Reactions of unsaturated azides; Part 27: 1Synthesis of 1,4-diazidobuta-1,3-dienes

Article abstract of DOI:10.1055/s-0030-1260000

Three different methods to prepare 1,4-diazidobuta-1,3-dienes are presented: nucleophilic substitution of electron-poor dichlorinated substrates, nucleophilic addition of hydrazoic acid at an electron-deficient diallene, and a sequence of prototropic isomerizations of propargyl sulfones followed by nucleophilic additions. In all cases, isolation and assignment of the diastereomeric products was possible, and some sequential reactions, such as reduction or 1,3-dipolar cycloaddition of the azido groups, were performed. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0030-1260000

PAPER
1561
Reactions of Unsaturated Azides; Part 27:1 Synthesis of 1,4-Diazidobuta-1,3-
dienes
S
ynthesis of 1,4-D
l
iazidob
a
uta-1,3-die
u
nes s Banert,*a Frank Köhler,a Antje Melzer,a Ingolf Scharf,a Gerd Rheinwald,b Tobias Rüffer,b Heinrich Langb
a
Chemnitz University of Technology, Organic Chemistry, Straße der Nationen 62, 09111 Chemnitz, Germany
Fax +49(371)53121229; E-mail: klaus.banert@chemie.tu-chemnitz.de
b
Chemnitz University of Technology, Inorganic Chemistry, Straße der Nationen 62, 09111 Chemnitz, Germany
Received 28 February 2011
R2
R1
Abstract: Three different methods to prepare 1,4-diazidobuta-1,3-
dienes are presented: nucleophilic substitution of electron-poor
dichlorinated substrates, nucleophilic addition of hydrazoic acid at
an electron-deficient diallene, and a sequence of prototropic isomer-
izations of propargyl sulfones followed by nucleophilic additions.
In all cases, isolation and assignment of the diastereomeric products
was possible, and some sequential reactions, such as reduction or
1,3-dipolar cycloaddition of the azido groups, were performed.
R1
R2
R2
Δ or hν
N3
HN
R1
NH
N3
R1
R2
1
2
Key words: allenes, alkynes, azides, cycloaddition, dienes, isomer-
isation, nucleophilic addition, nucleophilic substitution
hν or Ag+
Δ
R1
R2
X
Whereas vinyl azides are well-known for their manifold
reactions and can be prepared by various methods,2 all at-
tempts to synthesize 1,4-diazidobuta-1,3-dienes were
unsuccessful3 until recently. For example, the Hassner
reaction4,5 of buta-1,3-dienes – the addition of iodine
azide followed by base-induced elimination of hydrogen
iodide – did not bring about the desired title compounds.6
R1
R2
X
R1
R2
R2
N
R1
R2
R2
N
N
N
X = Cl, Br, I
X = N3
3
R1
R1
4
5
R1, R2 = H, alkyl, Ph
However, 1,4-diazidobuta-1,3-dienes of type
1
Scheme 1 The only known synthesis of 1,4-diazidobuta-1,3-dienes
(Scheme 1) were generated by electrocyclic conrotatory
ring opening of the diazidocyclobutenes 3 (X = N3),
which are available by nucleophilic substitution of the
corresponding dihalides 3 (X = Cl, Br, or I).7 The diazides
1 proved to be ideal precursors for long-sought3,8 bi-2H-
azirin-2-yls 2, which were produced by either photolysis
or thermal reaction of 1 in excellent yields.7 The highly
strained heterocycles 2 could not be isolated because they
isomerized nearly quantitatively to give pyridazines 4
even at low temperatures; pyrimidines 5 were also formed
by prolonged irradiation or in the presence of silver salts.
Thus, the reported7 aromatization of 2 shows that valence
isomerization to prepare pyridazines 4 is possible, al-
though rearrangements to generate other diazabenzenes
were postulated in the literature.3,8
Unfortunately, the substitution pattern of 1 is limited (R1,
R2 = H, small alkyl or phenyl), and the synthesis of 1 from
3 cannot be performed on a large scale. Herein, we present
three new methods that can be used to prepare 1,4-diazi-
dobuta-1,3-dienes with other substitution patterns without
limitations in scale.
and some of their reactions
The reaction of mucic acid (6) with phosphorus pen-
tachloride, followed by treatment with methanol is known
to give two diastereomeric 1,4-dichlorobuta-1,3-dienes 7
with melting points of 154 and 68 °C (Scheme 2).9 How-
ever, the stereochemistry of the products 7 is unknown.10–13
We found that the H and 13C NMR data of the isomer
1
with the lower melting point unequivocally identified the
(E,Z)-structure; those of the higher-melting diastereoiso-
mer was consistent with a more symmetrical structure
with either (E,E)- or (Z,Z)-configuration. The proton-cou-
pled 13C NMR spectrum of (E,Z)-7 indicated couplings of
3J(13C–1H) = 10.5 and 4.4 Hz for the carbonyl carbon at-
oms and the inner protons, which correspond to vicinal
trans and cis couplings, respectively, and are in agreement
with similar, known14 values. The 13C NMR signal result-
ing from the carbonyl group of the more symmetrical
dichloride 7 showed a more complex splitting pattern due
to the presence of an ABM3X system (Figure 1). Howev-
er, simulation of this experimental signal predicted a cou-
pling value of 3J(13C–1H) = 4.5 Hz for the vicinal coupling
to the inner proton, which provides strong evidence for cis
coupling and (Z,Z)-configuration of the higher-melting
diastereoisomer of 7.
SYNTHESIS 2011, No. 10, pp 1561–1568
x
x.
x
x
.
2
0
1
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Advanced online publication: 15.04.2011
DOI: 10.1055/s-0030-1260000; Art ID: T23411SS
© Georg Thieme Verlag Stuttgart · New York

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K. Banert et al.
PAPER
Treatment of (Z,Z)-7 with sodium azide in N,N-dimethyl-
formamide afforded the diazide (Z,Z)-8 as a yellow solid
with 78% yield. The stereochemistry of the product was
clarified by 1H and 13C NMR data and, especially, by the
characteristic vicinal coupling of the carbonyl carbon
atom with 3J(13C–1H) = 4.2 Hz. Moreover, the configura-
tion of (Z,Z)-8 was confirmed by single crystal X-ray
structure analysis (Figure 2). The analogous reaction of
(E,Z)-7 with sodium azide in N,N-dimethylformamide
also gave exclusively (Z,Z)-8, whereas when the same
starting material was treated with sodium azide in a mix-
ture of N,N-dimethylformamide and acetic acid, (E,Z)-8
was generated in 62% yield. In the transformation of elec-
tron-poor vinyl halides into vinyl azides, stereospecific
substitution with retention of configuration is common15
if the reaction is performed under kinetic control. Howev-
er, (Z,Z)-8 is clearly the thermodynamically favored prod-
uct in the synthesis of 8 from 7.16 Upon treatment of (Z,Z)-
8 with cyclooctyne,17 the cycloadduct (Z,Z)-9 was formed
in 80% yield.
