Formation of Polycyclic Skeletons by Photochemical Transformations of Pyridyl- and Thienylbutadiene Derivatives

Article abstract of DOI:10.1002/ejoc.201700481

In order to study the influence of heterocyclic nuclei on the photochemical behavior of conjugated butadiene systems, novel butadiene derivatives E,Z- and E,E-2/3-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene as well as E,Z- and E,E-3/4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine have been synthesized. The Wittig reaction was utilized in a two-step reaction course. During the first Wittig reaction, the corresponding aldehydes, namely 2/3-thiophenecarboxaldehyde and 3/4-pyridinecarboxaldehyde, reacted with formylmethylenetriphenylphosphorane to give the corresponding acrylaldehydes, which reacted with the diphosphonium salt of α,α′-o-xylenedibromide in the second Wittig reaction to give new butadiene derivatives. These butadiene derivatives afforded, by photochemical intramolecular cycloaddition, new fused tricyclic as well as tetracyclic derivatives. For the first time, a study of efficiency was conducted where the efficiency of intramolecular cycloaddition of these heterocyclic butadiene derivatives was investigated by simultaneous use of ferrioxalate and valerophenone actinometers.

Full text of DOI:10.1002/ejoc.201700481

A Journal of
Accepted Article
Title: Formation of polycyclic skeleton via photochemical
transformations of new pyridyl- and thienyl-butadiene derivatives
Authors: Ivana Šagud, Marko Levačić, Željko Marinić, and Irena Škorić
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201700481
Link to VoR: http://dx.doi.org/10.1002/ejoc.201700481
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10.1002/ejoc.201700481
European Journal of Organic Chemistry
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Formation of polycyclic skeleton via photochemical
transformations of new pyridyl- and thienyl-butadiene derivatives
Ivana Šagud[a], Marko Levačić[a], Željko Marinić[b] and Irena Škorić *[a]
Abstract: In order to study the influence of heterocyclic nuclei on the
photochemical behavior of the conjugated butadiene systems, novel
butadiene derivatives E,Z- and E,E-2/3-[4-(2-vinylphenyl)buta-1,3-
dienyl]thiophene as well as E,Z- and E,E-3/4-[4-(2-vinylphenyl)buta-
1,3-dienyl]pyridine have been synthesized. The Wittig reaction was
utilized in a two-step reaction course. During the first Wittig reaction
the corresponding aldehydes, namely 2/3-thiophenecarboxaldehyde
and 3/4-pyridinecarboxaldehyde, reacted with formylmethylene-
triphenylphosphorane to give the corresponding acrylaldehydes
which reacted with diphosphonium salt of ,’-o-xylenedibromide in
the second Wittig reaction to give new butadiene derivatives. These
butadiene derivatives afforded, by photochemical intramolecular
cycloaddition, new fused tricyclic as well as tetracyclic derivatives.
For the first time a study of efficiency was conducted where the
efficiency of intramolecular cycloaddition of these heterocyclic
butadiene derivatives was investigated by simultaneous use of
ferrioxalate and valerophenone actinometers.
were obtained for a whole library of polycyclic compounds which
include vast number of structures with
benzobicyclo[3.2.1]octadiene moiety (A-D) (Scheme 1).
a
Scheme 1. Benzobicyclo[3.2.1]octadiene derivatives.
It is worth mentioning that oxazole derivatives which have a
nitrogen atom along with an oxygen atom in the ring, do not
undergo a [1,3]-H shift and they either give a stable oxazoline
moiety with an isolated double bond (C) which can undergo
further transformations by addition or as is the case with the 5-
oxazole derivative, the oxazole opens spontaneously to give
formamide product D.[17] The natural continuation of
investigations in this direction led to studies of o-vinylphenyl
substituted butadienes.[19] Derivatives that have been
investigated so far have been the ones with the phenyl and 2-
furyl substituents (Scheme 2). From vast previous studies on the
excited state behavior conducted on stilbene moieties [7-18] it was
expected that butadiene derivatives would give, by
intramolecular photocycloaddition, a new line of polycyclic
products. Desired derivatives with benzobicyclo[3.2.1]octadiene
skeleton (G) as well as polycyclic products H were synthesized,
purified and described (Scheme 2).[19]
Introduction
Synthetic organic photochemistry can provide a fast and easy
access to complicated structures which are difficult and tasking
to obtain by classic synthetic approach and ground state
reactions.[1]
Bicyclo[3.2.1]octane skeleton is the basic framework of
numerous important biologically active natural compounds and
their diverse metabolites.[2] When properly functionalized,
bicyclo[3.2.1]octanes have proved to be useful reactive
intermediates in stereoselective transformations. This makes
these derivatives powerful building blocks in organic synthetic
strategies.[3,4] Benzobicyclo[3.2.1]octadiene skeleton can thus be
even more useful as it can be easily transformed by adding
various functional groups to the isolated double bond.[5]
During
our
long-standing
interest
in
photochemical
intramolecular cycloaddition reactions of various -heteroaryl-o-
divinylbenzenes such as furans [6-8], thiophenes [8-10], pyrroles
[11,12]
[13-15]
[16-18]
sydnones
and most recently oxazoles
routes
[a]
I. Šagud, M. Levačić, I. Škorić
Department of Organic Chemistry
Faculty of Chemical Engineering and Technology, University of
Zagreb
Scheme 2. Photochemistry products of butadiene derivatives.
Marulićev trg 19, 10000 Zagreb, Croatia
E-mail: iskoric@fkit.hr
Ž. Marinić
NMR Center
Rudjer Bošković Institute,
Bijenička cesta 54, 10000 Zagreb, Croatia
[b]
In this paper we describe the continuation of studies on the
butadiene derivatives where thiophene and pyridine rings were
added to the framework. Thiophene was added to this study
because it is the most aromatic of the heterocycles and
therefore most similar to phenyl. Furthermore pyridine was
Supporting information for this article is given via a link at the end of
the document.
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10.1002/ejoc.201700481
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added to see if the nitrogen atom with its lone pair of electrons
would have any influence on the mechanism and behavior in the
excited state reactions. This study also aimed to determine, for
the first time, the efficiency of the intramolecular
photocycloaddition reaction that takes place by utilizing chemical
actinometry measurements.
UV spectra of all of the butadiene compounds 1a-d clearly show
the influence of configuration as well as substituent influences
(Figures 1-3).
Results and Discussion
Synthesis of new butadiene derivatives
New
butadiene
derivatives
E,Z-
and
E,E-3/4-[4-(2-
vinylphenyl)buta-1,3-dienyl]pyridine (1a, 1b) as well as E,Z- and
E,E-2/3-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (1c, 1d)
were prepared by the Wittig reaction from diphosphonium salt of
,’-o-xylenedibromide and the corresponding acrylaldehydes
(4a-d) (Scheme 3).
Figure 1. Compounds 1a-d in E,E-configuration.
24000
cis,trans-1a
20000
trans,trans-1a
cis,trans-1b
16000
trans,trans-1b
12000
8000

4000
0
Scheme 3. Synthesis of 1a-d by Wittig reaction.
200
250
300
350
400
450
 / nm
The Wittig reaction was conducted according to the “one-pot”
procedure described in a previous paper[20] and gave a mixture
of isomers (1a-c E,Z : E,E = 3:4 and 1d E,Z : E,E = 1:1), in
moderate to good yields (44-71%).
Figure 2. UV spectra for 1a and 1b in 96% ethanol.
