First successful synthesis, isolation and characterization of open-chain 1,2-diazidoethenes

Article abstract of DOI:10.1016/j.tet.2005.07.025

Open-chain 1,2-diazidoethenes have been obtained from the recently reported acceptor-substituted propargyl azides by one-pot reactions with tetramethylguanidinium azide (TMGA) and in some cases via a two-step procedure starting with in situ production of the corresponding azidoallene followed by addition of hydrazoic acid with the help of TMGA. In a different synthetic pathway, the substitution reactions between 2-azido-3-haloacroleins and hexadecyltributylphosphonium azide (QN₃) have been used. In order to have more evidence for their structures, some diazido compounds were converted to their bis-triazole derivatives through 1,3-dipolar cycloaddition.

Full text of DOI:10.1016/j.tet.2005.07.025

Tetrahedron 61 (2005) 8904–8909
First successful synthesis, isolation and characterization of
open-chain 1,2-diazidoethenes*
*
Joseph Rodolph Fotsing, Manfred Hagedorn and Klaus Banert
Institute of Chemistry, Chemnitz University of Technology, Strasse der Nationen 62, 09111 Chemnitz, Germany
Received 29 April 2005; revised 30 June 2005; accepted 6 July 2005
Available online 28 July 2005
Abstract—Open-chain 1,2-diazidoethenes have been obtained from the recently reported acceptor-substituted propargyl azides by one-pot
reactions with tetramethylguanidinium azide (TMGA) and in some cases via a two-step procedure starting with in situ production of the
corresponding azidoallene followed by addition of hydrazoic acid with the help of TMGA. In a different synthetic pathway, the substitution
reactions between 2-azido-3-haloacroleins and hexadecyltributylphosphonium azide (QN3) have been used. In order to have more evidence
for their structures, some diazido compounds were converted to their bis-triazole derivatives through 1,3-dipolar cycloaddition.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
mechanism of the fragmentation of 1,2-diazidoethenes to
yield cyano derivatives. Unfortunately, open-chain 1,2-
diazidoethenes 6 were up to now only known as
spontaneously decomposing compounds.14,15 In this paper,
we report the first access to the open-chain 1,2-dia-
zidoethenes. Moreover, we show how the stability of these
compounds can be improved.
Cyclic 1,2-diazidoethenes 1 have been known for many
decades, and they have been used for various synthetic
purposes (Scheme 1).2–13 However, all attempts to isolate or
to observe the open-chain analogous compounds 6 failed.14,15
In fact, cyclic 1,2-diazidoethenes 1 can be synthesized on the
one hand via Diels–Alder reactions of 2,3-diazido-1,3-
butadiene derivatives with dienophiles,4,5 and on the other
hand by nucleophilic substitution of cyclic 1,2-dihalo-
alkenes activated by two flanking, electron-withdrawing
substituents.6–8,13 With regard to their reactivity, it is well-
known that cyclic 1,2-diazidoethenes of type 1 undergo
thermal4–10,16 and photochemical3–5 degradation to form the
corresponding dicyano derivatives 4. In order to rationalize
this degradation process, several intermediates had been
postulated.7–10 By photolysis of 1,2-diazidobenzene in an
inert matrix at low temperature, ortho-phenylene-bisnitrene
was generated.3 However, 2-azido-2H-azirines 2 and 3 are
the most plausible intermediates for the transformation of 1
to yield 4.17 Nevertheless, direct proof of such intermediates
had not yet been obtained. Most probably, 2 and 3 could not
be observed spectroscopically due to their anti-Bredt
structures. It emerges that open-chain 1,2-diazidoethenes 6
may led to spectroscopically observable 2-azido-2H-azirines.
Such observation should constitute evidence to the
2. Results and discussion
2.1. Open-chain 1,2-diazidoethenes from acceptor-sub-
stituted propargyl azides
Treatment of the recently accessible propargyl azide 718
with tetramethylguanidinium azide (TMGA) yielded regio-
selectively a mixture of the open-chain 1,2-diazidoethenes
* See Ref. 1.
Keywords: Propargyl azides; 1,2-Diazidoethenes; Triazoles; Huisgen’s 1,3-
dipolar cycloaddition; Nucleophilic addition; Nucleophilic substitution.
*
Corresponding author. Tel.: C49 371 531 1463; fax: C49 371 531 1839;
e-mail: klaus.banert@chemie.tu-chemnitz.de
Scheme 1.
