Too Short-Lived or Not Existing Species: N-Azidoamines Reinvestigated

Article abstract of DOI:10.1021/acs.joc.9b00034

Treatment of N-chlorodimethylamine with sodium azide in dichloromethane does not lead to N-azidodimethylamine, as thought for more than 50 years. Instead, surprisingly, (azidomethyl)dimethylamine is generated with good reproducibility. A plausible reaction mechanism to explain the formation of this product is presented. The reaction of lithium dibenzylhydrazide with tosyl azide does not result in the creation of an N-azidoamine, which can be detected by IR spectroscopy at ambient temperature, as it was claimed previously. Additional experiments with diazo group transfer to lithium hydrazides show that intermediate N-azidoamines are very short-lived or their formation is bypassed by direct generation of 1,1-diazenes via synchronous cleavage of two N-N bonds.

Full text of DOI:10.1021/acs.joc.9b00034

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Article
Too Short-Lived or Not Existing Species: N-Azidoamines Reinvestigated
Klaus Banert, and Tom Pester
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b00034 • Publication Date (Web): 19 Feb 2019
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Too Short-Lived or Not Existing Species:
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Klaus Banert* and Tom Pester
Chemnitz University of Technology, Organic Chemistry, Strasse der Nationen 62, 09111 Chemnitz, Germany
Supporting Information Placeholder
ABSTRACT: Treatment of N-chlorodimethylamine with sodium azide in dichloromethane does not lead to N-azidodimethylamine,
as thought for more than 50 years. Instead, surprisingly (azidomethyl)dimethylamine is generated with good reproducibility. A
plausible reaction mechanism to explain the formation of this product is presented. The reaction of lithium dibenzylhydrazide with
tosyl azide does not result in the creation of an N-azidoamine, which can be detected by IR spectroscopy at ambient temperature, as
it was claimed previously. Additional experiments with diazo group transfer to lithium hydrazides show that intermediate N-
azidoamines are very short-lived or their formation is bypassed by direct generation of 1,1-diazenes via synchronous cleavage of two
N–N bonds.
1. INTRODUCTION
Scheme 1. Attempts to Generate N-Azidoamines
The azido unit belongs to the most important functional groups
in chemistry because of a variety of applications, particularly in
the case of organic azides.[1] Not only carbon but also most
elements in the periodic table form a bond to azide;[2] however,
only a few of the corresponding covalent compounds are of
general interest, for example, as reagents in synthetic chemistry,
such as hydrazoic acid,[3] silyl azides,[4] phosphoryl azides,[5]
and sulfonyl azides.[5b,6] Especially, azides attached to another
nitrogen atom have only rarely been reported.[7a−d] Such azides,
in which the azide-bearing additional nitrogen atom is always
connected with at least one strongly electron-withdrawing
group, turned out to be very unstable. On the other hand, N-
azidoamines, particularly those derived from nitrogen
heterocycles,[7e−o], attracted attention in numerous quantum
chemical studies because these compounds are discussed as
high energy density compounds (HEDCs).
Me2N
X
(Me3Si)2N
X
1a
2a
1b X = Cl
2b X = N3
X = Cl
X = N3
O
?
?
N
N
NPh
O
 N2
1. BuLi
2. TsN3
Bn2N NH2
Bn2N N3
2c
Bn2N
N
3c
4c
O
N
Bn2N
N N
NPh
5
O
out, however, that a mixture of hexamethyldisilazane and 2-azi-
dotetrahydrofuran had been isolated instead of the supposed
product 2a.[8b] H. Bock and K.-L. Kompa reported on the
treatment of N-chlorodimethylamine (1b) with sodium azide in
dichloromethane, which was claimed to afford, after workup by
vacuum distillation, a 25% yield of N-azidoamine 2b, that
showed an IR signal at 2110 cm−1.[9,12] J.-P. Anselme and
In the case of N-azidoamines, four groups published their
results when they tried to generate such azides.[8−11] In 1962, N.
Wiberg and A. Gieren presented the almost quantitative
synthesis of azide 2a using the reaction of N-chloro compound
1a with lithium azide in tetrahydrofuran (Scheme 1).[8a] Later,
it turned
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coworkers reacted 1,1-dibenzylhydrazine (3c) with
butyllithium (1.0 equiv) and then with tosyl azide to get
products,
2b. Instead, we detected the ammonium salt 8b,[16] the
amidinium salts 9[17] and 11,[16,18] and the known[19] azide 13,
which were
1
2
3
4
5
6
generated with good reproducibility and nearly quantitatively
Scheme 2. Reaction of 1b with Sodium Azide in Dichloromethane (Yields Based on Weighed 1b and Weighed 1H NMR Standard)
N
+ NaN3
+ NaN3
N
N
N
 NaCl
 NaCl
 HN3
N
N
N3
2b
Cl
1b
7
6
7
8
9
+ NaN3
+ HN3
 NaCl
N3
N
N3
+ HN3
N
Cl
1b
+
N
N
NH2
N
H
N
10
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H2
10
12
N
 HN3
N
N
+
N3
H
H2
N
N
N3
N
Cl
1b
9
8b
, 33%
, 26%
 NaCl
N3
+ NaN3
+ HN3
N
13
, 16%
N3
N
H
N
11
, 22%
that were most probably derived from the short-lived 1,1-
diazene (aminonitrene) 4c.[10] When the transformation was
performed at low temperatures in the presence of 4-phenyl-
1,2,4-triazoline-3,5-dione (PTAD), the trapping product 5 was
isolated in 65% yield.[10b] The authors postulated the formation
of 4c via intermediate 2c, which was generated from 3c and
tosyl azide by diazo group transfer. Whereas interception of 4c
with the help of PTAD was successful, the stability of N-
azidoamine 2c remained unclear. At first an IR band at 2060
cm−1, which was detected with reduced intensity after workup
at room temperature, was assigned to azide 2c.[10a] Later, it was
stated that liberation of dinitrogen already occurred at about
−20 °C, and this pointed to lower stability of 2c.[10b]
N-Azidoamines 2b and 2c showed slightly divergent azido
bands in the IR spectra and quite different thermal stability.
