Overcrowded 1,8-diazafluorenylidene-chalcoxanthenes. Introducing nitrogens at the fjord regions of bistricyclic aromatic enes

Article abstract of DOI:10.1039/b303041e

The effects of introducing nitrogen atoms in the fjord regions and chalcogen bridges on the conformations of overcrowded bistricyclic aromatic enes were studied. The structures were studied by ¹H, ¹³C, ⁷⁷Se and ¹²⁵

Full text of DOI:10.1039/b303041e

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Overcrowded 1,8-diazafluorenylidene-chalcoxanthenes. Introducing
nitrogens at the fjord regions of bistricyclic aromatic enes
Amalia Levy, Shmuel Cohen and Israel Agranat*
Department of Organic Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904,
Israel. E-mail: isria@vms.huji.ac.il
Received 20th March 2003, Accepted 11th June 2003
First published as an Advance Article on the web 30th June 2003
The effects of introducing nitrogen atoms in the fjord regions and chalcogen bridges on the conformations of
overcrowded bistricyclic aromatic enes (1, X ≠ Y) (BAEs) were studied. 9-(9ЈH-1Ј,8Ј-Diazafluoren-9Ј-ylidene)-
9H-thioxanthene (12), 9-(9H-1Ј, 8Ј-diazafluoren-9Ј-ylidene)-9H-selenoxanthene (13), 9-(9ЈH-1Ј,8Ј-diazafluoren-
9Ј-ylidene)-9H-telluroxanthene (14), 9-(9ЈH-1Ј,8Ј-fluoren-9-ylidene)-9H-xanthene (15) and 9-(9ЈH-1Ј,8Ј-fluoren-
9Ј-ylidene)-9H-fluorene (16) were synthesized by two-fold extrusion coupling reactions of 1,8-diaza-9H-fluoren-
9-one (19)/chalcoxanthenthiones (24–27) (or /9H-fluorene-9-thione (30)). The 1Ј,8Ј-diazafluoren-9-ylidene-
chalcoxanthenes (11) were compared with the respective fluoren-9-ylidene-chalcoxanthenes (10). The structures
of 12–16 were established by 1H, 13C, 77Se, and 125Te NMR spectroscopies. The crystal and molecular structures of
12–14 were determined by X-ray analysis. The yellow molecules of 12–14 adopted mono-folded conformations with
folding dihedrals in the chalocoxanthylidene moieties of 62.7Њ (12), 62.4Њ (13) and 59.9Њ (14). The folding dihedrals
in the respective 1Ј,8Ј-diazafluorenylidene moieties were very small, ca. 2Њ, compared with 10.2/8.0Њ in (9ЈH-fluoren-
9Ј-ylidene)-9H-selenoxanthene (7). A 5Њ pure twist of C9᎐C9Ј in 14 is noted. The degrees of overcrowding in the fjord
᎐
regions of 12–14 (intramolecular non-bonding distances) were relatively small. The degrees of pyramidalization of
C9 and C9Ј were 17.0/3.0Њ (12), 17.4/2.4Њ (13) and 2.2/2.2Њ (14). These high values in 12 and 13 stem from the resistance
of the 1,8-diazafluorenylidene moiety to fold and from the limits in the degrees of folding of the thioxanthylidene and
selenoxanthylidene moieties (due to shorter S10–C4a/S10–C10a and Se10–C4a/Se10–C10a bonds, as compared with the
respective Te–C bonds in 14). The molecules of 15 and 16 adopt twisted conformations, a conclusion drawn from
the 1H NMR chemical shifts of the fjord regions protons (H1 and H8) at 8.70 (15) and 9.00 ppm (16) and from their
colors and UV/VIS spectra: 15 is purple (λmax = 521 nm) and 16 is orange–red. A comparison of the NMR spectra
of 11 and 10 (∆δ = δ(11) – δ(10)) showed substantial downfield shifts of 0.56–0.62 ppm of the fjord regions protons
of twisted 15 and 16: ∆δ (C9) were negative (upfield): Ϫ4.0 (12), Ϫ3.7 (13), Ϫ3.4 (14), Ϫ7.1 (15), Ϫ5.0 ppm (16), while
∆δ (C9Ј) were positive (downfield) = ϩ6.8 (12), ϩ6.5 (13), ϩ5.8 (14), ϩ11.7 (15), ϩ7.7 ppm (16). In 15, ∆δ (C9) – ∆δ
(C9Ј) = ϩ18.8 ppm, attributed to a push–pull character and significant contributions of zwitterionic structures in the
twisted conformation. The 77Se and 125Te NMR signals of 13 and 14 were shifted upfield relative to the respective
fluorenylidene-chalcoxanthene derivatives: ∆δ77Se = 17.2 ppm and ∆δ125Te = 22.0 ppm. The presence of the
nitrogen atoms (N1Ј and N8Ј) in 13 and 14 causes shielding of the selenium and tellurium nuclei.
Introduction
The bistricyclic aromatic enes (BAEs) (1) have fascinated
chemists since bifluorenylidene (2) and dixanthylene (3) were
synthesized and thermochromism was revealed in bianthrone
(4).1–5 They can be classified into homomerous bistricyclic enes
(1, X = Y) and heteromerous bistricyclic enes (1, X ≠ Y).3,6 The
BAEs are nonplanar and overcrowded in the fjord regions.
There are two principal modes of out-of-plane deformations
in 1: twisting around the central double bond (C9᎐C9Ј) and
᎐
out-of-plane bending,3,4 realized by folding of the tricyclic
moieties.3,4,7 In addition, C9 and C9Ј may be pyramidalized.1–4
The nonplanarity of 1 may introduce chirality.4,6 The major
mode of deviation from planarity is dependent on the sizes of
the central rings and on the bridges X, Y (bond lengths C–X
and C–Y, distances C4a ؒ ؒ ؒ C10a).3,8,9 A variety of conform-
ations have been revealed in the homomerous bistricyclic enes,
including twisted (t) bifluorenylidene10,11 (2), anti-folded (af )
dixanthylene12 (3), anti-folded (af ) bianthrone13 (4), and anti-
folded (af ) and syn-folded (sf ) 5,5Ј-bi(5H-dibenzo[a,d] cyclo-
of overcrowding in the fjord regions.15 Heteromerous 9-(9ЈH-
fluoren-9Ј-ylidene)-9H-selenoxanthene (7) and 9-(9ЈH-fluoren-
9Ј-ylidene)-9H-telluroxanthene (8), with central five-membered
and six-membered rings, adopted the anti-folded and folded
conformation with 56.3/62.0Њ and 10.2/8.0Њ (7) and 63.6Њ and
2.2Њ (8) folding dihedrals.16 We have also reported on the inter-
play between twisting and folding in the conformational space
of 9-(9ЈH-fluoren-9Ј-ylidene)-9H-xanthene (9).17 These three
systems belong to the fluorenylidene-chalcoxanthene (10, X: O,
S, Se, Te) series. It seemed interesting to extend the above stud-
ies to heteromerous BAEs by introducing nitrogen atoms at the
overcrowded fjord regions of 1. For this purpose, we have stud-
ied the 1,8-diazafluorenylidene-chalcoxanthene (11, X: O, S, Se,
Te) series. The present article describes the syntheses, molecular
and crystal structures, and NMR spectra, of 9-(9ЈH-1Ј,8Ј-
diazafluoren-9Ј-ylidene)-9H-thioxanthene (12), 9-(9ЈH-1Ј,8Ј-
diazafluoren-9Ј-ylidene)-9H-selenoxanthene (13), 9-(9ЈH-
hepten-5-ylidene)14 (1, X = Y = HC᎐CH).
