Push-pull triazenes derived from 1-(benzylideneamino)- and 1-(sulfonimido)-azolylidenes

Article abstract of DOI:10.1021/jo302697q

In-situ-generated neutral 1-(benzylideneamino)- and novel anionic 1-(sulfonimido)-azolylidenes react with organic azides to afford diverse classes of push-pull triazenes and triazene salts. The scope of the heterocyclic core and substituents at the N1 and

Full text of DOI:10.1021/jo302697q

Note
pubs.acs.org/joc
Push-Pull Triazenes Derived from 1‑(Benzylideneamino)- and
1‑(Sulfonimido)-azolylidenes
Davit Jishkariani,§ C. Dennis Hall,§ Aydin Demircan,§,∥ Blake J. Tomlin,§ Peter J. Steel,‡
and Alan R. Katritzky*,§,⊥
§Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United
States
∥Department of Chemistry, Nigde University, 51240 Nigde, Turkey
‡University of Canterbury, Christchurch, New Zealand
⊥Department of Chemistry, King Abdulaziz University, Jeddah 21589, Saudi Arabia
S
* Supporting Information
ABSTRACT: In-situ-generated neutral 1-(benzylideneamino)-
and novel anionic 1-(sulfonimido)-azolylidenes react with
organic azides to afford diverse classes of push-pull triazenes
and triazene salts. The scope of the heterocyclic core and
substituents at the N1 and N3 positions of NHC precursors
together with the thermal properties of resulting compounds
were examined.
he unique properties of compounds containing a triazene
linkage such as stability and adaptability to numerous
Synthetic methodologies reported for triazenes include: (i)
coupling of amines with aryl diazonium salts,24,25 (ii) addition
of organometallic reagents (RMgX, RLi, etc.) to organic
azides,26,27 and (iii) the reaction of N-heterocyclic carbenes
(NHCs) or their dimers with organic azides.22,28−31 Methods
(i) and (ii) are usually employed for the synthesis of Type II
triazenes, whereas Type I triazenes are produced by method
(iii).
While triazenes of Type II are numerous and extensively
investigated,1 surprisingly little is known about Type I
compounds. Herein, we report the synthesis, reactivity, and
thermal properties of push-pull triazenes derived from 1-
aminobenzimidazolium and 4-amino-1,2,4-triazolium salts,
from 1,3-dialkylbenzimidazolium and 1,3-dialkylimidazolium
salts and from 1,2,4-triazolium N-imides with diverse symmetric
or asymmetric N-substitution via in situ formation of neutral
and novel anionic NHCs. This method has significant
advantages in terms of safety, atom economy, and reaction
simplicity together with tolerance toward a broad array of
functional groups and structural variations.22,31−35 We found no
literature reports for the synthesis of such derivatives and
therefore investigated the substrate scope with respect to
substitution in the ring and at N1 and N3 together with the
chemical and electronic properties of the resultant Type I
triazenes.
T
synthetic transformations1 have encouraged current interest.
Triazenes have been utilized as masking groups,2,3 alkylating
agents for DNA,4,5 protecting groups for amines and diazonium
salts,6,7 photoactive materials,8 building blocks for the synthesis
of various phenylacetylene-based systems,1 ligands for tran-
sition metals,1,9 and intermediates for the synthesis of diverse
heterocycles including 1,2,3,5-tetrazinones, triazoles, benzotria-
zoles,10−12 cinnolines, isoindazoles,13,14 benzotriazinones,15,16
and azolium salts.17−19
Most triazenes are of Type I or II (Figure 1). In Type I
triazenes, the subject of this paper, the triazene group
Figure 1. Types of triazenes.
terminates with a CN double bond carrying electron-
donating substituents, which thus allows direct conjugation
through the triazene linkage (Figure 1).20 Type I triazenes are
also called “push-pull” or “donor-acceptor” triazenes.20,21
Earlier reports demonstrated that the presence of electron-
donating and electron-withdrawing groups on opposite sides of
donor-acceptor triazenes enhances the electronic communica-
tion even further.21−23 Although such Type I triazenes are
interesting chromophores for electronic applications,20 liter-
ature reports are limited to imidazole and benzimidazole
moieties with symmetric N-alkyl substituents.22
1-Benzylidineamino-3-alkyl-1,2,4-triazolium iodides 3a,b and
1-benzylidineamino-3-alkylbenzimidazolium iodides 3c−e were
prepared according to methodology previously described by
our group.36 Condensation of 4-amino-1,2,4-triazole 1a or 1-
Received: December 11, 2012
© XXXX American Chemical Society
A
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amino-benzimidazole 1b with various aromatic aldehydes,37
generated imines 2a−e in 79−98% yields. Quaternization of
imines 2a−e with the corresponding alkyl halides gave the
desired 1,2,4-triazolium 3a,b and benzimidazolium salts 3c−e
in near quantitative yields (Table 1).