OH OH
CO2H
HO2C
OH OH
6
1. PCl5
2. MeOH
ref. 9
Cl
H
H
MeO2C
Cl
CO2Me
CO2Me
+
MeO2C
H
Cl
H
Cl
(Z,Z)-7 mp 154 °C
(E,Z)-7 mp 68 °C
NaN3
DMF, AcOH
NaN3
DMF
NaN3
DMF
N3
H
MeO2C
H
CO2Me
CO2Me
MeO2C
N3
H
N3
H
N3
(Z,Z)-8
(E,Z)-8
N
80%
N
N
CO2Me
MeO2C
N
N
N
(Z,Z)-9
Scheme 2 Synthesis of 1,4-diazidobuta-1,3-dienes 8 by nucleo-
philic substitution and treatment with cyclooctyne
Figure 2 Molecular structure of (Z,Z)-8 from single crystal X-ray
analysis (ORTEP diagram with 50% probability level), see also the
Supporting Information
When diallene 10, which is easily available from hexa-
2,4-diyne-1,6-diol and chlorodiphenylphosphine,18 was
subjected to treatment with lithium or sodium azide in
aqueous ethanol, a very complex mixture of products was
formed (Scheme 3). However, use of 1,1,3,3-tetrameth-
ylguanidinium azide (TMGA) in chloroform, led to the
formation of a mixture of stereoisomeric 1,4-diazidobuta-
1,3-dienes 11 in 89% yield. Simple recrystallization fur-
nished (E,E)-11 with 50% yield based on 10. The consti-
tution of this diazide was confirmed by treatment with
cyclooctyne, which resulted in the formation of the cy-
cloadduct (E,E)-12 in 82% yield. Unfortunately, we were
not able to confirm the configuration of (E,E)-11 from its
13C NMR data due to complex AXX¢ systems, which did
3
not allow the J(31P–13C) coupling to be measured accu-
Figure 1 The signal of the carbonyl group in the proton-coupled 13
NMR spectrum of (Z,Z)-7
C
rately. Fortunately, storing a solution of (E,E)-11 at ambi-
ent temperature led to the formation of small amounts of
2H-azirine (E)-13. The vinylic methyl carbon of this prod-
Synthesis 2011, No. 10, 1561–1568 © Thieme Stuttgart · New York

PAPER
Synthesis of 1,4-Diazidobuta-1,3-dienes
1563
N3
OPPh2
C
Ph2PO
TMGA, CHCl3
89%
C
OPPh2
10
OPPh2
N3
11
(E,E)-isomer isolated
with 50% yield
NaBH4
45%
r.t.
some
weeks
82%
Ph2PO
N3
NH2
Ph2PO
N
N
N
N
Ph2PO
OPPh2
(E,E)-14
H2N
OPPh2
(E)-13
OPPh2
N
N
N
(E,E)-12
Scheme 3 Synthesis of 1,4-diazidobuta-1,3-dienes 11 by nucleophilic addition and some reactions of (E,E)-11
uct showed a cis coupling with 3J(31P–13C) = 4 Hz, which Finally, we tried to prepare 1,4-diazidobuta-1,3-dienes
corresponds to the E-configuration of (E)-13 and thus to starting from the known20 diyne 15 (Scheme 4). We envi-
the E,E-configuration of (E,E)-11, and is in agreement sioned that prototropic isomerization of 15 may generate
with similar known19 values. Furthermore, the stereo- either an electron-deficient allene21 or a diallene, which
chemistry of (E,E)-11 was confirmed by single crystal X- would be able to undergo nucleophilic addition of hydra-
ray structure analysis (Figure 3). The reaction of (E,E)-11 zoic acid to give the corresponding vinyl azides or diaz-
with sodium borohydride in ethanol furnished the stable ides of type 16, respectively. However, whereas treatment
enamine (E,E)-14 in 45% yield.
of 15 with triethylamine led only to degradation, the reac-
tion with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) af-
forded the rearrangement products (E,E)-18 and (E,Z)-18
in low yields. Fortunately, subjecting 15 to TMGA in
dichloromethane at low temperature furnished all three
diastereoisomers of 16 nearly quantitatively. When the
transformation was analyzed by 1H NMR spectroscopy, it
was found that (E,Z)-16 had been formed in 27% yield,
and the two more symmetrical isomers with 58 and 9%
yield. However, during work-up, the low stability of 16
led to the generation of the secondary products 19 and 20,
which were isolated in 2 and 13% yield, respectively.
Thus, after separation by chromatography, the yield of
(E,Z)-16 decreased to 15%, whereas those of the two more
symmetrical isomers diminished to 34 and 3%. The struc-
tures of 16, 19, and 20 were confirmed not only by stan-
dard spectroscopic methods but also by treatment with
cyclooctyne to give the cycloadducts 17 and 21, and by ir-
radiation to bring about formation of 2H-azirines 22 and
23.
In conclusion, 1,4-diazidobuta-1,3-dienes, which can en-
rich the multifarious chemistry of organic azides,22 are
now available by several methods. Currently, we are at-
tempting to transform the title compounds 8, 11, and 16
Figure 3 Molecular structure of (E,E)-11 from single crystal X-ray
analysis (ORTEP diagram with 50% probability level); one molecule
of water, connected to (E,E)-11 via an intermolecular hydrogen bond,
and two molecules of dichloromethane as packing solvents are omit-
ted for clarity
Synthesis 2011, No. 10, 1561–1568 © Thieme Stuttgart · New York

1564
K. Banert et al.
PAPER
N
SO2Ph
N
N
SO2Ph
N3
N3
Ph2OS
N
TMGA, CH2Cl2
–90 to –10 °C
94% (NMR)
N
SO2Ph
SO2Ph
SO2Ph
DBU
N
15
16
17
SO2Ph
N3
SO2Ph
N3
SO2Ph
SO2Ph
+
SO2Ph
N3
18
19
20
SO2Ph
hν
hν
SO2Ph
N
N
N
SO2Ph
SO2Ph
SO2Ph
N3
21
N
N
22
23
Scheme 4 Synthesis and reactions of 1,4-diazidobuta-1,3-dienes 16
Single Crystal X-ray Diffraction Analysis
into bi-2H-azirin-2-yls of type 2 in order to study the cor-
Data collection for (E,E)-11 was performed at 173 K with a Bruker
Smart CCD 1k diffractometer and for (Z,Z)-8 at 293 K on an Oxford
Gemini S diffractometer. All calculations, including structural solu-
tions and refinement by full-matrix least-squares on F2, were per-
formed using the SHELXTL program.23 CCDC 810574 [(Z,Z)-8]
and 810573 [(E,E)-11] contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
responding aromatization reactions.
