Photochemical formation of indanylpyrrole derivatives from 2,2'-(o- phenylenedivinylene)dipyrrole

Article abstract of DOI:10.1016/S0040-4020(00)00062-4

Photochemically induced intra- and inter-molecular reaction of 2,2'- (1,2-phenylenedivinylene)dipyrrole (4a) led to a mixture of geometric isomers of 5-{2-pyrrolyl[2-(2-pyrrolyl)-1-indanyl]methyl}-2,2'-(1,2- phenylenedivinylene)dipyrroles (8) in 40% yield

Full text of DOI:10.1016/S0040-4020(00)00062-4

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 1587–1593
Photochemical Formation of Indanylpyrrole Derivatives from
2,20-(o-Phenylenedivinylene)dipyrrole
a
a,†
b
a,
ˇ
ˇ
*
´
ˇ ´
´
Nikola Basaric, Slavica Tomsic, Zeljko Marinic and Marija Sindler-Kulyk
aDepartment of Organic Chemistry, Faculty of Chemical Engineering and Technology, University of Zagreb,
´
Marulicev trg 19, HR-10000 Zagreb, Croatia
b
ˇ
NMR Center, The Rugjer Boskovic Institute, Zagreb, Croatia
Received 19 November 1999; revised 22 December 1999; accepted 13 January 2000
Abstract—Photochemically induced intra- and inter-molecular reaction of 2,20-(1,2-phenylenedivinylene)dipyrrole (4a) led to a mixture of
geometric isomers of 5-{2-pyrrolyl[2-(2-pyrrolyl)-1-indanyl]methyl}-2,20-(1,2-phenylenedivinylene)dipyrroles (8) in 40% yield. The
compounds were isolated and characterized spectroscopically and by catalytic hydrogenation to 5-{2-pyrrolyl[2-(2-pyrrolyl)-1-indanyl]-
methyl}-2,20-(1,2-phenylenediethylene)dipyrrole (10). Traces of 4,5-dihydro-4-(2-pyrrolyl)benzo [5,6]cycloocta[1,2-b]pyrrole (7) were
isolated in addition to 8. Under the same conditions N,N0-dimethyl-2,20-(1,2-phenylenedivinylene) dipyrrole (4b) undergoes only
cis–trans-isomerization. ᭧ 2000 Elsevier Science Ltd. All rights reserved.
Introduction
products 2a,b occurs via photoinduced electron transfer,
followed by proton transfer and radical combination. In
order to exploit the potential of our efficient intermolecular
photodimerization of styrylpyrroles and to develop a short
route to pyrrole derivatives, which are new nitrogen hetero-
cycles, we synthesized the compounds 4 (Scheme 2).
As a result of our interest in the synthesis and photochem-
istry of unsaturated heterocyclic derivatives,1 we turned our
attention to styrylpyrroles 1 (Scheme 1).2
Irradiation of 1a or 1b gives products 2a and 2b, respec-
tively, by regiospecific intermolecular addition of the
pyrrole to the double bond. With 1a, no intramolecular
formation of bicyclic product 3a was observed, as we
expected on analogy with furan derivatives.1a The bimol-
ecular photoaddition does not occur upon irradiation of the
N-methylpyrrole derivative 1c and only traces of the
bicyclic product 3b were formed. In addition to cis–trans
isomerization, the formation of some tarry material was also
observed. We proposed2 that the formation of dimeric
Compound 4a upon irradiation might give the intermo-
lecular addition product 5. This could subsequently close
to the interesting larger aromatic pyrrole-containing
systems, the so-called ‘expanded’ porphyrin-like com-
pounds.3 More likely, because of the presence of the two
pyrrolyl-styrylgroups in the same molecule, an intra-
molecular ring closure is expected to give an annelated
azepine compound such as 6. Although Lewis4 and
co-workers reported the intramolecular photoaddition of
Scheme 1.
Keywords: indanes; hydrogenation; photochemistry; pyrroles.
* Corresponding author. Tel.: ϩ385-1-4597246; fax: ϩ985-1-4597250; e-mail: marija.sindler@pierre.fkit.hr
†
Present address: Pliva-Research Institute, Zagreb, Croatia.