Thus, it is not easy to understand that 2b can be isolated at
ambient temperature and 2c cannot. Attempts to generate
nitrogen triazide (N10) from nitrogen trichloride and sodium,
lithium, or silver azide resulted in the formation of dinitrogen
as the only product.[9b,11,13] To the best of our knowledge,
existence of simple N-azidoamines has not been further
investigated. The wariness of experimenters is possibly based
on the explosive properties of 2b. H. Bock and K.-L. Kompa
reported on a spontaneous explosion of 2b (50 mg), which led
to a serious injury of a laboratory technician.[9b]
(Scheme 2). The reaction of 1b with sodium azide was also re-
alized in deuterated dichloromethane to exclude any
incorporation of the solvent into one of the products, especially
the surprising azide 13. Diazidomethane[20] was produced in
very
small traces only; however, a significant proportion of this
dangerous azide (22–26% H NMR yield based on the azide
1
salt) was formed besides 8b, 9, 11, and 13, when the
experiments were performed with more soluble azide salts such
as hexadecyltributylphosphonium azide[21] instead of sodium
azide or in the presence of benzyltrimethylammonium chloride.
After recondensation[22] of the reaction mixture resulting from
1b and sodium azide in dichloromethane, 13 was the only
(volatile) product. When such a reaction mixture (without
recondensation) was treated with cyclooctyne, we did not get
the trapping product 14b, although 1-amino-1H-1,2,3-triazoles
are established as stable substances[23] (Scheme 3). Instead, we
obtained the 2H-1,2,3-triazole 16 (11% isolated yield based on
1b), which was formed from 13 by cycloaddition followed by
rapid rearrangement of the corresponding 1H-1,2,3-triazole,
and the product 15 (9% yield) that resulted from hydrazoic acid
and cyclooctyne. For comparison, we also prepared 15 and 16
from an excess of cyclooctyne and hydrazoic acid or 13,
respectively.
Herein, we describe a corrigendum to the structure of the
covalent azide that is formed from 1b and sodium azide in
dichloromethane. Furthermore, we present experiments, which
indicate that N-azidoamines are very short-lived and cannot be
isolated and characterized at room temperature.
Scheme 3. Reaction of 1b with Sodium Azide in
Dichloromethane Followed by Treatment with
Cyclooctyne
N
N
N
N
NaN3
N
CH2Cl2
Cl
2. RESULTS AND DISCUSSION
1b
14b
When we repeated the experiments with equimolar amounts of
1b and sodium azide in dichloromethane (rt, 24 h) several
times,[14] we were able to confirm all the reported[9b,c]
phenomena.[15] But after removal of the insoluble sodium salts,
we did not get any hint about the formation of N-azidoamine
N
N3
N
N
N
HN3
N
N
N
N
73%
91%
13
16
15
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Our results demonstrate that the structure of 2b was
erroneously assigned for the real product 13.[9] In Scheme 2, we
propose mechanisms to explain the formation of 8b, 9, 11, and
13 from 1b and sodium azide.[15] We assume that sodium azide
firstly acts as a base and induces 1,2-elimination[24] of hydrogen
chloride from 1b, which leads to the imine 6, sodium chloride,
and hydrazoic acid. The highly reactive species 6 is known[25]
to reversibly trimerize creating the cyclic aminal 7. Oxidation
of the latter compound with the help of 1b results in the
generation of the final products 8b and 9. Equilibration of 8b
with hydrazoic acid and dimethylamine facilitates the addition
of this secondary amine to imine 6, which furnishes the aminal
10. Such a species is then oxidized with the aid of 1b to produce
8b and amidinium salt 11. If 10 is transformed into the
hydrogen azide salt 12, cleavage of the latter compound and
particular, the IR data, reported by G. Koga and J.-P.
Anselm.[10a] However, it turned out that the IR signal at 2060
cm–1 did not result from N-azidoamine 2c because it has to be
assigned to lithium azide, which was formed as a byproduct
after attack of the lithium hydrazide at the sulfur atom of tosyl
azide. Consequently, we also detected known[27,28] 1,1-
dibenzyl-2-tosylhydrazine, that originated from the same
reaction. This unwanted side reaction was repressed by using
the sterically shielded 2,4,6-triisopropylbenzenesulfonyl azide
instead of tosyl azide; in this case, we observed an IR signal at
2060 cm–1 with significantly diminished intensity and thus a
lower proportion of lithium azide. However, we did not get any
proof of the existence of the azide 2c, and our attempts to trap
2c with the help of cyclooctyne were also in vain.
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attack
of
the
azide
anion
leads
to
N-
(azidomethyl)dimethylamine (13).
In control experiments, we treated commercially available
7 with 1b in dichloromethane (rt, 24 h) and obtained the
known[17,26] amidinium chloride, including the same cation as
amidinium azide 9, along with dimethylamine hydrochloride.