᎐
We have recently described the syntheses and stereochemistry
of homomerous and heteromerous selenium- and tellurium-
bridged bistricyclic aromatic enes 5–8. Homomerous 9,9Ј-
bi(9H-selenoxanthen-9-ylidene) (5) and 9,9Ј-bi(9H-tellur-
oxanthen-9-ylidene) (6) adopted anti-folded conformations
with 53.6Њ (5) and 53.1Њ (6) folding dihedrals between pairs of
benzene rings of the tricyclic moieties and showed low degrees
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 7 5 5 – 2 7 6 3
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1Ј,8Ј-diazafluoren-9Ј-ylidene)-9H-telluroxanthene (14), 9-(9ЈH-
1Ј,8Ј-diazafluoren-9Ј-ylidene)-9H-xanthene (15) and related
derivatives. This series contains six-membered central rings
with chalcogen bridges, five-membered central rings, and two
nitrogens (instead of carbons) at the fjord regions (positions 1Ј
and 8Ј). For comparison, we have also studied 9-(9ЈH-1Ј,8Ј-
diazafluoren-9Ј-ylidene)-9H-fluorene18 (16), as a 1,8-diaza-
derivative of bifluorenylidene (2), which was expected to be
twisted. The van der Waals radius of nitrogen, 150 pm, is
considerably shorter than that of carbon, 171 pm. This would
render the fjord regions of 11 less overcrowded, as compared
with 10.17 The fjord nitrogens of 11 may affect not only the
overcrowding. One of the pertinent aspects of the conform-
ational spaces of fluorenylidene-chalcoxanthenes (10) is their
potential push–pull character, in which the fluorenylidene and
the chalcoxanthylidene moieties may serve as an acceptor and a
donor, respectively. The 1,8-diazofluorenylidene moiety may
amplify this effect in 11 versus 10. Furthermore, the energetic
propensity of the fluorenylidene moiety against folding,
contrary to the chalcoxanthylidene moieties, may be enhanced
in the 1,8-diazafluorenylidene derivatives. The subtle balance
between twisting and folding revealed in 9 may also be affected
in the analogous 15. We note the recent reports of the synthesis
and crystal structure of the homomerous twisted 9,9Ј-bi-4,5-
diazafluorenylidene19 (17) and of a 4,5-diazafluorene-meth-
oxybenzo[a]xanthene based overcrowded ene.20 The synthesis
of the homomerous 9,9Ј-bi(1,8-diazafluorenylidene) (18) has
been reported.18
Synthesis
The 1Ј,8Ј-diazafluorenylidene-chalcoxanthenes 12–15 were
synthesized by applying Barton’s two-fold extrusion diazo–
thione coupling method (Scheme 1).25–27 In principle, both
the diazo-1,8-diazafluorene–chalcoxanthenthione and the 1,8-
diazafluorenthione–diazochalcoxanthene couplings could be
adopted. The former route was preferred, taking advantage of
the relatively convenient preparations of the reactants, their
stabilities (aromatic dipolar structures) and their reactivities as
carbon nucleophiles and carbon electrophiles, respectively, in
the diazo–thione couplings. The method is especially suited for
the synthesis of heteromerous bistricyclic enes. The starting
materials for 12–15 were the tricyclic ketones 9H-thioxanthen-
The 1,8-diazafluorenylidene functionality, which is at the
core of the present study, is an inherent constituent of 9H-1,8-
diazafluorenone (19) (DFO). DFO has proved to be the most
important fluorogenic reagent in forensic investigations for the
chemical development of latent fingerprints.21–24 DFO reacts
with α-amino acids to give a red dye which is highly fluorescent.
Scheme 1
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 7 5 5 – 2 7 6 3
2756

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9-one (20), 9H-selenoxanthen-9-one28,29 (21), 9H-telluro-
xanthen-9-one30,31 (22), 9H-xanthene-9-one (23), and 9H-1,8-
diazafluoren-9-one (19). 9H-Thioxanthene-9-thione (24),
9H-selenoxanthene-9-thione (25), 9H-telluroxanthene-9-thione
(26) and 9H-xanthene-9-thione (27) were prepared from 20–23,
respectively, using Lawesson’s Reagent,32–34 in boiling benzene,
as previously described.15 9-Diazo-9H-1,8 diazafluorene18 (28)
was prepared from 1935,36 in two steps by conversion to the
hydrazone 29, followed by oxidation, using Ag2O or HgO. The
diazo–thione coupling of thione 24, 25 and 27 and diazo 28 in
boiling benzene gave directly the desired ethylenes 12, 13, and
15, respectively, while the coupling between thione 26 and diazo
28 gave a mixture in a ratio 1 : 1 of 14 and the corresponding
thiiran. The latter intermediate was not isolated. Reaction
of this mixture with PPh3 in benzene gave 14. The known
homomerous
9-(9ЈH-1,8-diazafluoren-9Ј-ylidene)-9H-fluor-
ene18 (16) was prepared by a coupling reaction between the
diazo 28 and the 9H-flourene-9-thione32 (30) in boiling
benzene.
Fig. 1 ORTEP Diagram of the X-ray structure of 13.
Fig. 2 ORTEP Diagram of the X-ray structure of 14.
The overall conformations of the bistricyclic aromatic enes
are characterized by the pure twist of the central C9᎐C9Ј bond
᎐
and by the folding dihedral of the tricyclic moieties. The folding
dihedral is defined as the dihedral angle of the least-square-
planes of the carbons C1, C2, C3, C4, C4a, C9a and C5, C6, C7, C8,
C8a, C10a of the two benzene rings of a tricyclic moiety.3 The
pyramidalization angles χ9 and χ9Ј should also be considered.3
The molecular and crystal structures of 12–14 indicated that
they adopt (mono-) folded conformations (f-12, f-13, f-14). The
folding dihedrals in the chalcoxanthenylidene moieties of 12, 13
and 14 are 62.7Њ, 62.4Њ, and 57.9Њ, respectively. The folding
dihedrals in the diazafluorenylidene moieties of 12, 13 and 14
are very small, 1.5Њ, 1.8Њ and 2.1Њ, respectively. It is interesting to
compare these data to the related systems 7 and 8. There are
two independent molecules of 7 in the unit cell, labeled 7a and
7b. The folding dihedrals in the fluorenylidene moieties of 7a
and 7b are 10.2Њ and 8.0Њ, respectively. In the case of 8, the
folding dihedral in the fluorenylidene moiety is only 2.2Њ. The
presence of the nitrogen atoms at the 1Ј, 8Ј positions in the
diazafluorenylidene moieties does not enhance the folding as it
occurs in 7. It would be expected that the folding dihedral in the
telluroxanthenylidene moiety of 14 would at least be as high as
in 8 (63.6Њ). However, the data showed that this folding dihedral
is smaller, 57.9Њ. Furthermore, this folding dihedral is even
smaller than that of the selenoxanthenylidene moiety in 7b
(62.0Њ). One explanation of this is the twist angle of 5Њ in 14,
which causes the Te10 ؒ ؒ ؒ N8 and Te10 ؒ ؒ ؒ N1 distances 539 pm
Molecular and crystal structures
The crystal structures of bistricyclic aromatic enes (1) have been
reviewed.3 Recently we reported the molecular and crystal
structures of the homomerous 5 and 615 and the heteromerous
7 and 8.16 9-(9ЈH-1Ј,8Ј-Diazafluoren-9Ј-ylidene)-9H-thioxan-
thene (12) and 9-(9ЈH-1Ј,8Ј diazafluoren-9Ј-ylidene)-9H-
selenoxanthene (13) crystallized in the space group Pmn21.
Fig. 1 gives an ORTEP diagram of 13 as determined by X-ray
analysis. In 12 and 13 the benzene rings are reflected through
mirror planes that pass via the atoms S10, C9, C9Ј for 12 and
Se10, C9, C9Ј for 13. 9-(9ЈH-1Ј,8Ј-Diazafluoren-9Ј-ylidene)-9H-
telluroxanthene (14) crystallized in the space group P21/n.