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.07.025

J. R. Fotsing et al. / Tetrahedron 61 (2005) 8904–8909
8905
E/Z-8 (E/ZZ5:1) and traces of the expected isomer E-9
(Scheme 2). Fortunately, this mixture could be separated on
silica gel without any remarkable decomposition. The
overall yield was 72%. Surprisingly, E-8 isomerized slowly
to Z-8. A plausible rationalization of this isomerization may
be the formation of E-9 as an intermediate. However, during
the 1H NMR monitoring of this isomerization, E-9 could not
be observed. To prove the presence of two azido groups in
the structures of E-8 and E-9, they both were treated with
cyclooctyne to yield the corresponding bis-triazole deriva-
tives E-10 (55%) and E-11 (60%), respectively, as products
of Huisgen’s 1,3-dipolar cycloaddition reaction.
containing the four possible isomeric products (E/Z-16
and E/Z-17) of the addition of HN3 (Scheme 4). The
chromatography of this mixture on silica gel yielded firstly
E-16 as minor compound in a mixture (1:4) with E-17 and
secondly Z-16 as minor compound in a mixture (1:6) with
Z-17. The overall yield was 51%. Attempts to isolate the
desired products E-16 and Z-16 by crystallization were
unsuccessful. Moreover, we were not able to isomerize
E/Z-17 to 16 with the help of bases. This can be ascribed to
the significant lowering of the acidity of the allyl protons by
the additional methyl group. By storing a solution of E-16/
E-17 or Z-16/Z-17 in chloroform at room temperature for
several days, E-16 and Z-16 could be singularly decom-
posed to phenylsulfonylacetonitrile and acetonitrile
(compare to 4 in Scheme 1). This serves as proof of the
existence of an 1,2-diazidoethene unit in the structure of the
latter compounds. After starting with the mixture of E-16
and E-17 and decomposition of E-16, the presence of two
azido groups in the structure of remaining E-17 was proved
by its treatment with cyclooctyne giving the bis-triazole
compound E-18 with about 90% yield.
The reaction of the propargyl azide 1218 with TMGA
preceded highly regioselectively and afforded only the
desired open-chain derivatives E/Z-13 (E/ZZ1:1,
Scheme 3). Separation of the mixture of isomers on silica
gel was performed without any special precautions to obtain
26% of E-13 and 28% of Z-13. The presence of two azido
groups in the structures of E-13 and Z-13 was also verified
by their treatment with cyclooctyne yielding the bis-triazole
compounds E-14 (76%) and Z-14 (72%), respectively.
Due to the difficult separation of the desired open-chain
1,2-diazidoethenes E-16 and Z-16 from the mixture
obtained after using the one-pot procedure described
In contrast to the two precedent reactions, treatment of the
propargyl azide 1518 with TMGA afforded a mixture
Scheme 2.
Scheme 3.
Scheme 4.

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J. R. Fotsing et al. / Tetrahedron 61 (2005) 8904–8909
this context, considering one azido group as strong electron-
donating, we easily conclude that the stability of the 1,2-
diazidoethenes just like the one of the traditional vinyl
azides is decreased by electron-donating substituents.
Moreover, exploring the structures of the known cyclic
1,2-diazidoethenes,2–13 it is remarkable that all of them
enclose at least one electron-withdrawing group related to
the 1,2-diazidoethene unit, even if in some cases4,5 these
substituents have only a weak acceptor character. Probably,
the understanding of the influence of the electron-with-
drawing groups on the stabilization of these compounds
suffered from the fact that acceptor substituents were
commonly introduced into the starting materials just with
the aim of facilitating the nucleophilic substitution of the
leaving groups by the azide anion.
Scheme 5.
above, a two-step procedure via 19 was also executed
giving the products E/Z-16 (8%, E/ZZ2:3, Scheme 5).
Neither E- nor Z-17 could be observed in the reaction
mixture.
2.3. Open-chain 1,2-diazidoethenes from
2-azido-3-halopropenals
In order to confirm that the stability of the 1,2-
diazidoethenes can be improved by acceptor substituents,
we undertook the synthesis of derivatives bearing at least
one strong electron-withdrawing group. In this connection,
2-azido-3-halopropenals Z-24 and Z-2521 were treated with
nucleophiles containing the azide anion (Scheme 7). Both
the aldehydes Z-24 and Z-25 are bearing a b-chloro
substituent, which can be substituted by the azide anion
via the well-known addition–elimination mechanism. Such
reactions are known to proceed with retention of the
configuration at the C]C unit. However, using sodium
azide as source of the azide anion, only poor yields were
obtained. This can be ascribed to the lowering of the
nucleophilicity of the azide anion through the strong
association with the sodium cation. Fortunately, using
hexadecyltributylphosphonium azide (QN3),22 the desired
products Z-26 (from Z-24) and Z-27 (from Z-25) were
formed with a yield of 86 and 91%, respectively. In fact,
unlike sodium azide, the bulky QC cation of QN3 is weakly
associated to the azide anion, which is consequently very
reactive. The compounds Z-26 and Z-27 proved to be
relatively stable at room temperature confirming that the
thermal stability of 1,2-diazidoethenes can be improved by
electron-withdrawing groups.