When 7 was similarly exposed to 8b, the covalent azide 13 was
formed with 8% yield besides large amounts of unreacted 7. In
this case, 13 was most probably generated via the intermediates
6, 10, and 12. Even treatment of the extremely reactive imine
6[25a] with 8b under the same reaction conditions led to the
product 13 (7% yield) along with trimer 7 (82%).
When we reacted the known[29] hydrazine derivative 3d with
butyllithium (1.0 equiv) and then with 2,4,6-
triisopropylbenzenesulfonyl azide (1 h, –78 °C, then –20 °C),
we obtained the sulfonamide 20 and the known[29] azo
compound 21 (53% yield) after workup with water or methanol
(Scheme 4). We assumed that intermediate 17 was created in
the first step, and tautomerism to generate 18 was necessary to
induce the cleavage reaction which produced N-azidoamine 2d
and the anionic species 19. Whereas aqueous or methanolic
workup transformed 19 into 20, unstable azide 2d should
liberate dinitrogen to form the short-lived 1,1-diazene 4d that
led to the final product 21 via established [2,3]-sigmatropic
rearrangement. We tried to trap 2d with the help of cyclooctyne
in several experiments. Shortly after mixing the lithium
hydrazide and the sulfonyl azide, addition of cyclooctyne
resulted in the unwanted formation of 22[30], which was
identified as the only 1,2,3-triazole product. A 50% yield of 21
but no 1,2,3-triazole compound, such as desired 14d, was
observed when the cycloalkyne was added after nearly
complete consumption of the sulfonyl azide. This outcome
seems to indicate a very short lifetime of N-azidoamine 2d.
Other unstable azides, for example, trimethylsilylethynyl
When we repeated the experiments with equimolar amounts
of 3c and butyllithium followed by treatment with tosyl azide
(Scheme 1), we were able to confirm all the phenomena, in
Scheme 4. Attempts to Generate and Trap the
N-Azidoamine 2d
H
N
NH2
N
N
N
N
N
SO2
1. BuLi
17
3d
2.
SO2N3
3. H2O
azide[31] with
a
half-life period of 35 min at
N
N
N
N
N
H
SO2
–20 °C, can conveniently be trapped with the aid of cyclooctyne
to give the corresponding 1,2,3-triazoles in excellent yields.
Our additional experiments with lithium hydrazides derived
from other precursors, such as 1,1-dimethylhydrazine and 1,1-
diphenylhydrazine, or with other sulfonyl azides, for example,
nonafluorobutanesulfonyl azide, were also unsuccessful and did
not lead to direct spectroscopic evidence of N-azidoamines.
Moreover, our attempts to intercept these azido species with the
help of cyclooctyne, producing a 1-amino-1,2,3-triazole like
14b, were in vain. When we treated N-chloroamine 1d[32,33] with
sodium azide in dichloromethane, we identified the ammonium
salt 8d as one of the products and excluded the formation of azo
compound 21 (Scheme 4). Consequently, the reaction of 1d
with sodium azide did not comprise the generation of 2d and
4d.
18
N
N
N
N
N
N N N
HN SO2
14d
2d
 N2
19
H2O
 N2
N
N
N
N
[2,3]
H2N SO2
We interpret the product 21, which is formed after diazo
group transfer to 3d, as proof of short-lived 1,1-diazene 4d.
However, is it simultaneously a hint about the existence of
21
4d
20
N
Cl
NaN3
CH2Cl2
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referenced with the help of the solvent signals and recalculated
Page 4 of 8
intermediate 2d? If the cleavage of the species 18 occurs not
only at the N–NH bond, but also synchronously at a second N–
N bond (see the dashed arrow at the structure of 18 in Scheme
4), the 1,1-diazene 4d and dinitrogen will be created directly,
and the generation of N-azidoamine 2d is bypassed. In this case,
any attempt to trap 2d with retention of all four nitrogen atoms
will be unsuccessful.
1
2
3
4
5
6
7
8
relative to TMS. Data are presented as follows: chemical shift,
multiplicity (s = singlet, d = doublet, t = triplet, q = quartet,
quint = quintet, sext = sextet, sept = septet, m = multiplet, br =
broad), coupling constant in hertz (Hz), followed by the number
of hydrogen atoms. Assignments of NMR signals were further
supported by COSY, TOCSY, HSQC, and HMBC 2D-NMR
methods and also by comparison of the data of homologous
compounds in several cases. Signal assignment was omitted if
it was unclear. IR spectra were measured on a Nicolet iS 5
spectrometer (Thermo Fisher Scientific Inc., Waltham, MA,
USA) in a KBr cuvette for liquids. Mass spectra were obtained
from a micrOTOF QII spectrometer (Bruker Corp., Billerica,
MA, USA) utilizing an electrospray-ionization technique
(source = Apollo II ESI) or in case of compound 1d on a 15 T
solariX FT-ICR-MS (Bruker Corp., Billerica, MA, USA)
utilizing an electrospray-ionization technique. Quantitative
elementary analyses were performed on a vario Micro cube
(Elementar Analyensysteme GmbH, Langenselbold, HE,
Germany). Melting points (m.p.) were measured by the
BOETIUS method on a heating apparatus from VEB Analytik
3. CONLUSIONS
In summary, we have demonstrated that the claimed synthesis
of N-azidodimethylamine (2b)[9] led in actual fact to the
known[19] (azidomethyl)dimethylamine (13). The dangerous
properties reported[9b] for even small amounts of alleged 2b
should be considered, when explosive 13 is handled, because
distillation of 13 on multigram scale at normal pressure (b.p.