The corresponding E-3/4-(pyridin-3-yl)acrylaldehydes (4a, b)
were synthesized using formylmethylene-triphenylphosphorane
by the Wittig reaction from pyridine-3/4-carbaldehyde, as
described in literature.[21] The attempt to synthesize 2-pyridyl-
butadinene derivative gave the product 2-[4-(2-vinylphenyl)buta-
1,3-dienyl]pyridine in small quantities, insufficient for further
photochemical studies. This is due to the low yield of both of the
Wittig reactions utilized in this case, where the overall yield for 2-
pyrrdiyl-butadiene derivative was less than 1%.
For the synthesis of E-2/3-(thiophene-3-yl)acrylaldehydes two
methods were used, the Wittig reaction[21] and an aldol
condensation reaction between thiophene-2/3-carbaldehyde with
acetaldehyde in ethanol with NaOH as base[22] (see SI).
It is important to note that the Wittig reaction utilized for the
synthesis of acryladehydes, is stereospecific due to the high
stability of the betaine intermediate and accordingly gave only E-
isomers. The second Wittig reaction that uses a diphosphonium
salt of ,’-o-xylenedibromide and gives a less stabilized betaine
intermediate results in a mixture of both the E and Z isomers.
The isomers of compounds 1a-d were isolated by column
chromatography on silica gel and characterized by
spectroscopic methods (see SI).
E,E-isomers of both pyridine and thiophene derivatives show a
slight bathochromic shift along with the increase of absorption.
This shift is due to the increased molecular planarity present in
E,E that is trans,trans configuration which then facilitates better
delocalization of -electrons (Figure 1). 4-pyridyl 1b derivative
shows a slight bathochromic shift compared to the 3-pyridyl
derivative 1a (Figure 1, 2). This effect could be attributed to the
1b derivative being somewhat more planar than the 1a
derivative in both configurations due to the fact it has a pyridine
ring with an axis of symmetry and better delocalization of
electrons. When thiophene derivatives 1c and 1d are compared,
the 2-thienyl derivative 1c has a strong bathochromic shift
compared to the 3-thienyl derivative 1c and this can be
explained by prolonged -electron delocalization (Figures 1 and
3).
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10.1002/ejoc.201700481
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trans,trans-1d
2,5
2,0
1,5
1,0
0,5
0,0
24000
20000
16000
12000
0 s
1 s
2 s
4 s
cis,trans-1c
trans,trans-1c
cis,trans-1d
trans,trans-1d
8 s
16 s
32 s
64 s
128 s
256 s
512 s
1024 s
8000

4000
0
200
250
300
350
400
450
 / nm
200
250
300
350
400
450
 / nm
Figure 5. Irradiation of trans,trans-1d followed by UV spectrophotometric
measurements.
Figure 3. UV spectra for 1c and 1d in 96% ethanol.
It is important to note here that in these conditions 4-pyridine
derivative 1b reacts much slower than 3-pyridine derivative 1a
(Figure 4 and SI). Preliminary synthetic experiments in quartz
vessels followed and they were conducted at 300 nm and 350
nm (absorption maxima falls in this region) while differing
irradiation times. Experiments were performed in benzene and
toluene solutions that were flushed with argon. Wavelength of
350 nm gave better results and was used for most of the
preparative measurements.
To get a starting point for the photochemical experiments, pure
isomers of the derivatives 1a-d were irradiated in UV cuvettes
and the reaction course was followed by UV spectrophotometric
measurements at times indicated on the graph for E,E-1a and
1d (Figures 4 and 5, spectra for all of the compounds are given
in the SI).
Preparative photochemistry gave new polycyclic products in all
of the cases of irradiated starting compounds. Thiophene
derivatives 1c and 1d behaved differently in excited state. While
2-tiophene derivative 1c gave a mixture of tricyclic product rel-2-
[(9S)-tricyclo[6.3.1.02,7]dodeca-2,4,6,10-tetraen-9-yl]thiophene
(rel-(9S)-2c) with a 30% yield and tetracyclic product rel-2-
[(10S)-tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-10-
1,0
0,8
0,6
0,4
0,2
0,0
0 s
1 s
2 s
4 s
trans,trans-1a
8 s
16 s
32 s
64 s
128 s
256 s
512 s
1024 s
2048 s
yl]thiophene (rel-(10S)-3c) with
a 29% yield, 3-thiophene
derivative 1d gave only the tricyclic product rel-3-[(9S)-
tricyclo[6.3.1.02,7]dodeca-2,4,6,10-tetraen-9-yl]thiophene
(rel-
(9S)-2d) with a 37% yield (Scheme 4).
200
250
300
350
400
450
 /nm
Figure 4. Irradiation of trans,trans-1a followed by UV spectrophotometry
measurements.
These preliminary irradiation experiments in UV cuvettes
indicated that E-Z, that is, trans-cis isomerization takes place at
shorter irradiation times (under 10 s). Longer periods of
irradiation resulted in a major decrease of absorption. This can
be caused by formation of products with reduced conjugation.
Composition of the photostationary mixture would be very hard
to determine because there is a possibility of existence and
interconversion between four isomers: E,E-, E,Z-, Z,E- and Z,Z-
1a, b, c and d, respectively.
Scheme 4. Photochemistry of 1a-d.
Pyridine derivatives also showed dependence of the
photochemical reaction course on the heterocycle placement in
the butadiene system. 3-pyridine derivative 1a gave tricyclic
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10.1002/ejoc.201700481
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product rel-3-[(9S)-tricyclo[6.3.1.02,7]dodeca-2,4,6,10-tetraen-9-
yl]pyridine (rel-(9S)-2a) with a 44% yield (Scheme 4). 4-pyridine
derivative 1b gave a mixture of two products which were
separated by column chromatography. One was a tricyclic
compound,
rel-4-[(9S)-tricyclo[6.3.1.02,7]dodeca-2,4,6,10-
tetraen-9-yl]pyridine (rel-(9S)-2b) in 51% yield and the other a
tetracyclic compound in trace amounts (2.5%), rel-4-[(10S)-
tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-10-yl]pyridine
(rel-
(10S)-3b) (Scheme 4). Formerly described heterocyclic
butadiene derivative, 2-[4-(2-vinylphenyl)buta-1,3-dienyl]furan,
did not give the tetracyclic product unlike the described 4-
phenyl-1(2-vinylphenyl)-1,3-butadiene that did.[19] Compounds
1a-d behave similarly to the formerly described 2-furyl derivative
in that they gave the tricyclic products 2a-d, however, unlike the
2-furyl derivative the 2-thienyl derivative 1c also gives the
tetracyclic product 3c in a moderate yield of 29%.
All of the compounds were completely characterized by modern
spectroscopic methods (one and two-dimensional NMR spectra
are available in the SI). Tricyclic derivatives, that is,
benzobicyclo[3.2.1]octadienes 2a-d all have a specific pattern of
7 protons HA-HG between 6.5 and 1.5 ppm (Figure 6 and SI)
Scheme 5. Proposed mechanism for the photochemical reactions taking place.
which is characteristic for these types of compounds[19]
.
