an unidentified
colorless oil (1.84 g). Gradual elution (to EtOAc–PE, 1:4) gave pure
Z-isomer of the starting material followed by a mixture of this and
38, followed by 38; colorless oily solid; yield after a second column
chromatography: 47 mg (19%); pure by 1H NMR, although repeat-
ed attempts at crystallization did not afford sharp-melting-point ma-
terial; one spot Rf = 0.39 (EtOAc–PE, 1:1).
1H NMR (CDCl3): d = 10.28 (s, 1 H, H-1), 9.06 (br d, J = ca. 8.3 Hz,
1 H, H-12), 8.64 (d, J = 5.5 Hz, 1 H, H-3), 8.08 (d, J = 8.8 Hz, 1 H,
H-7), 8.07 (dd, J = 7.7, 1.4 Hz, 1 H, H-9), 8.02 (d, J = 8.8 Hz, 1 H,
H-8), 7.74 (td, J = 7.7, 1.4 Hz, 1 H, H-11), 7.72 (d, J = 5.5 Hz, 1 H,
UV (EtOH): lmax (e) = 409 (11680), 388 (12140), 376 (15510), 370
(14360), 357 (10400), 323 (5530), 300 (39030), 288 (32060), 277
(22060), 255 (21820), 219 (33990), 203 nm (47730).
Anal. Calcd for C21H11N: C, 90.95; H, 4.00; N, 5.05. Found: C,
90.45; H, 4.54; N, 4.50.
Acknowledgment
We thank the EPSRC for a studentship to R.S. and for support for
the NMR and MS instruments, and the Mass Spectrometry Service
(Swansea) for accurate mass measurements.
Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York

2174
M. J. E. Hewlins, R. Salter
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Synthesis 2007, No. 14, 2164–2174 © Thieme Stuttgart · New York