Caution: Care must be taken when handling and storing azides,
which are explosive. Especially, neat azides can lead to large explo-
sions on friction, impact, or heating.
Melting points were determined with a Pentakon Dresden Boetius
apparatus. FTIR spectra were recorded with a Bruker IFS 28 FTIR
spectrophotometer. IR measurements were made on solutions in
KBr cuvettes or as potassium bromide pellets. UV/Vis spectra were
acquired with a Specord UV/Vis instrument from Carl Zeiss, Jena.
1H NMR spectra were recorded with Varian Gemini 2000 or Unity
Inova 400 spectrometers operating at 300 and 400 MHz, respective-
ly; with the same spectrometers, 13C NMR data were recorded at 75
and 100 MHz, respectively. NMR signals were referenced to TMS
(d = 0 ppm) or solvent signals and recalculated relative to TMS.
The multiplicities of 13C NMR signals were determined with the aid
of DEPT135 experiments. 31P NMR data were recorded at 121.5
MHz using 85% H3PO4 as external standard (d = 0 ppm). MS and
HRMS (ESI) spectra were recorded with an Applied Biosystems
Mariner 5229 mass spectrometer or a Bruker micrOTOF-QII spec-
trometer. Elemental analyses were performed with a Vario EL ele-
mental analyzer from Elementar Analysensysteme GmbH Hanau or
with a Vario Micro Cube from Elementar. Elemental analyses of ex-
plosive azides and highly unstable azirines were not performed for
safety reasons. TLC was performed with Macherey–Nagel Poly-
gram SIL G/UV254 polyester sheets. Flash column chromatography
was performed with 32–63 mm silica gel. HPLC pump 64 (Knauer)
and UV/VIS photometer (l = 254 nm, Knauer) were utilized for
isolation of compounds by HPLC.
Dimethyl (Z,Z)-2,5-Dichlorohexa-2,4-dienedioate [(Z,Z)-7]
Prepared and isolated as described in the literature.9a
White solid; mp 154 °C (EtOH).
IR (CDCl3): 1731 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 3.87 (s, 6 H, OCH3), 7.83 (s, 2 H,
3/4-H).
1
13C NMR (75 MHz, CDCl3): d = 53.62 (q, J = 148.3 Hz, OCH3),
130.74 (d, 1J = 166.1 Hz, C-3/4), 131.04 (t, J = 4.7 Hz, C-2/5),
3
162.25 (C-1/6, simulation of the ABM3X system led to Jcis-H
=
4.5 Hz, 3JOMe = 3.9 Hz, 4JH = –0.1 Hz, 3J3-H,4-H = 11.5 Hz).
Dimethyl (2E,4Z)-2,5-Dichlorohexa-2,4-dienedioate [(E,Z)-7]
Prepared and isolated as described in the literature.9a
White solid; mp 68 °C (EtOH).
IR (CDCl3): 1729 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 3.88 (s, 3 H, OCH3), 3.90 (s, 3 H,
OCH3), 7.33 (d, 3J = 11.5 Hz, 1 H), 8.38 (d, 3J = 11.5 Hz, 1 H).
Synthesis 2011, No. 10, 1561–1568 © Thieme Stuttgart · New York

PAPER
Synthesis of 1,4-Diazidobuta-1,3-dienes
1565
1
13C NMR (75 MHz, CDCl3): d = 53.28 (q, J = 148.3 Hz, OCH3),
53.43 (q, 1J = 148.1 Hz, OCH3), 129.12 (t, J = 5.5 Hz), 129.81 (dd,
J = 6.7, 3.1 Hz), 130.80 (d, 1J = 168.9 Hz), 133.60 (d,
13C NMR (75 MHz, CDCl3): d = 21.65 (t), 24.07 (t), 24.65 (t), 25.45
(t), 26.01 (t), 27.55 (t), 53.23 (d, OCH3), 131.61 (d), 132.49 (s),
136.10 (s), 144.63 (s), 161.64 (s, C=O).
1J = 162.5 Hz), 161.98 (dqd, 3Jtrans-H = 10.5 Hz, JOMe = 3.9 Hz,
3
HRMS: m/z (%) calcd for [M + H]+ 469.2558; found: 469.2563
4JH = 0.6 Hz, C-1), 162.44 (dqd, 3Jcis-H = 4.4 Hz, JOMe = 3.9 Hz,
3
(100); calcd for [2M + H]+ 937.5043; found: 937.5086 (64).
4JH = 0.8 Hz, C-6).
Anal. Calcd for C24H32N6O4: C, 61.52; H, 6.88; N, 17.94. Found: C,
61.96; H, 6.61; N, 17.63.
Dimethyl (Z,Z)-2,5-Diazidohexa-2,4-dienedioate [(Z,Z)-8]
A solution of NaN3 (2.2 g, 34 mmol) and (Z,Z)-7 (1.0 g, 4.2 mmol)
in DMSO (60 mL) was stirred at 20 °C for 16 h. After dilution with
H2O (ca. 200 mL), the mixture was extracted with Et2O (3 × ca.
100 mL). The combined organic layers were washed with H2O (2 ×
ca. 100 mL) and dried with MgSO4. After removal of the solvent in
vacuo, (Z,Z)-8 was isolated as a yellow, temperature-sensitive solid.
Treatment of (E,Z)-7 in a similar way also led to (Z,Z)-8.
3,4-Bis(diphenylphosphinoyl)-2,5-diazidohexa-2,4-dienes (11)
To a solution of 1018 (2.00 g, 4.18 mmol) in anhydrous CHCl3 (40
mL) was added a solution of TMGA (1.40 g, 8.85 mmol) in CHCl3
(10 mL). The mixture was stirred for 2 h at r.t., washed with H2O
(ca. 50 mL) and dil. HCl (ca. 50 mL), and dried with MgSO4. After
removal of the solvent, a mixture of the diastereoisomers of 11 was
isolated as a viscous brown oil (2.10 g, 89%). Stirring this product
with slow addition of Et2O gave (E,E)-11.
Yield: 0.82 g (78%); mp 109 °C (CHCl3, dec.).
IR (CHCl3): 2131 (N3), 1722 (C=O), 1252 (N3) cm–1.
UV/Vis (MeCN): lmax (lg e) = 350 (4.49) nm.
Yield: 1.18 g (50%); beige solid; mp 99–102 °C (CH2Cl2–hexane,
dec.).
