Reactions of unsaturated azides; part 17:1 An efficient strategy for the synthesis of small-ring heterocycles via isomerization of 2-halo-2H-azirines

Article abstract of DOI:10.1055/s-2005-918513

New acceptor-substituted allenyl halides were synthesized. The addition of hydrazoic acid (HN₃) to these allenyl halides led to the formation of new 1-azido-2-haloethene derivatives. The photolysis of the latter compounds afforded the correspon

Full text of DOI:10.1055/s-2005-918513

PAPER
261
Reactions of Unsaturated Azides; Part 17:1 An Efficient Strategy for the
Synthesis of Small-Ring Heterocycles via Isomerization of 2-Halo-2H-azirines
R
eactions
o
of
U
nsaturat
s
ed
A
zide
s
eph Rodolph Fotsing, Klaus Banert*
Chemnitz University of Technology, Institute of Chemistry, Organic Chemistry, Strasse der Nationen 62, 09111 Chemnitz, Germany
Fax +49(371)5311839; E-mail: klaus.banert@chemie.tu-chemnitz.de
Received 5 April 2005; revised 29 July 2005
om.7b,c This rapid establishment of equilibrium made the
Abstract: New acceptor-substituted allenyl halides were synthe-
observation, isolation and conservation of pure isomers
sized. The addition of hydrazoic acid (HN3) to these allenyl halides
led to the formation of new 1-azido-2-haloethene derivatives. The
photolysis of the latter compounds afforded the corresponding 2-
only possible at low temperature.7b Consequently, studies
on this [1,2]-halogen shift in 2-halo-2H-azirines were lim-
halo-2H-azirines. At room temperature or below, they isomerized ited to some kinetic investigations7b,c without use in pre-
irreversibly by [1,2]-rearrangement of halogen to form other azirine
parative synthesis.
isomers in very good yields. It is the first time that such a complete
rearrangement of 2-halo-2H-azirines is observed. This synthetic
strategy offers the possibility to observe both azirine isomers in
their pure forms from single 1-azido-2-haloethene precursor.
H
H
X
X
EWG
H
EWG
C
ERG
ERG
Key words: allenes, azides, 2-halo-2H-azirines, addition reactions,
rearrangements, photochemistry, thermolysis
N3
1
2
2H-Azirines are highly strained nitrogen-containing het-
erocycles. Most of them are synthetic.2 However, exam-
ples of naturally occurring ones are also known.3 Methods
for their synthesis include thermolysis and photolysis of
vinyl azides2a,b,e and isoxazoles,2a,b Neber and modified
Neber reactions2a,b as well as thermolysis of oxazaphos-
pholines.2a,b 2H-Azirines are synthetic versatile com-
pounds, and their reactions have been intensively
explored. They can undergo thermal or photochemical
ring opening to afford 1,3-dipolar species, which can be
trapped through inter- and intramolecular reactions.2a–d
2H-Azirines are also known as good electrophiles.4 Some
amino derivatives such as amino acids,2a,4a,5 aziridines,4c,5
pyrazines,2h,4b and indoles6 can be prepared from 2H-azir-
ines. In addition to all these possibilities, 2-halo-2H-azir-
ines offer another reaction site by their halogen atoms. Up
to 1997, there were just a few 2-halo-2H-azirine deriva-
tives mentioned in the literature.7 This was mainly due to
the difficult access to appropriate precursors, the synthesis
of which needed the use of explosive XN3 reagents (X =
Cl, Br, I).7b,c But since 1997, with the development of a
new method8 for producing some 1-azido-2-haloethenes,
which are known as good precursors for the 2-halo-2H-
azirines, several of the latter compounds have been
prepared9 and utilized as intermediates9b,d in the synthesis
of many useful compounds. However, access to 1-azido-
2-haloethenes by this method was limited to specific
structures. On the other hand, some 2-halo-2H-azirines
proved to have a great tendency to equilibrate with their
azirine isomers through a [1,2]-shift of the halogen at-
X
X
ERG
EWG
EWG
ERG
N
N
4: 2-halo-2H-azirine of
second generation
3: 2-halo-2H-azirine
of first generation
X
ERG
N3
3
N
R
3
2
R1
2
EWG
R
6
5
X = halogen
ERG = electron-releasing group
EWG = electron-withdrawing group
Scheme 1
Here we report on how to turn this method into an efficient
one, which can be used in the preparation of pure azirines
of type 4 (Scheme 1). Compounds of type 4 may be ideal
precursors for the long-sought10–12 methylene-2H-azir-
ines, which were unknown13–15 until recently when they
were generated by photolysis of allenyl azides16,17 or other
azides.18 1-Azido-2-haloethenes of type 5 are possible
precursors for the azirines of type 4. However, access to
such 1-azido-2-haloethenes 5 proved to be very difficult.
In our synthetic strategy, the newly synthesized 1-azido-
2-haloethenes 2 are supposed to produce 2-halo-2H-azir-
ines of first generation 3, which have sufficiently high in-
ternal energies to cause an irreversible conversion into
more stable isomers 4. Note that 2H-azirines 6 are better
stabilized by donor substituents (R1) at the 3-position of
the ring, contrary to electron-withdrawing groups, which
induced instability when fixed at this position. Therefore,
the substitution pattern of 2-halo-2H-azirines of type 3 de-
scribed in this paper has been especially built up with the
SYNTHESIS 2006, No. 2, pp 0261–0272
x
x
.
x
x
.2
0
0
5
Advanced online publication: 21.12.2005
DOI: 10.1055/s-2005-918513; Art ID: T04705SS
© Georg Thieme Verlag Stuttgart · New York

262
J. R. Fotsing, K. Banert
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aim of facilitating their rearrangement into isomers of sired sulfonyl substituted allenyl halides 13a, 14a and 14b
type 4. On the way to the azirines of type 4, some key were obtained in good to very good yields.
steps were: a) access to new allenyl halides 1 bearing ac-
In the second pathway, the propargyl compounds 15a,22
ceptor substituents, b) synthesis of new 1-azido-2-halo-
ethenes 2, c) generation of 2-halo-2H-azirines of type 3
16a,23 17c,24 and 18c were treated with potassium
thiophenolate (PhSK) by analogy with the procedure de-
and d) implementation of the irreversible rearrangement
scribed in the literature25 affording the propargyl thio-
of the 2-halo-2H-azirines 3 into the final azirines 4.
ethers 19,26 20, 2127 and 22, respectively, in very good
yields (Table 2). By treatment of 19–22 with two equiva-
lents of m-chloroperoxybenzoic acid, the corresponding
Synthesis of Allenes of Type 1
sulfones 23, 24, 25,27 and 26, were obtained in very good
yields.
In order to produce the allenyl halides of type 1, two dif-
ferent synthetic pathways were used. In the first one, pro-
pargyl halides 7a19 and 7b19 were treated with n-
butyllithium by analogy with the procedure described in
the literature19 followed by addition of MeSO2SMe20 or
PhSCl21 leading to thioethers 9a, 10a and 10b (Table 1).
The reaction of 9a, 10a and 10b with two equivalents of
m-chloroperoxybenzoic acid afforded the sulfone deriva-
tives 11a, 12a and 12b, respectively. By prototropic rear-
rangement of 11a, 12a and 12b using triethyl amine or
1,4-diazabicyclo[2.2.2]octane (DABCO) as base, the de-
Addition of bromine to the alkynyl sulfones 23–26 in
dichloromethane led to the corresponding vicinal vinyl di-
bromides (E)-27b, (E)-28b, (E)-29b and (E/Z)-30b in
good to very good yields (Table 3). Finally, treatment of
27b–30b with triethyl amine afforded the required allenyl
halides 31b–34b. Except for 30b, which was obtained as
a mixture of E- and Z-isomers (E/Z = 26:1), the exclusive
formation of E-isomers was observed. Examples for the
stereoselective formation of E-isomers by addition of bro-
mine to alkynes are known.28,29 In many cases, acetic acid
was used as solvent instead of dichloromethane as we
used here.
Table 1 Synthesis of Sulfonyl-Substituted Allenyl Halides 13a, 14a and 14b
X
X
X
H
S
Me
X
X
MeSO2SMe
C
n-BuLi
or
Me MCPBA
Me
DABCO
or Et3N
Me
R
R
Me
R
O
Et2O–THF
S
S
PhSCl
O
Li
O
O
7a,b
8a,b
9a, 10a, 10b
11a, 12a, 12b
13a, 14a, 14b
a: X = Cl
b: X = Br
Starting alkyne
7a (X = Cl)
7a (X = Cl)
7b (X = Br)
Thioether
Yield (%)a
Alkynyl sulfone
Yield (%)a
Base
Allenyl sulfone
Yield (%)a
9a (R = Me)
10a (R = Ph)
10b (R = Ph)
94
99
60
11a
12a
12b
95
96
93
DABCO
DABCO
Et3N
13a
14a
14b
82
94
92
a All yields refer to isolated compounds.
Table 2 Synthesis of Sulfones 23–26
Ph
S
X
SPh
PhS K
MCPBA
O
O
R
R
R
15a, 16a
17c, 18c
19–22
23–26
a: X = Cl
c: X = OMs
R
Starting alkyne
15a (X = Cl)
Thioether
Yield (%)a
Sulfone
23
Yield (%)a
MeOCH2
n-C5H11
Ph
19
20
21
22
92
95
90
88
96
97
92
95
16a (X = Cl)
24
17c (X = OMs)
25
t-Bu
18c (X = OMs)
26
a All yields refer to isolated compounds.