chloride 4c were selected as model examples of symmetrically
and asymmetrically substituted N-alkyl azoles. 1,3-Dibenzyl-
benzimidazolium bromide 4a and 1-butyl-3-methyl-benzimida-
zolium iodide 4b were generated from commercially available
1H-benzimidazole in one- and two-step literature proce-
dures,38,39 while 1-butyl-3-methylimidazolium chloride 4c was
commercially available.
Table 1. Synthesis of 1,2,4-Triazolium and Benzimidazolium
Deprotonation of azolium halides 3a−e and 4a−c using
potassium tert-butoxide generated NHCs, which by reaction
with 1-azido-4-nitrobenzene 5 at −78 °C formed the
corresponding donor-acceptor triazenes 6a−h in 67−88%
yields (Table 2), all isolated by crystallization. The structures
of representative triazenes, 6d and 6f, were confirmed by single
crystal X-ray diffraction. X-ray crystal data revealed that in 6d
the carbon-nitrogen double bond of the triazene linkage adopts
an E geometry and the terminal nitrogen is hydrogen-bonded
to a molecule of methanol (see Supporting Information). On
the basis of this finding, E geometry was assigned to a carbon-
nitrogen double bond of similar systems.
The in situ generation of novel anionic NHCs 8a−d was
effected by the deprotonation of 1,2,4-triazolium N-imides 7a−
d with potassium tert-butoxide. The reaction of 8a−d with 1-
azido-4-nitrobenzene 5 generated the corresponding triazene
potassium salts 9a−d in 79−95% yields.
In addition, we examined the reactivity of the novel triazene
6f and salt 9a with various electrophiles. Given their push-pull
character, triazenes are expected to have increased electron
density on the terminal nitrogen of the triazene linkage
(Scheme 1). Our findings supported this argument. The
reaction of 6f with methyl iodide gave triazenium iodide 10
where the methyl group is located on the terminal nitrogen.
Salts 3a−e
R
Y
R1
reagent
product (%)
CH3O
Et2N
H
N
N
1a
1a
1b
1b
1b
2a
2c
2d
2e
2f
2a (95)
2b (98)
2c (94)
2d (92)
2e (79)
3a (99)
3b (99)
3c (99)
3d (99)
3e (99)
C-(CHCH)2-
C-(CHCH)2-
C-(CHCH)2-
N
CH3O
NO2
CH3O
Et2N
H
Me
Me
Bu
Bu
Bu
N
C-(CHCH)2-
C-(CHCH)2-
C-(CHCH)2-
CH3O
NO2
1,3-Dibenzyl-benzimidazolium bromide 4a, 1-butyl-3-methyl-
benzimidazolium iodide 4b, and 1-butyl-3-methylimidazolium
Table 2. Synthesis of Donor-Acceptor Triazenes
B
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Table 3. Synthesis of Donor-Acceptor Triazene Salts via Novel Anionic NHCs
novel classes of donor-acceptor triazenes in high yield and
purity. Furthermore, a novel class of anionic NHCs was
generated, and their reactivity was explored in the preparation
of push-pull triazenes. The chemical properties of triazenes
proved that the push-pull nature of triazenes increased the
electron density on the terminal nitrogen. X-ray analysis of key
products revealed the double bond geometry of the terminal
double bond of the triazene linkage. Thermal analysis of
selected targets by TGA demonstrated potential usefulness as
blowing agents.
Scheme 1. Reactivity of Push-Pull Triazenes
EXPERIMENTAL SECTION
■
Materials and Methods. All reactions were performed in single-
neck round-bottom flasks fitted with rubber septa under positive
nitrogen pressure. Solvents were freshly distilled and degassed.
Reaction progress was monitored by thin-layer chromatography
(TLC) and visualized by UV light. Melting points were determined
on a capillary point apparatus equipped with a digital thermometer and
are uncorrected. NMR spectra were recorded in CDCl3 or DMSO-d6
with TMS for 1H (300 MHz) and 13C (75 MHz) as an internal
reference. Compounds 1b, 2c−e, 3c−e, and 7a−d were prepared
according to literature procedures reported earlier by our group.36,41 4-
Amino-1,2,4-triazole 1a and 1-butyl-3-methylimidazolium chloride 4c
were purchased from Sigma-Aldrich and used without further
purification. 1-Azido-4-nitrobenzene 5 was prepared in one step
according to a literature procedure.42 Elemental analyses were
performed on a Carlo Erba EA 1108 instrument.