108–110 °C) was published[19a] without giving any hazard note.
Our additional experiments with diazo group transfer to lithium
hydrazides show that intermediate N-azidoamines cannot be
detected directly or trapped with the help of cyclooctyne.
Consequently, such azides are very short-lived or their
formation is bypassed by direct generation of 1,1-diazenes via
synchronous cleavage of two N–N bonds.
9
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21
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Dresden
74/0032.
PHMK
N,N-Dimethylamine. Into a 50-mL-two-necked flask, N,N-
dimethylamine hydrochloride (5.3 g, 65.0 mmol) suspended in
DCM (15 mL) was placed, and fine-powdered KOH (10.0 g,
180.0 mmol, 2.7 eq.) was slowly added in portions to hold the
temperature between –15 °C and –5 °C. After stirring for 1 h,
filtration led to a colorless solution of N,N-dimethylamine (14%
in DCM (calculated via NMR spectroscopy), 2.6 g N,N-
4. EXPERIMENTAL SECTION
General. CAUTION! All experiments dealing with the
synthesis of small N-chloroamines and/or small azides should
be done with extra safety arrangements, because of their
potential explosive character. Extra safety arrangements
include a safety windowpane and shatter protection gloves.
Isolation of highly explosive compounds should be avoided,
always handle such substances in diluted solutions.
Furthermore, the interaction of chlorinated solvents like DCM
with azide salts carry the risk of the formation of highly
explosive organic azides such as diazidomethane.
1
dimethylamine, 58.5 mmol, yield: 90%). H NMR (400 MHz,
CDCl3, 25°C): δ [ppm] = 1.39 (s, 1H, HN(CH3)2), 2.41 (s, 6H,
HN(CH3)2). 13C{1H} NMR (100.6 MHz, CDCl3, 25 °C): δ
[ppm] = 38.6 (q, HN(CH3)2).
N-Chloro-N,N-dimethylamine (1b).[9]Method A: Into a 25-
mL-two-necked flask, a solution of N,N-dimethylamine in
DCM (12%, 0.34 g N,N-dimethylamine, 4.0 mmol) was placed,
and NCS (1.06 g, 8.0 mmol, 2 eq.) was added in small portions
to keep the temperature between –15 °C and –5 °C. After
stirring for 5 h, volatile components were recondensed at
RT/6.8 · 10–3 mbar with the help of an U-tube-apparatus. The
condensate was dried over MgSO4. Filtration led to a colorless
solution of 1b in DCM (11% in DCM (calculated via NMR
spectroscopy), 0.28 g N-chloro-N,N-dimethylamine (1b), 3.5
mmol, yield: 88%). Method B: Into a 250-mL-two-necked
flask, N,N-dimethylamine hydrochloride (10.0 g, 120 mmol)
suspended in DCM (20 mL) was placed and cooled to –15 °C.
A solution of sodium hypochlorite (13%, 140 mL, 240 mmol, 2
eq.) was added dropwise to hold the temperature beneath 0 °C.
After stirring for 1 h, the phases were separated, and the
aqueous phase was extracted with DCM (5 x 20 mL). The
combined organic phases were washed with 1 N sulfuric acid (2
x 40 mL) and dried over Na2SO4 or MgSO4. Filtration led to a
solution 1b in DCM (1.83% (calculated via NMR
spectroscopy), 4.3 g N-chloro-N,N-dimethylamine (1b), 54
All reactions dealing with air- or moisture-sensitive compounds
were carried out in a dry reaction vessel under a positive
pressure of nitrogen. Air- and moisture-sensitive liquids and
solutions were transferred via a syringe. All reactions were
carried out with freshly distilled, in some cases, dry solvents.
Anhydrous solvents were distilled immediately before use.
Dimethylamine hydrochloride, NCS, trisyl chloride, and nBuLi
(2.5 M in hexanes) were obtained commercially from Acros
Organics (Belgium). Prenyl bromide, hexahydro-1,3,5-
trimethyl-1,3,5-triazine (7), and 1,1-diphenylhydrazine
hydrochloride were obtained commercially from Sigma-
Aldrich (Germany). N,N-Dibenzylhydrazine (3c) was obtained
commercially from TCI (Germany). Tosyl chloride,
benzyltrimethylammonium
dimethylhydrazine were obtained commercially from Merck
KGaA (Germany). Methylhydrazine was obtained
commercially from Fluka (Germany). QN3[21], Cyclooctyne[34]
chloride,
and
N,N-
,
[37]
[38]
TsN3 [35], TrisylN3[36], NfN3
and activated NaN3 were
prepared according to reported literature.
1
mmol, yield: 45%). H NMR (400 MHz, CDCl3, 25 °C): δ
NMR spectra were recorded with a UNITY INOVA 400 FT
spectrometer (Varian Inc., Palo Alto, CA, USA) operating at
400 MHz for 1H NMR and 100.6 MHz for 13C NMR;
ULTRASHIELD 500 FT spectrometer (Bruker Corp., Billerica,
MA, USA) operating at 500 MHz for 1H NMR and 125.8 MHz
for 13C NMR; ASCEND 600 FT spectrometer (Bruker Corp.,
[ppm] = 2.91 (s, ClN(CH3)2). 13C{1H} NMR (100.6 MHz,
CDCl3, 25 °C): δ [ppm] = 54.9 (qq, 1JC,H = 137.3 Hz, 3JC,H = 5.5
Hz, ClN(CH3)2).