It can be presumed that even if the 1,4-ring closure to 4 is
occurring this derivative is not stable enough and thermally
reverts back to B. The formation of the tetracyclic derivatives 3b
and c could be explained by utilizing three paths (a, b and c,
Scheme 5). Path a would go by five-membered ring closure via
A, followed by aromatization and intramolecular trapping of the
formed biradical. Path c would entail a six-membered ring
closure via intermediate D. Tetracyclic compound can also occur
by a second ring closure from 2. In the previous work the phenyl
butadiene derivative gave only the tetracyclic product when the
reaction was conducted at 300 nm (path b, Scheme 5). As
opposed to this the 4-pyridyl and 2-thienyl derivatives give both
the tricyclic 2b, c and the tetracyclic 3b and c products at 300
nm, as well as 350 nm without discrepancies and this points to
the path c mechanism via the six-membered ring closure
intermediate D. In this case there is a difference in the
mechanism when compared to the described phenyl and furyl
derivatives and this has to be related to the change in overall
electron distribution in the excited state brought on by the
nitrogen and sulphur atoms introduced to the butadiene system.
The efficiency of intramolecular photocycloaddition reaction (R),
that results in formation of tricyclic products 2a-d, was
investigated by simultaneous use of two actinometeres,
Figure 6. Structures of photoproducts 2 and 3.
Tetracyclic compounds 3a and d also have a pattern of protons
1
in H NMR that are distinguishable and completely differ from
the pattern in the compounds 2a-d. Here the protons HA-HG are
situated in the region between 3.7 and 1.2 ppm (Figure 4 and SI).
The stereochemistry at the sterogenic center was determined
with the help of two-dimensional NOE spectra (see SI). Unlike
the previously described phenyl and furyl derivatives that gave
as products stereoisomers that were predominantly but not
exclusively in the S form, both pyridyl and thienyl derivatives
gave only rel-S isomers. This high stereoselectivity of the
reaction can be ascribed to the stabilization of the transition
state in one orientation by the strong attractive intramolecular -
 interactions of the benzo-heteroaryl group which are increased
with the benzo-pyridyl and benzo-thienyl groups.
ferrioxalate (300 = 1.24)[23,24] and valerophenone (300,benzene
=
0.33).[23,25] These actinometeres were primarily chosen because
of their usability in the 300 nm region. The ferrioxalate
actinometer was used because it is also very stable and can be
easily synthesized. Its consumption can be followed with UV/Vis
spectrophotometry. Valerophenone was used as the second
actinometer because along with being inexpensive it can be
used at the wavelength of 300 nm and its conversion to
acetophenone, for which the quantum yield is known,[23,25] can
be monitored by HPLC/MS. The results gained by actinometry
measurements dare given in table 1.
From the mechanistic point of view the formation of tricyclic
structures 2a-d can be explained by intramolecular cycloaddition
and formation of resonance stabilized intermediate B followed
by 1,6-ring closure (Scheme 5).
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10.1002/ejoc.201700481
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interesting for future biological activity research. For the first time
the efficiency of photocycloaddition reactions of these types of
butadiene derivatives was investigated by utilizing chemical
actinometry methods and quantum yields are given for the
formation of tricyclic products 2a-d.
Table 1. Quantum yield of photocycloaddition
reaction and formation of 2a-d tricyclic derivatives
a
b
Compound]
R1
R2
2a
2b
2c
2d
0.03
0.01
0.07
0,11
0.04
0.01
0.07
0,10
Experimental Section
General remarks. Petroleum ether (PE), bp 40-60 ºC, was used.
Solvents were purified by distillation. Column chromatography was
carried out on columns with silica gel (Fluka 0.063-0.2 nm and Fluka 60
Å, technical grade). TLC was carried out using plates coated with silica
gel (0.2 mm, 0.5 mm, 1.0 mm, Kiselgel 60 F254). Organic layers were
routinely dried with anhydrous MgSO4 and evaporated using a rotary
evaporator. 1H and 13C NMR spectra were recorded on a spectrometer at
600 MHz. All NMR spectra were measured in CDCl3 using
tetramethylsilane as reference. The assignments of the signals are based
on 2D-CH correlations and 2D-HH-COSY correlations. The following
abbreviations were used: Sh – shoulder (in UV spectra), s - singlet; d -
doublet; t - triplet; q - quartet, dd - doublet of doublets; m - multiplet and
br - broad, PE – petroleum ether, E - ether. UV spectra were measured
on a UV/VIS spectrophotometer. IR spectra were recorded on a FTIR-
ATR and FTIR. Mass spectra were obtained on a GC-MS system.
Melting points were obtained using a microscope equipped apparatus
and are uncorrected. HRMS analysis were carried out on a mass
spectrometer (MALDI TOF/TOF analyzer), equipped with Nd:YAG laser
operating at 355 nm with firing rate 200 Hz in the positive (H+) or
negative (-H) ion reflector mode. Irradiation experiments of compound
solutions were performed in a tightly closed vessel in a photochemical
reactor (Rayonet and Luzchem) equipped with the UV lamps (300 and
360 nm). The solvents were removed on the rotary evaporator under
reduced pressure in a ventilated hood.
[a] Measured with ferrioxalate actinometer in toluene. Values obtained by
averaging values of two independent measurements. [b] Measured with
valerophenone actinometer in benzene. Values obtained by averaging values
of two independent measurements.
Values that were obtained for quantum yield show that the
process of formation of the tricyclic products 2a-d is relatively
inefficient regardless of the fact that those are the main products
gained in the reaction and this can be the result of several
reactions happening alongside the main one. Quantum yields
are measured in the first 20 minutes of irradiation because of the
requirements of the actinometers and in this period cis-trans
isomerization which uses photons is present. Two of the starting
compounds along with the tricyclic, as the main product, give
tetracyclic products as minor products. Starting compounds also
have an ortho-substituted vinyl group that can and does
polymerize a great deal and gives high molecular weight
products. It can be noted that quantum yield is higher for
thiophene derivatives 2c, d than it is for the pyridine 2a, b.
Quantum yields that were calculated are low but this
photochemical route uses light as a clean source of energy and
gives products that contain the much desired polycyclic skeleton
especially the benzobicyclo[3.2.1]octadiene skeleton that can be
further functionalized.
Synthesis of 3/4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridines (1a, b)
and 2/3-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (1c, d)
To a stirred solution of diphosphonium salt of ,’-o-xylenedibromide
(7.06 mmol) in absolute ethanol (100 ml, 3Å sieves) a solution of
corresponding acrylaldehyde (2a, b) (7.06 mmol) in 4 mL of ethanol and
half of a solution of sodium ethoxide (7.77 mmol, 1.1 equiv in 30 mL of
ethanol) was added simultaneously and dropwise in strictly anhydrous
conditions under nitrogen. Reaction mixture was left to stir for 1h. Under
the stream of dry nitrogen, gaseous formaldehyde (obtained by
decomposition of paraformaldehyde taken in excess, 1.0 g) was
introduced together with the second quantity of sodium ethoxide that was
added dropwise. Reaction mixture was stirred overnight. After removal of
the solvent the residue was worked up with ice-water, and extracted with
toluene (5 × 30 mL). Toluene extracts were dried over anhydrous MgSO4.
Evaporation of solvent under reduced pressure afforded 0.717 g (44%) of
product 1a and 1.459 g (47%) of product 1b as a mixture of Z,E- and
E,E-isomer in ration Z,E:E,E = 3:4.
Conclusions
New butadiene derivatives have been synthesized and
completely characterized, namely cis,trans- and trans,trans-2/3-
[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (cis- and trans-1a,b)
and 3/4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine (cis- and
trans-1c,d). In photochemical cycloaddition reactions they gave
3-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine
(1a).