1H NMR (300 MHz, CDCl3): d = 3.88 (s, 6 H, OCH3), 6.86 (s, 2 H,
3/4-H).
IR (CDCl3): 3061, 2101 (N3), 1577, 1438 (P–Ph), 1276, 1184 (P=O)
cm–1.
1
13C NMR (75 MHz, CDCl3): d = 52.99 (q, J = 148.0 Hz, OCH3),
UV/Vis (MeCN): lmax (lg e) = 210 (4.74) nm.
1H NMR (300 MHz, CDCl3): d = 1.71 (m, 6 H, CH3), 7.30–7.55 (m,
12 H, Ph), 7.70 (m, 4 H, Ph), 7.86 (m, 4 H, Ph).
1
2
117.87 (d, J = 166.6 Hz, C-3/4), 130.02 (t, J = 3.7 Hz, C-2/5),
3
162.77 (C-1/6, simulation of the ABM3X system led to Jcis-H
=
4.2 Hz, 3JOMe = 3.9 Hz, 4JH = –0.3 Hz, 3J3-H,4-H = 11.6 Hz).
13C NMR (75 MHz, CDCl3): d = 17.92 (CH3), 116.57 [dd, 1J(31P–
13C)+2J(31P–13C) = 111 Hz, C-3 and C-4], 127.81 [‘t’, 3J(31P–
13C)+6J(31P–13C) = 12.6 Hz, m-Ph], 128.20 [‘t’, 3J(31P–13C)+6J(31P–
13C) = 12.6 Hz, m-Ph], 131.42, 131.54, 131.9–132.3 (several sig-
nals of o- and p-Ph), 133.06 [dd, 1J(31P–13C)+4J(31P–13C) =
Dimethyl (E,Z)-2,5-Diazidohexa-2,4-dienedioate [(E,Z)-8]
NaN3 (1.1 g, 17 mmol) was dissolved in a mixture of freshly dis-
tilled DMF (25 mL) and AcOH (6 mL). At r.t., (E,Z)-7 (0.50 g, 2.1
mmol) was added in portions. After stirring for 16 h, H2O (100 mL)
was added and the mixture was extracted repeatedly with Et2O. The
combined organic layers were washed with H2O (2 × ca. 50 mL) and
dried with MgSO4. After removal of the solvent in vacuo, (E,Z)-8
was isolated as a yellow solid (0.38 g). Analysis by 1H NMR indi-
cated a product ratio with (E,Z)-8/(Z,Z)-8 = 6.4. Thus, the main
product was formed in 62% yield.
119.5 Hz, i-Ph, signal partly covered], 148.80 [‘dd’, J(31P–13C)+
2
3J(31P–13C) = 26.3 Hz, C-2 and C-5]; the carbon atoms and both
phosphorus atoms form several AXX¢ systems.
31P NMR (121.5 MHz, CDCl3): d = 28.70.
MS (ESI): m/z (%) = 565.3 (100) [M + 1]+, 537.3 (29) [M+ + 1 –
N2].
IR (CHCl3): 2119 (N3), 1708 (C=O), 1245 (N3) cm–1.
1H NMR (300 MHz, CDCl3): d = 3.86 (s, 3 H, OCH3), 3.90 (s, 3 H,
(E,E)-3,4-Bis(diphenylphosphinoyl)-2,5-bis(4,5,6,7,8,9-hexahy-
dro-1H-cyclooctatriazol-1-yl)hexa-2,4-diene [(E,E)-12]
Yield: 82%; white solid; mp 266–268 °C (CH2Cl2–hexane).
1H NMR (300 MHz, CDCl3): d = 1.0–1.6 (m, 16 H), 1.67 (br s, 6 H,
CH3), 2.04 (br m, 2 H), 2.46 (br m, 2 H), 2.74 (br m, 4 H), 7.3–7.7
(m, 16 H, Ph), 7.92 (m, 4 H, Ph).
OCH3), 6.85 (d, 3J = 11.6 Hz, 1 H), 7.79 (d, 3J = 11.6 Hz, 1 H).
1
13C NMR (75 MHz, CDCl3): d = 53.27 (q, J = 148.2 Hz, OCH3),
1
1
53.39 (q, J = 147.8 Hz, OCH3), 117.80 (d, J = 167.1 Hz, C-4),
1
127.59 (t, J = 5.1 Hz), 129.91 (d, J = 163.8 Hz, C-3), 132.91 (t,
J = 3.5 Hz), 162.31 (m, C=O), 162.44 (m, C=O).
13C NMR (75 MHz, CDCl3): d = 22.21 (t), 23.88 (t), 24.94 (t), 25.35
(t), 25.48 (q, CH3), 26.33 (t), 26.87 (t), 128.24 [d, 3J(31P–
13C) = 12.6 Hz, m-Ph], 128.37 [d, 3J(31P–13C) = 12.6 Hz, m-Ph],
128.54 [d, 1J(31P–13C) = 103.6 Hz, i-Ph], 129.66 [d, 1J(31P–
Treatment of Azides with Cyclooctyne; General Procedure
A solution of the azide or diazide in either CHCl3 or CH2Cl2 (ca. 0.1
to 0.01 M) was treated with an excess of cyclooctyne17 at r.t. Cool-
ing of the reaction mixture was appropriate in some cases, and the
13C) = 89.3 Hz,
i-Ph],
130.88
[‘t’,
2J(31P–13C)+5J(31P–
1
13C) = 9.7 Hz, o-Ph], 131.57 (s, p-Ph), 131.77 (s, p-Ph), 132.23 [‘t’,
2J(31P–13C)+5J(31P–13C) = 12 Hz, o-Ph], 134.26 (s), 136.00 [d,
1J(31P–13C) = 106.5 Hz, C-3 and C-4], 144.23 (s), 146.63 [‘d’,
2J(31P–13C)+3J(31P–13C) = 25.2 Hz, C-2 and C-5]; the carbon atoms
and both phosphorus atoms form several AXX¢systems.
progress of the cycloaddition processes could be monitored by H
NMR spectroscopy, which indicated nearly quantitative yields. The
necessary reaction times ranged from 30 min to 5 d [for (E,E)-12].
After removal of the solvent and the excess of cyclooctyne in vacuo,
the oily or viscous residue was treated with hexane or Et2O to give
a solid that was purified by recrystallization.
31P NMR (121.5 MHz, CDCl3): d = 29.28.
MS (ESI): m/z = 781.6 [M + 1]+.
Dimethyl (Z,Z)-2,5-Bis(4,5,6,7,8,9-hexahydro-1H-cycloocta-
triazol-1-yl)hexa-2,4-dienedioate [(Z,Z)-9]
Yield: 80%; white solid; mp 178–181 °C (Et2O–hexane).