Reaction of 1b with NaN3.9 To a solution of N-chloro-N,N-
dimethylamine (1b) in DCM (2.9%, 1 g, 12.6 mmol 1b) was added
sodium azide (0.8 g, 12.6 mmol, 1 eq.) in a flask connected with a
pneumatic apparatus. The mixture was stirred for 24 h cooled by
1
Billerica, MA, USA) operating at 600 MHz for H NMR and
150.9 MHz for 13C NMR. 1H NMR and 13C NMR signals were
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water bath at RT. After 24 h the reaction mixture was filtered and
with water/THF (0.1 mL/0.5 mL) when the temperature reached
–20 °C. 21 (107.0 mg, 0.95 mmol, yield: 53%, calculated by
internal naphthalene standard) was gained after filtration in
THF/hexanes with 20 and some further unknown impurities. 1H
NMR (400 MHz, CDCl3, 25 °C): δ [ppm] = 1.31 (s, 6H, (H3C)2–
C–), 3.76 (s, 3H, H3C–N=N–), 5.10–5.17 (m, 2H, H2C=CH–),
5.98 (dd, 3J = 17.8 Hz, 3J = 10.5 Hz, 1H, H2C=CH–). 13C{1H}
NMR (100.6 MHz, CDCl3, 25 °C): δ [ppm] = 24.5 (q, (H3C)2–
C–), 57.0 (q, H3C–N=N–), 71.0 (s, (H3C)2–C–), 113.3 (t,
H2C=CH–), 143.0 (d, H2C=CH–).
1
2
3
4
5
6
7
8
analyzed by NMR spectroscopie without futher purification,
obtaining a mixture of 8b (26%), 9 (33%), 11 (22%) and 13 (16%)
in DCM.14,15
Methylmethyleneimine (6).[25a] Note: We used the method
described in ref.[25a] since other procedures to prepare 6 (see
literature [25 b-e]) were less successful in our hands. In a vacuum
apparatus (see SI on page S3), N-methylaminoacetonitrile (2
mL, 1.84 g, 26 mmol) was evaporated at 60 °C/ 4·10–2 mbar
through a glass tube (Ø 1 cm, l = 30 cm) over a bed of KOtBu.
The gas flow passed then a first cooling trap cooled with
EtOH/N2(liq.) at –85 °C and was then recondensed on a cooling
finger cooled with liquid nitrogen. On the cooling finger, DCM
(3 mL) was beforehand recondensed. After completion of the
recondensation, the apparatus was ventilated with dry argon,
and warming of the recondensed DCM/6-mixture was realized
with an EtOH/N2(liq.)-bath at –85 °C. This method led to a
solution (7%) of 6 in DCM. The transfer (fast!) into a pre-
cooled (–90 °C, [D2]-DCM) NMR tube was executed with a
pipette pre-cooled in liquid nitrogen. 1H NMR (600 MHz, [D2]-
DCM, –80 °C): δ [ppm] = 3.23 (s, 3H, H2C=N–CH3), 7.00–7.10
(m, 1H, H2C=N–CH3), 7.30–7.40 (m, 1H, H2C=N–CH3).
13C{1H} NMR (150.9 MHz, [D2]-DCM, –80 °C): δ [ppm] =
50.0 (q, H2C=N–CH3), 154.9 (t, H2C=N–CH3).
9
1,3,5-Trimethyl-2,3,4,5-tetrahydro-1,3,5-triazin-1-ium
chloride.[17] To a solution of 7 (2.2 mL, 2 g, 15.5 mmol) in DCM
(10 mL), cooled with a water bath to RT, NCS (2.5 g, 18,5
mmol, 1.2 eq.) was added in small portions. The mixture was
stirred overnight and then filtered. Removing the solvent at a
rotary evaporator led to a pale yellow oil. The crude product
was then washed in a flask several times with DME (aprox. 10
times) with the help of an ultrasonic bath to remove succinimide
and then 4 times with Et2O. Removing the solvents was done
each time by decantation, and after the last washing step drying
was done at reduced pressure (ventilation with dry Ar!). 9 was
gained as a white, strongly hygroscopic solid (1.03 g, 6.3 mmol,
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yield: 41%). H NMR (600 MHz, CDCl3, 25 °C): δ [ppm] =
2.55 (s, 3H, –CH2–N(CH3)–CH2–), 3.23 (s, 6H, –CH–N–CH3),
N-Methyl-N-prenylhydrazine (3d).[29] In a 50-mL-two-
necked flask, methylhydrazine (3.7 g, 4.2 mL, 80 mmol, 6 eq.)
was emulsified in pentane (10 mL) and at –15 °C with strong
stirring treated with prenyl bromide (2.0 g, 1.55 mL, 13 mmol)
in hexanes (10 mL). The solution was stirred at this temperature
for 4 h and then treated with fine-powdered KOH (5 g, 90
mmol). After adding the base, the solution was stirred for at
least 1 h and then filtered. The insoluble salts were then
extracted with Et2O and the combined organic phases were
dried over MgSO4. Removing the solvents on a rotary
evaporater led to a pale yellow liquid of N-methyl-N-(3-
methylbut-2-en-1-yl)hydrazine (3d, 1.37 g, 12 mmol, yield:
92%). 1H NMR (400 MHz, CDCl3, 25 °C): δ [ppm] = 1.65 (s,
3H, (Z)-H3C–C=), 1.73 (s, 3H, (E)-H3C–C=), 2.43 (s, 3H, H3C–
N–), 2.73 (br, 2H, –NH2), 3.05 (d, 2H, 3J = 7.1 Hz, –CH2–N–),
5.25 (m, 1H, –C=CH–). 13C{1H} NMR (100.6 MHz, CDCl3, 25
°C): δ [ppm] = 18.1 (q, (Z)-H3C–C=), 25.9 (q, (E)-H3C–C=),
48.4 (q, H3C–N–), 61.0 (t, –C=CH–CH2–), 120.1 (d, –C=CH–),
136.5 (s, –C=CH–).