The formation of open-chain 1,2-diazidoethenes of type 22
by the reactions of the acceptor-substituted propargyl azides
of type 20 with TMGA can be rationalized by the pathways
A and B (Scheme 6). An evidence for the pathway A was
obtained by the formation of E/Z-16 from 15 via 19
(Scheme 5). Indeed the pathway B is also very plausible, its
evidence could not be proved directly since treatment of
E/Z-17 (Scheme 4) with bases failed to yield the
corresponding open-chain 1,2-diazidoethenes. However,
we cannot omit this pathway because similar transform-
ations are known.18
2.2. Possible factors influencing the stability of
1,2-diazidoethenes
Noteworthy, the solutions of the 1,2-diazidoethenes in
dichloromethane described above were relatively stable at
room temperature and could be stored at low temperature
for several months without decomposition. But why did
former attempts to prepare open-chain 1,2-diazidoethenes
lead to their spontaneous decomposition? It is well-known
that normal vinyl azides 5 (Scheme 1) with strong electron-
donating groups R1, R2 and R3 (e.g., R1, R2, R3ZPh, OR,
NR2) decomposed spontaneously at temperatures near
20 8C.19 In the structures of 1,2-diazidoethenes 6, the
substituent R3 (see 5) is replaced by an additional azido
group. However, the azido group is also known as strong
electron-donating group comparable to alkoxy groups.20 In
Scheme 7.
3. Conclusion
The synthesis of open-chain 1,2-diazidoethenes has been
accomplished for the first time starting with acceptor-
substituted propargyl azides and TMGA or 2-azido-3-halopro-
penals and QN3. Although the open-chain 1,2-azidoethenes
were only known as spontaneously decomposing compounds
Scheme 6.

J. R. Fotsing et al. / Tetrahedron 61 (2005) 8904–8909
8907
hitherto, those described in this paper could be synthesized
and isolated at room temperature without any special
precautions. Moreover, evidence was obtained that the
thermal stability of these open-chain 1,2-diazidoethenes can
be improved by electron-withdrawing groups. The photo-
chemical and thermal transformations of these 1,2-diazi-
doethenes are currently being examined in our laboratory
for purpose of mechanistic investigations.
E-(2,3-Diazidoprop-2-enylsulfinyl)-benzene (E-8): IR
(CDCl3, E/Z-8Z5:1): 2094 (N3), 1049 (SO) cmK1 1H
.
2
NMR (CDCl3): d 3.54 (d, JZ13.2 Hz, 1H, H-10), 3.70 (d,
2JZ13.2 Hz, 1H, H-10), 6.29 (s, 1H, H-30), 7.55 (m, 3H, Ph),
13
7.69 (m, 2H, Ph). C NMR (CDCl3): d 55.28 (t, C-10),
119.38 (d, C-30), 120.02 (s, C-20), 124.22 (d, 2C, Ph), 129.13
(d, 2C, Ph), 131.73 (d, p-Ph), 142.83 (s, i-Ph).
Z-(2,3-Diazidoprop-2-enylsulfinyl)-benzene (Z-8): IR
1
(CDCl3): 2115 (N3), 1022 (SO) cmK1. H NMR (CDCl3):
d 3.32 (d, 2JZ13.5 Hz, 1H, H-10), 3.39 (d, 2JZ13.5 Hz, 1H,
H-10), 5.88 (s, 1H, H-30), 7.56 (m, 3H, Ph), 7.63 (m, 2H, Ph).
13C NMR (CDCl3): d 59.97 (t, C-10), 116.07 (s, C-20),
119.37 (d, C-30), 123.96 (d, 2C, Ph), 129.39 (d, 2C, Ph),
131.68 (d, p-Ph), 142.39 (s, i-Ph).
4. Experimental
4.1. General remarks
1H and 13C NMR spectra were recorded at 300 and 75 MHz,
respectively, in CDCl3, unless otherwise noted. Chemical
shifts (d) are reported in parts per million (ppm) downfield
from TMS. Coupling constants (J) are reported in hertz
(Hz), and spin multiplicities are indicated by the following
symbols: s (singlet), d (doublet), t (triplet), q (quartet), m
(multiplet). Assignments of stereochemistry were supported
by homonuclear NOE experiments in the case of E/Z-8, E-9,
E/Z-13, E/Z-16, E/Z-17 and Z-24, whereas the stereochem-
istry of compounds E-10, E-11, E/Z-14, E-18, Z-26 and Z-27
was deduced from that of the respective precursors. Infrared
spectra were recorded as solutions in CDCl3. TLC was
performed on Macherey-Nagel precoated silica gel Poly-
gram Sil G/UV254 plates and viewed by UV. Chromato-
graphy refers to flash chromatography,23 carried out on
Fluka silica gel 60. For the elemental analyses, Vario El
(Elementar Analysensystem GmbH) was employed.