IR (CDCl3): 1732 (C=O) cm–1.
Anal. Calcd for C46H50N6O2P2·2CH2Cl2: C, 60.64; H, 5.72; N, 8.84.
Found: C, 60.56; H, 5.93; N, 8.63.
(E)-2-[2-Azido-1-(diphenylposphinoyl)prop-1-enyl]-2-(diphe-
nylphosphinoyl)-3-methyl-2H-azirine [(E)-13]
1H NMR (300 MHz, CDCl3): d = 1.45 (m, 8 H), 1.71 (m, 4 H), 1.77
(m, 4 H), 2.58 (m, 4 H), 2.94 (m, 4 H), 3.71 (m, 6 H, OCH3), 7.18
(s, 2 H).
1H NMR (300 MHz, CDCl3): d = 1.69 (br s, 3 H, CH3), 1.86 (br s,
3 H, CH3), 7.2–8.1 (m, 20 H, Ph).
3
13C NMR (75 MHz, CDCl3): d = 12.78 (CH3), 18.42 [d, J(31P–
13C) = 4 Hz, C-3¢], 35.84 [dd, 1J(31P–13C) = 116.2 Hz, 2J(31P–
Synthesis 2011, No. 10, 1561–1568 © Thieme Stuttgart · New York

1566
K. Banert et al.
PAPER
13C) = 8.6 Hz, C-2], 116.24 [dd, 1J(31P–13C) = 105.9 Hz, 2J(31P–
13C) = 13.2 Hz, C-1¢], 127.6–128.4 (Ph, several signals), 131.2–
134.0 (Ph, several signals), 154.49 [dd, 2J(31P–13C) = 20.6 Hz,
3J(31P–13C) = 2.9 Hz, C-2¢], 170.55 [d, 2J(31P–13C) = 2.9 Hz, C-3].
13C NMR (100 MHz, CDCl3): d = 92.95 (s, C≡), 121.17 (d, CH),
127.96 (d, Ph), 129.52 (d, Ph), 134.06 (d, Ph), 138.94 (s, i-Ph),
141.35 (d, CH).
HRMS (ESI): m/z [M + H]+ calcd for C18H15O4S2: 359.0400; found:
359.0406.
31P NMR (121.5 MHz, CDCl3): d = 27.04, 27.91.
Anal. Calcd for C18H14O4S2: C, 60.32; H, 3.94; S, 17.89. Found: C,
59.47; H, 3.94; S, 17.91.
(E,E)-3,4-Bis(diphenylphosphinoyl)hexa-2,4-diene-2,5-di-
amine [(E,E)-14]
NaBH4 (40 mg, 0.11 mmol) was added to a solution of (E,E)-11
(100 mg, 0.18 mmol) in EtOH (15 mL). The mixture was stirred at
r.t. for 24 h, then diluted with CH2Cl2 (ca. 50 mL) washed with H2O
(5 × ca. 20 mL), and dried with MgSO4. After removal of the sol-
vent, a yellow solid (90 mg) was isolated, and purified by HPLC (re-
verse phase column: Eurospher 100 C18, 2 × 20 cm, MeOH–H2O,
2:1). The solvents were removed in vacuo to give a residue that was
dissolved in CH2Cl2 and dried with MgSO4. After removal of the
solvent, (E,E)-14 was isolated.
1,6-Bis(phenylsulfonyl)hexa-1E,5Z-dien-3-yne [(E,Z)-18]
IR (CDCl3): 1325 (SO2), 1153 (SO2) cm–1.
1H NMR (400 MHz, CDCl3): d = 6.32 (dd, 3J = 11.0 Hz,
3
5J = 2.2 Hz, 1 H, Z-CH=CHSO2Ph), 6.73 (d, J = 11.0 Hz, 1 H, Z-
CH=CHSO2Ph), 6.81 (d, 3J = 15.4 Hz, 1 H, E-CH=CHSO2Ph), 6.92
3
5
(dd, J = 15.4 Hz, J = 2.2 Hz, 1 H, E-CH=CHSO2Ph), 7.49–7.72
(m, 6 H, Ph), 7.87–7.94 (m, 4 H, Ph).
13C NMR (100 MHz, CDCl3): d = 91.87 (s, C≡), 96.86 (s, C≡),
119.25 (d, CH), 121.47 (d, CH), 127.96 (d, Ph), 128.07 (d, Ph),
129.32 (d, Ph), 129.58 (d, Ph), 134.13 (d, 2C, Ph), 139.00 (s, i-Ph),
139.76 (s, i-Ph), 140.97 (d, CH), 141.32 (d, CH).
HRMS (ESI): m/z [M + H]+ calcd for C18H15O4S2: 359.0378; found:
359.0406.
Yield: 41 mg (45%); white solid; mp 172–175 °C (CH2Cl2).
IR (CDCl3): 1437 (P-Ph), 1188 (P=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 1.65 (s, 6 H, CH3), 6.69–6.78 (m,
2 H), 7.12–7.20 (m, 12 H), 7.31–7.45 (m, 4 H), 7.53–7.60 (m, 2 H).
1H NMR (300 MHz, DMSO-d6): d = 1.45 (s, 6 H, CH3), 6.45 (br s,
4 H, NH2), 6.55–6.65 (m, 4 H, Ph), 7.14–7.31 (m, 8 H, Ph), 7.34–
7.48 (m, 6 H, Ph), 7.60–7.67 (m, 2 H, Ph).
2,5-Diazido-1,6-bis(phenylsulfonyl)hexa-2,4-dienes (16)
In an NMR tube, a solution of 1520 (1.5 mg, 0.0042 mmol) and 1,4-
dioxane (0.18 mg, 0.0021 mmol, internal standard) in CD2Cl2 (0.75
mL) was cooled to –95 °C. A solution of TMGA (2.3 mg, 0.015
mmol) in CD2Cl2 (0.365 mL) was added dropwise. The NMR tube
3
13C NMR (75 MHz, CDCl3): d = 21.26 [‘t’, J(31P–13C)+4J(31P–
13C) = 4.0 Hz,
CH3],
92.15
[dd,
1J(31P–13C)+2J(31P–
13C) = 134.5 Hz, C-3 and C-4], 127.87 [‘t’, 3J(31P–13C)+6J(31P–
13C) = 12.1 Hz, m-Ph], 128.16 [‘t’, 3J(31P–13C)+6J(31P–
13C) = 12.0 Hz, m-Ph], 130.77 [d, 4J(31P–13C) = 1.2 Hz, p-Ph],
130.80 [d, 4J(31P–13C) = 1.2 Hz, p-Ph], 131.40 [‘t’, 2J(31P–
1
was warmed to 20 °C for 10 min and analyzed by H NMR spec-
troscopy, which indicated that 16 was formed with a total yield of
94% [(E,Z)-16 in 27% yield and two symmetrical stereoisomers
with 58 and 9% yield]. The products 19 and 20 could not be detect-
ed.