N-Chloro-N-methylprenylamine (1d). To a solution of N-
methyl-N-prenylamine (1 g, 10 mmol, traces of Et2O from
synthesis)[33] in DCM (10 mL), NCS (1.48 g, 11 mmol, 1.1 eq.)
was added at –20 °C and stirred for 1 h at –10 °C.
Recondensation at RT/6.8 · 10–2 mbar led to a colorless solution
of 1d in DCM (6.8%, 0.98 g 1d, 7.3 mmol, yield: 73%) 1H NMR
(500 MHz, CDCl3, 25 °C): δ [ppm] = 1.68 (s, 3H, (Z)-H3C–C=),
1.76 (s, 3H, (E)-H3C–C=), 2.89 (s, 3H, H3C–N–), 3.52 (d, 2H,
3J = 6.8 Hz, –CH2–N–), 5.30 (m, 1H, –C=CH–CH2–). 13C{1H}
NMR (125.8 MHz, CDCl3, 25 °C): δ [ppm] = 18.2 (q, (Z)-H3C–
C=), 25.9 (q, (E)-H3C–C=), 51.6 (q, H3C–N–), 63.4 (t, –C=CH–
CH2–), 119.7 (d, –C=CH–CH2–), 137.8 (s,–C=CH–CH2–).
HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C6H13NCl
134.0731; Found: 134.0731.
4.26 (s, 4H, –CH2–), 9.23 (s, 1H, –CH=). 13C{1H} NMR (150.9
1
MHz, CDCl3, 25 °C): δ [ppm] = 39.5 (qm, JCH = 140.6 Hz, –
1
3
CH–N–CH3), 40.4 (qquin, JCH = 136.2 Hz, JCH = 5.2 Hz, –
CH2–N(CH3)–CH2–), 66.9 (tm, 1JCH = 156.2 Hz, –CH2–), 153.5
(dm, JCH = 198.9 Hz, –CH=). Note: Using NBS (3.31 g, 18.5
1
mmol, 1.2 eq.) instead of NCS as oxidizing reagent led to the
corresponding bromide (2.31 g, 11.1 mmol, yield: 72%).
(E)-1-(Cyclooct-1-en-1-yl)-4,5,6,7,8,9-hexahydro-1H-
cycloocta-1,2,3-triazole (15). A HN3 solution (1.53 M in
CDCl3, 0.70 mL, 1 eq.) was treated with cyclooctyne (230 mg,
2.14 mmol, 2 eq.) at 0 °C. Within 1 h, the solution was allowed
to warm up to RT and was then stirred for additional 24 h. The
solvent and unreacted HN3 were then removed in vacuum to get
15 as a colorless oil (202 mg, 0.78 mmol, yield: 73%).1H NMR
(400 MHz, CDCl3, 25 °C): δ [ppm] = 1.40–1.52 (m, 4H), 1.58–
1.80 (m, 12H), 2.25–2.35 (m, 2H), 2.53–2.64 (m, 2H), 2.70–
2.80 (m, 2H), 2.84–2.94 (m, 2H), 5.74 (t, 3JC,H = 8.5 Hz, 1H, –
CH2–CH=C–). 13C{1H} NMR (100.6 MHz, CDCl3, 25 °C): δ
[ppm] = 22.0 (t), 24.4 (t), 25.3 (t), 25.5 (t), 26.0 (t), 26.1 (t), 26.1
(t), 27.7 (t), 28.0 (t), 28.2 (t), 29.3 (t), 30.2 (t), 128.4 (d, –CH2–
CH=C–), 133.0 (s), 137.0 (s, –CH2–CH=C–), 144.2 (s). An
assignment of all CH2 signals was not possible. HRMS (ESI-
TOF) m/z: [M + H]+ Calcd for C16H26N3 260.2121; Found:
260.2128. EA: Anal. Calcd for C16H25N3: C, 74.09; H, 9.71.
Found: C, 73.77; H, 9.87.
1-(4,5,6,7,8,9-Hexahydro-2H-cycloocta-1,2,3-triazol-2-yl)-
N,N-dimethylmethanamine (16). Into a 25-mL-flask, cooled
with H2O to RT, a solution of 13 in Et2O (12.3%, 1.0 g N-
azidomethyl-N,N-dimethylamine (13), 10.0 mmol)[19e] was
slowly treated with cyclooctyne (1.5 mL, 1.3 g, 12.0 mmol, 1.2
eq.) and stirred overnight. Volatile components were then
removed in vacuum, and the residue was worked up via flash
chromatography (silica 60, eluent: ethyl acetate, RF = 0.31). 16
was gained as a colorless oil (1.9 g, 9.1 mmol, yield: 91%). 1H
NMR (400 MHz, CDCl3, 25 °C): δ [ppm] = 1.44 (m, 4H, –N–
C–CH2–CH2–CH2–), 1.72 (m, 4H,–N–C–CH2–CH2–CH2–),
2.34 (s, 6H, (H3C)2N–), 2.80 (m, 4H, –N–C–CH2–), 5.02 (s,
2H,–N–CH2–). 13C{1H} NMR (100.6 MHz, CDCl3, 25 °C): δ
[ppm] = 23.6 (tm,1JC,H = 127 Hz, –N–C–CH2–CH2–CH2–), 25.4
(E)-1-Methyl-2-(2-methylbut-3-en-2-yl)diazene (21).[29] To
a solution of 3d (0.2 g, 1.8 mmol) in dry THF (1 mL) nBuLi (2.5
M in hexanes, 1.1 mL, 3.4 mmol, 1.5 eq.) was added at –78 °C.