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

PAPER
Reactions of Unsaturated Azides
263
Table 3 Synthesis of Allenyl Halides 31b–34b
Ph
O
O
Ph
Br
S
Ph
Br
S
O
Br2
Et3N
S
C
O
O
O
CH2Cl2
– HBr
R
R
H
R
Br
31b–34b
(E)-27b-(E)-29b
(E/Z)-30b
23–26
R
Propargyl sulfone
vic-Vinyl dibromide Yield (%)a
E/Z ratio
1:0
Allenyl bromide
Yield (%)a
MeOCH2
n-C5H11
Ph
23
24
25
26
(E)-27b
(E)-28b
(E)-29b
(E/Z)-30b
93
94
89
86
31b
32b
33b
34b
70
44
67
82
1:0
1:0
t-Bu
26:1
a All yields refer to isolated compounds.
namically more stable isomer was always the major one.
Consequently, we thought that it would be possible to iso-
Synthesis of 1-Azido-2-haloethenes of Type 2
Previous results30 on the addition of hydrazoic acid to ac- late exclusively the thermodynamically more stable iso-
ceptor-substituted allenes of type 35 led to the formation mer, if the energy difference between the isomers is high
of vinyl azides of type 37 (Scheme 2). In some cases the enough.
formation of mixtures of isomers of type 36 and 37 had
In this connection, we first irradiated a solution of 1-azi-
do-2-haloethenes (E)-40b and (Z)-40b in CDCl3 at –30 °C
with UV light affording the 2-bromo-2H-azirine 44b to-
been observed.2h,30 The latter reaction course was also ob-
served when tetramethylguanidinium azide (TMGA) was
used as source of HN3.30
gether with traces of the isomer 46b (Scheme 3). Since the
observed rearrangement is a thermal process,7b,c traces of
H
46b were formed during the measurement of 1H NMR da-
ta, which took place at 19 °C. At room temperature the
equilibrium between both isomers was established 10–15
minutes later (ratio of isomers at equilibrium 44b/46b =
1:1). This equilibrium showed that the difference between
the electronic effects of the substituents at 2- and 3-pos-
tion of the azirines 44b and 46b is small. In fact, the
PhSO2CH2 group and the MeOCH2 group31 can be consid-
ered as weak acceptor substituents, which consequently
led to approximately the same thermodynamic stability of
the isomers 44b and 46b. The rearrangement itself is
known7b to take place through an intermediate cation,
which should have the structure of 45b in our case. The
establishment of this equilibrium is a result comparable to
those reported in the literature.7b,c
R
R
N3
H
R
R
EWG
H
R
R
EWG
N3/H
C
EWG
+
N3
H
37
35
36
Scheme 2
However, treatment of the novel sulfonyl substituted alle-
nyl halides with TMGA at about 0 °C for shorter reaction
times led only to 1-azido-2-haloethenes of type 36
(Scheme 2). In fact, the reaction of 13a, 14a,b and 31b–
34b with TMGA gave the corresponding 1-azido-2-halo-
ethenes (E/Z)-38a, (E/Z)-39a, (E/Z)-39b, (E/Z)-40b,
(E/Z)-41b, (E/Z)-42b and (Z)-43b, in excellent yields
(Table 4). The exclusive formation of (Z)-43b was ratio-
nalized by the stereodirecting effect of the bulky tert-butyl
group.
When CDCl3 solutions of (E/Z)-39b, (E/Z)-41b, (Z)-43b
were irradiated under the same conditions followed by
measurement of NMR data at 19 °C, the corresponding
azirines 48b, 49b, 51b were obtained, together with their
rearranged isomers 53b, 54b and 56b, respectively
(Table 5). However, in contrary to the equilibrium ob-
tained before, the complete rearrangement of the azirines
48b, 49b, 51b into more stabilized isomers 53b, 54b and
56b, respectively, was observed by keeping the samples at
room temperature. The stability of the azirines 53b, 54b
and 56b has been induced by the +I-effect of methyl, n-
pentyl and tert-butyl groups, respectively, which are fixed
at the 3-position of the corresponding azirines. Thus the
Photolysis of 1-Azido-2-haloethenes and Rearrange-
ment of the Resulting 2-Halo-2H-azirines of Type 3
As we already mentioned in the introduction, some 2-
halogen-2H-azirines undergo a thermal rearrangement
through [1,2] halogen shift.7b,c However, this rearrange-
ment always led to an equilibrium between the isomers
formed. The ratio of the isomers at equilibrium proved to
depend on the solvent polarity, whereas the thermody-
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

264
J. R. Fotsing, K. Banert
PAPER
Table 4 Synthesis of 1-Azido-2-haloethenes
R2
O
R2
H
O
H
X
S
H
X
S
TMGA
N3/H
O
C
O
R1
R1
N3
13a, 14a,b
31b–34b
38a, 39a,b
40b–43b
X
R1
R2
Allene
13a
Ethene
E/Z ratio
5:1.5
3:2
Yield (%)a
Cl
Cl
Br
Br
Br
Br
Br
Me
Me
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
(E/Z)-38a
(E/Z)-39a
(E/Z)-39b
(E/Z)-40b
(E/Z)-41b
(E/Z)-42b
(Z)-43b
98
97
92
95
99
92
94
14a
14b
31b
32b
33b
34b
5:1
MeOCH2
n-C5H11
Ph
2:1
3:1
1:2
t-Bu
0:1
a All yields refer to the isolated compounds.
er is the rearrangement time. By variation of the substitu-
ent R2, for example 38a (R2 = Me) and 39a (R2 = Ph), the
time necessary for the rearrangement of the resulting azir-
ines (47a → 52a and 48a → 53a) proved to be only weak-
ly influenced if compared to the effects of the substituents
R1 and X (X = halogen). In each rearrangement described
in this paper, the formation of the rearranged azirines took
place in excellent yield, without any evidence of polymer-
ization.
Ph
Br
S
O
Br
MeO
hν/CDCl3
Ph
2
3
S
O
–30 °C, 60 min
MeO
MeO
O
O
N3
N
44b
40b
∆
r.t.
Br
Br
3
2
∆
Ph
O
MeO
S
In summary, we succeeded in the synthesis of new accep-
tor-substituted allenyl halides and their conversion into
novel vicinal vinyl azidohalides. Their photolysis led to
new 2-halo-2H-azirines. The first irreversible rearrange-
ment of such small-ring heterocycles into more stable iso-
meric azirines is highlighted in this paper as a newly
adapted and effective way to 2-halo-2H-azirines. This
isomerization took place under mild conditions and in ex-
cellent yields. From the first step, substituents were selec-
tively introduced into intermediates with aim of
facilitating the irreversible conversion of the first azirines
into their rearranged azirine isomers. Since the C–X
bonds have to be broken and recombined during the pro-
cess, the nature of halogen also greatly influences the rate
of the rearrangement because of the difference in
strengths of the C-X bonds. Although there was a possi-
bility of reaction between the nitrogen lone pair and the
intermediate cation, no evidence of polymerization was
found. The strategy developed in this paper is very effi-
cient although several steps are involved. It opens a way
to new and clean 2-halo-2H-azirines. In a further publica-
tion we will show that these compounds are very conve-
nient precursors to generate 2-methylene-2H-azirines.
O
S
r.t.
N
O
O
N
Ph
45b
46b
Scheme 3
yields of the rearrangement products were excellent. In
the case of the transformation of (E/Z)-42b (R1 = Ph) into
55b (97%), the rearrangement was so fast that the corre-
sponding azirine intermediate 50b could only be observed
at lower temperature. The half-lifetime of the conversion
of 50b was found to be ca. 709 seconds in CDCl3 at –30
°C with k = ca 9.77 × 10–4 s–1.
In order to study the influence of the halogen on the rear-
rangement process, (E/Z)-39a (X = Cl) was irradiated to
give 48a (X = Cl, 99%), and the rate of its rearrangement
to yield 53a was then compared with the analogous trans-
formation of 48b (X = Br) into 53b. We found that at room
temperature the complete rearrangement of 48a into 53a
took about four hours, which corresponded to approxi-
mately 24 times the duration of 48b → 53b (ca. 10 min).
Therefore, we can say that the time of the halogen dis-
placement considerably depends on the strength of the C–
X bond (Cl > Br). The stronger the C–X bond is, the long-
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

PAPER
Reactions of Unsaturated Azides
265
Table 5 Synthesis of Azirines
R2
X
X
R1
R1
R2
X
S
O
R2
O
3
2
hν/CDCl3
∆
2
3
S
O
S
R1
O
O
N
N3
N
O
52a, 53a,b
54b–56b
38a, 39a,b
41b–43b
47b, 48a,b, 49b
50b, 51b
X
R1
R2
Ethene
First azirine Yield (%) or remark Time (min) Rearranged azirine Yield (%)
Cl
Cl
Br
Br
Br
Br
Me
Me
(E/Z)-38a
(E/Z)-39a
(E/Z)-39b
(E/Z)-41b
(E/Z)-42b
(Z)-43b
47a
48a
48b
49b
50b
51b
99a
180b
240b
~10b
~5b
52a
53a
53b
54b
55b
56b
99a
Me
Ph
Ph
Ph
Ph
Ph
99a
99a
Me
48b/53b = 1:1c
49b/54b = 1:4c
50b/55b = 5:2f
51b/56b = 1:3c
96a,d
97d,e
97a,d
99a,d
n-C5H11
Ph
~709 sg
~10b
t-Bu
a Yield determined by NMR.
b Relative rearrangement time at 19 °C.
c Ratio determined from the first 1H NMR spectrum taken at 19 °C after photolysis at –30 °C.
d Yield based on the ethene compound.
e Yield of isolated product.
f Ratio determined from the first 1H NMR spectrum taken at –50 °C after photolysis at –50 °C.
g Half-lifetime at –30 °C.
1H and 13C NMR spectra were recorded at 300 MHz and 75 MHz,
respectively, on a Varian Gemini in CDCl3, unless otherwise noted.