Fig. 2 gives an ORTEP diagram of 14 as determined by X-ray
analysis. Table
1 gives the conformations and selected
geometrical parameters derived from crystal structures of 5–8
and 12–14.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 7 5 5 – 2 7 6 3
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Table 1 Conformations and selected geometrical parameters of 5–8, 12–14 derived from crystal structures and PM3 calculations
Folding
angle/Њ
Pure
twist pm
C1 ؒ ؒ ؒ N1Ј/ C8 ؒ ؒ ؒ N8Ј/ N1 ؒ ؒ ؒ H1/ N8 ؒ ؒ ؒ H8Ј/ X10 ؒ ؒ ؒ N1Ј/ X10 ؒ ؒ ؒ N8/ X10 ؒ ؒ ؒ C9/
a
Y
X
Method
pm
pm
pm
pm
pm
pm
14 Te
—
—
—
—
—
—
X-ray
X-ray
X-ray
X-ray
X-ray
X-ray
f
57.9
63.6
62.4
2.1 5.0
2.2 0.5
1.8 0.0
288
325
295
307
315
290
324
326
296
248
295
240
251
290
327
319
302
331
279
297
307
258
327
319
276
279
502
516
539
265
516
255
249
517
356
348
320
315
307
308
305
306
323
308
8
Te
f
f
13 Se
7a Se
7b Se
au 56.3 10.2 0.7
au 62.0
62.7
8.0 2.5
1.5 0.0
12
6
5
S
f
258
517
Te Te X-ray
Se Se X-ray
af 53.1 53.1 0.0
af 52.5 54.7 1.6
a Conformation: f: folded; au: unevenly anti-folded.
a
Y
X
Method
C9᎐C9Ј/pm
C9a–C9–C8a/Њ
χ9/Њ
2.2
χ9Ј/Њ
C–X/pm
C–X–C/Њ
C4a ؒ ؒ ؒ C10a/pm
᎐
14
8
13
7a
7b
12
6
5
Te
Te
Se
Se
Se
S
—
—
—
—
—
—
Te
Se
X-ray
X-ray
X-ray
X-ray
X-ray
X-ray
X-ray
X-ray
f
135.2
135.0
134.9
134.7
135.1
134.5
134.9
133.9
113.1
111.0
111.5
111.7
111.1
111.0
115.2
112.8
103.8
2.2
15
2.4
0.9
2.1
3.0
212.2
212.4
191.4
190.8
190.6
177.5
211.4
190.7
88.8
88.1
92.5
94.2
93.3
93.4
89.3
94.3
295
295
277
279
277
263
297
280
f
105.0
104.0
104.2
104.5
104.0
8
f
17.4
2.8
3.9
17.0
1.7
0.5
au
au
f
Te
Se
af
af
and 502 pm to vary, resulting in a non-centered Te atom. The
degrees of overcrowding in the fjord regions of 14 as reflected
in the intramolecular non-bonding distances between the
fjord regions nitrogens and carbons/hydrogens, H8 ؒ ؒ ؒ N8Ј,
H1 ؒ ؒ ؒ N1Ј, C8 ؒ ؒ ؒ N8Ј and C1 ؒ ؒ ؒ N1Ј, are relatively small, 276
pm, 302 pm, 296 pm, and 288 pm, respectively. For comparison,
the respective van der Waals contact distances are 321 pm
(C ؒ ؒ ؒ N), 265 pm (H ؒ ؒ ؒ N).37 Thus, the penetration in 14 is
up to 12%. The Te10 ؒ ؒ ؒ C9 non-bonding distance in 14 is 320
pm, while in 8, the Te ؒ ؒ ؒ C9 non-bonding distance is 315 pm,
both considerably shorter than the van der Waals contact dis-
tance Te ؒ ؒ ؒ C 379 pm.37,38 The pyramidalization angles χ9 and
χ9Ј in 14 are negligible. The stress of the overcrowding in 14 is
solved by folding and a slight twisting. In 13, the folding
dihedral of the selenoxanthenylidene moiety is similar to 7b,
62.6Њ versus 62.0Њ. The diazafluorenylidene moiety in 13 is
almost planar. The penetration in the fjord regions of 13 and 12
are relatively small, up to 9% (13) and 10% (12), as reflected in
the C1 ؒ ؒ ؒ N1Ј 295 ppm (13) and 290 pm (12). The most interest-
ing feature in the molecular structures of the 1,8-diazafluor-
enylidene-chalcoxanthenes 12–14 is the high degrees of
pyramidalization of C9 (χ9) 17.4Њ (13) and 17.0Њ (12), as com-
pared with the small χ9 values in 14, 7, and 8, 2.2Њ (14), 2.8Њ (7a)
and 8Њ (8). On the other hand, χ9Ј is negligible. The high degree
of pyramidalization in 13 points at an additional mode for sol-
ving the distress of overcrowding in the fjord regions when the
fluorenylidene moiety is almost planar and the chalcoxanthe-
nylidene moiety is highly folded. The high degrees of pyramid-
alization in 13 and 12 stem from the resistance of the diazaflu-
orenylidene moieties in 12 and 13 to folding and from the limits
in the degrees of folding of the selenoxanthylidene and thioxan-
thylidene moieties (due to the shorter Se10–C4a /Se10–C10a bonds
and S10–C4a/S10–C10a bonds as compared with the Te10–C4a/Te10–
C10a bonds in the telluroxanthylidene moiety of 14). It should
also be noted that this burden falls on C9 in the chalcoxanthe-
nylidene moieties and not on C9Ј of the diazafluorenylidene
moieties. The crystal structure of 14 revealed short Te10 ؒ ؒ ؒ C3
and Te10 ؒ ؒ ؒ C8a non-bonding distances 369.4 pm, and 364.3
pm, respectively (Fig. 3), shorter than the van der Waals
Te ؒ ؒ ؒ C contact distance 379 pm.37,38 The crystal structures of
12 and 13 didnЈt indicate analogous short intermolecular non-
bonding distances. In contrast to the crystal structures of 6 no
short intermolecular Te ؒ ؒ ؒ Te distances between the tellurium
atom of one molecule and tellurium atom of neighboring mole-
cules were found in the crystal structure of 14.
Fig. 3 Short Te–C intermolecular distances in the crystal structure of
14.
NMR Spectroscopy
1H-, 13C-, 77Se-, and 125Te-NMR spectroscopic studies of the
1Ј,8Ј-diazafluorenylidene-chalcoxanthenes were carried out.
1
Table 2 gives the H-NMR chemical shifts of 1Ј,8Ј-diazafluor-
enylidene-chalcoxanthenes (11) versus fluorenylidene-chalco-
xanthenes (10) and related homomerous bistricyclic enes. Table 3
gives the 13C-NMR chemical shifts of 11 versus 10 and related
homomerous bistricyclic enes. Table 4 gives the 77Se- and 125Te-
NMR chemical shifts of 14, 13, and related compounds.
Complete assignments were made through 2-dimensional
correlation spectroscopy [COSY, heteronuclear single quantum
coherence (HSQC), heteronuclear multiple bond coherence
(HMBC)]. It is possible to distinguish qualitatively among the
twisted conformation, the anti-folded conformation and the
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 7 5 5 – 2 7 6 3
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Table 2 1H NMR Chemical shifts (δ) of 2, 3, 5–10, 12–17a
H1, H8
H1Ј,H8Ј
H2, H7
H3, H6
H3Ј H6Ј
H4, H5
b
1
Y
X
H2Ј, H7Ј
H4Ј, H5Ј
8
Te
Te
Se
Se
S
—
—
—
—
—
—
—
—
au
f
7.733
6.934
7.832
7.344
6.934
7.293
8.256
7.330
6.946
7.303
8.282
7.332
6.975
7.318
8.302
7.124
7.066
7.162
8.447
7.211
7.212
8.626
7.31
7.198
7.247
7.162
7.137
7.257
7.257
7.238
7.154
7.332
7.273
7.318
7.161
7.360
7.268
7.506
7.189
7.332
7.342
7.258
8.77
8.004
7.658
7.947
7.833
7.823
7.659
7.761
7.888
7.703
7.547
7.633
7.890
7.366
7.724
7.388
8.054
7.709
7.587
8.003
14
7
au
f
7.778
7.192
7.980
13
10 (Y = S)
au
f
7.829
7.358
8.109
12
9
S
O
O
t
8.134
7.889
8.701
15
t
2
16
—
—
—
—
t
t
8.386
9.001
1719
6
5
3
—
Te
Se
O
—
Te
Se
O
t
8.43
af
af
af
6.796
6.787
7.146
6.879
6.904
6.877
6.963
7.072
7.226
7.801
7.656
7.270
a In CDCl3 (relative to CHCl3 δ = 7.26 ppm). b Conformation: au: unevenly anti-folded; af: anti-folded; t: twisted.