The mixture was stirred for 1 h and then treated with trisyl azide
(0.6 g, 1.9 mmol, 1.1 eq) in dry THF (1 mL) at –78 °C. The
suspension was then stirred for another 1 h and finally treated
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Page 6 of 8
(tm, 1JC,H = 123 Hz, –N–C–CH2–CH2–CH2–), 28.8 (tm, 1JC,H
=
T.P. made the experimental work and the Supporting Information,
and K.B. wrote the manuscript.
1
1
2
3
4
5
6
7
8
125 Hz, J, –N–C–CH2–CH2–CH2–), 42.2 (qm, JC,H = 134 Hz,
(H3C)2N–), 75.1 (tm, 1JC,H = 152 Hz, –N–CH2–), 146.0 (s, –N–
C–CH2–). HRMS (ESI-TOF) m/z: [M − H]+ Calcd for C11H19N4
207.1604; Found: 207.1609.
Notes
The authors declare no competing financial interest.
1-((2,4,6-Triisopropylphenyl)sulfonyl)-4,5,6,7,8,9-
hexahydro-1H-cycloocta-1,2,3-triazole (22). In a 10-mL-flask,
cooled with NaCl/ice/water, trisyl azide (0.5 g, 1.6 mmol) was
dissolved in THF (3 mL) and slowly treated with cyclooctyne
(0.25 g, 2.4 mmol). After stirring for 1 h, all volatile
components were removed under reduced pressure. After TLC
(silca 60, eluent: hexanes:Et2O = 5:1), 22 was gained as a white
ACKNOWLEDGMENTS
We thank Dr. Christian Berndt for the synthesis of 15, Dr. Manfred
Hagedorn for his assistance with NMR measurements, and Dr.
Andreas Ihle for his help with preparing the manuscript.
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1
DEDICATION
solid (0.65 g, 1.6 mmol, yield: 100%). H NMR (400 MHz,
CDCl3): δ [ppm] = 1.16 (d, 12H, 3J = 6.6 Hz, ortho–CH(CH3)2),
1.26 (d, 6H,3J = 6.7 Hz, para–CH(CH3)2), 1.36–1.45 (m, 4H, –
CH2–), 1.68–1.75 (m, 4H, –CH2–), 2.85–2.88 (m, 2H,–CH2–),
2.93 (sept, 1H, 3J = 6.7 Hz, para–CH(CH3)2), 3.01–3.05 (m, 2H,
–CH2–), 4.01 (sept, 2H,3J = 6.6 Hz,ortho–CH(CH3)2), 7.22 (s, 2H,
–CHaromat.–). 13C{1H} NMR (100.6 MHz, CDCl3): δ [ppm] =
This work is dedicated to Professor Ernst Schaumann on the
occasion of his 75th birthday.
REFERENCES
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21.6 (t, –C–CH2–), 23.4 (q, para–CH(CH3)2), 24.4 (q,ortho
–
CH(CH3)2), 24.5 (t,–CH2–), 24.9 (t, –C–CH2–), 25.6 (t,–CH2–),
26.5 (t,–CH2–), 28.7 (t,–CH2–), 29.8 (d, ortho–CH(CH3)2), 34.3
(d, para–CH(CH3)2), 124.3 (d, –CHaromat.–), 129.7 (s, –C–SO2–),
134.5 (s,–C–CH2–), 145.7 (s, –C–CH2–), 152.5 (s, –C–C–SO2–
), 155.8 (s, –CH–C–CH–). m.p.: 94–95 °C. HRMS (ESI-TOF)
m/z: [M + H]+ Calcd for C23H36N3O2S 418.2523; Found:
418.2538.
N',N'-Dibenzyl-4-methylbenzenesulfonohydrazide.[27] In a
50-mL-flask, a mixture of triethylamine (2.91 mL, 2.12 g, 21
mmol, 1 eq.), tosyl chloride (4 g, 21 mmol, 1 eq.), and 1,1-
dibenzylhydrazine (4.45 g, 21 mmol, 1 eq.) in DCM (30 mL)
was refluxed for 4 h and then stirred overnight. The resulting
solution was then washed with 10% HCl (4 x 20 mL), water (4
x 20 mL) and then dried over MgSO4. After removing the
solvent, the desired product was gained after flash
chromatography (silica 60, eluent: petrol ether/DCM/NEt3 =
13/6/1, RF = 0.53) as a beige solid (4.85 g, 13.2 mmol, yield:
1
63%) with small impurities. H NMR (400 MHz, CDCl3): δ
[ppm] = 2.41 (s, 3H, –Carom.–CH3), 3.74 (s, 4H, –CH2–), 5.60 (s,
1H, –NH–), 7.15–7.21 (m, 6H), 7.25–7.30 (m, 6H), 7.74 (d, 2H,
J = 8.3 Hz). 13C{1H} NMR (100.6 MHz, CDCl3): δ [ppm] = 21.5
(q, –Carom.–CH3), 59.8 (t, –CH2–), 127.6 (d), 128.2 (d), 128.4
(d), 129.3 (d), 129.7 (d), 135.0 (s), 135.4 (s), 143.5 (s).