13C)+5J(31P–13C) = 9.8 Hz, o-Ph], 131.56 [‘t’, J(31P–13C)+5J(31P–
2
13C) = 9.7 Hz,
o-Ph],
134.91
[dd,
1J(31P–13C)+4J(31P–
13C) = 104.8 Hz, i-Ph], 135.23 [dd, 1J(31P–13C)+4J(31P–
13C) = 112.8 Hz, i-Ph], 157.74 [‘t’, 2J(31P–13C)+3J(31P–
13C) = 25.1 Hz, C-2 and C-5]; the carbon atoms and both phospho-
rus atoms form several AXX¢ systems.
A solution of 15 (500 mg, 1.4 mmol) in anhydrous CH2Cl2 (75 mL)
was cooled to –95 °C. At this temperature, a solution of TMGA
(0.76 g, 4.8 mmol) in anhydrous CH2Cl2 (25 mL) was added drop-
wise within 15 min, which led to the formation of a white suspen-
sion. The reaction mixture was warmed to –10 °C within 2 h,
generating a yellow solution that became orange and then brown.
Thereafter, the cold solution was washed with HCl (3%; 3 × 25 mL,
precooled to –2 °C) and with H2O (5 × 25 mL, 0 °C) and dried with
MgSO4 at –20 °C. After removal of the drying agent under anhy-
drous nitrogen, the solvent was removed in vacuo at low tempera-
ture to give a brown solid that was then treated with CHCl3 (30 mL).
This led to a single stereoisomer of 16 with low solubility (symmet-
rical minor isomer, 18 mg, 3%) and a solution, which was liberated
from CHCl3. The residue was dissolved in CH2Cl2 and used for
flash chromatography (Et2O) to give 19 (9 mg, 2%) and a yellow
solid (490 mg) that consisted of 20 and the other two isomers of 16.
After separation of this mixture by flash chromatography
(40 × 8 cm column; CH2Cl2–Et2O, 20:1 very slow elution), the
symmetrical major isomer of 16 (210 mg, 34%), 20 (78 mg, 13%),
and (E,Z)-16 (92 mg, 15%) were isolated. Separation of the latter
mixture was also possible by HPLC (LiChrospher Si60; 5 mm;
20 × 2 cm; CH2Cl2–Et2O, 20:1).
31P NMR (121.5 MHz, CDCl3): d = 34.66.
MS (ESI): m/z = 513.2 [M + 1]+.
Anal. Calcd for C30H30N2O2P2·H2O: C, 67.92; H, 6.08; N, 5.28.
Found: C, 67.61; H, 6.46; N, 4.71.
1,6-Bis(phenylsulfonyl)hexa-1,5-dien-3-ynes (18)
A solution of 1520 (1.00 g, 2.79 mmol) in anhydrous CH2Cl2 (300
mL) was cooled to –95 °C, and a solution of DBU (0.86 g, 0.87 mL,
5.7 mmol) in anhydrous CH2Cl2 (25 mL) was added dropwise. The
reaction mixture changed color to yellow immediately, then to red
and once more to yellow. Upon warming to 22 °C, the mixture
changed color again to brown, then red, and finally to greenish-
brown. The mixture was washed with HCl (3%; 3 × 100 mL) and
H2O (3 × 100 mL) and dried with MgSO4. After removal of the sol-
vent in vacuo, the residue was dissolved in CH2Cl2 and filtered
through silica gel, eluting with Et2O. The filtrate was concentrated
and recrystallized (CH2Cl2–Et2O) to give (E,E)-18 (45 mg, 4.5%) as
a pink solid that was then dried in vacuo. The mother liquor was
concentrated in vacuo to afford (E,Z)-18 (45 mg, 4.5%) as a yellow
oil.
(E,Z)-2,5-Diazido-1,6-bis(phenylsulfonyl)hexa-2,4-diene [(E,Z)-
16]
Yellow solid; mp 80–83 °C (CH2Cl2–Et2O, dec.).
IR (CDCl3): 2131 (N3), 2091 (N3), 1327 (SO2), 1154 (SO2) cm–1.
1,6-Bis(phenylsulfonyl)hexa-1E,5E-dien-3-yne [(E,E)-18]
Mp 200–204 °C (CH2Cl2–Et2O).
IR (CDCl3): 1325 (SO2), 1151 (SO2) cm–1.
1H NMR (400 MHz, CDCl3): d = 3.69 (s, 2 H, CH2), 3.96 (s, 2 H,
3
3
CH2), 5.27 (d, J = 11.3 Hz, 1 H, CH), 6.26 (d, J = 11.3 Hz, 1 H,
1H NMR (400 MHz, CDCl3): d = 6.77 (d, 3J = 14.8 Hz, 2 H, CH),
6.88 (d, 3J = 14.8 Hz, 2 H, CH), 7.52–7.59 (m, 4 H, Ph), 7.62–7.69
(m, 2 H, Ph), 7.85–7.90 (m, 4 H, Ph).
CH), 7.53–7.74 (m, 6 H, Ph), 7.81–7.98 (m, 4 H, Ph).
13C NMR (100 MHz, CDCl3): d = 56.94 (t), 59.62 (t), 115.36 (d,
CH), 116.73 (d, CH), 125.05 (s, CN3), 128.54 (d), 128.65 (d),
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PAPER
Synthesis of 1,4-Diazidobuta-1,3-dienes
1567
128.75 (s, CN3), 129.33 (d, Ph), 129.44 (d, Ph), 134.33 (d, Ph),
134.49 (d, Ph), 137.79 (s, i-Ph), 138.18 (s, i-Ph).
Yield: 93%; white solid; mp 260 °C (CH2Cl2, dec.).
IR (KBr): 1326 (SO2), 1146 (SO2) cm–1.
1H NMR (400 MHz, DMSO-d6): d = 1.37–1.56 (m, 8 H, CH2),
1.59–1.69 (m, 4 H, CH2), 1.78–1.89 (m, 4 H, CH2), 2.67–2.78 (m,
8 H, CH2), 5.14 (s, 4 H, CH2SO2Ph), 6.99 (s, 2 H, CH), 7.50–7.58
(m, 4 H, Ph), 7.63–7.75 (m, 6 H, Ph).