Mariner 5229 from Applied Biosystems was used for
MS-spectra. The method applied was the electrospray
ionization. For UV/vis spectra, Lambda 40 (Perkin-Elmer)
was used.
E-(2,3-Diazidoprop-1-enylsulfinyl)-benzene (E-9): IR
(CDCl3): 2111 (N3), 1262 (N3), 1039 (SO) cmK1 1H
.
2
NMR (CDCl3): d 4.11 (d, JZ13.8 Hz, 1H, H-30), 4.43 (d,
2JZ13.8 Hz, 1H, H-30), 6.09 (s, 1H, H-10), 7.55 (m, 3H, Ph),
13
7.65 (m, 2H, Ph). C NMR (CDCl3): d 48.75 (t, C-30),
123.55 (d, C-10), 124.12 (d, 2C), 129.60 (d, 2C), 131.27 (d,
p-Ph), 143.37 (s, i-Ph), 146.51 (s, C-20).
4.1.2. (E-3-Phenylsulfinylprop-1-en-1,2-diyl)-bis-4,5,6,7,
8,9-hexahydro-1H-cyclooctatriazole (E-10). To a stirred
solution of E/Z-8 (10.0 mg, 0.038 mmol, E/ZZ5:1) in
CH2Cl2 (1 mL), cyclooctyne (13 mg, 0.122 mmol) was
added. Stirring was continued at room temperature for 2 h.
The solvent and the rest of cyclooctyne were removed at
10K3 Torr, and the residue was chromatographed on silica
gel with Et2O/MeOH (97:3) yielding E-10 (10.0 mg,
0.021 mmol, 55%) as yellow oil. The presence of Z-10 in
the remaining fractions could not be proved. 1H NMR
(CDCl3): d 1.48 (m, 8H), 1.79 (m, 8H), 2.70 (m, 2H), 2.89
2
2
(m, 6H), 4.56 (d, JZ13.0 Hz, 1H,0 H-30), 4.93 (d, JZ
13.0 Hz, 1H, H-30), 7.04 (s, 1H, H-1 ), 7.40 (m, 3H), 7.60
(m, 2H). 13C NMR (CDCl3): d 21.74 (t), 22.41 (t), 24.14 (t),
24.18 (t), 24.24 (t), 24.99 (t), 25.32 (t), 25.47 (t), 26.03 (t),
27.32 (t), 27.69 (t), 28.00 (t), 60.02 (t, C-30), 123.43 (d),
123.94 (d, 2C), 125.16 (s), 128.96 (d, 2C), 131.06 (d),
134.35 (s), 134.80 (s), 142.98 (s), 144.53 (s), 145.17 (s). MS
(ESI); m/z: 465.20 [MCHC].
Warning: Elemental analyses of azides could not be
performed because of explosive decomposition. Caution
should be exercised during isolation of azide, which may be
explosive. In the case of solutions of tetrabutylammonium
azide in CH2Cl2, an explosion probably caused by
diazidomethane was reported.24 Therefore, special caution
is also necessary in the case of tetramethylguanidinium
azide (TMGA) in CH2Cl2, although we never observed any
incident.
4.1.3. (E-3-Phenylsulfinylprop-2-en-1,2-diyl)-bis-4,5,6,7,
8,9-hexahydro-1H-cyclooctatriazole (E-11). Compound
E-11 (60%, yellow oil) was obtained from E-9 by analogy
The known compounds 7,18 12,18 15,18 19,18 and 2521 were
synthesized according to the literature.
1
to the procedure described for E-10. H NMR (CDCl3): d
1.18–1.80 (m, 18H), 2.35 (m, 2H), 2.73 (m, 4H), 5.85 (d,
2
2JZ15.0 Hz, 1H, H-30), 6.02 (d, JZ15.0 Hz, 1H, H-30),
4.1.1. E/Z-(2,3-Diazidoprop-2-enylsulfinyl)-benzene (E/Z-
8) and E-(2,3-diazidoprop-1-enylsulfinyl)-benzene (E-9).
Compound718 (150 mg, 0.732 mmol) in CH2Cl2 (10 mL) was
cooled down to 0 8C and treated in small portions with TMGA
(150 mg, 0.949 mmol). Stirring was continued at room
temperature for additional 40 min. The solvent was partially
removed (neat substance can be very explosive) and the
residue was chromatographed on silica gel with Et2O/n-
hexane 4:1 to give a mixture (yellow oil, 115 mg,
0.464 mmol, 63%) of E-8 and Z-8 (E/ZZ3:1), pure Z-8
(5.00 mg, 0.020 mmol, 2.8%, yellow oil) and pure E-9
(10.0 mg, 0.040 mmol, 6%, yellow oil). Addition of TMGA
to 7 in CH2Cl2 at room temperature instead of 0 8C, led to a
mixture of E-8 and Z-8 (E/ZZ5:1) and only traces of E-9.