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00062-4

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N. Basaric et al. / Tetrahedron 56 (2000) 1587–1593
1588
Scheme 2.
the o-(aminoalkyl)stilbenes and formation of benzazepines,
to the best of our knowledge no intramolecular secondary
amine-like photoaddition of a pyrrole to a double bond has
been previously observed. The intermolecular 1,4-photo-
addition of aliphatic amines and pyrrole to benzene5 and
naphthalene6 is well known. Besides the photodimerization
of styrylpyrroles,2 Gilbert’s report of the photoaddition of
pyrrole to styrenes7 and photochemical coupling between
pyrrole and pyridone derivatives,8 and the photoaddition
reactions of indole, carbazole and phenothiazine to trans-
stilbene in the mixed crystal state as well as in solution have
been described.9
from p-substituted triphenylphosphonium salts and 1-methyl-
2-pyrrole-carboxaldehyde but lower than those described
for similar styrylpyrroles.10b In our case, because the diphos-
phonium salt is a starting material, a double Wittig reaction
must occur to give 4a or 4b. Because of the lower reactivity
of the pyrrolecarboxaldehydes, steric hindrance due to
o-substitution and NH acidity of the pyrrole in a competing
side reaction,11 formation of a certain amount of styryl-
pyrroles 1b and 1d is unavoidable (see Experimental). In
addition, the pyrrole derivatives are quite unstable in air and
decompose during attempts at purification.
The geometric isomers of 4a were separated by repeated
column chromatography on silica gel and identified spectro-
scopically. The corresponding isomers 4b have not been
obtained pure because of poor chromatographic separation.
All three isomers of 4a and 4b show a strong absorption in
the region of 270–360 nm.
In the present paper we describe formation and structure
determination of novel compounds 7 and 8 obtained by photo-
chemical intra- and inter-molecular reaction of 4a in benzene.
Results and Discussion
Irradiation of a degassed benzene solution of 4a [10Ϫ3 M],
followed by evaporation of the solvent, gave a dark residue
from which a mixture of dimeric stereoisomers 8 was
isolated in 40% yield after chromatography, besides traces
of a minor product 7. Starting material 4a (40%, a mixture
of isomers) was also recovered (Scheme 3).
The starting compounds 4a and 4b, new pyrrole derivatives,
were prepared as the mixtures of stereoisomers in 30 or 40%
yield, respectively, by using the general procedure
described for the heteroarylstilbene analogues.1b–d The
yields are higher than those reported10a for Wittig reactions
Scheme 3.

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1589
To improve the yield of the photoreaction, irradiation of 4a
(pure isomer or as a mixture of isomers) was performed at
different wavelengths and irradiation times but without
substantial influence on the reaction course. The yield of
photoproducts did not increase due to their competitive
absorbtion at the same wavelength as the starting material.
On prolonged irradiation of isolated mixture of isomers 8,
some tetrameric structures are found in MS. No products
were obtained from 4a in a tube, which has been kept in
darkness during the irradiation experiments. Irradiation of
N-methyl derivative 4b, a compound that cannot react as a
secondary amine, failed to yield products other than the
intractable tars deposited on the irradiation flask walls.
The only detectable process was cis–trans isomerization.
protons of 4a. From the COSY experiments it is shown
that protons A–E are in mutual interaction. The 13C NMR
spectra of 8b and 8c show three doublets and one triplet in
the aliphatic region. This corresponds to the carbons C(1)–
C(4). In the aromatic region there are twenty-three doublets
and nine singlets. When added to the aliphatic signals, this
makes thirty-six total signals. Analysis of each 13C NMR
signal, assisted with HETCOR, results in the following
assignments. The eleven doublets (not twelve) between d
105–120 correspond to pyrrole carbons. Three pyrrole
doublets (not four) are at d 117–120 indicating that the
product has one pyrrole ring substituted at the 2- and 5-
positions. The four signals near d 120 can be assigned to
ethylenic carbons. Eight doublets at d 125–130 correspond
to benzene carbons and nine singlets at d 130–145 belong to
quaternary benzene and pyrrole carbons. Four isomers are
possible for the two double bonds in 8, but more are possible
because of different configurations on the indane ring. Since
the chemical shifts of the aliphatic protons of separable
isomers of 8 differ hardly at all, and the coupling constants
are nearly identical, we conclude that isomers 8a–c all have
the same configuration in the indane, and differ only in the
configuration of the double bonds. Cis- and trans-coupling
constants are very similar in indanes and the stereochemical
relationship of the 1,2-substituents cannot readily be eval-
uated from coupling constant data.13 However, it is clear
from the NOESY spectra of 8 that protons A and C interact
more strongly than protons B and C. The cross peak in the
spectrum from A and C shows that they are on the same side
of the indane ring. Consequently, products 8 should have the
trans-configuration of the pyrrolic substituents on the
indane ring.