Column
chromatography on silica gel using petroleum ether/ether (variable ratio)
as eluent afforded 0.308 g of Z,E-1a and 0,410 g of E,E-1a. Z,E-3-[4-(2-
vinylphenyl)buta-1,3-dienyl]pyridine (Z,E-1a) as oil: Rf (PE / E = 3:7) =
0.43; UV (EtOH) max/nm (/dm3mol-1cm-1): 235 (12427), 262 (Sh, 10294),
314 (13004); 1H NMR (CDCl3, 600 MHz) /ppm: 8.56 (d, Jpy1,py2 = 1.5 Hz,
1H, H-Py1), 8.42 (dd, Jpy1,py2 = 1.5 Hz, Jpy2,py3 = 5.1 Hz, 1H, H-Py2), 7.64
(dt, Jar = 8.0 Hz, Jar = 6.1 Hz, 1H, H-ar), 7.58-7.57 (m, 1H, H-ar), 7.33-
new
tricyclic
and tetracyclic
derivatives with high
stereoselectivity. The tricyclic 2a-d derivatives have
a
benzobicyclo[3.2.1]butadiene skeleton with the isolated double
bond which can easily be further modified[5] into functionalized
structural parts resulting in the total synthesis of biologically
active compounds. The tetracyclic 3a and d derivatives contain
a polycyclic skeleton which is almost impossible to synthesize in
ground state chemistry. These new tricyclic and tetracyclic
derivatives with the isolated double bond also contain a
heterocyclic ring, either pyridine or thiophene that makes them
7.27 (m, 3H, H-ar), 7.26-7.25 (m, 2H, H-ar), 7.20 (dd, Jar = 7.9 Hz, Jar
=
7.0 Hz, 1H, H-ar), 7.09 (dd, J1,2 = 15.6 Hz, J2,3 = 11.2 Hz, 1H, H-2), 6.92
(dd, Ja,b = 11.2 Hz, Ja,c = 17.5 Hz, 1H, H-c), 6.71 (d, J3,4 = 11.2 Hz, 1H,
H-4), 6.65 (d, J1,2 =15.6 Hz, 1H, H-1), 6.52 (t, J3,4 = J2,3 = 11.1 Hz, 1H, H-
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10.1002/ejoc.201700481
European Journal of Organic Chemistry
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3), 5.7 (dd, Ja,b = 1.14 Hz, Ja,c = 17.5 Hz, 1H, H-a), 5,31 (dd, Ja,b = 1.0 Hz,
Ja,c = 11.1 Hz, 1H, H-b); 13C NMR (CDCl3, 150 MHz) /ppm: 147.9 (d),
136.0 (s), 134.8 (s), 134.5 (d), 132.5 (s), 132.2 (d), 130.3 (d), 130.1 (d),
129.8 (d), 129.6 (d), 127.3 (d), 127.1 (d), 126.9 (d), 125.3 (d), 122.9 (d),
115.3 (t); MS m/z (%, fragment) (EI): 233 (100%, M+), 118 (58%); HRMS
(m/z): [M+H]+ calcd for C17H15N 234.1283 found 234.1294.
E,E-3-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine (E,E-1a) as oil: Rf (PE
/ E = 3:7) = 0.37; UV (EtOH) max/nm (/dm3mol-1cm-1) : 240 (10559), 259
(Sh, 9624), 325 (20352); IR max/cm-1 (NaCl): 3582, 2925, 2851, 1739,
1470, 985; 1H NMR (CDCl3, 600 MHz) /ppm: 8,66 (d, Jpy1,py2 = 1.4 Hz,
1H, H-Py1), 8.46 (d, Jpy1,py2 = 1.4 Hz, Jpy2,py3 = 3.6 Hz, 1H, H-Py2), 7.76
(dt, 1H, H-ar), 7.54-7.53 (m, 1H, H-ar), 7,47-7.45 (m, 1H, H-ar), 7,27-7,25
(m, 3H, H-ar2/3), 7,08 (d, Jet = 15.3 Hz, 1H, H-1/4), 7.06 (dd, Ja,b = 10.5
Hz, Ja,c = 15.8 Hz, 1H, H-c), 6.87 (dd, Jet = 10.5 Hz, Jet = 15.3 Hz, 1H, H-
2/3), 6.65 (d, Jet =15.3 Hz, 1H, H-1/4), 5.65 (dd, Ja,b = 1.2 Hz, Ja,c = 17.3
Hz, 1H, H-a), 5.38 (dd, Ja,b =1.2 Hz, Ja,c = 10.9 Hz, 1H, H-b); 13C NMR
(CDCl3, 150 MHz)/ppm:147.92 (d), 147.87 (d), 136.06 (s), 134.48 (s),
134,42 (d), 132.54 (s), 132.00 (d), 131.24 (d), 130.95 (d), 130.20 (d),
128.40 (d), 127.44 (d), 127.34 (d), 126.29 (d), 125.46 (d), 123.01 (d),
116.31 (t); MS m/z (%, fragment) (EI): 233 (100%, M+), 118 (58%).
Hz, H-b); 13C NMR (CDCl3, 600 MHz) /ppm: 131.5 (d), 130.1 (d), 129.7
(d), 128.6 (d), 127.3 (d), 127.2 (d), 127.6 (d), 127.0 (d), 126.9 (d), 125.5
(d), 125.3 (d), 124.8 (d), 115.2 (t, C-a,b); HRMS (m/z): C16H14S-H+ calcd
for C16H14S 237.0738 found 237.0748.
E,E-2-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (E,E-1c) as yellow
powder; mp = 69-72 oC; Rf (PE / E = 2:7) = 0.48; UV (EtOH) max/nm
(/dm3mol-1cm-1): 204 (11850), 237 (6781), 268 (6397), 337(Sh 19953),
350 (22023), 369 (Sh 14063); IR max/cm-1 (NaCl): 3065, 1673, 1614,
1418, 981; 1H NMR (CDCl3, 600 MHz) /ppm: 7.51 (dd, Jar = 8.1 Hz, Jar
=
1.2 Hz, 1H, H-ar), 7.45 (dd, Jar = 7.2 Hz, Jar = 1.1 Hz, 1H, H-ar), 7.23 (d,
Jet = 15.4 Hz, 1H, H-et), 7.27-7.22 (m, 1H, H-ar), 7.18 (d, Jar = 4.8 Hz, 1H,
H-ar), 7.06 (dd, Ja,c= 17.4 Hz, Jb,c = 11.0 Hz, 1H, H-c), 7.01-6.98 (m, 2H,
H-et), 6.94 (d, Jet = 15.0 Hz, 1H, H-et), 6.82-6.77 (m, 3H, H-ar), 5.62 (dd,
Ja,c = 17.4 Hz, Ja,b = 1.1 Hz, 1H, H-a), 5.36 (dd, Jb,c = 11.0 Hz; Ja,b = 1.01
Hz, 1H, H-b); 13C NMR (CDCl3, 600 MHz) /ppm: 142.9 (s), 136.3 (s),
135.3 (s), 124.9 (d), 130.8 (d), 130.1 (d), 129.3 (d), 127.8 (d), 127.7 (d),
127.6 (d), 126.7 (d), 126.0 (d), 125.8 (d), 124.5 (d), 116.6 (t, C-a,b).
3-[4-(2-vinylphenyl)buta-1,3-dienyl]tiophene (1d)
Purification of raw reaction mixture gave 0.823 g (I = 49%) of isomers
mixture Z,E:E,E = 1:1 which were separated by multiple column and thin
layer chromatography.
4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine
(1b).
Column
chromatography on silica gel using petroleum ether/ether (variable ratio)
as eluent afforded 0.648 g of Z,E-1b and 0.857g of E,E-1b.