The structure of 10 was unambiguously confirmed by X-ray
crystallography (see Supporting Information). Reaction of 9a
with 1 NHCl, methyl iodide, and benzyl bromide, however,
resulted in the formation of neutral compounds 11a−c;
evidently the sulfonamide moiety is the most nucleophilic
center of 9a. The spectra of 11b and 11c were identical to those
obtained by the reaction of 1-azido-4-nitrobenzene 5 with 1,2,4-
triazolium salts 12a and 12b under basic conditions (Scheme
1).
Exploration of the thermal properties of 9a−d and 11a by
TGA revealed their exceptional thermal stability. Most
compounds were found to be stable at temperatures over 200
°C. Compounds 11a and 9d, however, showed sharp
decomposition at 176 and 251 °C, losing 22% and 54% of
their mass over 1 and 2 min, respectively (Figure 2). Such rapid
decomposition at high temperatures could make these
compounds promising blowing agents for energetic formula-
tions.40
General Method for the Preparation of Imines 2a,b. 4-
Amino-1,2,4-triazole (4.2 g, 50 mmol) and the corresponding aldehyde
(1.05 equiv) were dissolved in absolute ethanol (50 mL) and stirred
under reflux in the presence of a catalytic amount of conc sulfuric acid.
After 5 h, the reaction mixture was cooled to room temperature and
concentrated under reduced pressure, and the residue was recrystal-
lized from EtOAc/hexanes to obtain pure 2a−e.
(E)-N-(4-Methoxybenzylidene)-4H-1,2,4-triazol-4-amine
(2a).43 White crystals (9.6 g, 95%), mp 164−165 °C (lit.43 mp 164
1
°C); H NMR (CDCl3) δ 8.59 (s, 2H), 8.52 (s, 1H), 7.80 (d, J = 9.3
Hz, 2H), 7.01 (d, J = 9.0 Hz, 2H), 3.90 (s, 3H); 13C NMR (CDCl3) δ
163.4, 156.7, 138.2, 130.7, 124.1, 114.7, 55.6. Anal. Calcd For
C10H10N4O: C, 59.40; H, 4.98; N, 27.71. Found: C, 59.57; H, 5.34; N,
27.96.
(E)-N-(4-(Diethylamino)benzylidene)-4H-1,2,4-triazol-4-
amine (2b).44 Green crystals (11.9 g, >98%), mp 176−180 °C; H
1
NMR (DMSO-d6) δ 9.04 (s, 2H), 8.81 (s, 1H), 7.64 (d, J = 8.7 Hz,
2H), 6.77 (d, J = 9.0 Hz, 2H), 3.42 (q, J = 7.0 Hz, 4H), 1.13 (t, J = 6.9
Hz, 6H); 13C NMR (DMSO-d6) δ 158.1, 150.3, 138.7, 130.4, 118.0,
111.0, 43.8, 12.3.
In conclusion, in situ generated 1-(benzylideneamino) and 1-
(sulfonimide) azolylidenes react with organic azides to afford
C
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Figure 2. TGA data for 9a−d and 11a.
General Method for the Preparation of Benzimidazolium
and 1,2,4-Triazolium Salts 3a,b. A mixture of iodomethane (3
equiv) and the corresponding imines 2a,b (2.0 g) was stirred without
solvent under reflux. After 5 h, excess iodomethane was removed
under reduced pressure to give pure salts 3a,b in near quantitative
yields.
N,N-Diethyl-4-((E)-(((E)-1-methyl-5-((E)-(4-nitrophenyl)triaz-
2-en-1-ylidene)-1,5-dihydro-4H-1,2,4-triazol-4-yl)imino)-
methyl)aniline (6b). Purple crystals (0.18 g, 68%), mp 305−307 °C;
1H NMR (CDCl3) δ 8.99 (s, 1H), 7.99 (d, J = 9.3 Hz, 2H), 7.81 (d, J
= 8.7 Hz, 2H), 7.25 (d, J = 9.6 Hz, 2H), 6.77 (d, J = 9.0 Hz, 2H), 3.54
(s, 3H), 3.45 (q, J = 6.9 Hz, 4H), 1.14 (t, J = 7.1 Hz, 6H); 13C NMR
(CDCl3) δ 162.3, 160.1, 159.7, 155.4, 150.4, 138.3, 131.2, 125.0, 122.1,
117.2, 110.8, 43.8, 28.6, 12.3; HRMS (+ESI-TOF) m/z for
C20H24N9O2 [M + H]+ calcd 422.2059, found 422.2059.