Table 3 13C NMR Chemical shifts (δ) of 2, 3, 5–10, 12–17a
C1, C8
C2, C7
C3, C6
C4, C5
C4a, C10a
C8a, C9a
C9
1
Y
X
C1Ј, C8Ј
C2Ј, C7Ј
C3Ј, C6Ј
C4Ј, C5Ј
C4aЈ, C10aЈ
C8aЈ, C9aЈ
C9Ј
8
Te
Te
Se
Se
S
—
—
—
—
—
—
—
—
129.10
125.65
131.38
127.57
126.36
127.07
147.94
126.60
126.22
124.86
147.80
126.12
126.07
124.20
147.65
122.79
125.85
122.45
147.41
126.85
127.07
148.11
122.91
127.02
126.18
122.40
127.16
128.26
125.96
122.26
127.25
128.25
127.31
122.31
127.30
128.32
127.68
122.26
129.93
127.44
132.16
120.64
129.15
130.97
122.41
151.41
126.57
126.68
128.12
136.99
119.31
135.84
126.68
131.23
119.33
129.81
126.68
128.68
119.34
127.00
126.65
117.63
119.43
117.07
126.95
119.89
119.24
127.28
118.94
140.90
116.26
131.34
133.55
140.94
131.38
131.17
136.53
140.98
134.75
131.00
154.02
140.28
153.11
128.81
141.31
142.94
131.65
158.48
118.01
132.42
155.48
142.39
137.96
141.18
156.50
136.61
137.99
136.91
156.40
137.29
138.07
135.17
156.32
124.80
139.34
123.02
157.00
138.28
138.48
156.99
131.89
141.27
137.44
124.92
145.74
131.37
151.60
127.95
140.33
131.55
146.78
127.90
137.29
131.65
144.09
127.68
130.86
130.99
142.59
123.92
141.01
148.71
136.01
136.52
143.69
137.44
121.44
14
7
129.30
125.59
132.13
13
10 (Y = S)
129.03
125.54
132.20
12
9
S
O
O
130.03
124.27
133.74
15
2
16
—
—
—
—
126.73
130.57
1719
6
5
3
—
Te
Se
O
—
Te
Se
O
133.52
130.67
130.47
128.31
134.98
129.47
117.08
a In CDCl3 (relative to CDCl3 δ = 77.01 ppm).
Table 4 77Se and 125Te NMR chemical shifts of bistricyclic enes and related compounds
Se Compd
X
Y
δ77Sea (ppm)
∆δ (ppm)b
Te Compd
X
Y
δ
125Te c (ppm)
∆ δ (ppm)d
0.0
147.5
145.8
73.7
δTe/δSe
21
7
13
5
334.7
398.2
381.0
366.3
0.0
63.5
46.3
31.6
22
8
14
6
473.4
620.9
589.9
574.1
1.40
1.56
1.55
1.49
Se
Se
Se
—
—
Se
Te
Te
Te
—
—
Te
a In CDCl3 (relative to Me2Se in CDCl3).40 b Relative to selenoxanthone.40 c In CDCl3 (relative to Me2Te in C6D6).40 d Relative to telluroxanthone.
syn-folded conformation of homomerous BAEs 1 in solution,
using 1H-NMR chemical shifts of the fjord protons H1, H8, H1Ј,
H8Ј.15 In heteromerous BAEs the task is less straightforward
but still manageable. In 12–14, the fjord region protons H1 and
H8 of the chalcoxanthenylidene moiety appear at 8.109,
7.980, and 7.832 ppm, respectively. These molecules adopt
folded conformations not only in the solid state but also in
solution, as indicated in the chemical shifts of their fjord
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 7 5 5 – 2 7 6 3
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protons and in their yellow color. In 15, the bridge in the central
six membered ring is oxygen and the color of this molecule is
purple. BAE 16, in which both central rings are five-membered,
is red. The chemical shifts of the fjord protons H1, H8, of 15
and 16 appear at low field, 8.701, 9.001 ppm, respectively. We
conclude that both 15 and 16 adopt twisted conformations.
This conclusion was verified by the UV/VIS spectra of 15. Its
purple color was recognized by the longest wavelength absorp-
tion at 521 nm. For comparison, the respective absorptions of
9, 2, 12, 13, 14, 16, 17 and 18 appear at 53317(9), 45839 (2), 402
(12), 402 (13), 426 (14), 43318 (16), 41619 (17) and 425–435 nm
(sh)18 (18). The related HOMO–LUMO gaps in 9 and 15, as
compared with 2 and 17 are attributed to higher degrees of pure
planar. This effect is perhaps due to the differences in the
distances H1 ؒ ؒ ؒ N1Ј, 258 pm (12), 279 pm (13), and 302 pm
(14). The variance in the chemical shifts of H1, H8 (chalco-
xanthenylidene moiety) in 12–14 is wider than that of H1, H8
(chalcoxanthenylidene moiety) in 10: e.g., δ(12) Ϫ δ(14) = 0.277
versus δ(10, Y = S) Ϫ δ(7) = 0.096.
The 13C-NMR spectra of 2, 3, 5–10, 12–16 (Table 3) indicate
that chemical shifts of the fjord regions C1 and C8 of the chal-
coxanthenylidene moieties of 12–16 are very similar: 132.20
(12), 132.13 (13), 131.38 (14), 133.74 (15), 130.57 (16). The fjord
carbons are less sensitive to the overall conformations, folded or
twisted, as compared with the fjord hydrogens. There is a
certain shift to a low field in comparison to 10 and to 2. A
comparison of 10 and 11 indicates that chemical shifts of C1
and C8 do shift to low field: the range of the shift is 2.3–3.8
ppm. The shifts are somewhat larger in the twisted 15 and 16 as
compared to the folded 12–14.
twist of C9᎐C9Ј and the dipolar aromatic structures in the
᎐
former (ω = 40Њ(9),17 30.2Њ(2),6 30.1Њ(17)19).
1
Comparisons between H- and 13C-NMR chemical shifts of
the 1Ј,8Ј-diazafluorenylidene-chalcoxanthenes (11) and fluor-
enylidene-chalcoxanthenes (10), are summarized in Fig. 4: 14 vs.
8, 13 vs. 7, 12 vs. 10 (Y = S), 15 vs. 9, and 16 vs. 2. These
comparisons illustrate the effect of the fjord nitrogens at
positions 1Ј and 8Ј in 12–17 on the chemical shifts of the chal-
coxanthylene and fluorenylide moieties. In the anti-folded 12–
14, the fjord protons are shifted downfield by 0.1–0.3 ppm,
while in the twisted 15 and 16 the respective shifts are 0.56–0.62
ppm. In the anti-folded 12–14, the fjord protons of the
chalcoxanthene moieties are above or below the pyridine rings
of the fluorenylidene moieties. This alignment minimizes the
effect of the nitrogens. However, in the twisted 15 and 16,
the fjord protons are bucking towards the fjord nitrogens.
Consequently, the effect of the nitrogens is more pronounced.