1H NMR (400 MHz, CDCl3): d = 1.36–1.60 (m, 8 H, CH2), 1.67–
1.78 (m, 4 H, CH2), 1.83–1.94 (m, 4 H, CH2), 2.68–2.82 (m, 8 H,
CH2), 4.85 (s, 4 H, CH2SO2Ph), 6.76 (s, 2 H, CH), 7.50–7.58 (m,
4 H, Ph), 7.63–7.75 (m, 6 H, Ph).
13C NMR (100 MHz, DMSO-d6): d = 21.99 (t), 23.47 (t), 24.06 (t),
25.51 (t), 26.03 (t), 27.49 (t), 56.54 (t, CH2SO2Ph), 126.03 (d, CH),
127.33 (d, Ph), 128.74 (s, CHCN), 129.21 (d, Ph), 133.95 (d, Ph),
134.52 (s), 138.42 (s), 143.64 (s).
2,5-Diazido-1,6-bis(phenylsulfonyl)hexa-2,4-diene (16; Sym-
metrical, Major Isomer)
Yellow solid; mp 69–73 °C (CH2Cl2–Et2O, dec.).
IR (CDCl3): 2093 (N3), 1324 (SO2), 1152 (SO2) cm–1.
1H NMR (400 MHz, CDCl3): d = 3.87 (s, 4 H, CH2), 5.80 (s, 2 H,
CH), 7.56–7.64 (m, 4 H, Ph), 7.67–7.74 (m, 2 H, Ph), 7.88–7.92 (m,
4 H, Ph).
1H NMR (400 MHz, DMSO-d6): d = 4.51 (s, 4 H, CH2), 5.86 (s,
2 H, CH), 7.58–7.72 (m, 4 H, Ph), 7.73–7.80 (m, 2 H, Ph), 7.81–
7.87 (m, 4 H, Ph).
13C NMR (100 MHz, CDCl3): d = 56.64 (t), 115.27 (d, CH), 128.06
(s, CN3), 128.62 (d, Ph), 129.54 (d, Ph), 134.44 (d, Ph), 137.99 (s,
i-Ph).
13C NMR (100 MHz, DMSO-d6): d = 54.75 (t), 116.50 (d, CH),
127.18 (s, CN3), 128.15 (d, Ph), 129.20 (d, Ph), 134.01 (d, Ph),
138.01 (s, i-Ph).
HRMS (ESI): m/z [M + H]+ calcd for C34H41N6O4S2: 661.2602;
found: 661.2625.
1,6-Bis(phenylsulfonyl)-2-(4,5,6,7,8,9-hexahydrocycloocta-1H-
1,2,3-triazol-1-yl)hex-2-en-4-yne (21)
Prepared from 20 following the general procedure.
2,5-Diazido-1,6-bis(phenylsulfonyl)hexa-2,4-diene (16; Sym-
metrical, Minor Isomer)
White solid; mp 82 °C (CHCl3, dec.).
Yield: 95%; colorless needles; mp 176–179 °C (CHCl3–Et2O).
IR (CDCl3): 1327 (SO2), 1160 (SO2) cm–1.
1H NMR (400 MHz, CDCl3): d = 1.39–1.84 (m, 8 H, CH2), 2.70–
IR (CDCl3): 2115 (N3), 2087 (N3), 1601 (C=C), 1325 (SO2), 1157
(SO2) cm–1.
1H NMR (400 MHz, CDCl3): d = 3.95 (s, 4 H, CH2), 5.40 (s, 2 H,
CH), 7.54–7.66 (m, 4 H, Ph), 7.68–7.75 (m, 2 H, Ph), 7.85–7.94 (m,
4 H, Ph).
1H NMR (400 MHz, DMSO-d6): d = 4.60 (s, 4 H, CH2), 5.42 (s,
2 H, CH), 7.63–7.88 (m, 10 H, Ph).
13C NMR (100 MHz, DMSO-d6): d = 58.25 (t), 116.14 (d, CH),
125.80 (s, CN3), 128.05 (d, Ph), 129.33 (d, Ph), 134.24 (d, Ph),
137.85 (s, i-Ph).
2.82 (m, 4 H, CH2), 4.15 (d, 5J = 2.2 Hz, 2 H, ≡CCH2), 4.76 (s, 2 H,
5
=CCH2), 5.74 (t, J = 2.2 Hz, 1 H, CH), 7.41–7.49 (m, 2 H, Ph),
7.54–7.76 (m, 6 H, Ph), 8.00–8.06 (m, 2 H, Ph).
13C NMR (100 MHz, CDCl3): d = 22.45 (t), 24.19 (t), 25.02 (t),
25.50 (t), 27.45 (t), 27.81 (t), 49.45 (t, ≡CCH2), 59.00 (t, =CCH2),
80.90 (s, C≡), 87.00 (s, C≡), 110.79 (d, CH), 127.95 (d, Ph), 128.71
(d, Ph), 129.10 (d, Ph), 129.50 (d, Ph), 133.94 (d, Ph), 134.06 (s),
134.62 (d, Ph), 136.97 (s), 137.80 (s), 138.81 (s), 145.63 (s).
HRMS (ESI): m/z [M + H]+ calcd for C26H28N3O4S2: 510.1529;
found: 510.1516.
Anal. Calcd for C26H27N3O4S2: C, 61.27; H, 5.34; S, 12.58. Found:
C, 60.41; H, 5.38; S, 12.64.
2,6-Diazido-1-(phenylsulfonyl)hex-2-en-4-yne (19)
Colorless oil.
IR (CDCl3): 2106 (N3), 1331 (SO2), 1152 (SO2) cm–1.
2-(3-Azidoprop-1-ynyl)-3-[(phenylsulfonyl)methyl]-2H-azirine
(22)
A solution of diazide 19 (13 mg, 0.044 mmol) in CDCl3 (0.75 mL)
was degassed, cooled to –50 °C in an NMR tube, and irradiated us-
ing a mercury high-pressure lamp. The progress of the reaction was
monitored by 1H NMR spectroscopy, which indicated a maximum
yield of 22 of 92% after an irradiation time of 105 s.
1H NMR (400 MHz, CDCl3): d = 3.86 (d, 5J = 2.3 Hz, 2 H, ≡CCH2),
4.14 (s, 2 H, N3CCH2), 5.40 (t, 5J = 2.3 Hz, 1 H, CH), 7.54–7.64 (m,
2 H, Ph), 7.66–7.73 (m, 1 H, Ph), 7.89–7.97 (m, 2 H, Ph). Assign-
ments of CH2 1H NMR signals were supported by the 13C,1H corre-
lation 2D NMR spectrum.
13C NMR (100 MHz, CDCl3): d = 40.49 (t, CH2N3), 57.80 (t,
N3CCH2), 81.13 (s, C≡), 88.47 (s, C≡), 100.87 (d, CH), 128.83 (d,
Ph), 129.21 (d, Ph), 134.32 (d, Ph), 138.15 (s), 139.84 (s).
Colorless oil.