Chemical shifts (d) are reported in ppm downfield from TMS. Cou-
pling constants (J) are reported in Hz, and spin multiplicities are in-
dicated by the following symbols: s (singlet), d (doublet), t (triplet),
q (quartet), m (multiplet). IR spectra were recorded as solutions in
CDCl3. TLC analyses were performed on Macherey–Nagel precoat-
ed silica gel Polygram Sil G/UV254 plates and visualized by UV.
Chromatography refers to flash chromatography32 carried out on
Fluka silica gel 60. The photolyses were performed with a 150-W-
Hg high-pressure lamp (polychromatic) TQ 150 from Quarz-
lampen-Gesellschaft. In order to get good yields of the 2H-azirines
by preventing succeeding photochemical reactions, solutions in
CDCl3, which function as UV filter, were used. For the elemental
analyses, Vario El instrument (Elementar Analysensystem GmbH)
was employed. Mariner 5229 from Applied Biosystems was used
for HRMS spectra. The method applied was the electrospray ioniza-
tion. But, in the case of vinyl azides, the intensity of the M+ signal
was so small that high resolution could not be realized.
(3-Chlorobut-1-ynylsulfanyl)benzene (10a)
Under Ar atmosphere, a solution of 3-chlorobut-1-yne (7a;19 2.00 g,
22.6 mmol) in anhyd Et2O (30 mL) was cooled to –80 °C. A solu-
tion of n-BuLi (9.10 mL, 2.5 M) in n-hexane was added dropwise
while stirring at –80 °C. After additional stirring at –80 °C for 45
min, PhSCl21 (2.96 g, 20.5 mmol) was added dropwise at the same
temperature. The mixture was stirred for 20 min and then warmed
to r.t. within 45 min. Then H2O (35 mL) was added while stirring
vigorously. The organic phase was separated, and the aqueous
phase was extracted several times with Et2O. The combined organic
layers were dried over MgSO4 and the solvent was removed to give
10a (3.99 g, 20.3 mmol, 99%) as a yellow oil.
1H NMR (CDCl3): d = 1.85 (d, 3J = 6.9 Hz, 3 H, CH3), 4.90 (q, 3J =
6.9 Hz, 1 H, H-3¢), 7.24–7.28 (m, 1 H, p-Ph), 7.35–7.45 (m, 4 H).
13C NMR (CDCl3): d = 26.4 (q, CH3), 44.9 (d, C-3¢), 73.2 (s, C≡),
97.4 (s, C≡), 126.4 (d, 2 × C), 126.8 (d, p-Ph), 129.3 (d, 2 × C),
131.9 (s, i-Ph).
HRMS (ESI): m/z [M + H+, 35Cl] calcd for C10H9ClS: 197.0139;
found: 197.0159.
Elemental analyses of azides could not be performed because of ex-
plosive decomposition. For a few compounds, derivatives were pre-
pared to perform the elemental analysis or HRMS, respectively, or
this characterization was realized for the next product within a se-
quence of synthetic steps. Caution should be exercised during isola-
tion of azide, which may be explosive. In the case of solutions of
tetrabutylammonium azide in dichloromethane, an explosion prob-
ably caused by diazidomethane was reported.33 Therefore special
caution is also necessary in the case of TMGA in dichloromethane
although we never observed any incidence.
(3-Bromobut-1-ynylsulfanyl)benzene (10b)
According to the procedure used for 10a, compound 10b (2.03 g,
8.4 mmol) was obtained in 60% yield as a yellow oil from the pro-
pargyl bromide 7b,19 n-BuLi (2.5 M solution in hexane) and
PhSCl.21
1H NMR (CDCl3): d = 2.02 (d, 3J = 6.9 Hz, 3 H, CH3), 4.89 (q, 3J =
6.9 Hz, 1 H, H-3¢), 7.28–7.48 (m, 5 H, Ph).
13C NMR (CDCl3): d = 27.2 (q, CH3), 32.1 (d, C-3¢), 73.9 (s, C≡),
98.0 (s, C≡), 126.3 (d, 2 × C), 126.8 (d, p-Ph), 129.3 (d, 2 × C),
132.0 (s, i-Ph).
The known compounds were synthesized according to the corre-
sponding literature for 7a,19 7b,19 15a,22 16a,23 and 17c24 or accord-
ing to the literature25 for 1926 and 21.27 The synthesis of 2527 was
performed according to the procedure used for 11a. The stereo-
chemistry and the assignment of the 1H NMR signals were clarified
with aid of NOE experiments or by comparison of the NMR data.
3-Chloro-1-methylsulfonylbut-1-yne (11a)
According to the literature,19 we obtained 9a (94%) as a colorless oil
from the propargyl chloride (7a),19 n-BuLi (2.5 M solution in hex-
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

266
J. R. Fotsing, K. Banert
PAPER
ane) and S-methyl methanethiosulfonate (MeSO2SMe).20 In contact
with air, 9a was oxidized from colorless to dark-brown.
13C NMR (CDCl3): d = 22.5 [q, C(CH3)], 42.8 (q, SO2CH3), 103.2
(d, C-1), 110.8 (s, C-3), 202.6 (s, C-2).
Anal. Calcd for C5H7ClO2S: C, 36.04; H, 4.23. Found: C, 36.14; H,
4.36.
9a
1H NMR (CDCl3): d = 1.73 [d, 3J = 6.9 Hz, 3 H, C(CH3)], 2.37 (s, 3
H, SCH3), 4.75 (q, 3J = 6.9 Hz, 1 H, H-3).
13C NMR (CDCl3): d = 18.9 (q, SCH3), 26.4 [q, C(CH3)], 45.2 (d,
C-3), 78.3 (s, C≡), 91.4 (s, C≡).
(3-Chlorobuta-1,2-dienylsulfonyl)benzene (14a)
To a stirred solution of 12a (65 mg, 284 mmol) in CDCl3 (0.5 mL),
DABCO (32 mg, 286 mmol) was added. After 2 h, the mixture was
filtered on silica gel with Et2O, and the solvent was removed to af-
ford 14a (0.06 g, 263 mmol, 94%) as a yellow oil. For larger
amounts, the reaction was repeated in CH2Cl2 at 15–20 °C for 2.5 h.
While stirring at 0 °C, a solution of the compound 9a (1.50 g, 11.2
mmol) in CH2Cl2 (40 mL) was treated dropwise with a solution of
70% MCPBA (6.00 g, 24.3 mmol) in CH2Cl2 (20 mL). This mixture
was kept overnight at 6 °C. Thereafter, it was diluted with CH2Cl2
and washed with a sat. solution of Na2CO3 (3 ×). The organic layer
was dried over MgSO4 and concentrated to afford the sulfone 11a
(1.75 g, 10.5 mmol, 95%) as a colorless liquid.
IR (CDCl3): 1966 (C=C=C), 1321 (SO2), 1147 (SO2) cm–1.
1H NMR (CDCl3): d = 2.16 (d, 5J = 3.0 Hz, 3 H, CH3), 6.34 (q, 5J =
3.0 Hz, 1 H, H-1¢), 7.54–7.60 (m, 2 H, m-Ph), 7.64–7.68 (m, 1 H, p-
Ph), 7.90–7.94 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 22.4 (q, CH3), 104.5 (d, C-1¢), 110.7 (s, C-
3¢), 127.9 (d, 2 × C), 129.3 (d, 2 × C), 133.9 (d, p-Ph), 139.8 (s, i-
Ph), 202.6 (s, C-2¢).
IR (CDCl3): 2202 (C≡C), 1325 (SO2), 1150 (SO2) cm–1.
1H NMR (CDCl3): d = 1.78 [d, 3J = 6.9 Hz, 3 H, C(CH3)], 3.21 (s, 3
H, SO2CH3), 4.70 (q, 3J = 6.9 Hz, 1 H, H-3).
13C NMR (CDCl3): d = 24.6 [q, C(CH3)], 40.9 (q, SO2CH3), 46.4 (d,
C-3), 80.1 (s, C≡), 90.0 (s, C≡).
Anal. Calcd for C10H9ClO2S: C, 52.52; H, 3.96; S, 13.98. Found: C,
52.78; H, 4.02; S, 13.71.
MS (ESI): m/z = 166.98 [M + H+, 35Cl].
(3-Bromobuta-1,2-dienylsulfonyl)benzene (14b)
While stirring at 0 °C, compound 12b (1.20 g, 4.40 mmol) in
CH2Cl2 (5 mL) was treated with Et3N (1.33 g, 13.2 mmol). The mix-
ture was stirred for 100 min at 5 °C and then filtered on silica gel
with Et2O to afford the allene 14b (1.10 g, 4.03 mmol, 92%) as a
colorless oil.
Anal. Calcd for C5H7ClO2S: C, 36.04; H, 4.23; S, 19.24. Found: C,
36.12; H, 4.26; S, 18.89.
(3-Chlorobut-1-ynylsulfonyl)benzene (12a)
According to the procedure used for 11a, compound 10a was treat-
ed with 70% MCPBA to afford 12a (96%) as a yellow oil.
IR (CDCl3): 2200 (C≡C), 1331 (SO2), 1159 (SO2) cm–1.
1H NMR (CDCl3): d = 1.74 (d, 3J = 6.9 Hz, 3 H, CH3), 4.66 (q, 3J =
6.9 Hz, 1 H, H-3¢), 7.57–7.63 (m, 2 H, m-Ph), 7.68–7.74 (m, 1 H, p-
Ph), 7.98–8.02 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 24.7 (q, CH3), 41.1 (d, C-3¢), 81.7 (s, C≡),
91.8 (s, C≡), 127.5 (d, 2 × C), 129.4 (d, 2 × C), 134.5 (d, p-Ph),
140.8 (s, i-Ph).
IR (CDCl3): 1320 (SO2), 1145 (SO2) cm–1.