6.46 (s, 1H, H-10), 7.60 (m, 3H), 8.02 (m, 2H). 13C NMR
(CDCl3): d 21.26 (t), 21.30 (t), 24.07 (t), 24.18 (t), 24.30 (t),
24.82 (t), 25.10 (t0), 25.60 (t), 25.91 (t), 26.76 (t), 28.10 (t,
2C), 46.29 (t, C-3 ), 124.37 (d, 2C), 129.63 (d, 2C), 131.61
(d), 134.47 (s), 135.01 (s), 135.51 (d), 137.29 (s), 142.78 (s),
144.36 (s), 145.82 (s). MS (ESI); m/z: 465.20 [MCHC].
4.1.4. E- and Z-(2,3-Diazidoprop-2-enylsulfonyl)-ben-
zene (E-13 and Z-13). Compound 1218 (600 mg,
2.71 mmol) in CH2Cl2 (25 mL) was cooled to 15 8C and
treated portionwise with TMGA (600 mg, 3.80 mmol).
Stirring was continued at the same temperature for
additional 90 min. The solvent was partially removed

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J. R. Fotsing et al. / Tetrahedron 61 (2005) 8904–8909
(neat substance can be very explosive) and the residue was
chromatographed on silica gel with Et2O/n-hexane 1:9 to
afford E-13 (181 mg, 0.69 mmol, 26%, yellow oil), Z-13
(200 mg, 0.76 mmol, 28%, yellow oil) and a mixture of
E-13 and Z-13 (11 mg, 0.04 mmol, 1.5%) after very careful
removal of the solvent under vacuum.
for 20 min at room temperature, the solvent was partially
removed. The residue was filtrated through silica gel with
Et2O, and the solvent was partially evaporated. By standing
at K18 8C, the product crystallized slowly. The solid was
filtrated and washed with Et2O/n-hexane (3:2). The filtrate
was concentrated, dissolved in a small amount of Et2O, and
crystallization was repeated for several times to give the
desired products E/Z-16 (100 mg, 0.36 mmol, 7.6%, E/ZZ
2:3) as yellow-orange solid. IR (CDCl3, mixture): n~Z2110
E-(2,3-Diazidoprop-2-enylsulfonyl)-benzene (E-13): IR
1
(CDCl3): 2096 (N3), 1322 (SO2), 1153 (SO2) cmK1. H
NMR (CDCl3): d 3.97 (s, 2H, H-10), 6.23 (s, 1H, H-30), 7.60
(m, 2H, m-Ph), 7.70 (m, 1H, p0-Ph), 7.96 (m, 2H, o-Ph). 13C
NMR (CDCl3): d 54.22 (t, C-1 ), 118.30 (s, C-20), 120.29 (d,
C-30), 128.78 (d, 2C), 128.98 (d, 2C), 134.28 (d, p-Ph),
138.15 (s, i-Ph).
(N3), 1325 (SO2), 1139 (SO2) cmK1 1H NMR (CDCl3,
.
mixture): d 1.77 (s, 3H, H3C, E-isomer), 1.83 (s, 3H, H3C,
Z-isomer), 3.92 (s, 2H, H-10, Z-isomer), 4.12 (s, 2H, H-10,
E-isomer), 7.61 (m, 2!2H, m-Ph), 7.71 (m, 2!1H, p-Ph),
7.91 (m, 2!2H, o-Ph). 13C NMR (CDCl3, mixture): d 12.68
(q, H3C), 14.47 (q, H3C), 53.30 (t, C-10), 56.30 (t, C-10),
109.61 (s), 111.36 (s), 126.79 (s), 127.33 (s), 128.27 (d, 2C),
128.62 (d, 2C), 128.66 (d, 2C), 129.48 (d, 2C), 134.41 (d),
134.59 (d), 136.92 (s, 2C).
Z-(2,3-Diazidoprop-2-enylsulfonyl)-benzene (Z-13): IR
1
(CDCl3): 2117 (N3), 1324 (SO2), 1157 (SO2) cmK1. H
NMR (CDCl3): d 3.71 (s, 2H, H-10), 5.89 (s, 1H, H-30), 7.61
(m, 2H, m-Ph), 7.70 (m, 1H, p0-Ph), 7.92 (m, 2H, o-Ph). 13C
NMR (CDCl3): d 58.52 (t, C-1 ), 115.27 (s, C-20), 120.73 (d,
C-30), 128.51 (d, 2C), 129.39 (d, 2C), 134.39 (d, p-Ph),
137.82 (s, i-Ph).