Z,E-4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine (Z,E-1b) as oil: Rf (PE
/ E = 3:7) = 0.31; UV (EtOH) max/nm (/dm3mol-1cm-1): 233 (14436), 261
(Sh, 10941), 320 (17200); IR max/cm-1 (NaCl): 3026, 1599, 1415, 1217,
990; 1H NMR (CDCl3, 600 MHz) /ppm: 8.50 (d, 2H, H-Py1,Py2), 7.58 (d,
Z,E-3-[4-(2-vinylphenyl)buta-1,3-dienyl]tiophene (Z,E-1d) as oil: Rf
(PE / E = 2:9) = 0.32; UV (EtOH) max/nm (/dm3mol-1cm-1): 206 (15419),
237 (11267), 307 (16626); IR max/cm-1 (NaCl): 3049, 1624, 1474, 1246,
984; 1H NMR (CDCl3, 600 MHz) /ppm: 7.56-7.55 (m, 1H, H-tf), 7.29-7.28
(m, 3H, H-ar), 7.23-7.22 (m, 1H, H-tf), 7.15-7.12 (m, 2H, H-ar, tf), 6.91
(dd, Ja,c = 17.6 Hz, Jb,c = 10.9 Hz, 1H, H-c), 6.85 (dd, J1,2 = 15.5 Hz, J2,3
11.3 Hz, 1H, H-et2), 6.69 (d, J1,2 = 15.5 Hz, 1H, H-et1), 6.59 (d, J3,4 = 11.3
Hz, 1H, H-et4), 6.44 (t, J2,3 = J3,4 = 11.3 Hz, 1H, H-et3), 5.69 (dd, Ja,c
=
1H, H-ar), 7.34-7.27 (m, 3H, H-ar), 7.18 (d, 2H, H-Py2), 7.20 (dd, J1,3
=
15.7 Hz, J2,3 = 11.2 Hz, 1H, H-3), 6.90 (dd, Ja,b = 11.0 Hz, Ja,c = 17.5 Hz,
1H, H-c), 6.79 (d, J3,4 = 11.2 Hz, 1H, H-4), 6.60 (d, J1,3 = 15.7 Hz, 1H, H-
=
17.6 Hz, Ja,b = 1.1 Hz, 1H, H-a), 5.29 (dd, Jb,c = 10.9 Hz, Ja,b = 1.1 Hz, 1H,
H-b); 13C NMR (CDCl3, 150 MHz) /ppm: 139.7 (s), 135.9 (s), 135.3 (s),
134.7 (d,C-c), 130.7 (d, C-et3), 129.7 (d, C-ar), 128.4 (d, C-et4), 127.9 (d,
C-et1), 126.9 (d, C-ar), 126.8 (d, C-ar), 125.5 (d, C-ar), 125.2 (d, C-ar),
125.1 (d, C-et2), 124.6 (d, C-ar), 121.9 (d, C-ar), 115.0 (C-a,b); MS m/z
(%, fragment) (EI): 238 (100%, M+), 123 (30%).
E,E-3-[4-(2-vinylphenyl)buta-1,3-dienyl]tiophene (E,E-1d) as oil: Rf
(PE / E = 2:9) = 0.28; UV (EtOH) max/nm (/dm3mol-1cm-1): 255 (6832),
332 (21159), 352 (Sh, 12370); IR max/cm-1 (NaCl): 3050, 1480, 1320,; 1H
NMR (CDCl3, 600 MHz) /ppm: 7.51 (d, Jar = 7.6 Hz, 1H, H-ar2/3), 7.44 (d,
Jar = 7.6 Hz, 1H, H-ar2/3), 7.30-7.22 (m, 5H, H-ar), 7.20 (dd, Ja,c = 17.6 Hz,
Jb,c = 10.9 Hz, 1H, H-c), 6.93 (d, Jet = 14.5 Hz, 1H, H-et1/4), 6.82-6.79 (m,
2H, H-et2/3), 6.69 (d, Jet = 14.5 Hz, 1H, H-et1/4), 5.63 (dd, Ja,c = 17.6 Hz,
Ja,b = 1.1 Hz, 1H, H-a), 5.36 (dd, Jb,c = 10.9 Hz, Ja,b = 1.1 Hz, 1H, H-b);
13C NMR (CDCl3, 150 MHz) /ppm: 139.7 (s), 135.8 (s), 134.9 (s), 134.5
(d, C-c), 130.8 (d, C-et2/3), 129.3 (d, C-et2/3), 129.0 (d, C-et1/4), 127.3 (d,
C-ar), 127.0 (d, C-ar), 126.6 (d, C-et1/4), 126.2 (d, C-ar), 125.6 (d, C-ar),
125.3 (d, C-ar), 124.4 (d, C-ar), 121.7 (d, C-ar), 116.0 (t, C-a,b); HRMS
(m/z): C16H14S+ calcd for C16H14S 238.0816 found 238.0813.
1), 6.52 (t, J2,3 = J3,4 = 11.2 Hz, 1H, H-2), 5.71 (dd, Ja,b = 1.0 Hz, Ja,c
17.5 Hz, 1H, H-a), 5.32 (dd, Ja,b = 0.9 Hz, Ja,c = 11.0 Hz, 1H, H-b);13
=
C
NMR (CDCl3, 150 MHz) /ppm: 149.6 (d), 144.1 (s), 136.1 (s), 134.6 (s),
134.5 (d), 131.9 (d), 130.9 (d), 129.7 (d), 129.6 (d), 129.3 (d), 127.5 (d),
126.9 (d), 125.4 (d), 120.3 (d), 115.5 (t); MS m/z (%, fragment) (EI): 233
(100%, M+), 128 (55%), 115 (78%).
E,E-4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine (E,E-1b) as oil: Rf (PE
/ E 3:7) = 0.33; UV (EtOH) max/nm (/dm3mol-1cm-1): 234 (14084), 262
(Sh, 10964), 326 (21783); IR max/cm-1 (NaCl): 2926, 1741, 1597, 1415,
989; 1H NMR (CDCl3, 600 MHz)/ppm: 8.55 (d, Jar = 1.7 Hz, 2H, H-
Py1,Py2), 7.54-7.52 (m, 1H, H-Py), 7.47-7.45 (m, 1H, H-Py), 7.30-7.25 (m,
4H, H-ar), 7.18 (dd, Jet = 10.50 Hz, Jet = 15.40 Hz, 1H, H-2/3), 7.10 (d, Jet
= 15.53 Hz, 1H, H-1/4), 7.06 (dd, Ja,b = 10.81 Hz, Ja,c = 17.52 Hz, 1H, H-
c), 6.87 (dd, Jet = 10.50 Hz, Jet = 15.40 Hz, 1H, H-2/3), 6.60 (d, Jet
=
15.53 Hz, 1H, H-1/4), 5.66 (dd, Ja,b = 1.50 Hz, Ja,c = 17.52 Hz, 1H, H-a),
5.40 (dd, Ja,b = 1.50 Hz, Ja,c = 10.81 Hz, 1H, H-b); 13C NMR (CDCl3, 150
MHz) /ppm: 149.65 (d), 144.08 (s), 136.24 (s), 134.23 (d), 133.25 (d),
132.81 (d), 129.72 (d), 129.42 (d), 127.73 (d), 127.36 (d), 126.37 (d),
125.54 (d), 120.13 (d), 116.53 (t); MS m/z (%, fragment) (EI): 233 (100%,
M+), 128 (55%), 115 (78%); HRMS (m/z): [M+H]+ calcd for C17H15N
234.1283 found 234.1273.