1H NMR (CDCl3): d = 2.29 (d, 5J = 3.0 Hz, 3 H, CH3), 6.11 (q, 5J =
3.0 Hz, 1 H, H-1¢), 7.53–7.59 (m, 2 H, m-Ph), 7.62–7.68 (m, 1 H, p-
Ph), 7.89–7.92 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 23.8 (q, CH3), 95.8 (s, C-3¢), 103.0 (d, C-1¢),
127.9 (d, 2 × C), 129.3 (d, 2 × C), 133.9 (d, p-Ph), 139.9 (s, i-Ph),
201.1 (s, C-2¢).
MS (ESI): m/z (%) = 272.94 (95) [M + H+, 79Br], 274.94 (100)
[M + H+, 81Br].
Anal. Calcd for C10H9ClO2S: C, 52.52; H, 3.96; S, 13.98. Found: C,
53.02; H, 4.01; S, 13.62.
HRMS (ESI): m/z [M + H+, 79Br] calcd for C10H9BrO2S: 272.9532;
found: 272.9516.
(3-Bromobut-1-ynylsulfonyl)benzene (12b)
According to the procedure used for 11a, compound 10b was treat-
ed with 70% MCPBA to afford 12b (93%) as a yellow oil.
IR (CDCl3): 2195 (C≡C), 1333 (SO2), 1162 (SO2) cm–1.
1H NMR (CDCl3): d = 1.85 (d, 3J = 6.9 Hz, 3 H, CH3), 4.56 (q, 3J =
6.9 Hz, 1 H, H-3¢), 7.55–7.61 (m, 2 H, m-Ph), 7.65–7.69 (m, 1 H, p-
Ph), 7.95–7.99 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 25.2 (q, CH3), 26.3 (d, C-3¢), 81.1 (s, C≡),
92.6 (s, C≡), 127.3 (d, 2 × C), 129.4 (d, 2 × C), 134.4 (d, p-Ph),
140.7 (s, i-Ph).
(4,4-Dimethylpent-2-ynylsulfanyl)benzene (22)
By analogy with the procedure described in the literature,24 com-
pound 18c was obtained as a colorless liquid in quantitative yield
from the corresponding alcohol.34
Compound 18c
1H NMR (CDCl3): d = 1.20 [s, 9 H, C(CH3)], 3.09 (s, 3 H, SO2CH3)
4.81 (s, 2 H, H-1).
13C NMR (CDCl3): d = 27.5 [s, C(CH3)], 30.4 [q, 3 × C, C(CH3)],
38.9 (q, SO2CH3) 58.7 (t, C-1), 70.8 (s, C≡), 98.8 (s, C≡).
MS (ESI): m/z (%) = 272.94 (90) [M + H+, 79Br], 274.93 (100)
[M + H+, 81Br].
Compound 22 (88%) was obtained as a colorless oil from 18c ac-
cording to the procedure described in the literature.25 On contact
with air, its colorless aspect changes slowly to yellow. This was due
to its oxidation to the corresponding sulfoxide.
3-Chloro-1-methylsulfonylbuta-1,2-diene (13a)
While stirring at 15 °C, compound 11a (1.10 g, 6.61 mmol) in
CHCl3 (4 mL) was treated with DABCO (0.67 g, 5.98 mmol). The
mixture was stirred for 50 min at 15–20 °C and then filtered on sil-
ica gel with Et2O. After removal of the solvent and crystallization
from Et2O–n-pentane, the allene 13a (0.90 g, 5.41 mmol, 82%) was
obtained as white crystals; mp 60–61 °C.
MS (ESI): m/z = 221.10 [M + H+].
Compound 22
1H NMR (CDCl3): d = 1.16 (s, 9 H, CH3), 3.61 (s, 2 H, H-1¢), 7.25–
7.33 (m, 3 H, Ph), 7.45–7.48 (m, 2 H, Ph).
IR (CDCl3): 1968 (C=C=C), 1318 (SO2), 1138 (SO2) cm–1.
13C NMR (CDCl3): d = 23.3 (t, C-1¢), 27.4 (s, C-4¢), 30.9 (q, 3 × C,
CH3), 74.0 (s, C≡), 92.7 (s, C≡), 126.7 (d, p-Ph), 128.7 (d, 2 × C),
130.5 (d, 2 × C), 135.4 (s, i-Ph).
1H NMR (CDCl3): d = 2.28 [d, 5J = 3 Hz, 3 H, C(CH3)], 3.04 (s, 3
H, SO2CH3), 6.35 (q, 5J = 3 Hz, 1 H, H-1).
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

PAPER
Reactions of Unsaturated Azides
267
MS (ESI): m/z = 205.09 [M + H+].
GC–MS: m/z = 204 [M+].
mmol) in CH2Cl2 (25 mL). The mixture was stirred for 100 min at
7 °C. The solvent was then removed at 0 °C under vacuum using a
flask-receptor cooled at –10 °C and previously filled with a CH2Cl2
solution of cyclohexene as trap for the rest of bromine. The residue
was purified by chromatography on silica gel eluting with Et2O–n-
hexane (11:9) to give (E)-27b (4.60 g, 12.0 mmol, 93%) as a white
solid; mp 55–57 °C (Et2O).
(4-Methoxybut-2-ynylsulfonyl)benzene (23)
Compound 23 (96%, yellow oil) was obtained from 1926 according
to the procedure used for 11a.
IR (CDCl3): 1327 (SO2), 1141 (SO2) cm–1.
1H NMR (CDCl3): d = 3.22 (s, 3 H, OCH3), 4.01 (t, 5J = 2.2 Hz, 2
H), 4.05 (t, 5J = 2.2 Hz, 2 H), 7.52–7.57 (m, 2 H, m-Ph), 7.62–7.66
(m, 1 H, p-Ph), 7.92–7.95 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 48.5 (t, C-1¢), 57.4 (q, OCH3), 59.5 (t, C-4¢),
74.0 (s, C≡), 83.7 (s, C≡), 128.6 (d, 2 × C), 129.0 (d, 2 × C) 134.1
(d, p-Ph), 137.5 (s, i-Ph).
IR (CDCl3): 1327 (SO2), 1153 (SO2) cm–1.
1H NMR (CDCl3): d = 3.23 (s, 3 H, OCH3), 4.27 (s, 2 H, H-4¢), 4.54
(s, 2 H, H-1¢), 7.50–7.56 (m, 2 H, m-Ph), 7.62–7.68 (m, 1 H, p-Ph),
7.90–7.94 (m, 2 H, o-Ph); the assignment of the signals was sup-
ported by NOE experiments.
13C NMR (CDCl3): d = 57.7 (q, OCH3), 66.3 (t, C-1¢), 75.0 (t, C-4¢),
109.3 (s, CBr), 128.1 (s, CBr), 128.7 (d, 2 × C), 129.2 (d, 2 × C),
134.3 (d, p-Ph), 138.3 (s, i-Ph).
HRMS (ESI): m/z [M + H+] calcd for C11H12O3S: 225.0580; found:
2251.0582.
Anal. Calcd for C11H12Br2O3S: C, 34.40; H, 3.15; S, 8.35. Found: C,
34.45; H, 3.07; S, 8.13.
(Oct-2-ynylsulfonyl)benzene (24)
Compound 20 (95%) was obtained as a colorless oil from 16a23
according to the procedure described in the literature.25
(E)-(2,3-Dibromooct-2-enylsulfonyl)benzene [(E)-28b]
Compound 24 (4.00 g, 16.0 mmol) in anhyd CH2Cl2 (30 mL) was
treated dropwise at 0 °C with bromine (5.00 g, 31.25 mmol) in
CH2Cl2 (20 mL). After stirring for 2 h at 10 °C, the mixture was
washed with a sat. solution of Na2SO3 (3 ×). The organic layer was
dried over MgSO4 and evaporated to give (E)-28b (6.14 g, 15.0
mmol, 94%) as a colorless oil.
Compound 20
1H NMR (CDCl3): d = 0.90 (t, 3J = 7.2 Hz, 3 H, H-8¢), 1.31 (m, 4
H), 1.47 (m, 2 H), 2.17 (tt, 3J = 7.2 Hz, 5J = 2.4 Hz, 2 H, H-4¢), 3.64
(t, 5J = 2.4 Hz, 2 H, H-1¢), 7.20–7.25 (m, 1 H, p-Ph), 7.29–7.34 (m,
2 H, Ph), 7.42–7.47 (m, 2 H, Ph).
IR (CDCl3): 1325 (SO2), 1151 (SO2) cm–1.
13C NMR (CDCl3): d = 13.9 (q, C-8¢), 18.7 (t), 22.1 (t), 22.9 (t), 28.2
(t), 30.9 (t), 75.4 (s, C≡), 84.1 (s, C≡), 126.4 (d, p-Ph), 128.7 (d, 2 ×
C), 129.6 (d, 2 × C), 135.6 (s, i-Ph).
1H NMR (CDCl3): d = 0.89 (t, 3J = 7.2 Hz, 3 H, H-8¢), 1.26 (m, 4
H), 1.42 (m, 2 H), 2.61 (t, J = 7.5 Hz, 2 H, H-4¢), 4.50 (s, 2 H, H-1¢),
7.51–7.57 (m, 2 H, m-Ph), 7.64–7.70 (m, 1 H, p-Ph) 7.93–7.95 (m,
2 H, o-Ph).
13C NMR (CDCl3): d = 13.9 (q, C-8¢), 22.3 (t), 26.9 (t), 30.6 (t), 41.2
(t, C-4¢), 66.4 (t, C-1¢), 105.7 (s, CBr), 129.0 (d, 2 × C), 129.1 (d,
2 × C), 132.0 (s, CBr), 134.2 (d, p-Ph), 138.9 (s, i-Ph).
Compound 24 (97%) was then obtained as a colorless oil from 20
according to the procedure used for 11a.
IR (CDCl3): 1324 (SO2), 1137 (SO2) cm–1.