4.1.8. E/Z-(2,3-Diazidobut-2-enylsulfonyl)-benzene (E/Z-
16) and E/Z-(2,3-Diazidobut-1-enylsulfonyl)-benzene
(E/Z-17). Compound 1518 (400 mg, 1.70 mmol) in
CH2Cl2 (25 mL) was treated with TMGA (0.30 g,
1.90 mmol) at K10 8C over a period of 2 min. Stirring
was continued at K5 8C for 2 h. The solvent was partially
removed, and the residue was chromatographed on silica gel
with Et2O/n-hexane (3:2). E-17 was obtained as major
product in a mixture with E-16 (150 mg, 0.54 mmol, 32%,
E-17/E-16Z18:1) and then Z-17 as major product in a
mixture with Z-16 (90.0 mg, 0.324 mmol, 19%, Z-17/Z-
16Z6:1). When the reaction was executed at 0 8C instead of
room temperature, E-17/E-16 (4:1) and Z-17/Z-16 (6:1)
were obtained after chromatography. For the data of E/Z-16,
see Section 4.1.7.
4.1.5. (E-3-Phenylsulfonylprop-1-en-1,2-diyl)-bis-4,5,6,7,
8,9-hexahydro-1H-cyclooctatriazole (E-14). Compound
E-14 (76%) was obtained from E-13 by analogy to the
procedure described for E-10. White solid: mp (CH2Cl2/
Et2O) 158–159 8C. 1H NMR (CDCl3): d 1.52 (m, 8H), 1.82
(m, 8H), 2.65 (m, 2H), 2.92 (m, 6H), 5.36 (s, 2H, H-30), 7.02
(s, 1H, H-10), 7.45 (m, 2H, m-Ph), 7.54 (m, 1H, p-Ph), 7.81
(m, 2H, o-Ph). 13C NMR (CDCl3): d 21.73 (t), 22.55 (t),
24.19 (t), 24.20 (t), 24.30 (t), 25.01 (t), 25.41 (t), 25.54 (t),
26.03 (t), 27.48 (t), 27.70 (t), 28.10 (t), 57.51 (t, C-30),
121.86 (s), 124.36 (d), 128.09 (d, 2C), 128.95 (d, 2C),
133.81 (d), 134.40 (s), 134.79 (s), 138.78 (s, i-Ph), 144.57
(s), 145.30 (s). Anal. Calcd for C25H32N6O2S (480.63): C,
62.47; H, 6.71; N, 17.49. Found: C, 62.67; H, 6.61; N, 17.47.
E-(2,3-Diazidobut-1-enylsulfonyl)-benzene (E-17): IR
(CDCl3, mixture of E-17/E-16): 2113 (N3), 1246 (N3),
1307 (SO2), 1153 (SO2) cmK1. 1H NMR (CDCl3): d 1.40 (d,
3JZ6.6 Hz, 3H, H3C), 5.49 (q, 3JZ6.6 Hz, 1H, H-30), 6.02
(s, 1H, H-10), 7.58 (m, 2H, m-Ph), 7.66 (m, 1H, p-Ph), 7.91
(m, 2H, o-Ph). 13C NMR (CDCl3): d 17.36 (q, H3C), 52.16
(d, C-30), 115.70 (d, C-10), 127.14 (d, 2C), 129.507 (d, 2C),
133.84 (d, p-Ph), 141.32 (s, i-Ph), 154.35 (s, C-2 ).
4.1.6. (Z-3-Phenylsulfonylprop-1-en-1,2-diyl)-bis-4,5,6,7,
8,9-hexahydro-1H-cyclooctatriazole (Z-14). Compound
Z-14 (72%) was obtained from Z-13 by analogy to the
procedure described for E-10. White solid: mp (CH2Cl2/
Et2O) 184–185 8C. 1H NMR (CDCl3): d 1.43 (m, 10H), 1.70
(m, 4H), 1.78 (m, 2H), 2.27 (br s, 2H), 2.63 (m, 2H), 2.84
(m, 4H), 4.56 (s, 2H, H-30), 7.16 (s, 1H, H-10), 7.54 (m, 2H,
m-Ph), 7.65 (m, 1H, p-Ph), 7.82 (m, 2H, o-Ph). 13C NMR
(CDCl3): d 21.44 (t), 21.93 (t), 23.96 (t), 24.10 (t), 24.19 (t),
24.36 (t), 24.69 (t), 25.070 (t), 25.91 (t), 26.04 (t), 27.04 (t),
27.99 (t), 60.94 (t, C-3 ), 119.52 (s), 122.91 (d), 127.85 (d,
2C), 129.42 (d, 2C), 134.32 (d), 134.35 (s), 135.53 (s),
138.35 (s, i-Ph), 144.13 (s), 144.43 (s). Anal. Calcd for
C25H32N6O2S (480.63): C, 62.47; H, 6.71; N, 17.49. Found:
C, 61.81; H, 6.72; N, 17.30.