The most interesting observation derived from the com-
parison of the NMR chemical shifts of the diazafluorenylidene
series 11 with the fluorenylidene series 10 is the trend in the
chemical shifts of C9 and C9Ј (Table 3 and Fig. 4) ∆δ (C9Ј) =
δ(11) Ϫ δ(10) are negative (upfield) Ϫ3.4 (14), Ϫ3.7 (13), Ϫ4.0
(12), Ϫ7.1 (15), Ϫ5.0 ppm (16) while ∆δ (C9) = δ(11) Ϫ δ(10) are
positive (downfield) ϩ5.8 (14), ϩ6.5 (13), ϩ6.8 (12), ϩ11.7 (15),
ϩ7.7 ppm (16). These differences are more pronounced in the
twisted BAEs than in the anti-folded BAEs. The twisted
oxygen-bridged pair 15/9 shows the highest values of ∆δ.
Moreover in 9, δ (C9) Ϫ δ(C9Ј) = Ϫ0.13 ppm, while in 15, δ (C9)
Ϫ δ (C9Ј) = ϩ18.7 ppm. In the anti-folded BAEs there is a slight
decrease in ∆δ (C9) and ∆δ (C9Ј) in the series S(12) > Se (13) >
Te (14). In order to obtain a deeper comprehension of the
significance of the differences in the chemical shifts in the
twisted pairs 15/9 and 16/2, it is helpful to consider the respect-
ive differences in the precursors 9-diazo-9H-1,8-diazafluorene
(28) and 9H-1,8-diazafluoren-9-one (19) versus 9-diazo-9H-
fluorene (31) and 9H-fluoren-9-one (32), respectively. (Fig. 5).
These systems were selected for comparison because of the
opposite character of their substituents: the carbonyl oxygen of
19 and 32 is an acceptor while the diazo groups of 28 and 31 are
1
Fig. 4 Comparison between H and 13C-NMR chemical shifts of 11
and 10.
Within the 11 series, upon going down in the chalcogen
(column 16), from S to Te, the fjord protons are shifted upfield,
in spite of the fact that the folding dihedrals of the diazafluor-
enylidene moieties are similar and are very small in 12–14, 1.5–
1.2Њ, indicating that the diazafluorenylidene moieties are almost
Fig. 5 Comparison of 1H and 13C-NMR chemical shifts: 32 versus 19
and 31 versus 28.
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Table 5 Crystallographic data for 12–14
Compound
12
13
14
Space group
Crystal system
a/pm
b/pm
c/pm
α/deg
Pmn21
Orthorhombic
1881.1(4)
970.2(3)
463.9(1)
90.0
Pmn21
Orthorhombic
1871.3(3)
955.3(2)
483.1(1)
90.0
P21/n
Monoclinic
1257.9(2)
1192.0(2)
1220.2(2)
90.0
β/deg
90.0
90.0
92.68(1)
90.0
γ/deg
90.0
90.0
V/pm3
846.6 × 106
863.6 × 106
2
1827.6 × 106(6)
4
Z
2
1.42
17.67
ρcalc/g cmϪ3
1.57
21.59
1.66
16.38
µ(Kα)/cmϪ1
Diffractometer
Radiation λ/pm
2θmax/deg
No. of unique reflections
No. of reflections with I>3σI
R
ENRAF-NONIUS CAD4
154.178
140
998
880
0.038
0.050
Philips PW1100/20
71.069
55
1206
1002
0.036
0.042
Philips PW1100/20
71.069
60
5561
3444
0.047
0.065
Rw
donors. In these pairs the carbons that are in close proximity to
the fjord nitrogens, C2, C7, C8a and C9a, are shifted downfield:
∆δ (C2, C7) = 22.3 (19/32) and 23.7 ppm (28/31) ∆δ (C8a, C9a) =
17.1 (19/32) and 20.4 ppm (28/31); This effect is maintained in
all the pairs under study (Fig. 4): 14/8, 13/7, 12/10 (X = S), 15/9,
and 16/2. Thus, the chemical shifts of the neighboring C2, C7,
C8a, and C9a, in the 1,8-diazafluorene moiety are primarily
determined by N1 and N8. An analogous picture emerges in the
chemical shifts ∆δ (C1Ј) of the other aromatic carbons of the
fluoreylidene/1,8-diazafluorenylidene moieties. They are hardly
sensitive to the bridge of the opposing tricyclic moiety. The
special character of twisted 15 is manifold in the remarkably
high value of ∆δδ (15/9) = [δ(C9)(15) Ϫ δ(C9Ј)(15)] Ϫ [δ(C9)(9) Ϫ
δ(C9Ј)(9)] = 18.8 ppm, as compared with the respective ∆δδ
value of 14/8 (9.3 ppm), 13/7 (10.1 ppm), 12/10 (10.8 ppm), and
16/2 (12.7 ppm). This effect may be interpreted in terms of
significant contributions of zwitterion structures. It is doubtful,
however, whether the contributions of the aromatic xanthyl-
ium-diazafluorenide structure (15a) is more pronounced in 15
than that of the xanthylium-fluorenide structure (9a) in 9.
The 77Se and 125Te NMR chemical shifts of 13 and 14 (Table 4)
were very helpful, due to their sensitivity, in monitoring the pro-
gress of the syntheses leading to these selenium- and tellurium-
bridged heteromerous bistricyclic enes. The chemical shifts of
the chalcogen atoms in the 13 and 14 are shifted upfield, relative
to 7 and 8, δ77Se (13) Ϫ δ77Se (7) = Ϫ17.2 ppm and δ125Te (14) –
Experimental
Melting points are uncorrected. All NMR spectra were
recorded with a Bruker DRX 400 spectrometer; 1H NMR spec-
tra were recorded at 400.1 MHz using CDCl3 as solvent and as
internal standard (δ(CHCl3) = 7.26 ppm). 13C NMR spectra
were recorded at 100.6 MHz using CDCl3 as solvent and as
internal standard (δ(CDCl3) = 77.01 ppm). 77Se NMR spectra
were recorded at 76.3 MHz using CDCl3 as a solvent and
selenoxanthone (21) as external standard δ = 334.7 ppm
(relative to Me2Se in CDCl3).40 125Te NMR spectra were
recorded at 126.2 MHz using CDCl3 as solvent and tel-
luroxanthone (22) as external standard δ = 473.6 ppm (relative
to Me2Te in C6D6, in DMSO-d6, δ(22) = 471.5 ppm).40 UV/VIS
spectra were measured using an UVIKON 860 spectrometer. IR
spectra were measured with a Perkin Elmer System 2000 FT-IR
spectrometer.
Elemental microanalyses were determined by Chemisar
Laboratories Inc., N. Guelph, Ontario Canada. Single crystals
were obtained by slow sublimation in a high vacuum sealed
tube at 200–250 ЊC in a Büchi GKR 50 oven.
X-Ray crystallographic analysis: the crystal data of 12–14 are
given in Table 5.† The lattice parameters were obtained by a
least-squares fit of 24 centered reflections. Intensity data were
collected using the ω–2θ technique. The scan width, ∆ω, for
each reflection was 1.00 ϩ 0.35tanθ for Mo radiation and 0.80
ϩ 0.15tanθ for Cu radiation. The intensities of three standard
reflections were monitored during data collection, and no decay
was observed. Intensities were corrected for Lorentz and polar-
ization effects. The positions of all non-hydrogen atoms were
obtained using the results of the SHELXS-86 direct method
analysis.41 After several cycles of refinements the positions of
the hydrogen atoms were either found, for compound 14, or
calculated, for 12 and 13, and added to the refinement process.
All non-hydrogen atoms were refined anisotropically, while the
positions of hydrogen atoms were refined isotropically for 14 or
kept fixed, using a riding model for compounds 12 and 13.