The structures of the products were determined spectro-
1
scopically and by chemical means. The H NMR spectrum
of compound 7 was taken in three different solvents, CDCl3,
C6D6 and (CD3)2CO, to facilitate the structure determination
and full assignment of the resonances. Combining the data
from all three spectra it is evident that the molecule has one
conjugated double bond in the cis-configuration, five
pyrrolic CH, two NH and three aliphatic protons of a
CH2–CH moiety, according to the coupling constants and
chemical shifts. Using COSY experiments, three pyrrole
protons were ascribed to one ring and two to the other.
Based on their chemical shifts and corresponding coupling
constants, we concluded that the second pyrrole ring has to
be substituted in positions 2 and 3. The three protons in the
CH2–CH moiety might give a similar pattern either as a part
of a seven-membered ring, as in structure 6, or as a part of an
eight-membered ring. The mass spectrum showed the frag-
ment MϩϪ66 (MϩϪpyrrole) which confirmed the structure
7 and eliminated the cycloheptene-like structure, for which
the preferred fragmentation would be MϩϪ80 (MϩϪpyrrolyl-
methyl)12 with formation of the tropylium-like cation.
To confirm that the only difference among 8a–c is the
configuration on the double bonds, hydrogenation was
carried out (Scheme 4). The procedure was tried first for
model compound 4a, which gave a new compound 9.
Then, catalytic hydrogenation of the isomers 8 gave only
one product 10 that was evident from the 1H NMR spectrum
of the crude reaction mixture prior to separation. The mass
spectrum of the hydrogenated product 10 shows a molecular
ion that is four units higher than compound 8 and a base
peak at m/z 342 from the same fragmentation as in 8. The
The main product 8 consists mainly of three isomers accor-
1
ding to H NMR in a ratio 1:3:1 (8a:8b:8c). From the
C,H-elemental analysis it is evident that the mixture consists
only of dimeric isomers and not additional products. All
three isomers 8a–c show the molecular ion in the mass
spectrum (Mϩ 520) and the base peak of m/z 338 which
corresponds to the mass of 4a increased by a pyrrolylmethyl-
enic group. 1H NMR spectra of all three products 8a–c show
four signals from 2.0 to 4.5 ppm in a ratio of 1:1:1:2 in the
aliphatic region. The aromatic region is complicated but the
pattern resembles a structure with twice the number of pyr-
role and benzene protons with respect to starting compound
4a. However, in this multiplet, parts of AB-quartets could be
detected. These are similar to cis- and trans-ethylenic
1
aliphatic region in the H NMR spectrum of 10 shows five
indane protons (Fig. 1) in addition to resonances for eight
CH2 protons that are similar to those found in compound 9.
An attempt to make simpler derivatives of the compounds 8
by ozonolysis gave, as found with the model compound 4a,
polymeric material.
A plausible mechanism for the formation of photoproducts 7
Scheme 4.

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N. Basaric et al. / Tetrahedron 56 (2000) 1587–1593
1590
Me4Si as an internal standard. The assignment of the signals
is based on 2D-CH correlation and 2D-HH-COSY and
NOESY experiments. UV spectra were measured on
Perkin–Elmer LAMBDA 20 Spectrophotometer. HRMS
spectra were measured on an Auto Spec Q (VG Analytical).
Elemental analyses were carried out in the Microanalytical
Laboratory at the Rugjer Boskovic Institute. Melting points
were obtained on a Original Kofler Mikroheitztisch appa-
ratus (Reicherdt, Wien) and are uncorrected.
Pyrrole-2-carboxaldehyde and N-methylpyrrole-2-carbox-
aldehyde were obtained from commercial source and used
without further purification.
Notation of H atoms in NMR assignments: e.g. H5pˆH in
pyrrole at the position 5, HetˆH in ethylene, Het-ctcˆH in
cis-ethylene part of cis–trans isomer, Het-cttˆH in trans-
ethylene part of cis–trans isomer etc.
Preparation of 2,20-(1,2-phenylenedivinylene)dipyrrole
(4a) and N,N0-dimethyl-2,20-(1,2-phenylenedivinylene)-
1
Fig. 1. H NMR spectra of: (a) 10; and (b) 8b.