Photochemistry of 3/4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridines
(1a, b)
2-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (1c)
Irradiation of 3-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine (1a). 100
mg of mixture of isomers of compound 1a was dissolved in 115 mL of
benzene and transferred to a quartz vessel, purged with argon for 20
minutes and irradiated with 16 UV lamps at 350 nm for 7h. After removal
of the solvent, 1H NMR spectra showed no unreacted starting material
and only one product. Crude product was purified by column and thin
layer chromatography on silica gel using petroleum ether/ether as eluent.
Purification of raw reaction mixture gave 1.174 g (I = 70%) of isomers
mixture Z,E:E,E = 3:4 which were separated by multiple column and thin
layer chromatography.
Z,E-2-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (Z,E-1c) (with 25%
of E,E-1c as impurity, because of their similar Rf values) as oil; Rf (PE / E
= 2:7) = 0.49; UV (EtOH) max/nm (/dm3mol-1cm-1): 204 (13392), 241
(8131), 334 (14063); IR max/cm-1 (NaCl): 3068, 1672, 1417, 982; 1H
NMR (CDCl3, 600 MHz) /ppm: 7.56-7.55 (t, 1H, H-ar), 7.30-7.27 (m, 3H,
H-ar), 7.13 (d, Jar = 4,84 Hz, 1H, H-ar), 6.98-6.94 (m, 2H, H-ar), 6.90 (dd,
0.044
g
(44%) of compound rel-3-[(9S)-tricyclo[6.3.1.02,7]dodeca-
2,4,6,10-tetraen-9-yl]pyridine (rel-(9S)-2a) was isolated as oil: Rf (PE/E
= 1:1) = 0.37; UV (EtOH) max/nm (/dm3mol-1cm-1): 258 (Sh, 3958), 264
(Sh, 4313), 270 (Sh, 3772); IR max/cm-1 (NaCl): 2903, 1630, 1390; 1H
NMR (CDCl3, 600 MHz) /ppm: 8.42 (dd, Jpy2,py3 = 4.5 Hz, 1H, H-Py2),
8.17 (d, Jpy1,py4 = 1.7 Hz, 1H, H-Py1), 7.14 (d, Jar =7.1 Hz, 1H, H-ar),
7.06-7.03 (m, 2H, H-ar, Py3), 6.85 (t, Jar = 7.9 Hz, 1H, H-ar), 6.81 (dt,
Ja,c = 17.4 Hz, Jb,c = 11.0 Hz, 1H, H-c), 6.82 (dd, J1,2 = 15.2 Hz, J2,3
=
10.7 Hz, 1H, H-et2), 6.81 (d, J1,2 =15.2 Hz, 1H, H-et1), 6.59 (d, J3,4 = 10.7
Hz, 1H, H-et4), 6.42 (dd, J2,3 = J3,4 = 10.7 Hz, 1H, H-et3), 5.68 (dd, 1H,
Ja,c = 17.4 Hz, Ja,b = 0.9 Hz, H-a), 5.29 (dd, 1H, Jb,c = 11.0 Hz, Ja,b = 1.0
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700481
European Journal of Organic Chemistry
FULL PAPER
JPy1,Py4 = 1.7 Hz, JPy3,Py4 = 7.8 Hz, 1H, H-Py4), 6.43 (ddd, JA,B = 5.0 Hz,
JA,C = 5.1 Hz, JA,E = 8.0 Hz, 1H, H-A), 6.21 (d, Jar = 7.4 Hz, 1H, H-ar),
5.26 (dt, JA,B = 5.0 Hz, JB,C = 4.7 Hz, JB,D = 4.6 Hz, 1H, H-B), 4.00 (ddd,
JA,C = 5.1 Hz, JB,C = 4.7 Hz, 1H, H-C), 3.37 (t, JB,D = JD,F = 4.6 Hz, 1H, H-
D), 3.32 (dd, JA,E = 8.0 Hz, JD,F = 9.6 Hz, 1H, H-E), 2.56-2.53 (m, 1H, H-
F), 2.41 (d, JF,G = 10.3 Hz, 1H, H-G); 13C NMR (CDCl3, 150 MHz)/ppm:
151.7 (s), 149.4 (d, C-Py1), 147.3 (d, C-Py2), 140.9 (s), 137.4 (s), 135.4
(d, C-A), 135.3 (d, C-ar), 126.0 (d, C-Ar), 125.7 (d, C-Ar), 124.8 (d, C-B),
124.7 (d, C-ar), 122.2 (d, C-ar), 120.0 (d, C-Ar), 47.9 (d, C-D), 43.6 (t, C-
F,G), 43.4 (d, C-C), 39.8 (d, C-E), MS m/z (%, fragment) (EI): 233 (100%,
M+), 128 (55%), 115 (78%).; HRMS (m/z): [M+H]+ calcd for C17H15N
234.1283 found 234.1280.
the solvent was evaporated and the raw reaction mixture was purified by
thin layer chromatography on silica gel using petroleum ether/ether (3%)
as
eluent
and
gave
10
mg
(30%)
of
rel-2-[(9S)-
tricyclo[6.3.1.02,7]dodeca-2,4,6,10-tetraen-9-yl]thiophene (rel-(9S)-2c)
with 40% of rel-2-[(10R)-tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-
10-yl]thiophene (rel-(10R)-3c) as impurity and 8 mg (29%) of rel-2-
[(10S)-tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-10-yl]thiophene
(rel-(10S)-3c).
rel-3-[(9S)-tricyclo[6.3.1.02,7]dodeca-2,4,6,10-tetraen-9-yl]thiophene
(rel-(9S)-2c) as oil; Rf (PE/E = 3%) = 0.7; 1H NMR (CDCl3, 600 MHz)
/ppm: 7.20-7.19 (m, 1 H, H-ar), 7.13-7.12 (m, 1H, H-ar), 7-09-7.08 (m,
1H, H-ar), 7.04-7.01(m, 1H, H-ar), 6.87-6.86 (m, 1H, H-ar), 6.47 (d, Jar
=
Irradiation of 4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine (1b)
100 mg of mixture of isomers of compound 1b was dissolved in 115 mL
of benzene and transferred to a quartz vessel, purged with argon for 20
minutes and irradiated with 16 UV lamps at 350 nm for 23h. After
removal of the solvent, 1H NMR spectra show no unreacted starting
material and two products. Crude product was purified by column and
thin layer chromatography on silica gel using petroleum ether/ether as
eluent and gave 0.041 g (51%) of rel-4-[(9S)-tricyclo[6.3.1.02,7]dodeca-
7.3 Hz, 1H, H-ar), 6.41 (dd, JA,B = 5.5 Hz, JA,E = 3.4 Hz, 1H, H-A), 6.38-
6.35 (m, 1H, H-ar), 5.36 (dd, JA,B = 5.5 Hz, JB,C = 9.6 Hz, 1H, H-B), 4,25
(dd, JB,C = 9.6 Hz, JC,E = 4.3 Hz, 1H, H-C), 3.49 (t, JC,D = JD,F = 6.0 Hz, 1H,
H-D), 3.28 (ddd, JA,E = 3.4 Hz, JE,F = 6.3 Hz, 1H, H-E), 2.50 (ddd, JD,F
=
6.0 Hz, JF,G = 10.3 Hz, JE,F = 6.3 Hz, 1H, H-F), 2.35 (d, JF,G = 10.3 Hz, 1H,
H-G); 13C NMR (CDCl3, 600 MHz) /ppm: 152.2 (s), 141.6 (s), 143.8 (d),
125.9 (d), 125.8 (d), 125.7 (d), 125.4 (d), 125.3 (d), 124.8 (d), 123.9 (d) ,
123.5 (d), 122.3 (d), 119.7 (d), 116.6 (s), 43.2 (t); HRMS .(m/z): .C16H14S-
H+ calcd for C16H14S 237.0738 found 237.0733.