(E)-4-((4-Methoxybenzylidene)amino)-1-methyl-4H-1,2,4-tri-
azol-1-ium Iodide (3a).45 Yellow crystals (3.4 g, >99%), mp 185−
186 °C (lit.45 mp 185 °C); H NMR (DMSO-d6) δ 10.70 (s, 1H),
1
9.81 (s, 1H), 9.21 (s, 1H), 7.91 (d, J = 9.0 Hz, 2H), 7.20 (d, J = 8.7
Hz, 2H), 4.14 (s, 3H), 3.89 (s, 3H); 13C NMR (DMSO-d6) δ 164.1,
163.6, 139.7, 139.2, 131.4, 122.8, 115.0, 55.7, 39.1. Anal. Calcd For
C11H13IN4O: C, 38.39; H, 3.81; N, 16.28. Found: C, 38.68; H, 3.94;
N, 16.24.
(E)-N-((E)-3-Butyl-2-((E)-(4-nitrophenyl)triaz-2-en-1-ylidene)-
2,3-dihydro-1H-benzo[d]imidazol-1-yl)-1-phenylmethanimine
(6c). Red crystals (0.22 g, 78%), mp 157−158 °C; 1H NMR (CDCl3)
δ 9.42 (s, 1H), 8.05 (d, J = 9.0 Hz, 2H), 7.89 (d, J = 9.0 Hz, 2H),
7.59−7.42 (m, 6H), 7.38−7.20 (m, 3H), 4.33 (t, J = 7.5 Hz, 2H),
1.96−1.81 (m, 2H), 1.48−1.34 (m, 2H), 0.94 (t, J = 6.0 Hz, 3H); 13C
NMR (CDCl3) δ 162.8, 156.2, 151.7, 145.8, 133.1, 132.3, 130.2, 129.7,
129.0, 128.6, 124.6, 123.9, 123.5, 121.9, 110.3, 109.2, 45.5, 31.0, 20.1,
13.9; HRMS (+ESI-TOF) m/z for C24H24N7O2 [M + H]+ calcd
442.1986, found 442.1993.
(E)-4-((4-(Diethylamino)benzylidene)amino)-1-methyl-4H-
1,2,4-triazol-1-ium Iodide (3b). Yellow crystals (3.16 g, >99%), mp
1
187−188 °C; H NMR (DMSO-d6) δ 10.58 (s, 1H), 9.71 (s, 1H),
8.92 (s, 1H), 7.70 (d, J = 9.0 Hz, 2H), 6.84 (d, J = 9.0 Hz, 2H), 4.10
(s, 3H), 3.47 (q, J = 7.1 Hz, 4H), 1.15 (t, J = 6.9 Hz, 6H); 13C NMR
(DMSO-d6) δ 163.9, 151.5, 139.4, 139.2, 131.6, 116.0, 111.2, 43.9,
39.0, 12.3. Anal. Calcd For C14H20IN5: C, 43.65; H, 5.23; N, 18.18.
Found: C, 43.79; H, 5.09; N, 18.18.
(E)-N-((E)-3-Butyl-2-((E)-(4-nitrophenyl)triaz-2-en-1-ylidene)-
2,3-dihydro-1H-benzo[d]imidazol-1-yl)-1-(4-methoxyphenyl)-
1
methanimine (6d). Red crystals (0.26 g, 88%), mp 95−97 °C; H
NMR (CDCl3) δ 9.24 (s, 1H), 8.07 (d, J = 9.0 Hz, 2H), 7.88 (d, J =
9.0 Hz, 2H), 7.58 (d, J = 9.0 Hz, 2H), 7.52−7.44 (m, 1H), 7.36−7.24
(m, 3H), 7.01 (d, J = 9.0 Hz, 2H), 4.37 (t, J = 7.5 Hz, 2H), 3.91 (s,
3H), 2.01−1.85 (m, 2H), 1.52−1.37 (m, 2H), 0.98 (t, J = 6.0 Hz, 3H);
13C NMR (CDCl3) δ 163.9, 163.1, 156.3, 151.5, 145.6, 130.6, 130.2,
129.7, 125.5, 124.5, 123.8, 123.4, 121.8, 114.5, 110.2, 109.2, 55.6, 50.8,
45.1, 31.0, 20.1, 13.9; HRMS (+ESI-TOF) m/z for C25H25N7O3Na [M
+ Na]+ calcd 494.1911, found 494.1907.