Scheme 5.
and 8 is shown in Scheme 5. After photoexcitation of 4a, an
electron transfer followed by hydrogen transfer can occur2,7
to give the intermediate 11. This could close (path a) to the
indane derivative 12 that easily reacts with the starting
compound 4a and give dimeric products 8. Compound 7
can be formed from the same intermediate 11 but by the
different intramolecular ring closure (path b) (Scheme 5).
dipyrrole (4b) by the Wittig reaction from diphosphonium
salt o-C6H4(CH2PPh3Br)2 and corresponding aldehydes,
pyrrole-2-carboxaldehyde and N-methylpyrrole-2-carbox-
aldehyde, respectively. To a stirred solution of o-xylylene-
bis(triphenylphosphonium bromide)1 (7.88 g, 10 mmol) and
the corresponding aldehyde (20 mmol) in 250 ml of abso-
lute ethanol a solution of sodium ethoxide (700 mg,
30 mmol in 20 ml ethanol) was added dropwise. Stirring
was continued under a stream of dry nitrogen for two days
at 30ЊC (4a) and 24 h under reflux (4b), respectively. After
removal of the solvent, the residue was worked up with
water and benzene. The benzene extracts were dried and
concentrated. The crude reaction mixture was chromato-
graphed on silica gel with dichloromethane to separate the
products 4a and 4b, respectively, from triphenylphosphine
oxide and unreacted aldehydes, which remained on the
column. The cis- and trans-isomers were separated and
fully characterized by repeated column chromatography
using petroleum ether/dichloromethane mixture as eluent.
Based on the results thus far obtained, we can conclude that
the preferred process in the photochemical reaction of
1,2-di(pyrrolylvinyl)benzene is ring closure to the substi-
tuted indanes followed by nucleophilic attack of the starting
compound. Although the absolute configurations on the
chiral centers of the isolated isomers 8 are not known, all
of them have trans-configuration of the pyrrolic substituents
on the indane ring.
Experimental
General
2,20-(1,2-Phenylenedivinylene)dipyrrole (4a). 0.845 g,
yield 32.5%: a mixture of 14% cis, cis-4a, 32% cis, trans-
4a and 54% trans, trans-4a. In the first fractions cis- and
trans-2-(2-methylstyryl)pyrrole (1b) were isolated as by
products and were identical to a sample obtained previously.2
1
The H NMR and 13C NMR spectra were recorded on a
Varian GEMINI 300 spectrometer at 300 and 75 MHz,
respectively, in CDCl3 and when necessary in C6D6 with

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1591
cis, cis-4a: colorless crystals, mp 75–76ЊC; UV (EtOH)
lmax (e) 285 (11529), 325 (13872); IR (KBr) 3400 (N–H)
cmϪ1; 1H NMR (CDCl3) d 7.92 (bs, 2H, NH), 7.50–7.58 (m,
2H, Har), 7.30–7.38 (m, 2H, Har), 6.54 (dt, 2H, H5p, Jˆ2.6,
1.3 Hz), 6.41 (d, 2H, Het, Jˆ12.2 Hz), 6.23 (d, 2H, Het,
Jˆ12.2 Hz), 6.15 (ddd, 2H, H4p, Jˆ3.5, 2.6, 1.3 Hz), 6.10
(dt, 2H, H3p, Jˆ3.5, 2.6 Hz); 13C NMR (CDCl3) d 137.71
(s), 129.54 (s), 129.28 (d), 127.83 (d), 121.99 (d), 120.86
(d), 118.91 (d), 111.71 (d), 108.83 (d); MS m/z 260 (Mϩ,
90%), 193 (70), 180 (100), 145 (98), 80 (90); HRMS for
C18H16N2 260.1313, found 260.1311; Anal. Calcd for
C18H16N2: C, 83.04; H, 6.20; N, 10.76. Found: C, 82.85;
H, 6.19; N, 11.00.
(2d, 2H, Jˆ15.9 Hz, Het), 6.64 (m, 1H, H5p), 6.49 (m, 1H,
H3p), 6.16 (m, 1H, H4p), 3.65 (s, 3H, N–CH3), 2.38 (s, 3H,
ar-CH3); 13C NMR (CDCl3) d 136.81 (s), 135.37 (s),
132.31(s), 130.31 (d), 126.93 (d), 126.07 (d), 124.68 (d),
123.89 (d), 123.44 (d), 118.29 (d), 108.10 (d), 106.48 (d),
33.87 (q), 19.68 (q); MS m/z 197 (Mϩ, 100%), 182 (64), 167
(93), 165 (95), 152 (47), 141 (26), 139 (27), 115 (43). Anal.
Calcd for C14H15N: C, 85.24; H, 7.66. Found: C, 85.14; H,
7.44.