δ
125Te (8) = 31.0 ppm, although the δ125Te/δ77Se ratio between
the heteromerous bistricyclic enes pairs 14/13 and 8/7 is almost
the same, 1.55 and 1.56, respectively. Thus, the presence of the
nitrogens at positions 1Ј,8Ј in 13 and 14 causes shielding of the
selenium and the tellurium, relative to 7 and 8, in spite the fact
that the diazafluorenylidene moieties are almost planar.
Conclusion
In conclusion, the introduction of nitrogen atoms in the fjord
regions of 12–16 generates a new heterocyclic series of bistri-
cyclic aromatic enes based on the 1,8-diazafluorenylidene
functionality. This variation of the theme affects the modes of
deviations from planarity due to overcrowding. The potential
push–pull character of 1Ј,8Ј-diazafluorenylidene-chalco-
xanthenes 12–15 is possibly indicated in twisted 15, but not in
folded 12–14. On the other hand, 1,8-diazafluoren-9-one (19),
the important latent fingerprint agent and the starting material
in the syntheses of 12–16, is not a push–pull, but a “pull–pull”
system. Its diazafluorenylidene and carbonyl functionalities are
polarized in the same direction.
The refinement proceeded to convergence by minimizing the
function Σw(|Fo| Ϫ |Fc|)2 with w = σF
.
Ϫ2
9H-1,8-Diazafluoren-9-one (19)
Ketone 19, purchased from Fluka, is a yellow powder, mp 229–
231 ЊC (lit.35,36 mp 205 ЊC, 209 ЊC). H NMR (CDCl3): δ 7.409
1
† CCDC reference numbers 207024–207026. See http://www.rsc.org/
suppdata/ob/b3/b303041e/ for crystallographic data in .cif or other
electronic format.
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(td, 3J = 7.7 Hz,3J = 4.9 Hz, 2H, H3, H6), 7.908 (dd, 3J = 7.7 Hz,
4J = 1.5 Hz, 2H, H4, H5), 8.671 (dd, 3J = 4.9 Hz, 4J = 1.4 Hz, 2H,
H2, H7). 13C NMR (CDCl3): δ 127.75 (C3, C6), 128.59 (C4, C5),
137.85 (C4a, C4b), 151.11 (C8a, C9a), 151.24 (C2, C7), 191.46 (C9).
(C2Ј, C7Ј), 156.32 (C8aЈ, C9aЈ). UV/VIS (cyclohexane): c = 9.392 ×
10Ϫ5 M. λmax/nm (ε): 339 (13,032), 402 (12819). Calc. for
C24H14N2S: C, 79.53; H, 3.89; N, 7.72; S, 8.84. Found: C, 79.17;
H, 3.96; N, 7.60; S, 8.78%.
9-(9ЈH-1,8-Diazafluoren-9Ј-ylidene)-9H-selenoxanthene (13)
9H-1,8-Diazafluoren-9-one hydrazone (29)
To a stirred solution of diazo 28 (0.090 g, 0.464 mmol) in
anhydrous benzene (30 mL) and protected by a CaCl2 tube,
thione 25 (0.127 g, 0464 mmol) was added. The reaction
mixture was refluxed for 52 h. The termination of the reaction
was determined by NMR. The color of the reaction mixture
was dark. The mixture was cooled to rt, and the solvent was
removed under reduced pressure Trituration of the crude
product in hot ethanol gave a precipitate, which was filtered off.
A greenish yellow powder of 13 was obtained 0.136 g, yield
72%; mp 279–281 ЊC. A sample of 13 for analysis was purified
by column chromatography on silica gel using CH2Cl2 as
Hydrazone 29 was prepared from 19 according to the literature,
yield 78%; dec 186–188 ЊC (lit.18 dec 176 ЊC). 1H NMR (CDCl3):
δ 7.237 (td, 3J = 7.7 Hz, 3J = 5.0 Hz, 1H, H6), 7.304 (td, 3J = 7.7
Hz, 3J = 5.0 Hz, 1H, H3), 7.972 (dd, 3J = 7.7 Hz, 4J = 1.5 Hz, 1H,
H5), 8.061 (dd, 3J = 7.7 Hz, 4J = 1.5 Hz, 1H, H4), 8.564 (dd, 3J =
5.0 Hz, 4J = 1.5 Hz, 1H, H7), 8.602 (dd, 3J = 5.0 Hz, 4J = 1.5 Hz,
1H, H2). 13C NMR (CDCl3): δ 121.39 (C–H), 121.92 (C-H),
127.75 (C-H), 127.76 (C-H), 128.51 (C), 129.94 (C), 134.57 (C),
147.53 (C-H), 149.46 (C-H), 151.34 (C), 154.68 (C). IR, Nujol
νmax/cmϪ1: 3300 (N–H).
1
3
3
eluent. H NMR (CDCl3): δ 7.154 (t, J = 7.7 Hz, J = 4.9 Hz,
9-Diazo-9H-1,8-diazafluorene (28)
3
4
2H, H3Ј, H6Ј), 7.238 (td, J = 7.5 Hz, J = 1.4 Hz, 2H, H3, H6),
7.303 (td, 3J = 7.4 Hz, 4J = 1.4 Hz, 2H, H2, H7), 7.761 (ddd, 3J =
7.6 Hz, 4J = 1.3 Hz, 5J = 0.5 Hz, 2H, H4, H5), 7.888 (dd, 3J = 7.7
Hz, 4J = 1.7 Hz, 2H, H4Ј,H5Ј), 7.980 (ddd, 3J = 7.6 Hz, 4J = 1.7
(a) Diazo 28 was prepared from 29 according to the literature,18
with certain modifications. Dried hydrazone 29 (0.199 g, 1.02
mmol), mercuric oxide (0.453 g, 2.09 mmol) and anhydrous
sodium sulfate (0.261 g, 1.83 mmol) were ground together for a
few minutes then transferred to a dry flask equipped with a
magnetic stirrer protected by a CaCl2 tube and containing dry
Et2O (20 mL). After 1 h, a freshly prepared, concentrated
solution of KOH in ethanol was added (10 drops). The color of
the solution changed gradually from yellow to grey–black. The
reaction was stirred at rt for 4 h. The progress of the reaction
was monitored by TLC on silica gel (toluene–chloroform–Et3N
9 : 1 : 1 Rf = 0.63). The solution was filtered off and the residue
was washed with Et2O. The combined organic fractions were
evaporated under reduced pressure, to give 28 as orange crystals
0.143 g, yield 73%; mp 92–96 ЊC (lit.18 mp 94–95 ЊC).
3
4
Hz, 2H, H1, H8), 8.282 (dd, J = 4.8 Hz, J = 1.7 Hz, 2H, H2Ј,
H7Ј). 13C NMR (CDCl3): δ 122.31 (C3Ј, C6Ј), 124.86 (C2, C7),
126.68 (C4Ј, C5Ј), 127.31 (C3, C6), 127.90 (C9Ј), 129.81 (C4,C5),
131.17 (C4aЈ, C4bЈ), 131.38 (C4a, C10a), 132.13 (C1, C8), 136.91
(C8a, C9a), 146.78 (C9), 147.80 (C2Ј, C7Ј), 156.40 (C8aЈ, C9aЈ).
77Se NMR (CDCl3): δ 381.03. UV/VIS (cyclohexane): c =
4.352 × 10Ϫ5 M. λmax/nm (ε): 333 (11098), 402 (6570). Calc. for
C24H14N2Se: C, 76.66; H, 3.93; N, 6.84; Se, 19.38. Found: C,
76.63; H, 3.94; N, 6.72; Se, 19.05%.