Z-(2,3-Diazidobut-1-enylsulfonyl)-benzene (Z-17): IR
(CDCl3, mixture of Z-17/Z-16Z6:1): 2121 (N3), 1309
(SO2), 1151 (SO2) cmK1. 1H NMR (CDCl3): d 1.51 (d, 3JZ
3
6.6 Hz, 3H, H3C), 4.19 (q, JZ6.6 Hz, 1H, H-30), 5.98 (s,
H-10), 7.55 (m, 2H, m-Ph), 7.63 (m, 1H, p-Ph), 7.98 (m, 2H,
o-Ph). 13C NMR (CDCl3): d 17.82 (q, H3C), 58.50 (d, C-30),
115.82 (d, C-10), 127.72 (d, 2C), 129.03 (d, 2C), 133.58 (d,
p-Ph), 141.29 (s, i-Ph), 148.77 (s, C-20).
4.1.9. (E-1-Phenylsulfonylbut-1-en-2,3-diyl)-bis-4,5,6,7,
8,9-hexahydro-1H-cyclooctatriazole (E-18). A mixture
(85.0 mg, 0.306 mmol) of E-16 and E-17 (1:18) in CH2Cl2
(10 mL) was stored at room temperature over a period of
4.1.7. E/Z-(2,3-Diazidobut-2-enylsulfonyl)-benzene (E/Z-
16). Compound 1518 (1.12 g, 4.77 mmol) in CHCl3 (10 mL)
was treated with DABCO (1.07 g, 9.5 mmol) at 18 8C.
Stirring was continued at the same temperature for
additional 90 min. The solvent was partially removed, and
the residue was filtrated through silica gel with Et2O. The
etheric phase, which contained the allenyl azide 19,18 was
concentrated and dissolved rapidly in CH2Cl2 (10 mL).
Then TMGA (0.75 g, 4.77 mmol) was added. After stirring
1
48 h. The H NMR spectra proved the total decomposition
of E-16. The mixture was then treated with cyclooctyne
according to the procedure described for E-10 and
chromatographed to give E-18 (136 mg, 0.275 mmol,
1
90%) as yellow oil. H NMR (CDCl3): d 1.27–1.90 (m,
18H), 2.03 (d, 3JZ7.2 Hz, 3H, H3C), 2.76 (m, 6H), 6.33 (s,

J. R. Fotsing et al. / Tetrahedron 61 (2005) 8904–8909
8909
3
1H, H-10), 6.87 (q, JZ7.2 Hz, 1H, H-30), 7.62 (m, 2H, m-
Ph), 7.70 (m, 1H, p-Ph), 7.94 (m, 2H, o-Ph). 13C NMR
(CDCl3): d 18.69 (q, H3C), 21.20 (t), 21.48 (t), 23.87 (t),
24.21 (t), 24.36 (t), 24.46 (t), 25.40 (t), 25.82 (t), 25.98 (t),
26.05 (t), 27.29 (t), 28.22 (t), 51.81 (d, C-30), 127.64 (d, 2C),
129.79 (d, 2C), 132.42 (d), 134.06 (s), 134.85 (d), 135.00
(s), 138.97 (s), 143.86 (s), 144.47 (s), 145.29 (s). HRMS
(ESI): m/z calcd for C26H34N6O2S [MCHC]: 495.2463;
found: 495.2451.
References and notes
1. Part 18 of the series ‘Reactions of unsaturated azides’. For part
17, see Fotsing, J. R.; Banert, K. Synthesis 2005, accepted.
2. Adams, R.; Moje, W. J. Am. Chem. Soc. 1952, 74,
5560–5562.
3. Nicolaides, A.; Nakayama, T.; Yamazaki, K.; Tomioka, H.;
Koseki, S.; Stracener, L. L.; McMahon, R. J. J. Am. Chem. Soc.
1999, 121, 10563–10572.
4. Banert, K. Angew. Chem. 1987, 99, 932–934. Angew. Chem.,
Int. Ed. Engl. 1987, 26, 879–885.
4.1.10. Z-2-Azido-3-chloro-3-phenyl-propenal (Z-24).
Compound Z-24 (70%, yellow, light-sensitive solid after
recrystallization from Et2O) was obtained from 2-azido-1-
phenyl-ethanone25 by analogy to the procedure described by
Perumal and co-workers;21 decomposition above room
5. Banert, K. Chem. Ber. 1989, 122, 123–128.
6. Pearce, D. S.; Lee, M.-S.; Moore, H. W. J. Org. Chem. 1974,
39, 1362–1368.
7. Pearce, D. S.; Locke, M. J.; Moore, H. W. J. Am. Chem. Soc.
1975, 97, 6181–6186.
temperature. IR (CDCl3): 2113 (N3), 1674 (CHO) cmK1
.