1
4b (overall yield 1.27 g, according to H NMR spectrum a
mixture of 13% cis, cis-4b, 67% cis, trans-4b and 20%
trans, trans-4b): viscous oil which crystallizes by standing
in refrigerator; UV(EtOH) lmax (e) of the mixture 324.0
1
cis, trans-4a: colorless crystals, mp 95–97ЊC; UV (EtOH)
lmax (e) 242 (10228), 325 (21571), 340 (24546); IR (KBr)
(18598); H NMR (CDCl3) d 7.10–7.65 (m, Har, 2Het-tt),
7.05 and 6.89 (2d, 2H, Jˆ16.1 Hz, Het-ctt), 6.85 (d, 2H,
Jˆ15.9 Hz, Het-tt), 6.65 (m, 2H, H5p-tt), 6.62 (m, 1H,
H5p-ctt), 6.48–6.55 (m, 5H, 2H5p-cc, H5p-ctc, 2H3p-tt), 6.52
(s, 2H, Het-ctc), 6.41 (bs, 5H, 4Het-cc, H3p-ctt), 6.17 (m, 2H,
H4p-tt), 6.13 (m, 1H, H4p-ctt), 5.96 (m, 2H, H4p-cc), 5.92 (m,
1H, H4p-ctc), 5.88 (m, 2H, H3p-cc), 5.77 (m, 1H H3p-ctc),
3.69 (s, 6H, CH3-tt), 3.66 and 3.60 (2s, 6H, CH3-ct), 3.55
(s, 6H, CH3-cc); MS m/z 288 (Mϩ, 64%), 207 (31), 206 (46),
194 (80), 173 (100), 165 (43), 152 (29), 115 (30), 94 (59), 81
(40); Anal. Calcd for C20H20N2: C, 83.30; H, 6.99. Found: C,
83.33; H, 7.19.
1
3380 (N–H), 3440 (N–H) cmϪ1; H NMR (CDCl3) d 8.29
(bs, 1H, NH), 7.89 (bs, 1H, NH), 7.67 (d, 1H, Har,
Jˆ7.6 Hz), 7.20–7.38 (m, 3H, Har), 6.95 (d, 1H, Het,
Jˆ16.5 Hz), 6.82 (d, 1H, Het, Jˆ16.5 Hz), 6.79 (dt, 1H,
0
H5 p, Jˆ2.6, 1.3 Hz), 6.54 (d, 1H, Het, Jˆ12.1 Hz), 6.53
(dt, 1H, H5p, Jˆ2.6, 1.3 Hz), 6.36 (d, 1H, Het, Jˆ12.1 Hz),
0
0
6.31 (ddd, 1H, H4 p, Jˆ3.5, 2.6, 1.3 Hz), 6.22 (dt, 1H, H3 p
,
Jˆ3.5, 2.6 Hz), 6.19 (ddd, 1H, H4p, Jˆ3.5, 2.6, 1.3 Hz), 6.10
(dt, 1H, H3p, Jˆ3.5, 2.6 Hz); 13C NMR (CDCl3) d 136.43
(s), 136.07 (s), 130.81 (s), 129.70 (s), 129.50 (d), 127.95 (d),
127.20 (d), 125.04 (d), 121.89 (d), 121.44 (d), 120.67 (d),
120.37 (d), 119.35 (d), 119.31 (d), 111.85 (d), 109.92 (d),
109.75 (d), 108.65 (d).
Irradiation experiments
A solution of 4a and 4b, respectively, in 500 ml of benzene
(2×10Ϫ3 M) was purged with argon for 30 min and
irradiated in a quartz tube in the Rayonet reactor for 18 h
at 300 nm (4a) and at 350 nm (4b) at rt. Solvent was
removed in vacuum and the dark oily residue chromato-
graphed on the silica gel column using petroleum ether–
dichloromethane as eluents.
trans, trans-4a: colorless crystals, mp 151–152ЊC; UV
(EtOH) lmax (e) 312 (30446), 325 (24710); IR (KBr)
3430 (N–H) cmϪ1 1H NMR (CDCl3) d 8.37 (bs, 2H,
;
NH), 7.45–7.50 (m, 2H, Har), 7.20–7.25 (m, 2H, Har),
6.95 (d, 2H, Het, Jˆ16.1 Hz), 6.83 (d, 2H, Het,
Jˆ16.1 Hz), 6.81 (dt, 2H, H5p, Jˆ2.6, 1.3 Hz), 6.37 (ddd,
2H, H4p, Jˆ3.5, 2.6, 1.3 Hz), 6.26 (dt, 2H, H3p, Jˆ3.5,
2.6 Hz); 13C NMR (CDCl3) d 135.68 (s), 131.07 (s),
127.21 (d), 126.25 (d), 121.44 (d), 121.35 (d), 119.21 (d),
110.09 (d), 109.24 (d).
Irradiation of 2,20-(1,2-phenylenedivinylene)dipyrrole
(4a). Unreacted 4a was isolated in first fractions (110 mg,
41%) followed by traces of 7 and then 108 mg (40%) of the
dimeric products 8. After repeated and tedious column
chromatography of the dimeric mixture of 8 the enreached
fractions of 8a, 8b and 8c, respectively were isolated with
dichloromethane/petroleum ether (7:4) as eluents.