9-(9ЈH-1,8-Diazafluoren-9Ј-ylidene)-9H-telluroxanthene (14)
To a stirred solution of thione 26 [freshly prepared from ketone
22 (0.200 g, 0.649 mmol) and Lawesson’s reagent (0.134 g,
0.325 mmol), in dried benzene (30 mL)] in anhydrous benzene
(30 mL) protected by a CaCl2 tube, diazo derivative 28 (0.125 g,
0.664 mmol) was added. The reaction mixture was refluxed for
48 h. The color of the reaction mixture was dark. The mixture
was cooled to rt, and the solvent was removed under reduced
pressure. Trituration of the crude product in hot ethanol gave a
precipitate, which was filtered off. A greenish yellow powder
was obtained, 0.154 g. NMR showed that a mixture of 14 and
the corresponding thiiran was obtained. The latter was not
isolated. This mixture, protected by a CaCl2 tube, was treated
with PPh3 (0.081 g, 0.310 mmol) in anhydrous benzene (30 mL)
and refluxed for 8 h. The solvent was removed under reduced
pressure. Trituration of the crude product in hot ethanol gave a
precipitate, which was filtered off. A yellow powder of 14 was
obtained 0.130 g; mp 299–300 ЊC. A sample of 14 for analysis
was purified by column chromatography on silica gel using
CH2Cl2 as eluent. Trituration 1H NMR (CDCl3): δ 7.137 (t, 3J =
7.6 Hz, 3J = 4.8 Hz, 2H, H3Ј, H6Ј), 7.162 (td, 3J = 7.5 Hz, 4J = 1.4
Hz, 2H, H3, H6), 7.293 (td, 3J = 7.5 Hz, 4J = 1.2 Hz, 2H, H2, H7),
(b) A stirred solution of hydrazone 29 (0.300 g, 1.53 mmol) in
anhydrous Et2O (50 mL) protected by a CaCl2 tube, was cooled
to 0 ЊC, whereupon MgSO4 (0.350 g), Ag2O (0.530 g, 2.29
mmol) and a saturated solution of KOH in methanol (1 mL)
were added. The reaction mixture was stirred for 4 h at ca. 0 ЊC
and the temperature raised to rt and stirred for 20 h. The color
changed gradually from yellow to orange. The reaction was
monitored with TLC (toluene–chloroform–Et3N 9 : 1 : 1 Rf =
0.63). Workup as in procedure (a) gave orange crystals of 28
(0.214 g), yield 72%; mp 92–96 ЊC (lit.18 mp 94–95 ЊC). 1H NMR
(CDCl3): δ 7.284 (td 3J = 7.8 Hz, 3J = 4.9 Hz, 2H, H3, H6), 8.177
(td, 3J = 7.7 Hz, 3J = 1.6 Hz, 2H, H4, H5), 8.581 (dd, 3J = 4.9 Hz,
4J = 1.4 Hz, 2H, H4, H5). 13C NMR (CDCl3): δ 63.75 (C9),
119.37 (C3, C6), 122.49 (C4a, C4b), 128.53 (C4, C5), 148.21 (C2,
C7), 151.86 (C8a, C9a). IR, KBr λmax/cmϪ1: 2083 (N᎐N).
᎐
᎐
9-(9ЈH-1,8-Diazafluoren-9Ј-ylidene)-9H-thioxanthene (12)
To a stirred solution of diazo 28 (0.087 g, 0.448 mmol) in
anhydrous benzene (30 mL) and protected by a CaCl2 tube,
thione 24 (0.102 g, 0448 mmol) was added. The reaction
mixture was refluxed for 80 h. The termination of the reaction
was determined by NMR. The color of the reaction mixture
was dark. The mixture was cooled to rt, and the solvent was
removed under reduced pressure. Trituration of the crude
product in hot ethanol gave a precipitate, which was filtered off.
A greenish yellow powder was obtained 0.124 g, yield 77%; mp
261–263 ЊC. A sample of 12 for analysis was purified by column
chromatography on silica gel using CH2Cl2 as eluent. 1H NMR
(CDCl3): δ 7.161 (t, 3J = 7.7 Hz, 3J = 4.9 Hz, 2H, H3Ј, H6Ј), 7.318
(m, 4H, H2, H7, H3, H6), 7.633 (m, 2H, H4, H5), 7.890 (dd, 3J =
7.6 Hz, 3J = 1.6 Hz, 2H, H4Ј,H5Ј), 8.109 (m, 2H, H1, H8), 8.302
(dd, 3J = 4.8 Hz, 4J = 1.7 Hz, 2H, H2Ј, H7Ј). 13C NMR (CDCl3): δ
122.26 (C3Ј, C6Ј), 124.20 (C2, C7), 126.65 (C4Ј, C5Ј), 127.00 (C4,
C5), 127.46 (C3, C6), 127.68 (C9Ј), 131.00 (C4aЈ, C4bЈ), 132.20 (C1,
C8), 134.75 (C4a, C10a), 135.17 (C9a, C8a), 144.09 (C9), 147.65
3
4
5
7.832 (ddd, J = 7.7 Hz, J = 1.4 Hz, J = 0.4 Hz, 2H, H1, H8),
3
3
7.883 (dd, J = 7.7 Hz, J = 1.7 Hz, 2H, H4Ј, H5Ј), 7.947 (ddd,
3J = 7.6 Hz, 4J = 1.4 Hz, 5J = 0.4 Hz, 2H, H4, H5), 8.256 (dd, 3J =
4.8 Hz, 4J = 1.7 Hz, 2H, H2Ј, H7Ј). 13C NMR (CDCl3): δ 116.26
(C4a, C10a), 122.26 (C3Ј, C6Ј), 125.96 (C2, C7), 126.68 (C4Ј, C5Ј),
127.07 (C3, C6), 127.95 (C9Ј), 131.34 (C4aЈ, C4bЈ), 131.38 (C1, C8),
135.84 (C4, C5), 141.18 (C8a, C9a), 147.94 (C2Ј, C7Ј), 151.60 (C9),
156.50 (C8aЈ, C9aЈ). 125Te NMR (CDCl3): δ 589.95. UV/VIS
(cyclohexane): c = 1.15 × 10Ϫ4 M. λmax/nm (ε): 333 (12991), 426
(2125). Calc. for C24H14N2Te: C, 62.94; H, 3.08; N, 6.11; Te,
27.90. Found: C, 62.89; H, 2.87; N, 6.07; Te, 27.49%.
9-(9ЈH-1,8-Diazafluoren-9Ј-ylidene)-9H-xanthene (15)
To a stirred solution of diazo 28 (0.050 g, 0.255 mmol) in
anhydrous benzene (10 mL) and protected by a CaCl2 tube,
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 7 5 5 – 2 7 6 3
2762

View Article Online
3 P. U. Biedermann, J. J. Stezowski and I. Agranat, in: Advances in
Theoretically Interesting Molecules, Vol. 4, ed., R. P. Thummel, JAI
Press, Stamford, CN, 1998, p. 245.
4 P. U. Biedermann, J. J. Stezowski and I. Agranat, Eur. J. Org. Chem.,
2001, 15.
5 P. U. Biedermann, J. J. Stezowski and I. Agranat, Chem. Commun.,
2001, 954.
6 P. U. Biedermann, A. Levy, J. J. Stezowski and I. Agranat, Chirality,
1995, 7, 199.
7 W. Luef and R. Keese, Top. Stereochem., 1991, 20, 231.
8 Y. Tapuhi, M. R. Suissa, S. Cohen, P. U. Biedermann, A. Levy and
I. Agranat, J. Chem. Soc., Perkin Trans. 2, 2000, 93.
9 B. L. Feringa, W. F. Jager and B. de Lange, Tetrahedron Lett., 1992,
33, 2887.
10 N. A. Bailey and S. E. Hull, Acta Crystallogr., Sect. B, 1978, 34,
3289.