1H NMR (CDCl3): d = 0.85 (t, 3J = 7.2 Hz, 3 H, H-8¢), 1.23 (m, 4
H), 1.40 (m, 2 H), 2.11 (tt, 3J = 7.2 Hz, 5J = 2.4 Hz, 2 H, H-4¢), 3.93
(t, 5J = 2.4 Hz, 2 H, H-1¢), 7.53–7.58 (m, 2 H, m-Ph), 7.64–7.70 (m,
1 H, p-Ph), 7.93–7.97 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 13.9 (q, C-8¢), 18.6 (t), 22.0 (t), 27.7 (t), 30.8
(t), 48.9 (t, C-1¢), 67.3 (s, C≡), 88.9 (s, C≡), 128.7 (d, 2 × C), 128.9
(d, 2 × C), 134.0 (d, p-Ph) 137.7 (s, i-Ph).
MS (ESI): m/z = 410.92 [M + H+, 81Br].
(E)-(1,2-Dibromo-3-phenylsulfonylprop-1-enyl)benzene [(E)-
29b]
Compound (E)-29b (89%) was obtained as a white solid from 2527
according to the procedure used for (E)-28b; mp 108–110 °C
(Et2O–n-pentane).
MS (ESI): m/z = 251.09 [M + H+].
HRMS (ESI): m/z [M + H+] calcd for C14H18O2S: 251.1100; found:
IR (CDCl3): 1326 (SO2), 1148 (SO2) cm–1.
1H NMR (CDCl3): d = 4.69 (s, 2 H, H-3¢), 7.15–7.20 (m, 2 H, PhC-
1¢), 7.33–7.36 (m, 3 H, PhC-1¢), 7.59–7.65 (m, 2 H, m-PhSO2),
7.70–7.76 (m, 1 H, p-PhSO2), 8.03–8.07 (m, 2 H, o-PhSO2).
13C NMR (CDCl3): d = 66.8 (t, C-3¢), 107.9 (s), 126.1 (s), 128.3 (d,
2 × C), 128.4 (d, 2 × C), 129.1 (d, 2 × C), 129.2 (d, 2 × C), 129.3 (d),
134.4 (d), 138.3 (s), 139.7 (s).
251.1117.
(4,4-Dimethylpent-2-ynylsulfonyl)benzene (26)
The sulfone 26 (4.20 g, 17.7 mmol, 95%) was obtained as white
crystals (mp 55–57 °C) from 22 according to the procedure used for
11a.
IR (CDCl3): 1324 (SO2), 1137 (SO2) cm–1.
Anal. Calcd for C15H12Br2O2S: C, 43.30; H, 2.91; S, 7.71. Found: C,
43.40; H, 2.90; S, 7.26.
1H NMR (CDCl3): d = 1.10 (s, 9 H, CH3), 3.91 (s, 2 H, H-1¢), 7.52–
7.58 (m, 2 H, m-Ph), 7.64–7.70 (m, 1 H, p-Ph), 7.94–7.97 (m, 2 H,
o-Ph).
13C NMR (CDCl3): d = 27.4 (s, C-4¢), 30.4 (q, 3 × C, CH3), 48.9 (t,
C-1¢), 66.3 (s, C-2¢), 96.6 (s, C-3¢), 128.8 (d, 2 × C), 129.0 (d, 2 ×
C), 134.0 (d, p-Ph), 137.5 (s, i-Ph).
(2,3-Dibromo-4,4-dimethylpent-2-enylsulfonyl)benzene [(E/Z)-
30b]
Compound 26 (3.50 g, 13.06 mmol) in anhyd CH2Cl2 (50 mL) was
treated dropwise at 0 °C with bromine (4.00 g, 25.0 mmol) in
CH2Cl2 (20 mL). The mixture was stirred at 20 °C for 4 h. The
workup was performed according to the procedure used for (E)-28b
to afford a yellow liquid (4.45 g, 11.24 mmol, 86%) containing (E)-
30b and (Z)-30b in a ratio of 26:1.
IR (CDCl3, mixture): 1323 (SO2), 1145 (SO2) cm–1.
MS (ESI, mixture): m/z = 396.90 [M + H+, 81Br].
Anal. Calcd for C13H16O2S: C, 66.06; H, 6.82; S, 13.57. Found: C,
65.61; H, 6.61; S, 13.77.
(E)-(2,3-Dibromo-4-methoxybut-2-enylsulfonyl)benzene [(E)-
27b]
The sulfone 23 (2.90 g, 13.1 mmol) in anhyd CH2Cl2 (50 mL) was
treated dropwise at 0 °C with a solution of bromine (2.30 g, 14.4
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268
J. R. Fotsing, K. Banert
PAPER
(E)-30b
HRMS (ESI): m/z [M + H+, 79Br] calcd for C14H17BrO2S: 329.0159;
found: 329.0149.
1H NMR (CDCl3): d = 1.33 (s, 9 H, CH3), 4.69 (s, 2 H, H-1¢), 7.51–
7.57 (m, 2 H, m-Ph), 7.64–7.70 (1 H, p-Ph), 7.93–7.97 (m, 2 H, o-
Ph).
(1-Bromo-3-phenylsulfonylpropa-1,2-dienyl)benzene (33b)
White solid; mp 121–122 °C (Et2O–n-hexane).
IR (CDCl3): 1323 (SO2), 1153 (SO2) cm–1.
13C NMR (CDCl3): d = 30.6 (q, 3 × C, CH3), 41.4 (s, C-4¢), 70.8 (t,
C-1¢), 103.6 (s, CBr), 128.9 (d, 2 × C), 129.1 (d, 2 × C), 134.1 (d, p-
Ph), 138.5 (s), 141.5 (s).
1H NMR (CDCl3): d = 6.51 (s, 1 H, H-3¢), 7.34–7.39 (m, 3 H, Ph),
7.44–7.49 (m, 2 H, Ph), 7.51–7.58 (m, 2 H, Ph), 7.62–7.68 (m, 1 H,
Ph), 7.94–7.98 (m, 2 H, Ph).
13C NMR (CDCl3): d = 100.8 (s, C-1¢), 105.5 (d, C-3¢), 127.6 (d,
2 × C), 128.0 (d, 2 × C), 128.7 (d, 2 × C), 129.3 (d, 2 × C), 130.1 (d),
130.5 (s, i-Ph at C-1), 134.1 (d), 139.9 (s, i-PhSO2), 203.1 (s, C-2¢).
(Z)-30b
1H NMR (CDCl3): d = 1.43 (s, 9 H, CH3), 4.75 (s, 2 H, H-1¢), 7.46–
7.51 (m, 2 H, Ph), 7.64–7.70 (1 H, p-Ph), 8.00–8.06 (m, 2 H, Ph).
13C NMR (CDCl3): d = 32.1 (q, 3 × C, CH3).
Due to the low concentration, only one 13C NMR signal of (Z)-30b
Anal. Calcd for C15H11BrO2S: C, 53.75; H, 3.31; S, 9.56. Found: C,
53.48; H, 3.35; S, 9.39.
was detected.
Synthesis of the Allenyl Bromides 30b–34b (Table 6); General
Procedure
(3-Bromo-4,4-dimethylpenta-1,2-dienylsulfonyl)benzene (34b)
White solid; mp 75–76 °C (n-hexane).
IR (CDCl3): 1961 (C=C=C), 1334 (SO2), 1156 (SO2) cm–1.
1H NMR (CDCl3): d = 1.08 (s, 9 H, CH3), 6.17 (s, 1 H, H-1¢), 7.52–
7.58 (m, 2 H, m-Ph), 7.62–7.67 (1 H, p-Ph), 7.89–7.92 (m, 2 H, o-
Ph).
13C NMR (CDCl3): d = 28.3 (q, 3 × C, CH3), 37.2 (s, C-4¢), 103.8 (d,
C-1¢), 113.2 (s, C-3¢), 128.0 (d, 2 × C), 129.2 (d, 2 × C), 133.1 (d, p-
Ph), 139.7 (s, i-Ph), 199.0 (s, C-2¢).
The synthesis of 31b, 32b, 33b and 34b was performed by treatment
of the anhyd CH2Cl2 solutions of the vinyl bromides (E)-27b, (E)-
28b, (E)-29b and (E/Z)-30b, respectively, with Et3N at 0 °C. After
stirring at the temperature and for the time given in Table 6, purifi-
cation was performed with the help of chromatography on silica gel
using Et2O–n-hexane as eluent.
(3-Bromo-4-methoxybuta-1,2-dienylsulfonyl)benzene (31b)
White solid; mp 41–42 °C (Et2O–n-hexane).
Anal. Calcd for C13H15BrO2S: C, 49.53; H, 4.79; S, 10.17. Found:
C, 49.47; H, 4.75; S, 10.24.
IR (CDCl3): 1322 (SO2), 1160 (SO2) cm–1.
1H NMR (CDCl3): d = 3.32 (s, 3 H, OCH3), 4.12 (d, 5J = 2.4 Hz, 2
H, H-4¢), 6.27 (t, 5J = 2.4 Hz, 1 H, H-1¢), 7.50–7.56 (m, 2 H, m-Ph),
7.60–7.66 (m, 1 H, p-Ph), 7.86–7.90 (m, 2 H, o-Ph).
Synthesis of the 1-Azido-2-haloethenes 38a, 39a,b and 40b–43b
(Table 7); General Procedure
13C NMR (CDCl3): d = 58.1 (q, OCH3), 72.8 (t, C-4¢), 97.1 (s, C-3¢),
105.3 (d, C-1¢), 127.8 (d, 2 × C), 129.3 (d, 2 × C), 134.0 (d, p-Ph),
139.8 (s, i-Ph), 200.8 (s, C-2¢).