2,4,6,10-tetraen-9-yl]pyridine (rel-(9S)-2b) and 0.002
g (2.5%) of
compound rel-4-[(10S)-tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-10-
yl]pyridine (rel-(10S)-3b).
rel-2-[(10R)-tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-10-
yl]thiophene (rel-(10R)-3c) (PE/E = 3%) = 0.7; 1H NMR (CDCl3, 600
MHz) /ppm (only aliphatic protons): 3.34-3.35 (m, 1H, H-a), 3.00 (d, J =
= 4.5 Hz, 1H, H-b), 2.75 (s, , 1H, H-c), 2.20-2.12 (m, 1H, H-d, e), 1.92-
1.87 (m, 1H, H-f), 0.97 (d, Jd,g = 12.1 Hz, 1H, H-g);
rel-2-[(10S)-tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-10yl]
thiophene (rel-(10S)-3c) as white powder: mp = 79-88 oC; Rf (PE/E =
3%) = 0.65; IR max/cm-1 (NaCl): 2943, 1731, 1636, 1486; UV (EtOH)
rel-4-[(9S)-tricyclo[6.3.1.02,7]dodeca-2,4,6,10-tetraen-9-yl]pyridine
(rel-(9S)-2b); oil: Rf (PE/E = 1:1) = 0.31; UV (EtOH) max/nm (/dm3mol-
1cm-1): 258 (4873), 265 (Sh, 4529), 275 (Sh, 3301); IR max/cm-1 (NaCl):
1
3022, 2951, 1677, 1598, 1469, 1412; H NMR (CDCl3, 600 MHz) /ppm:
8.40 (d, JPy = 5.90 Hz, 2H, H-Py2), 7.13 (d, Jar = 7.5 Hz, 1H, H-ar1/4),
7.04 (dt, Jar =7.5 Hz, Jar =1.0 Hz,1H, H-ar2/3), 6.81 (t, Jar =7.5 Hz, Jar
=1.0 Hz,1H, H-ar2/3), 6.69 (d, J = 6.7 Hz, 2H, H-Py2), 6.44 (dt, JA,B = 5.00
Hz, JA,C = 5.13 Hz, JA,E = 8.00 Hz, 1H, H-A), 6.20 (d, Jar = 7.5 Hz, 1H, H-

max/nm (/dm3mol-1cm-1):229 (7236), 320 (2826), 333 (Sh 2603), 349 (Sh
1442); 1H NMR (CDCl3, 600 MHz) δ/ppm: 7.29 (d, Jar =7.4 Hz, 1H, H-ar),
7.14 (dd, Jar = 8.5 Hz, Jar = 9.8 Hz, 1H, H-ar2/3), 6.99 (dd, Jar = 9.8 Hz, Jar
= 8.5 Hz, 1H, H-ar2/3), 6.88 (d, Jtf =5.3 Hz, 1H, H-tfa/c), 6.82 (d, Jar = 7.4
Hz, 1H, H-ar1/4), 6.66 (dd, Jtf = 4.8 Hz, Jtf = 5.3 Hz, 1H, H-tfb), 6.48 (d, Jtf =
4.8 Hz, 1H, H-tfa/c), 3.64 (dd, JA,B = 4.5 Hz, JA,E = 5.2 Hz, JA,E = 6.0 Hz, 1H,
H-A), 3.21 (dd, JA,B = JB,D = 4.5 Hz, 1H, H-B), 2.31 (dd, JC,E = JC,F = 7.2 Hz,
1H, H-C), 2.12 (ddd, JB,D = 4.5 Hz, JD,F = 6.1 Hz, JD,G = 11.7 Hz, 1H, H-D),
1.96 (ddd, JA,E = 6.0 Hz, JC,E = 7.2 Hz, JE,F = 4.5 Hz, 1H, H-E), 1.79 (ddd,
JC,F = 7.2 Hz, JD,F = 6.1 Hz, JE,F = 4.5 Hz, 1H, H-F), 1.21 (d, JD,G = 11.7 Hz,
1H, H-G); 13C NMR (CDCl3, 150 MHz) δ/ppm: 143.9 (s), 136.1 (s), 135.0
(s), 125.6 (d, C-ar2/3), 125.3 (d, C-ar1/4), 125.3 (d, C-tfb), 124.9 (d, C-ar1/4),
123.9 (d, C-ar2/3), 123.7 (d, C-tfa/c), 122.8 (d, C-tfa/c), 42.5 (d, C-B), 39.7
(d, C-A), 29.2 (t, C-D,G), 22.3 (d, C-E), 17.9 (d, C-C), 16.3 (d, C-F);
HRMS (m/z): C16H14S-H+ calcd for C16H14S 237.0738 found 237.0730.
Irradiation of 3-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (1d)
114 mg of mixture of isomers of compound x was dissolved in 160 mL of
benzene and transferred to a quartz vessel, purged with argon for 20
minutes and irradiated at 350 nm for 5h. After removal of the solvent, 1H
NMR spectra show no unreacted starting material and only one product.
Crude product was purified by column and thin layer chromatography on
silica gel using petroleumether/ether as eluent. 0.042 g (37%) of
ar), 5.27 (dt, JA,B = 5.00 Hz, JB,C = 9.60 Hz, 1H, H-B), 3.95 (ddd, JA,C
=
5.13 Hz, JB,C = 9.60 Hz, JC,D = 4.70 Hz, 1H, H-C), 3.37 (dd, JC,D = 4.70
Hz, 1H, H-D), 3.33 (t, JA,E = 8.00 Hz, JE,F = 4.73 Hz, 1H, H-E), 2.56-2.52
(m, 1H, H-F), 2.37 (d, JF,G = 10.3 Hz, 1H, H-G); 13C NMR (CDCl3, 150
MHz) /ppm: 151.6 (s), 151.3 (s), 148.7 (d, C-Py1), 140.7 (s), 135.7 (d, C-
A), 126.0 (d, C-Ar), 125.4 (d, C-Ar), 124.8 (d, C-Ar), 124.0 (d, C-B), 123.1
(d, C-Py2), 120.0 (d, C-Ar), 47.4 (d, C-D), 45.1 (d, C-C), 43.6 (t, F,G),
39.8 (d, C-E). MS m/z (%, fragment) (EI): 233 (100%, M+), 128 (55%),
115 (78%); HRMS (m/z): [M+H]+ calcd for C17H15N 234.1283 found
234.1286.