IR (CDCl3): 2106 (N3), 1336 (SO2), 1158 (SO2) cm–1.
5
1H NMR (400 MHz, CDCl3): d = 2.47 (t, J = 1.4 Hz, 1 H, CH),
2-Azido-1,6-bis(phenylsulfonyl)hex-2-en-4-yne (20)
Yellow oil.
IR (CDCl3): 2112 (N3), 1331 (SO2), 1162 (SO2) cm–1.
3.84 (d, 5J = 1.4 Hz, 2 H, CH2N3), 4.64 (s, 2 H, CH2SO2Ph), 7.57–
7.65 (m, 2 H, Ph), 7.69–7.76 (m, 1 H, Ph), 7.95–8.00 (m, 2 H, Ph).
13C NMR (100 MHz, CDCl3): d = 19.10 (d, CH), 39.94 (t), 53.66 (t),
71.64 (s, C≡), 85.99 (s, C≡), 128.48 (d, Ph), 129.65 (d, Ph), 134.90
(d, Ph), 138.06 (s, i-Ph), 161.68 (s, C=N).
1H NMR (400 MHz, CDCl3): d = 3.94 (d, 4J = 2.2 Hz, 2 H, ≡CCH2),
4.02 (s, 2 H, N3CCH2), 5.31 (t, 5J = 2.2 Hz, 1 H, CH), 7.51–7.75 (m,
6 H, Ph), 7.87–7.98 (m, 4 H, Ph). Assignments of CH2 1H NMR sig-
nals were supported by the 13C,1H correlation 2D NMR spectrum.
13C NMR (100 MHz, CDCl3): d = 49.46 (t, ≡CCH2), 57.61 (t,
N3CCH2), 81.91 (s, C≡), 83.89 (s, C≡), 100.64 (d, CH), 128.62 (d,
Ph), 128.78 (d, Ph), 129.15 (d, Ph), 129.34 (d, Ph), 134.25 (d, Ph),
134.46 (d, Ph), 137.85 (s), 138.33 (s), 140.66 (s).
3-[(Phenylsulfonyl)methyl]-2-[3-(phenylsulfonyl)prop-1-ynyl]-
2H-azirine (23)
A solution of azide 20 (10 mg, 0.025 mmol) in CDCl3 (0.75 mL)
was degassed, cooled to –50 °C in an NMR tube, and irradiated for
30 min using a mercury high-pressure lamp. The progress of the re-
action was monitored by 1H NMR spectroscopy, which indicated a
maximum yield of 85%.
2,5-Bis(4,5,6,7,8,9-hexahydrocycloocta-1H-1,2,3-triazol-1-yl)-
1,6-bis(phenylsulfonyl)hexa-2,4-diene (17)
Prepared from 16 (symmetrical, major isomer) following the gener-
al procedure.
IR (CDCl3): 1333 (SO2), 1163 (SO2) cm–1.
Synthesis 2011, No. 10, 1561–1568 © Thieme Stuttgart · New York

1568
K. Banert et al.
PAPER
(10) (a) Treibs, W.; Walther, H. Chem. Ber. 1955, 88, 396.
1H NMR (400 MHz, CDCl3): d = 2.37 (t, J = 1.6 Hz, 1 H, CH),
5
5
3.90 (d, J = 1.6 Hz, 2 H, ≡CCH2), 4.57 (s, 2 H, CH2C=N), 7.55–
(b) Roeding, A.; Kiepert, K. Chem. Ber. 1955, 88, 733.
(c) Treibs, W.; Zimmermann, G. Chem. Ber. 1957, 90, 1146.
(11) The trans,trans structure of the higher-melting
diastereoisomer of 7 was discussed,12 and the crystal and
molecular structure of dimethyl trans,trans-2,5-dichloro-
muconate was determined by single-crystal X-ray
diffraction techniques.13 In the latter case, however, neither
the melting point nor other information on 7 including the
method used to prepare this compound were given. Thus, the
found (Z,Z)-configuration could not be assigned to the
substances depicted in Scheme 2.
7.64 (m, 4 H, Ph), 7.66–7.75 (m, 2 H, Ph), 7.92–7.98 (m, 4 H, Ph).
13C NMR (100 MHz, CDCl3): d = 19.21 (d, CH), 48.72 (t), 53.82 (t),
67.32 (s, C≡), 86.52 (s, C≡), 123.97 (d, Ph), 124.35 (d, Ph), 124.70
(d, Ph), 125.20 (d, Ph), 129.34 (d, Ph), 130.43 (d, Ph), 133.08 (s, i-
Ph), 133.50 (s, i-Ph), 161.36 (s, C=N).
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.
(12) Takei, S.; Nakajima, M.; Tomida, I. Chem. Ber. 1956, 89,
263.
(13) Einspahr, H.; Donohue, J. Acta Crystallogr., Sect. B: Struct.
Sci. 1973, 29, 1875.
(14) (a) Vögeli, U.; von Philipsborn, W. Org. Magn. Reson.
1975, 7, 617. (b) Braun, S. Org. Magn. Reson. 1978, 11,
197.
Acknowledgment
We gratefully acknowledge financial support from the Deutsche
Forschungsgemeinschaft (Ba 903/10-1–3) and the Fonds der Che-
mischen Industrie (FCI). Furthermore, we thank Dr. N. Ramezanian
for assistance with the manuscript.
(15) (a) Nesmeyanov, A. N.; Rybinskaya, M. I.; Kelekhsaeva, T.
G. J. Org. Chem. USSR (Engl. Transl.) 1968, 4, 897.
(b) Rybinskaya, M. I.; Nesmeyanov, A. N.; Kochetkov, N.
K. Russ. Chem. Rev. (Engl. Transl.) 1969, 38, 433.
(16) For another example of configuration change due to the
formation of the thermodynamically favored vinyl azide,
see: Jonas, J.; Mazal, C.; Rappoport, Z. J. Phys. Org. Chem.
1994, 7, 652.
References
(1) For part 26, see: Firdous, S.; Banert, K.; Auer, A. A. Chem.
Eur. J. 2011, 17, in press.
(2) For reviews on vinyl azides, see: (a) Banert, K. In Houben-
Weyl, Vol. E15; Kropf, H.; Schaumann, E., Eds.; Thieme:
Stuttgart, 1993, 818–875. (b) Hassner, A. In Azides and
Nitrenes; Scriven, E. F. V., Ed.; Academic Press: Orlando,
1984, 35–76. (c) Banert, K. In Organic Azides: Syntheses
and Applications; Bräse, S.; Banert, K., Eds.; Wiley:
Chichester, 2010, 115–166. (d) Collier, S. J. In Science of
Synthesis, Vol. 33; Molander, G. A., Ed.; Thieme: Stuttgart,
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