The 1-azido-2-haloethenes (E/Z)-38a, (E/Z)-39a, (E/Z)-39b, (E/Z)-
40b, (E/Z)-41b, (E/Z)-42b and (Z)-43b were obtained by treatment
of the stirred CH2Cl2 solutions of the allenes 13a, 14a, 14b, 31b,
32b, 33b and 34b, respectively, with TMGA at 0 °C. After stirring
at the temperature and for the time given in Table 7, the solvent was
partially removed. Purification was performed by filtration of the
residue through silica gel using Et2O.
Anal. Calcd for C11H11BrO3S: C, 43.58; H, 3.66; S, 10.57. Found:
C, 43.48; H, 3.72; S, 10.38.
(3-Bromoocta-1,2-dienylsulfonyl)benzene (32b)
Yellowish oil.
IR (CDCl3): 1322 (SO2), 1146 (SO2) cm–1.
(E/Z)-2-Azido-3-chloro-1-methylsulfonylbut-2-ene [(E/Z)-38a]
Yellowish solid; mp 74–77 °C (Et2O–n-hexane, mixture).
1H NMR (CDCl3): d = 0.87 (t, 3J = 7.2 Hz, 3 H, H-8¢), 1.26 (m, 4
H), 1.44 (m, 2 H), 2.41 (td, 3J = 7.5 Hz, 5J = 2.7 Hz, 2 H, H-4¢), 6.16
(t, 5J = 2.7 Hz, 1 H, H-1¢), 7.55–7.59 (m, 2 H, m-Ph), 7.63–7.66 (m,
1 H, p-Ph) 7.89–7.93 (m, 2 H, o-Ph).
IR (CDCl3, mixture): 2160 (N3), 2113 (N3), 1319 (SO2), 1127 (SO2)
cm–1.
MS (ESI, mixture): m/z (%) = 182.03 (100), 210.11 (ca. 3) [M + H+,
35Cl].
13C NMR (CDCl3): d = 13.8 (q, C-8¢), 22.1 (t), 27.0 (t), 30.4 (t), 36.7
(t, C-4¢), 101.3 (s, C-3¢), 103.6 (d, C-1¢), 127.8 (d, 2 × C), 129.2 (d,
2 × C), 133.8 (d, p-Ph), 139.9 (s, i-Ph), 201.0 (s, C-2¢).
(E)-38a
1H NMR (CDCl3): d = 2.19 [s, 3 H, C(CH3)], 3.01 (s, 3 H, SO2CH3),
4.22 (s, 2 H, H-1).
MS (ESI): m/z (%) = 143.00 (100), 329.00 (65) [M + H+, 79Br].
Table 6 Synthesis of Compounds 31b–34b
Dibromide
n
CH2Cl2
(mL)
Et3N
(mmol)
Temp
(°C)
Time
(min)
Et2O–n-
hexane
Allene
n
Yielda
(%)
(mmol)
(mmol)
(E)-27b
(E)-28b
(E)-29b
(E)-30b
6.12
2.44
0.84
10.1
15
10
8
15.8
7.32
2.52
40.4
16
5
60
240
60
1:1
1:4
1:1
1:3
31b
32b
33b
34b
4.29
1.06
0.56
8.23
70
44
67
82
6
30
20
720
a Yield of isolated compound.
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

PAPER
Reactions of Unsaturated Azides
269
Table 7 Synthesis of 1-Azido-3-haloethenes
Starting
allene
n
CH2Cl2
(mL)
TMGA
(mmol)
Temp
(°C)
Time
(min)
1-Azido-2- E/Z ratio
n
Yielda
(mmol)
haloethene
(E/Z)-38a
(E/Z)-39a
(E/Z)-39b
(E/Z)-40b
(E/Z)-41b
(E/Z)-42b
(Z)-43b
(mmol)
(%)
98
97
92
95
99
92
94
13a
14a
14b
31b
32b
33b
34b
3.840
0.263
0.249
0.264
0.182
0.191
0.209
2
1
1
1
1
1
1
4.110
0.534
0.498
0.506
0.275
0.478
0.838
5
5
15
15
5:1.5
3:2
5:1
2:1
3:1
1:2
0:1
3.770
0.254
0.228
0.249
0.180
0.209
0.223
20
15
5
20
20
25
15
5
20
240
a Yield of isolated compound.
13C NMR (CDCl3): d = 21.3 [q, C(CH3)], 40.9 (q, SO2CH3), 54.6 (t,
(Z)-39b
C-1), 122.8 (s), 125.8 (s).
1H NMR (CDCl3): d = 1.94 (s, 3 H, CH3), 4.07 (s, 2 H, H-1¢), 7.53–
7.59 (m, 2 H, m-Ph), 7.66–7.72 (m, 1 H, p-Ph), 7.91–7.95 (m, 2 H,
o-Ph).
(Z)-38a
1H NMR (CDCl3): d = 2.25 [s, 3 H, C(CH3)], 3.01 (s, 3 H, SCH3),
13C NMR (CDCl3): d = 24.0 (q, CH3), 55.6 (t, C-1¢), 115.1 (s), 122.8
(s), 128.4 (d, 2 × C), 129.4 (d, 2 × C), 134.4 (d, p-Ph), 137.3 (s, i-
Ph).
3.94 (s, 2 H, H-1).
13C NMR (CDCl3): d = 22.9 [q, C(CH3)], 40.9 (q, SCH3), 55.2 (t, C-
1), 120.9 (s), 126.4 (s).
(E/Z)-(2-Azido-3-bromo-4-methoxybut-2-enylsulfonyl)benzene
[(E/Z)-40b]
Mixture of isomers obtained as a yellow oil.
(E/Z)-(2-Azido-3-chlorobut-2-enylsulfonyl)benzene [(E/Z)-39a]
Yellow solid; mp 64–67 °C (Et2O–n-hexane, mixture).
IR (CDCl3, mixture): 2155 (N3), 2110 (N3), 1325 (SO2), 1143 (SO2)
cm–1.
IR (CDCl3, mixture): 2152 (N3), 2110 (N3), 1327 (SO2), 1159 (SO2)
cm–1.
MS (ESI, mixture): m/z (%) = 244.05 (100), 272.13 (ca. 3) [M + H+,
(E)-40b
35Cl].
1H NMR (CDCl3): d = 3.18 (s, 3 H, OCH3), 4.12 (s, 2 H, CH2), 4.37
(s, 2 H, CH2), 7.50–7.59 (m, 2 H, m-Ph), 7.63–7.68 (m, 1 H, p-Ph),
7.85–7.92 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 57.4 (q, OCH3), 58.0 (t, C-1¢), 70.5 (t, C-4¢),
119.2 (s), 127.5 (s), 128.6 (d, 2 × C), 129.2 (d, 2 × C), 134.4 (d, p-
Ph), 137.6 (s, i-Ph).
(E)-39a
1H NMR (CDCl3): d = 2.02 (s, 3 H, CH3), 4.28 (s, 2 H, H-1¢), 7.53–
7.73 (m, 3 H, Ph), 7.91–7.95 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 21.1 (q, CH3), 56.0 (t, C-1¢), 122.0 (s), 126.8
(s), 128.7 (d, 2 × C), 129.2 (d, 2 × C), 134.4 (d, p-Ph), 137.9 (s, i-
Ph).
(Z)-40b
1H NMR (CDCl3): d = 3.17 (s, 3 H, OCH3), 3.80 (s, 2 H, CH2), 4.23
(s, 2 H, CH2), 7.50–7.59 (m, 2 H, m-Ph), 7.63–7.68 (m, 1 H, p-Ph),
7.85–7.92 (m, 2 H, o-Ph).
(Z)-39a
1H NMR (CDCl3): d = 1.83 (s, 3 H, CH3), 4.03 (s, 2 H, H-1¢), 7.53–
7.73 (m, 3 H, Ph), 7.91–7.95 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 55.6 (t, C-1¢), 57.7 (q, OCH3), 72.8 (t, C-4¢),
115.1 (s), 126.9 (s), 128.3 (d, 2 × C), 129.4 (d, 2 × C), 134.5 (d, p-
Ph), 137.4 (s, i-Ph).
13C NMR (CDCl3): d = 22.1 (q, CH3), 56.5 (t, C-1¢), 121.1 (s), 125.3
(s), 128.5 (d, 2 × C), 129.6 (d, 2 × C), 134.5 (d, p-Ph), 137.7 (s, i-
Ph).
(E/Z)-(2-Azido-3-bromooct-2-enylsulfonyl)benzene [(E/Z)-41b]
(E/Z)-(2-Azido-3-bromobut-2-enylsulfonyl)benzene [(E/Z)-39b]
Mixture of isomers obtained as a yellow oil.
(E)-41b
IR (CDCl3, mixture): 2145 (N3), 2104 (N3), 1325 (SO2), 1310 (SO2),
1143 (SO2), 1132 (SO2) cm–1.
Yellow oil.
IR (CDCl3): 2104 (N3), 1325 (SO2), 1158 (SO2) cm–1.
1H NMR (CDCl3): d = 0.88 (t, 3J = 7.2 Hz, 3 H, H-8¢), 1.27 (m, 6
H), 2.45 (t, J = 7.5 Hz, 2 H, H-4¢), 4.35 (s, 2 H, H-1¢), 7.52–7.57 (m,
2 H, m-Ph), 7.65–7.71 (m, 1 H, p-Ph), 7.91–7.96 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 13.9 (q, C-8¢), 22.3 (t), 27.4 (t), 30.6 (t), 35.8
(t), 58.2 (t, C-1¢), 123.2 (s), 124.9 (s), 128.9 (d, 2 × C), 129.2 (d,
2 × C), 134.3 (d, p-Ph), 137.8 (s, i-Ph).
(E)-39b
1H NMR (CDCl3): d = 2.21 (s, 3 H, CH3), 4.32 (s, 2 H, H-1¢), 7.53–
7.59 (m, 2 H, m-Ph), 7.66–7.72 (m, 1 H, p-Ph), 7.91–7.95 (m, 2 H,
o-Ph).