rel-4-[(10S)-tetracyclo[7.2.1.02,11.03,8]dodeca-3,5,7-trien-10-yl]pyridine
o
(rel-(10S)-3b); white powder: mp = 100-104 C; Rf (PE/E = 1:1) = 0.15;
UV (EtOH) max/nm (/dm3mol-1cm-1): 252 (Sh, 911), 258 (1079), 265 (Sh,
732); IR max/cm-1: 3024, 2925, 1599,1486, 1413; 1H NMR (CDCl3, 600
MHz) δ/ppm: 8.22 (d, J = 5.8 Hz, 2H, H-Py2), 7.27 (d, Jar = 7.0 Hz, 1H, H-
ar1/4), 7.08 (dt, Jar = 7.2 Hz, Jar = 5.7 Hz, 1H, H-ar2/3), 6.90 (t, Jar = 7.2
Hz, Jar = 5.7 Hz, 1H, H-ar2/3), 6.83 (d, J = 5.7 Hz, 2H, H-Py1), 6.65 (d, Jar
= 7.5 Hz, 1H, H-ar1/4), 3.42 (dd, JA,B = 4.00 Hz, JA,D = 4.30 Hz, 1H, H-A),
3.27 (dd, JA,B = JB,C = 4.00 Hz, 1H, H-B), 2.17 (ddd, JB,C = 4.00 Hz, JC,E
=
4.40 Hz, JC,G = 11.60 Hz, 1H, H-C), 1.94 (dd, JA,D = 4.30 Hz, JD,E = 11.00
Hz, 1H, H-D), 1.85 (dd, JC,E = 4.40 Hz, JD,E = 11.00 Hz, 1H, H-E), 1.33-
1.29 (m, 1H, H-F), 1.25 (d, JC,G = 11.60 Hz, 1H, H-G); 13C NMR (CDCl3,
150 MHz) δ/ppm: 149.65 (s), 148.38 (d, C-Py1), 135.23 (s), 134.56 (s),
125.74 (d, C-Ar1/4), 125.15 (d, C-Ar2/3), 124.35 (d, C-Ar2/3), 124.10 (d,
C-Py2), 122.55 (d, C-Ar1/4), 65.35 (s), 43.11 (d, C-A), 42.00 (d, C-B),
29.57 (t, C-C,G), 19.07 (d, C-F), 15.98 (d, C-E). MS m/z (%, fragment)
(EI): 233 (100%, M+), 128 (55%), 115 (78%); HRMS (m/z): [M+H]+ calcd
for C17H15N 234.1283 found 234.1284.
Photochemistry of 2/3-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophenes
(1c, d)
Irradiation of 2-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene (1c)
34 mg of compound x was dissolved in 50 mL of toluene (c = 3 × 10-3
mol/L) in a quartz cuvette and flushed with argon for 30 minutes. The
solution was irradiated at 350 nm (16 lamps) for 5.30 h. After irradiation
compound
yl]thiophene (rel-(9S)-2d) was isolated as oil: Rf (PE/E = 3:1) = 0.30; IR
rel-3-[(9S)-tricyclo[6.3.1.02,7]dodeca-2,4,6,10-tetraen-9-

max/cm-1 (NaCl): 2945, 1469, 751; UV (EtOH) max/nm (/dm3mol-1cm-
1):243 (7525), 266 (4345), 312 (Sh 771); 1H NMR (CDCl3, 600 MHz)
/ppm: 7.18 (dd, 1H, Jtfab= 5.0 Hz, Jtfad = 4.9 Hz, H-tfa), 7.10 (d, 1H, Jar=
7.3 Hz, H-ar 1/4), 7.02 (dd, Jar = 7.3 Hz, Jar = 8.6 Hz, 1H, H-ar2/3), 6.84
(dd, Jar = 7.3 Hz, Jar = 8.6 Hz, 1H, H-ar2/3), 6.70 (dd, Jtfab = 5.0 Hz, Jtfbd
=
1.0 Hz, 1H, H-ar), 6.52-6.51 (m, 1H, H-tfd), 6.34 (d, Jar = 7.3 Hz, 1H, H-
ar1/4), 6.32 (ddd, JA,B = 6.0 Hz, JA,C = 5.2 Hz, JA,E = 5.8 Hz, H-A), 5.33
(ddd, JA,B = 6.0 Hz, JB,C = 5.6 Hz, JB,d = 4.5 Hz, 1H, H-B), 4.06 (ddd, JA,C
= 5.2 Hz, JB,C = 5.6 Hz, JC,E = 7.2 Hz, 1H, H-C), 3.43 (dd, JB,D = 4.5 Hz,
JD,F = 4.7 Hz, H-D), 3.27 (ddd, 1H, JA,E = 5.8 Hz, JC,E = 7.2 Hz, JE,F = 6.0
Hz, 1H, H-E), 2.49 (ddd, JD,F = 7.9 Hz, JF,G = 10.1 Hz, JE,F = 6.0 Hz 1H,
H-F), 2.33 (d, 1H, JF,G = 10.1 Hz, H-G); 13C NMR (CDCl3, 150
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10.1002/ejoc.201700481
European Journal of Organic Chemistry
FULL PAPER
MHz)/ppm: 152.1 (s), 142.9 (s), 141.9 (s), 134.2 (d, C-A), 127.3 (d, C-
tfb), 125.8 (d, C-B), 125.6 (d, C-ar), 125.3 (d, C-ar), 124.7 (d, C-ar),
124.1 (d, C-tfa), 120.3 (d, C-tfd), 119.7 (d, C-ar), 47.5 (d, C-D), 43.1 (t, C-
F,G), 41.5 (d, C-C), 40.0 (d, C-E). MS m/z (%, fragment) (EI): 238 (100%,
M+), 123 (30%); HRMS (m/z): C16H14S-H+ calcd for C16H14S 237.0738
found 237.0728.
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absorbance of 0.4−0.8 at 300 nm. 0.012
M
solution of
K2[Fe(C2O4)3]x3H2O in 0.05 M H2SO4 was prepared and 0.1 M solution of
valerophenone in benzene was prepared. The solutions were purged
with a stream of argon (10 min each), and then sealed with a cap.
Solutions of compounds and actinometers were irradiated in quartz
cuvettes, with the same geometry, at the same time with 4 lamps (300
nm) for 20 minutes in Luzchem reactor. One cuvette with ferrioxalate
actinometer was kept in the dark. After irradiation to both the irradiated
cuvette of ferrioxalate actinometer, as well as to the one kept in the dark,
phenantroline was added. Quantity of Fe(II) ions that are formed in the
photochemical reaction reacts with the added phenantroline and forms a
complex that absorbs at 510 nm and this can be easily measured by
UV/Vis spectrophotometer. Valerophenone solution when irradiated at
300 nm yields acetophenone and the formation of acetophenone was
measured by HPLC-MS. Conversion for valerophenone to acetophenone
was in our conditions 10%. The similar values for the amount of
absorbed photons n were obtained for both actinometers. The value for
the ferrioxalate actinometer was nFe (absorbed photons, 20 min) = 8,14 x
10-8 and for the valerophenone actinometer it was nVal (absorbed photons,
20 min) = 7.50 x 10-8. The equations for calculation of amount of
absorbed photons as well as the needed parameters are given in SI.
Quantity of tricyclic products 2a-d was measured (HPLC/MS), and this
value was used for calculating quantum yields (table 1). Measurements
were done two times in two independent experiments and the mean
value is given.
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Acknowledgements
University of Zagreb short term scientific support under the title
“Photocatalytic oxygenation of organic substrates using
manganese and cobalt porphyrins” is gratefully acknowledged.
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Keywords: butadiene • photochemistry • polycyclic • pyridine •
thiophene
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10.1002/ejoc.201700481
European Journal of Organic Chemistry
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Entry for the Table of Contents
FULL PAPER
To study the influence of heterocyclic
nuclei on the photochemical behavior
of the conjugated butadiene systems
novel butadiene derivatives have been
synthesized by multiple use of the
Wittig reaction. These butadiene
derivatives afforded by photochemical
intramolecular cycloaddition, new
fused tricyclic as well as tetracyclic
products.
Butadiene Photochemistry
Ivana Šagud, Marko Levačić, Željko
Marinić, Irena Škorić*
Page No. – Page No.
Formation of polycyclic skeleton via
photochemical transformations of
new pyridyl- and thienyl-butadiene
derivatives
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