1H NMR (CDCl3): d 7.42–7.45 (m, 4H, Ph), 7.47–7.51 (m,
1H, p-Ph), 9.41 (s, 1H, CHO). 13C NMR (CDCl3): d 128.54
(d), 130.27 (d), 130.86 (d), 133.43 (s), 140.21 (s), 184.14 (d,
CHO). One 13C NMR signal could not be detected.
8. VanAllan, J. A.; Priest, W. J.; Marshall, A. S.; Reynolds, G. A.
J. Org. Chem. 1968, 33, 1100–1102.
9. Hall, J. H. J. Am. Chem. Soc. 1965, 87, 1147–1148.
10. Hall, J. H.; Patterson, E. J. Am. Chem. Soc. 1967, 89,
5856–5861.
4.1.11. Z-2,3-Diazido-3-phenyl-propenal (Z-26). To a
stirred solution of Z-24 (0.94 g, 4.53 mmol) in CHCl3
(16 mL), QN3 (2.28 g, 4.86 mmol) was added. The mixture
was stirred over a period of 90 min. The solvent was
partially removed, and the residue was purified by flash
chromatography on silica gel with Et2O yielding Z-26
(0.83 g, 3.87 mmol, 86%) as yellow, light-sensitive solid
after recrystallization from Et2O; decomposition above
11. Awad, W. I.; Omran, S. M. A. R.; Nagieb, F. Tetrahedron
1963, 19, 1591–1601.
12. Klump, S. P.; Shechter, H. Tetrahedron Lett. 2002, 43,
8421–8423.
13. Grundmann, G. In Stroh, R., Ed.; Houben–Weyl; Thieme:
Stuttgart, 1965; Vol. 10/3, pp 777–836.
14. Hassner, A.; Isbister, R. J.; Friederang, A. Tetrahedron Lett.
1969, 2939–2942.
room temperature. IR (CCl4): 2102 (N3), 1669 (CHO) cmK1
.
1H NMR (CDCl3):d 7.34–7.42 (m, 2H, Ph), 7.49–7.58 (m, 3H,
Ph), 9.16 (s, 1H, CHO). 13C NMR (CDCl3): d 123.31 (s),
127.81 (s), 129.12 (d), 129.61 (d), 131.38 (d), 145.43 (s),
185.70 (d, CHO). UV/vis (cyclohexane): lmax/nm (log 3)
326 (3.96), 251 (3.89).
15. Ko¨hler, F. Dissertation, TU Chemnitz, 2002, p 54.
16. Smolinsky, G.; Pryde, C. A. J. Org. Chem. 1968, 33,
2411–2416.
17. Monocyclic 2-azido-2H-azirines were produced by another
method, see Gallagher, T. C.; Storr, R. C. Tetrahedron Lett.
1981, 22, 2905–2908.
4.1.12. Z-2,3-Diazido-3-(4-chlorophenyl)-propenal (Z-27).
For the synthesis of Z-27 (91%, yellow, light-sensitive solid
after recrystallization from Et2O) from 2521 see the
procedure for Z-26; decomposition above room tempera-
18. Fotsing, J. R.; Banert, K. Eur. J. Org. Chem. 2005, in press.
19. Banert, K. In Kropf, H., Schaumann, E., Eds.; Houben–Weyl;
Thieme: Stuttgart, 1993; Vol. E15, pp 818–875.
¨
20. Banert, K.; Kohler, F. Angew. Chem. 2001, 113, 173–176.
1
ture. IR (CDCl3): 2107 (N3), 1666 (CHO) cmK1. H NMR
Angew. Chem., Int. Ed. 2001, 40, 174–177.
21. Majo, V. J.; Perumal, P. T. J. Org. Chem. 1998, 63,
7136–7142.
(CDCl3): d 7.36 (AA0BB0, 2H, Ph), 7.51 (AA0BB0, 2H, Ph),
9.20 (s, 1H, CHO). 13C NMR (CDCl3): d 125.26 (s), 127.48
(s), 129.52 (d), 131.23 (d), 137.74 (s), 143.59 (s), 184.66 (d,
CHO). UV/vis (cyclohexane): lmax/nm (log 3) 328 (3.89),
260 (3.95), 243 (3.99).
22. Banert, K. Chem. Ber. 1985, 118, 1564–1574 and references
cited therein.
23. Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43,
2923–2925.
24. (a) Dharanipragada, R.; VanHulle, K.; Bannister, A.; Bear, S.;
Kennedy, L.; Hruby, V. J. Tetrahedron 1992, 48, 4733–4748.
(b) Hruby, V. J.; Boteju, L.; Li, G. Chem. Eng. News 1993, 71,
2.
Acknowledgements
Joseph Rodolph Fotsing gratefully thanks the German
Academic Exchange Service (DAAD) for a generous
fellowship. The research was supported by the Fonds der
Chemischen Industrie.
25. Yadav, J. S.; Nanda, S.; Reddy, P. T.; Rao, A. B. J. Org. Chem.
2002, 67, 3900–3903.