N,N0-Dimethyl-2,20-(1,2-phenylenedivinylene)dipyrrole
(4b). In the first fractions cis- and trans-N-methyl-2-
(2-methylstyryl)pyrrole (1d) were isolated as by products
(745 mg, cis:transˆ2:3, 26.9%, based on the quantity of
diphosphonium bromide) follwed by a mixture of cis, cis-
4b, cis, trans-4b and trans, trans-4b (44%). Unreacted
pyrrolecaroxaldehyde remained on the column by elution
with dichloromethane.
4,5-Dihydro-4-(2-pyrrolyl)-benzo[5,6]cycloocta[1,2-b]-
pyrrole (7): colorless crystals, mp 112ЊC; 1H NMR (CDCl3)
d 7.76 (bs, 1H, NH), 7.65 (bs, 1H, NH), 6.98–7.20 (m, 4H,
Har), 6.63 (m, 1H, Hp), 6.61 (dd, 1H, Het, Jˆ12.1 Hz), 6.55
(dd, 1H, Het, Jˆ12.1 Hz), 6.55 (m, 1H, Hp), 6.16 (m, 1H,
Hp), 6.13 (m, 1H, Hp), 5.96 (m, 1H, Hp), 4.62 (t, 1H,
cis-1d: light yellow oil; UV(EtOH) lmax (e) 233 (13586),
1
1
294 (14554); H NMR (CDCl3) d 7.08–7.32 (m, 4H, Har),
Jˆ6.4 Hz), 3.23 (d, 2H, Jˆ6.3 Hz); H NMR (C6D6) d
6.53 (dd, 1H, J3,5ˆ1.6, J4,5ˆ2.7 Hz, H5p), 6.47 and 6.44
(ABq, 2H, Jˆ12.2 Hz, Het), 5.92 (dd, 1H, J3,4ˆ3.7,
J4,5ˆ2.7 Hz, H4p), 5.68 (dd, 1H, J3,4ˆ3.7, J3,5ˆ1.6 Hz,
H3p), 3.58 (s, 3H, N–CH3), 2.26 (s, 3H, CH3); 13C NMR
(CDCl3) d 137.66 (s), 135.85 (s), 129.86 (d), 129.58 (s),
128.46(d), 126.96 (d), 125.84 (d), 125.64 (d), 122.33(d),
118.57 (d), 108.24 (d), 107.55 (d), 33.87 (q), 19.61 (q).
6.80–7.22 (m, 6H, H4ar, 2 NH), 6.48 (d, 1H, Het,
Jˆ12.4 Hz), 6.32 (m, 1H, Hp), 6.25 (m, 1H, Hp), 6.19 (m,
1H, Hp), 6.14 (d, 1H, Het, Jˆ12.4 Hz), 6.08 (m, 1H, Hp),
5.98 (m, 1H, Hp), 4.64 (dd, 1H, Jˆ3.1 Hz), 3.30 (dd, 1H,
1
Jˆ3.0, 12.6 Hz), 3.16 (dd, 1H, Jˆ8.4, 12.6 Hz); H NMR
((CD3)2CO) d 9.80 (bs, 1H, NH), 9.60 (bs, 1H, NH), 7.20–
7.36 (m, 4H, Har), 6.79 (d, 1H, Het, Jˆ12.3 Hz), 6.68–6.73
(m, 2H, Hp), 6.66 (d, 1H, Het, Jˆ12.3 Hz), 6.05 (m, 1H, Hp),
5.96 (m, 1H, Hp), 5.92 (m, 1H, Hp), 4.58 (dd, 1H, Jˆ3.2,
10.8 Hz), 3.43 (dd, 1H, Jˆ12.5, 10.8 Hz), 3.21 (dd, 1H,
Jˆ12.5, 3.2 Hz); 13C NMR (C6D6) d 140.18 (s), 138.14
trans-1d: light yellow crystals, mp 44ЊC; UV (EtOH) lmax
(e) 237 (10660), 335 (16793); 1H NMR (CDCl3) d 7.53 (d,
1H, Jˆ7.3 Hz, Har), 7.10–7.30 (m, 3H, Har), 6.85 and 7.07

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1592
(s), 137.34 (s), 131.46 (d), 127.77 (d), 127.68 (d), 125.86
(d), 122.94 (d), 117.79 (d), 116.40 (d), 113.17 (d), 108.48
(d), 105.85 (d), 41.35 (d), 40.42 (t), 3 signals are covered;
MS m/z 260 (Mϩ, 100%), 244 (33), 194 (28).
was isolated followed by 10 mg (22%) of high molecular
weight products. MS m/z 1041.3 (MHϩ, 2%), 858.3 (18),
577.5 (60), 338.2 (65), 259.1 (100).