13C NMR (CDCl3): d = 23.5 (q, CH3), 58.0 (t, C-1¢), 118.2 (s), 123.5
(s), 128.6 (d, 2 × C), 129.1 (d, 2 × C), 134.3 (d, p-Ph), 137.7 (s, i-
Ph).
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

270
J. R. Fotsing, K. Banert
PAPER
(Z)-41b
Yellow oil.
2-Bromo-3-methoxymethyl-2-phenylsulfonylmethyl-2H-azir-
ine (46b)
1H NMR (CDCl3): d = 3.55 (s, 3 H, OCH3), 3.65 (d, 2J = 15.0 Hz, 1
H, O2SCH2), 4.34 (d, 2J = 15.0 Hz, 1 H, O2SCH2), 4.87 (d, 2J = 18.6
Hz, 1 H, OCH2), 5.00 (d, 2J = 18.6 Hz, 1 H, OCH2), 7.55–7.62 (m,
2 H, m-Ph), 7.66–7.73 (m, 1 H, p-Ph), 7.87–7.92 (m, 2 H, o-Ph).
IR (CDCl3): 2107 (N3), 1325 (SO2), 1141 (SO2) cm–1.
1H NMR (CDCl3): d = 0.86 (t, 3J = 7.2 Hz, 3 H, H-8¢), 1.15 (m, 2
H), 1.24 (m, 2 H), 1.41 (m, 2 H), 2.12 (t, J = 7.5 Hz, 2 H, H-4¢), 4.07
(s, 2 H, H-1¢), 7.58–7.64 (m, 2 H, m-Ph), 7.69–7.75 (m, 1 H, p-Ph),
7.91–7.96 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 13.9 (q, C-8¢), 22.3 (t), 28.0 (t), 30.8 (t), 36.3
(t), 56.0 (t, C-1¢), 122.6 (s), 122.6 (s), 128.6 (d, 2 × C), 129.6 (d,
2 × C), 134.6 (d, p-Ph), 137.7 (s, i-Ph).
13C NMR (CDCl3): d = 41.4 (s, C-2), 59.8 (q, OCH3), 66.7 (t, CH2),
67.8 (t, CH2), 128.3 (d, 2 × C), 129.4 (d, 2 × C), 134.4 (d, p-Ph),
138.7 (s, i-Ph), 176.9 (s, C-3).
Azirine 47a and its Rearrangement into Azirine 52a
Compound (E/Z)-38a (50.0 mg, 239 mmol) in CDCl3 (0.6 mL) was
irradiated at –30 °C for 45 min to afford the azirine 47a in over 99%
NMR yield. By keeping the obtained solution at r.t. for 3 h, 47a re-
arranged to give 52a in over 99% NMR yield.
(E/Z)-(2-Azido-1-bromo-3-phenylsulfonylprop-1-enyl)benzene
[(E/Z)-42b]
Mixture of isomers obtained as a yellow oil.
IR (CDCl3, mixture): 2160 (N3), 2113 (N3), 1325 (SO2), 1154 (SO2)
cm–1.
2-Chloro-2-methyl-3-methylsulfonylmethyl-2H-azirine (47a)
1H NMR (CDCl3): d = 1.96 [s, 3 H, C(CH3)], 3.13 (s, 3 H, SO2CH3),
4.62 (s, 2 H, CH2).
13C NMR (CDCl3): d = 27.8 (q, [C(CH3)], 41.9 (q, SO2CH3), 51.9
(t, CH2), 57.0 (s, C-2), 175.7 (s, C-3).
MS (ESI, mixture): m/z (%) = 157.05 (100), 163.09 (63), 348.11
(50), 350.08 (15), 378.13 (ca. 5) [M + H+, 79Br].
1H NMR (CDCl3, mixture): d = 4.11 (s, 2 H, H-3¢, Z-isomer), 4.48
(s, 2 H, H-3¢, E-isomer), 6.85–8.05 (m, 20 H, Ph).
13C NMR (CDCl3, mixture): d = 56.5 (t, C-3¢), 59.7 (t, C-3¢), 125.1
(s), 125.6 (s), 128.2 (d), 128.5 (d), 129.0 (d), 129.1 (d), 134.3 (d),
134.5 (d), 136.6 (s), 136.8 (s), 137.9 (s).
2-Chloro-3-methyl-2-methylsulfonylmethyl-2H-azirine (52a)
White crystals; mp 74–75 °C (Et2O).
IR (CDCl3): 1766 (C=N), 1320 (SO2), 1134 (SO2) cm–1.
Some signals were not detected. The assignment of the NMR sig-
nals and the stereochemistry was performed by comparison with the
data of (E/Z)-39a,b and (E/Z)-40b.
1H NMR (CDCl3): d = 2.67 [s, 3 H, C(CH3)], 3.02 (s, 3 H, SO2CH3),
3.38 (d, 2J = 15.9 Hz, 1 H, CH2), 4.16 (d, 2J = 15.9 Hz, 1 H, CH2).
13C NMR (CDCl3): d = 12.2 [q, C(CH3)], 42.2 (q, SO2CH3), 52.5 (s,
C-2), 64.9 (t, CH2), 175.6 (s, C-3).
(Z)-(2-Azido-3-bromo-4,4-dimethylpent-2-enylsulfonyl)ben-
zene [(Z)-43b]
White crystals (Et2O–n-hexane); decompose at 40 °C.
IR (CDCl3): 2148 (N3), 2106 (N3), 1325 (SO2), 1149 (SO2) cm–1.
Anal. Calcd for C5H8ClNO2S: C, 33.06; H, 4.44; N, 7.71; S, 17.65.
Found: C, 33.09; H, 4.68; N, 7.71; S, 16.68.
Azirine 48a and its Rearrangement into Azirine 53a
Compound (E/Z)-39a (0.03 g, 110 mmol) in of CDCl3 (0.5 mL) was
irradiated at –30 °C for 90 min to afford the azirine 48a in over 99%
NMR yield. By keeping the obtained solution at r.t. for 4 h or by
warming at 35 °C for 3 h, 48a rearranged to give 53a in over 99%
NMR yield.
1H NMR (CDCl3): d = 1.32 (s, 9 H, CH3), 4.37 (s, 2 H, H-1¢), 7.57–
7.63 (m, 2 H, m-Ph), 7.68–7.74 (1 H, p-Ph), 7.92–7.96 (m, 2 H, o-
Ph).
13C NMR (CDCl3): d = 31.6 (q, 3 × C, CH3), 40.6 (s, C-4¢), 56.5 (t,
C-1¢), 121.8 (s), 128.4 (d, 2 × C), 129.5 (d, 2 × C), 134.5 (d, p-Ph),
136.2 (s), 138.6 (s).
2-Chloro-2-methyl-3-phenylsulfonylmethyl-2H-azirine (48a)
1H NMR (CDCl3): d = 1.87 (s, 3 H, CH3), 4.68 (d, 2J = 15.9 Hz, 1
H, CH2), 4.74 (d, 2J = 15.9 Hz, 1 H, CH2), 7.59–7.65 (m, 2 H, m-
Ph), 7.70–7.76 (m, 1 H, p-Ph), 7.96–8.00 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 27.8 (q, CH3), 53.7 (t, CH2), 57.0 (s, C-2),
128.3 (d, 2 × C), 129.6 (d, 2 × C), 134.9 (d, p-Ph), 138.0 (s, i-Ph),
175.5 (s, C-3).
Azirine 44b and its Rearrangement into Azirine 46b
Compound (E/Z)-40b (86 mg, 249 mmol) in CDCl3 (0.6 mL) was ir-
1
radiated at –30 °C for 60 min. The first H NMR spectrum, mea-
sured at 19 °C, proved the formation of 44b and traces of 46b. By
keeping the mixture at r.t. for 10 min, a second 1H NMR spectrum
showed both isomers in a 1:1 ratio of 44b:46b. This ratio remained
unchanged for the rest of time, although decomposition was ob-
served after long storage. The initial combined NMR yield was
98%.
2-Chloro-3-methyl-2-phenylsulfonylmethyl-2H-azirine (53a)
IR (CDCl3): 1766 (C=N), 1323 (SO2), 1143 (SO2) cm–1.
IR (CDCl3, 1:1 mixture): 1746 (C=N), 1325 (SO2), 1158 (SO2),
1141 (SO2) cm–1.
1H NMR (CDCl3): d = 2.66 (s, 3 H, CH3), 3.40 (d, 2J = 15.3 Hz, 1
H, CH2), 4.28 (d, 2J = 15.3 Hz, 1 H, CH2), 7.57–7.63 (m, 2 H, m-
Ph), 7.67–7.73 (m, 1 H, p-Ph), 7.91–7.96 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 12.2 (q, CH3), 51.7 (s, C-2), 67.1 (t, CH2),
128.3 (d, 2 × C), 129.4 (d, 2 × C), 134.3 (d, p-Ph), 138.9 (s, i-Ph),
174.8 (s, C-3).
2-Bromo-2-methoxymethyl-3-phenylsulfonylmethyl-2H-azir-
ine (44b)
1H NMR (CDCl3): d = 3.18 (s, 3 H, OCH3), 3.81 (d, 2J = 12.0 Hz, 1
H, OCH2), 3.86 (d, 2J = 12.0 Hz, 1 H, OCH2), 4.74 (s, 2 H, O2SCH2),
7.55–7.62 (m, 2 H, m-Ph), 7.66–7.73 (m, 1 H, p-Ph), 7.80–8.03 (m,
2 H, o-Ph).
Anal. Calcd for C10H10ClNO2S: C, 49.28; H, 4.14; N, 5.74; S, 13.15.
Found: C, 49.66; H, 4.66; N, 5.25; S, 12.84.