(7) (a) Holfter, H.; Klapötke, T. M.; Schulz, A. PREPARATION OF
ASSOCIATED CONTENT
Supporting Information
THE FIRST IMINODISULFURYLAZIDE:
A
NITROGEN
BOUND COVALENT AZIDE CONTAINING AN N4 UNIT.
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SYNTHESE UNSYMMETRISCHER TRIAZACARBOCYANINE
AUS AZIDINIUMSALZEN UND 2-DIAZO-AZO-3-ÄTHYL-
BENZTHIAZOLIN. Justus Liebigs Ann. Chem. 1963, 663, 103−107.
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Meng, Z.-Y.; Zhao, F.-Q.; Ju, X.-H. Density functional study of
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performance, and decomposition mechanism of four azidoazoles.
Struct. Chem. 2015, 26, 1077−1082. (g) Zamani, M.; Keshavarz, M.
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The Supporting Information is available free of charge on the ACS
Publications website.
Experimental details for new reactions and printed IR and
NMR spectra (PDF)
AUTHOR INFORMATION
Corresponding Author
* E-mail: klaus.banert@chemie.tu-chemnitz.de.
ORCID
Klaus Banert: 0000-0003-2335-7523
Author Contributions
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The Journal of Organic Chemistry
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explosive properties. After addition of toluene, which has a similar
boiling point, distillation under reduced pressure is possible.
(23) Alternative synthesis of 1-amino-1H-1,2,3-triazoles, see: (a) Bennett,
I. S.; Brooks, G.; Broom, N. J. P.; Calvert, S. H.; Coleman, K.;
9
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METHYLENE)PENEMS,
POTENT BROAD SPECTRUM INHIBITORS OF BACTERIAL β-
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Verbindungen der 1.2.3-Triazole. Liebigs. Ann. Chem. 1968, 716,
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Schmid, K. H. N-HALOGEN-SILYLAMINE III. ZUR CHEMIE
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N-HALOGEN-HEXAMETHYLDISILAZANE.
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(14) We performed these experiments about 40 times using CH2Cl2 with
different proportions of water (from anhydrous to saturated with
water). Precursor 1b was prepared from dimethylamine and NaOCl
or NCS or from dimethylamine hydrochloride and NaOCl. Normal
NaN3 or activated NaN3 were utilized.
(26) For comparison, we also prepared this amidinium chloride from 7
and NCS (1.0 equiv) in 41% isolated yield.
(27) Emmett, E. J.; Richards-Taylor, C. S.; Nguyen, B.; Garcia-Rubia, A.;
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(28) We prepared this tosyl hydrazide from 3c and tosyl chloride with
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(29) Baldwin, J. E.; Brown, J. E.; Höfle, G. Sigmatropic Rearrangements
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(15) For details, see the Supporting Information.
(16) For comparison, we prepared 8b and 11 from HN3 and
dimethylamine
respectively.
or
known[18]
N,N,N'-trimethylformamidine,
(17) For an alternative procedure to prepare the corresponding chloride,
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metal monohydrides. Chem. Sci. 2012, 3, 1300–1303.
(18) Bredereck, H.; Effenberger, F.; Simchen, G. Synthese von N.N.N´-
Trimethyl-formamidin und Bis-dimethyl-amino-methoxy-methan
(Aminalester). Chem. Ber. 1964, 98, 1078–1080.
(19) (a) Böhme, H.; Morf, D. Azidomethyl-amine und Azidomethyl-
ammoniumsalze. Chem. Ber. 1958, 91, 660–662. (b) Altova, E. P.;
Nabiev, O. G.; Karasev, N. M.; Kostyanovsky, R. G.; Khaikin, L. S.;
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dimethylamine according to gas-phase electron diffraction data and
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Cyanomethylamines and azidomethylamines: new general methods
(30) For
comparison,
we
prepared
22
from
2,4,6-
triisopropylbenzenesulfonyl azide and cyclooctyne in quantitative
yield.
(31) Banert, K.; Hagedorn, M.; Wu, Z.; Zeng, X. Synthesis,
Characterization and Reactions of (Azidoethynyl)trimethylsilane.
Molecules 2015, 20, 21328–21335.
(32) We prepared 1d from the known[33] secondary amine and NCS in
73% yield.
(33) Doyle, M. P.; Kalinin, A. V. Highly Enantioselective Intramolecular
Cyclopropanation Reactions of N-Allylic-N-methyldiazoacetamides
Catalyzed by Chiral Dirhodium(II) Carboxamidates. J. Org. Chem.
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(34) Tietze, L. F.; Eicher, T. Reaktionen und Synthesen im organisch-
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(35) Keipour, H.; Jalba, A.; Delage-Laurin, L.; Ollevier, T. Copper-
Catalyzed Carbenoid Insertion Reactions of α-Diazoesters and α-
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Aeruginosin Serine Protease Inhibitors through the Nucleophilic
(37) Yang, T.; Zhuang, H.; Lin, X.; Xiang, J.-N.; Elliott, J. D.; Liu, L.;
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