5-{2-Pyrrolyl[2-(2-pyrrolyl)-1-indanyl]methyl}-2,20-(1,2-
phenylenedivinylene)dipyrroles (8), according to 1H
NMR: 8a (20%), 8b (60%), 8c (20%): UV(EtOH) lmax
(e) of the mixture: 323 (5739), 344 (6659), 207 sh
(11383); IR (KBr) of the mixture: 3385 (N–H), 3096,
3017, 2922, 2851, 1628 cmϪ1; Anal. Calcd for C36H32N4:
C, 83.04; H, 6.20. Found: C, 83.23; H, 6.23.
Hydrogenation experiments
To a benzene solution of 4a or 8 (25 mg in 25 ml) a catalytic
amount of Pd/C was added and the solution was purged with
hydrogen for 3–5 days at rt. The solvent was removed in
vacuum and the residue chromatographed on silica gel
column using dichloromethane–petroleum ether (8:2 for 9
and 7:3 for 10, respectively) as eluent. Unreacted 4a or 8
was isolated from the first fractions followed by 9 or 10,
respectively.
8a: light yellow crystals, too small a quantity to be analyzed
1
completely; H NMR (C6D6) d 5.7–7.8 (m, Har, Het, Hp),
4.11 (d, 1H, Jˆ5.7 Hz), 3.79 (t, 1H, Jˆ5.7 Hz), 3.41 (m,
1H), 2.86–2.66 (m, 2H); MS m/z 521 (MHϩ, 31%), 338
(100).
Hydrogenation of 4a (cis–trans): 2,20-(1,2-phenylene-
diethylene)dipyrrole (9). 19 mg (75%), oil; UV(EtOH)
lmax (e) 211.6 (22190); IR (neat) 3383 (N–H), 3099,
1
3051, 2918, 2850 cmϪ1; H NMR (C6D6) d 7.05–7.10 (m,
1
8b: light yellow crystals, 80–85ЊC (decomp.); H NMR
2H, Har), 6.99–7.04 (m, 2H, Har), 6.79 (bs, 2H, N–H), 6.30
(m, 2H, Hp), 6.26 (m, 2H, Hp), 6.02 (m, 2H, Hp), 2.65 (m,
4H, Het), 2.55 (m, 4H, Het); 13C NMR (C6D6) d 140.35 (s),
131.83 (s), 129.80 (d), 126.95 (d), 116.68 (d), 108.93 (d),
106.15 (d), 33.37 (t), 29.64 (t); MS m/z 264 (Mϩ, 100%),
184 (61), 80 (42); Anal. Calcd for C18H20N2: C, 81.77; H,
7.63. Found: C, 81.68; H, 7.46.
(C6D6) d 5.7–7.8 (m, Har, Het, Hp), 3.92 (d, 1H,
Jˆ5.4 Hz), 3.65 (t, 1H, Jˆ5.4 Hz), 3.23 (ddd, 1H, Jˆ5.4,
6.0, 7.8 Hz), 2.70 (dd, 1H, Jˆ16.2, 7.8 Hz), 2.63 (dd, 1H,
Jˆ16.2, 6.0 Hz); 13C NMR (C6D6) d 144.49 (s), 144.10(s),
137.23 (s), 136.89 (s), 136.24 (s), 135.14 (s), 131.32 (s),
130.26 (s), 130.06 (d), 129.63 (s), 128.92 (d), 127.92 (d),
127.91 (d), 127.19 (d), 125.83 (d), 125.54 (d), 125.06 (d),
122.40 (d), 121.77 (d), 121.43 (d), 120.87 (d), 120.02 (d),
117.67 (d), 117.07 (d), 113.25 (d), 110.92 (d), 110.36 (d),
108.76 (d), 108.75 (d), 108.35 (d), 107.75 (d), 105.09 (d),
51.17 (d), 42.56 (d), 41.93 (d), 39.58 (t); MS m/z 520 (Mϩ,
18%), 338 (100), 271 (10), 180 (25), 145 (26), 80 (20);
HRMS for C36H32N4 520.2627, found 520.2627.
Hydrogenation of 8: 5-{2-pyrrolyl[2-(2-pyrrolyl)-1-inda-
nyl]methyl}-2,20-(1,2-phenylenediethylene) dipyrrole (10).