13C NMR (CDCl3): d = 51.0 (s, C-2), 53.6 (t, O2SCH2), 58.9 (q,
OCH3), 75.9 (t, OCH2), 128.6 (d, 2 × C), 129.5 (d, 2 × C), 134.8 (d,
p-Ph), 138.1 (s, i-Ph), 173.0 (s, C-3).
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

PAPER
Reactions of Unsaturated Azides
271
Azirine 48b and its Rearrangement into Azirine 53b
at 19 °C, proved only the presence of the rearranged azirine 55b in
97% NMR yield. When the irradiation and the measurement of the
NMR data were performed in CDCl3 at –50 °C, 50b could be ob-
served. However, even at that temperature (–50 °C), the rearrange-
ment of 50b to 55b took place slowly.
Compound (E/Z)-39b (0.03 g, 110 mmol) in CDCl3 (0.5 mL) was ir-
1
radiated at –30 °C for 60 min. The first H NMR spectrum, mea-
sured at 19 °C, proved the presence of a mixture (1:1) of 48b and
53b. By keeping this mixture at r.t. for about 10 min, a second H
1
NMR spectrum proved only the presence of 53b in over 96% NMR
yield.
2-Bromo-2-phenyl-3-phenylsulfonylmethyl-2H-azirine (50b)
Yellow in CDCl3 solution at –50 °C.
2-Bromo-2-methyl-3-phenylsulfonylmethyl-2H-azirine (48b)
1H NMR (CDCl3): d = 2.05 (s, 3 H, CH3), 4.69 (d, 2J = 15.9 Hz, 1
H, CH2), 4.75 (d, 2J = 15.9 Hz, 1 H, CH2), 7.59–7.64 (m, 2 H, m-
Ph), 7.67–7.73 (m, 1 H, p-Ph), 7.96–8.00 (m, 2 H, o-Ph).
Due to the rapid rearrangement, the 13C NMR data of 48b are not
available.
1H NMR (CDCl3, –50 °C): d = 4.76 (d, 2J = 13.0 Hz, 1 H, CH2), 4.82
(d, 2J = 13.0 Hz, 1 H, CH2), 7.15–7.17 (m, 2 H), 7.29–7.32 (m, 3 H),
7.44–7.50 (m, 2 H), 7.57–7.73 (m, 3 H).
13C NMR (CDCl3, –50 °C): d = 50.1 (s, C-2), 52.7 (t, CH2), 126.5
(d), 128.2 (d), 128.8 (d), 130.8 (d, overlaps of two signals), 135.0
(d), 136.5 (s), 138.1 (s), 171.2 (s, C-3).
2-Bromo-3-methyl-2-phenylsulfonylmethyl-2H-azirine (53b)
Yellow oil.
IR (CDCl3): 1764 (C=N), 1322 (SO2), 1142 (SO2) cm–1.
1H NMR (CDCl3): d = 2.67 (s, 3 H, CH3), 3.61 (d, 2J = 15.0 Hz, 1
H, CH2), 4.28 (d, 2J = 15.0 Hz, 1 H, CH2), 7.59–7.64 (m, 2 H, m-
Ph), 7.67–7.73 (m, 1 H, p-Ph), 7.89–7.93 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 12.4 (q, CH3), 41.7 (s, C-2), 68.3 (t, CH2),
128.4 (d, 2 × C), 129.4 (d, 2 × C), 134.3 (d, p-Ph), 138.9 (s, i-Ph),
176.3 (s, C-3).
2-Bromo-3-phenyl-2-phenylsulfonylmethyl-2H-azirine (55b)
Whitish solid; mp 82–83 °C (Et2O–CH2Cl2).
IR (CDCl3): 1736 (C=N), 1324 (SO2), 1159 (SO2) cm–1.
1H NMR (CDCl3, 19 °C): d = 3.85 (d, 2J = 15.3 Hz, 1 H, CH2), 4.53
(d, 2J = 15.3 Hz, 1 H, CH2), 7.52–7.74 (m, 6 H), 7.90–7.93 (m, 2 H),
8.11–8.15 (m, 2 H).
13C NMR (CDCl3, 19 °C): d = 42.7 (s, C-2), 68.0 (t, CH2), 121.3 (s),
128.3 (d, 2 × C), 129.3 (d, 2 × C), 129.4 (d, 2 × C), 130.8 (d, 2 × C),
134.2 (d), 134.9 (d), 139.2 (s), 173.3 (s, C-3).
MS (ESI): m/z = 288.23 [M + H+, 81Br].
Anal. Calcd for C15H12BrNO2S: C, 51.44; H, 3.45; N, 4.00; S, 9.15.
Found: C, 51.34; H, 3.51; N, 3.98; S, 8.87.
Azirine 49b and its Rearrangement into Azirine 54b
Compound (E/Z)-41b (0.03 g, 80.6 mmol) in CDCl3 (0.5 mL) was
irradiated at –30 °C for 60 min. The first 1H NMR spectrum, mea-
sured at 19 °C, proved the presence of a mixture (1:2) of 49b and
54b. By keeping this mixture at r.t. for about 5 min, a second H
NMR spectrum proved only the presence of 54b (28 mg, 78.2 mmol,
96%).
Azirine 51b and its Rearrangement into Azirine 56b
The vinyl azide (Z)-43b (60.0 mg, 167 mmol) in CDCl3 (0.6 mL)
1
was irradiated at –30 °C for 60 min. The first H NMR spectrum,
1
measured at 19 °C, proved the presence of a mixture (1:3) of 51b
and 56b. By keeping this mixture at r.t. for approximately 10 min,
a second 1H NMR spectrum proved only the presence of 56b in 99%
NMR yield.
2-Bromo-2-pentyl-3-phenylsulfonylmethyl-2H-azirine (49b)
1H NMR (CDCl3): d = 0.85 (t, 3J = 7.2 Hz, 3 H, CH3), 1.24 (m, 2 H),
1.39 (m, 4 H), 1.82 (m, 2 H, CH2 at C-2), 4.70 (s, 2 H, SO2CH2),
7.51–7.63 (m, 2 H, m-Ph), 7.66–7.72 (m, 1 H, p-Ph), 7.98–8.02 (m,
2 H, o-Ph).
Due to the rapid rearrangement, the 13C NMR data of 49b are not
available.
2-Bromo-2-tert-butyl-3-phenylsulfonylmethyl-2H-azirine (51b)
1H NMR (CDCl3): d = 0.97 (s, 9 H, CH3), 4.68 (s, 2 H, SO2CH2),
7.54–7.62 (m, 2 H, m-Ph), 7.64–7.70 (m, 1 H, p-Ph), 8.02–8.06 (m,
2 H, o-Ph).
Due to the rapid rearrangement, the 13C NMR data of this compound
are not available.
2-Bromo-3-pentyl-2-phenylsulfonylmethyl-2H-azirine (54b)
Yellow oil.
IR (CDCl3): 1753 (C=N), 1323 (SO2), 1141 (SO2) cm–1.
2-Bromo-3-tert-butyl-2-phenylsulfonylmethyl-2H-azirine (56b)
White solid; mp 68–70 °C.
IR (CDCl3): 1741 (C=N), 1323 (SO2), 1146 (SO2) cm–1.
1H NMR (CDCl3): d = 0.92 (t, 3J = 7.2 Hz, 3 H, CH3), 1.41 (m, 4 H),
1.83 (m, 2 H), 2.94 (dt, 2J = 17.4 Hz, 3J = 7.5 Hz, 1 H, CH2 at C-3),
3.05 (dt, 2J = 17.4 Hz, 3J = 7.5 Hz, 1 H, CH2 at C-3), 3.62 (d, 2J =
15.3 Hz, 1 H, SO2CH2), 4.35 (d, 2J = 15.3 Hz, 1 H, SO2CH2), 7.51–
7.63 (m, 2 H, m-Ph), 7.66–7.72 (m, 1 H, p-Ph), 7.89–7.93 (m, 2 H,
o-Ph).
13C NMR (CDCl3): d = 13.8 (q, CH3), 22.1 (t), 23.4 (t), 26.8 (t), 31.1
(t), 42.3 (s, C-2), 68.4 (t, SO2CH2), 128.3 (d, 2 × C), 129.4 (d, 2 ×
C), 134.3 (d, p-Ph), 138.9 (s, i-Ph), 178.8 (s, C-3).
1H NMR (CDCl3): d = 1.42 (s, 9 H, CH3), 3.70 (d, 2J = 15.0 Hz, 1
H, CH2), 4.29 (d, 2J = 15.0 Hz, 1 H, CH2), 7.54–7.62 (m, 2 H, m-
Ph), 7.64–7.70 (m, 1 H, p-Ph), 7.92–7.96 (m, 2 H, o-Ph).
13C NMR (CDCl3): d = 25.9 (q, CH3), 34.5 [s, C(CH3)], 44.0 (s, C-
2), 68.3 (t, CH2), 128.5 (d, 2 × C), 129.3 (d, 2 × C), 134.2 (d, p-Ph),
139.4 (s, i-Ph), 184.2 (s, C-3).
Anal. Calcd for C13H16BrNO2S: C, 47.28; H, 4.88; N, 4.24; S, 9.71.
Found: C, 47.18; H, 4.84; N, 4.24; S, 10.00.
HRMS (ESI): m/z [M + H+, 79Br] calcd for C14H18BrNO2S:
344.0267; found: 344.0275.
Acknowledgment
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.
Azirine 50b and its Rearrangement into Azirine 55b
Compound (E/Z)-42b (50.0 mg, 132 mmol) in CDCl3 (0.5 mL) was
irradiated at –30 °C for 60 min. The 1H NMR spectrum, measured
Synthesis 2006, No. 2, 261–272 © Thieme Stuttgart · New York

272
J. R. Fotsing, K. Banert
PAPER
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