11 J.- S. Lee and S. C. Nyburg, Acta Crystallogr., Sect. C, 1985, 41, 560.
12 J. F. D. Mills and S. C. Nyburg, J. Chem. Soc., 1963, 308.
13 E. Harnik and G. M. J. Schmidt, J. Chem. Soc., 1954, 3295.
14 K. S. Dichmann, S. C. Nyburg, F. H. Pickard and J. A. Potworowski,
Acta Crystallogr., Sect. B, 1974, 30, 27.
thione 27 (0.051 g, 0.243 mmol) was added. The reaction
mixture was refluxed for 125 h. The termination of the reaction
was determined by NMR. The solution was evaporated under
reduced pressure. Crude 15 dissolved in CH2Cl2 was introduced
on top of the chromatography column. The color of the
fractions on the column containing 15 were blue. NMR showed
that 15 partially decomposed to 23 on the silica gel. Further
purification was performed by sublimation at 170 ЊC/0.05 torr.
Purple crystals of 15, with gold sparkling were obtained by the
sublimation. 1H NMR (CDCl3): δ 7.162 (td, 3J = 8.3 Hz, 3J = 6.9
Hz, 4J = 1.3 Hz, 2H, H2, H7), 7.189 (t, 3J = 7.6 Hz, 3J = 4.8 Hz,
2H, H3Ј, H6Ј), 7.388 (ddd, 3J = 8.3 Hz, 4J = 1.3 Hz, 5J = 0.4 Hz,
2H, H4, H5), 7.506 (td, 3J = 8.4 Hz, 3J = 7.0 Hz, 4J = 1.5 Hz, 2H,
H3, H6), 8.054 (dd, 3J = 7.7 Hz, 4J = 1.7 Hz, 2H, H4Ј, H5Ј), 8.447
(dd, 3J = 4.8 Hz, 4J = 1.7 Hz, 2H, H2Ј, H7Ј), 8.701 (ddd, 3J = 8.3
4
5
Hz, J = 1.6 Hz, J = 0.4 Hz, 2H, H1, H8). 13C NMR (CDCl3):
δ 117.07 (C4, C5), 120.64 (C3Ј, C6Ј), 122.45 (C2, C7), 123.02 (C8a,
C9a), 123.92 (C9Ј), 126.95 (C4Ј, C5Ј), 128.81 (C4aЈ, C4bЈ), 132.16
(C3, C6), 133.74 (C1, C8), 142.59 (C9), 147.41 (C2Ј, C7Ј), 153.11
(C4a, C10a), 157.00 (C8aЈ, C9aЈ). UV/VIS (cyclohexane quali-
15 A. Levy, P. U. Biedermann, S. Cohen and I. Agranat, J. Chem. Soc.,
Perkin Trans. 2, 2000, 725.
16 A. Levy, P. U. Biedermann, S. Cohen and I. Agranat, J. Chem. Soc.,
Perkin Trans. 2, 2001, 2329.
tative): λmax/nm: 521, 386, 354. MS, m/z (% molecular ion):
347.11027 (6.13%,
C
13C2H13N2O), no molecular ion (0%
22
12
17 A. Levy, P. U. Biedermann and I. Agranat, Org. Lett., 2000, 2,
C H14N2O), 346.10674 (35.18%, 12C2313C1H13N2O), 345.10363
12
24
1811.
12
12
(100%, C24H13N2O), 173.55619 (1.74%,
C
13C2H13N2O/2,),
22
18 A. Schönberg and K. Junghans, Chem. Ber., 1962, 94, 2137.
19 M. Riklin, A. von Zelewsky, A. Bashall, M. McPartlin, A. Baysal,
J. A. Connor and J. D. Wallis, Helv. Chim. Acta, 1999, 82,
1666.
173.05420 (6.87%,
C
13C1H13N2O/2), 172.54895 (4.86%.
23
12
C H13N2O), 172.04688 (16.04%, 12C24H12N2O/2).
12
24
20 M. Querol, H. Stoekli-Evans and P. Belser, Org. Lett., 2002, 4, 1067.
21 C. A. Pounds, R. Grigg and T. Mongkolaussavaratana, J. Forensic
Sci., 1990, 35, 169–175.
9-(9ЈH-1,8-Diazafluoren-9Ј-ylidene)-9H-fluorene (16)
To a stirred solution of diazo 28 (0.100 g, 0.555 mmol) in
anhydrous benzene (30 mL) and protected by a CaCl2 tube,
thione 30 (0.114 g, 0.580 mmol) was added. The reaction
mixture was refluxed for 1 h and then kept at 70 ЊC (oil bath) for
72 h. The termination of the reaction was determined by NMR.
The mixture was cooled to rt, and the solvent was removed
under reduced pressure Trituration of the crude product in hot
ethanol gave a precipitate, which was filtered off. Red 16 was
obtained. Mp 245–247 ЊC (dec) (lit.18 243 ЊC). 1H NMR
(CDCl3): δ 7.212 (td, 3J = 7.9 Hz, 3J = 7.5 Hz, 4J = 1.2 Hz, 2H,
H2, H7), 7.258 (td, 3J = 7.7 Hz, 3J = 5.0 Hz, 2H, H3Ј, H6Ј), 7.342
22 R. Grigg, T. Mongkolaussavaratana, C. A. Pounds and
S. Sivagnanam, Tetrahedron Lett., 1990, 31, 7215–7218.
23 R. E. Grigg, C. A. Pounds, T. Mongkolaussavaratana, “Fingerprint
Reagent”, U. S. Patent 5,221,627, 22.06.1993 (Priority date
09.11.1988 GB 8,826,237); EP Patent 442959 B1, 31.08.1994.
24 J. Almog, “Fingerprints Development by Ninhydrin and Its
Analogues”, in Advances in Forensic Technology, 2nd Edition,
H. C. Lee and R. E. Gaensslen, Eds., CRC Press, Boca Raton, FL,
2001, pp. 177–209.
25 D. H. R. Barton, Ed., Reason and Imagination: Reflections on
Research in Organic Chemistry: Selected Papers of Derek H. R.
Barton, Imperial College Press and World Scientific, Singapore,
1996, Vol. 6, pp. 489.
3
4
3
(td, J = 7.4 Hz, J = 1.0 Hz, 2H, H3, H6), 7.587 (ddd, J = 7.5
Hz, 4J = 1.2 Hz, 5J = 0.7 Hz, 2H, H4, H5), 8.003 (dd, 3J = 7.7 Hz,
4J = 1.4 Hz, 2H, H4Ј,H5Ј), 8.626 (dd, 3J = 4.8 Hz, 4J = 1.6 Hz, 2H,
H2Ј, H7Ј), 9.001 (dd, 3J = 7.9 Hz, 4J = 1.0 Hz, 5J = 0.7 Hz, 2H, H1,
H8). 13C NMR (CDCl3): δ 119.24 (H4, H5), 122.41 (C3Ј, C6Ј),
127.07 (C2, C7), 127.28 (C4Ј, C5Ј), 130.57 (C1, C8), 130.97 (C3,
C6), 131.65 (C4aЈ, C4bЈ), 136.01 (C9Ј), 138.48 (C8a, C9a), 142.94
(C4a, C4b), 148.11 (C2Ј, C7Ј), 148.71 (C9), 156.99 (C8aЈ, C9aЈ).
26 D. H. R. Barton and B. J. Wills, J. Chem. Soc., Perkin Trans. 1, 1972,
305.
27 D. H. R. Barton, F. S. Guziec and I. Shahak, J. Chem. Soc., Perkin
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28 R. Lesser and R. Weiß, Ber. Dtsch. Chem. Ges., 1914, 47, 2510.
ˇ
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Soedin., 1980, 1342.
32 S. Scheibye, R. Shabana and S.-O. Lawesson, Tetrahedron, 1982, 38,
Acknowledgements
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34 B. S. Pedersen, S. Scheibye, N. H. Nilsson and S.-O. Lawesson, Bull.
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The authors thank Mr. P. Ulrich Biedermann for fruitful
discussions and helpful comments.
35 J. Druey and P. Schmidt, Helv. Chim. Acta, 1950, 33, 1080.
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O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 7 5 5 – 2 7 6 3
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