4 mg (16.5%); light yellow crystals, 47–48ЊC; UV(EtOH)
lmax (e) 212 (39300); IR (as oil) 3386 (N–H), 2921,
1
2851 cmϪ1; H NMR (C6D6) d 5.8–7.6 (m, Har, Hp), 4.05
(d, 1H, Jˆ6.6 Hz), 3.79 (t, 1H, Jˆ6.6, 5.1 Hz), 3.43 (ddd,
1H, Jˆ5.1, 6.3, 8.1 Hz), 2.91 (dd, 1H, Jˆ16.2, 8.1 Hz), 2.80
(dd, 1H, Jˆ16.2, 6.3 Hz); 13C NMR (C6D6) d 144.98 (s),
144.10 (s), 140.35 (s), 140.26 (s), 136.60 (s), 131.86 (s),
131.60 (s), 131.57 (s), 131.46 (s), 129.85 (d), 128.92 (d),
128.92 (d), 127.06 (d), 126.92 (d), 126.85 (d), 125.99 (d),
125.09 (d), 117.64 (d), 117.04 (d), 116.74 (d), 109.06 (d),
108.75 (d), 108.75 (d), 108.29 (d), 107.07 (d), 106.26 (d),
106.13 (d), 105.03 (d), 57.29 (d), 42.96 (d), 42.22 (d), 39.55
(t), 33.38 (t), 33.26 (t), 29.64 (t), 29.34 (t); MS m/z 524 (Mϩ,
2%), 522 (12), 342 (100), 158 (40), 80 (75); Anal.
Calcd for C36H40N4: C, 81.77; H, 7.63. Found: C,
81.74; H, 7.80.
1
8c: light yellow crystals, 100–103ЊC (decomp.); H NMR
(C6D6) d 5.9–7.7 (m, Har, Het, Hp), 4.14 (d, 1H, Jˆ5.9 Hz),
3.77 (dd, 1H, Jˆ5.4, 5.6 Hz), 3.39 (ddd, 1H, Jˆ5.9, 7.9,
5.4 Hz), 2.84 (dd, 1H, Jˆ16.0, 7.9 Hz), 2.72 (dd, 1H,
Jˆ15.9, 5.9 Hz); 13C NMR (C6D6) d 144.50 (s), 144.13
(s), 136.63 (s), 136.60 (s), 136.27 (s), 134.86 (s), 131.55
(s), 131.21 (s), 130.86 (s), 127.77 (d), 127.77 (d), 127.69
(d), 127.22 (d), 126.94 (d), 126.91 (d), 125.76 (d), 125.28
(d), 122.19 (d), 121.94 (d), 121.63 (d), 121.40 (d), 119.87
(d), 117.97 (d), 117.28 (d), 110.65 (d), 110.47 (d), 109.90
(d), 109.26 (d), 108.82 (d), 108.81 (d), 108.80 (d),
105.24(d), 57.09 (d), 42.70 (d), 42.07 (d), 39.56 (t); MS
m/z 520 (Mϩ, 5%), 338 (100), 271 (20), 260 (38), 180
(43), 145 (28), 67 (48); HRMS for C36H32N4 520.2627,
found 520.2579.
Ozonolysis of 4a. Into a dichloromethane solution of 4a
(35 mg in 30 ml) a stream of O3 was introduced at Ϫ70ЊC
for 15 min. The color of the solution changed from yellow to
green. After warming up the reaction mixture to rt the
solvent was evaporated. The residue of powdery material
is not soluble in chloroform, benzene and only slightly
soluble in acetone.
Irradiation of N,N0-dimethyl-2,20-(1,2-phenylenediviny-
lene)dipyrrole (4b). Irradiation was performed under the
same conditions as 4a. This afforded only cis–trans
isomerization, besides some tarry material.
Irradiation of 5-{2-pyrrolyl[2-(2-pyrrolyl)-1-indanyl]-
methyl}-2,20-(1,2-phenylenedivinylene)dipyrroles (8). A
benzene solution of dimeric products 8 (45 mg in 17 ml,
0.09 M) was purged with nitrogen and irradiated in the
Rayonet reactor at 300 nm for 1 h at rt. After removal of
the solvent the dark brown residue was chromatographed on
silica gel with dichloromethane–petroleum ether (7:3) as
eluent. In the first fractions 21 mg (47%) of unreacted 8
Acknowledgements
We thank Prof. D. C. Neckers for critically reading the
manuscript. Financial support from the Ministry of Science
and Technology of the Republic of Croatia under contract
125004 is gratefully acknowledged.

´
N. Basaric et al. / Tetrahedron 56 (2000) 1587–1593
1593
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