(E)-N-((E)-3-Butyl-2-((E)-(4-nitrophenyl)triaz-2-en-1-ylidene)-
2,3-dihydro-1H-benzo[d]imidazol-1-yl)-1-(4-nitrophenyl)-
methanimine (6e). Red crystals (0.21 g, 67%), mp 226−227 °C; 1H
NMR (CDCl3) δ 10.12 (s, 1H), 8.36−8.23 (m, 4H), 8.12 (d, J = 9.0
Hz, 2H), 7.75−7.62 (m, 3H), 7.43−7.34 (m, 2H), 7.33−7.24 (m, 1H),
4.43 (t, J = 7.5 Hz, 2H), 2.08−1.87 (m, 2H), 1.55−1.35 (m, 2H), 0.99
(t, J = 7.5 Hz, 3H); 13C NMR (CDCl3) δ 155.7, 155.4, 151.9, 149.1,
146.3, 139.9, 130.4, 129.7, 128.8, 124.8, 124.4, 124.0, 123.9, 121.9,
111.0, 109.0, 46.9, 31.3, 20.0, 13.9; HRMS (+ESI-TOF) m/z for
C24H22N8O4Na [M + Na]+ calcd 509.1656, found 509.1646.
General Method for the Preparation of Push-pull Triazene
6a−h. Potassium tert-butoxide (0.08 g, 0.8 mmol) was added to a
mixture of 1-azido-4-nitrobenzene 5 (0.10 g, 0.63 mmol) and
corresponding azolium halide 3a−e, 4a−c (0.63 mmol) in dry THF
(10 mL) at −78 °C. After 10 min, the reaction mixture was warmed to
room temperature and stirred. After 24 h the precipitate was removed
by filtration, and the filtrate was concentrated under reduced pressure.
The residue was recrystallized from MeOH to obtain pure triazene
6a−h.
(E)-1-(4-Methoxyphenyl)-N-((E)-1-methyl-5-((E)-(4-
nitrophenyl)triaz-2-en-1-ylidene)-1,5-dihydro-4H-1,2,4-triazol-
4-yl)methanimine (6a). Red crystals (0.18 g, 74%), mp 219−220
°C; 1H NMR (DMSO-d6) δ 9.08 (s, 1H), 9.01 (s, 1H), 8.14 (d, J = 9.0
Hz, 2H), 7.86 (d, J = 9.0 Hz, 2H), 7.58 (d, J = 9.0 Hz, 2H), 7.15 (d, J
= 9.0 Hz, 2H), 3.93 (s, 3H), 3.87 (s, 3H); 13C NMR (DMSO-d6) δ
162.7, 161.8, 156.7, 151.3, 144.4, 135.6, 130.6, 124.6, 124.4, 121.2,
114.7, 55.5, 38.8; HRMS (+ESI-TOF) m/z for C17H16N8O3Na [M +
Na]+ calcd 403.1238, found 403.1239.
D
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(E)-1,3-Dibenzyl-2-((4-nitrophenyl)triaz-2-en-1-ylidene)-2,3-
dihydro-1H-benzo[d]imidazole (6f). Red crystals (0.0.23 g, 77%),
mp 190−191 °C; 1H NMR (CDCl3) δ 7.99 (d, J = 8.4 Hz, 2H), 7.39−
7.29 (m, 10H), 7.20−7.15 (m, 6H), 5.65 (s, 4H); 13C NMR (CDCl3)
δ 156.1, 154.9, 145.5, 135.5, 131.4, 129.0, 128.0, 126.7, 124.5, 123.7,
121.7, 109.9, 48.4. Anal. Calcd For C27H22N6O2: C, 70.12; H, 4.76; N,
18.17. Found: C, 70.26; H, 4.87; N, 18.19.
mmol) in CH3CN (3 mL) and stirred under reflux. After 5 h, the
reaction mixture was concentrated under reduced pressure to afford 10
as red crystals (0.13g, >99%), mp 223 °C, dec; 1H NMR (DMSO-d6)
δ 8.14 (d, J = 9.3 Hz, 1H), 8.13 (d, J = 9.3 Hz, 1H), 8.03−7.94 (m,
2H), 7.68−7.59 (m, 2H), 7.48−7.30 (m, 12H), 5.92 (s, 4H), 3.99 (s,
3H); 13C NMR (DMSO-d6) δ 148.8, 146.7, 145.5, 134.8, 130.5, 128.8,
127.9, 126.8, 126.5, 124.6, 120.0, 112.9, 48.5, 36.5.
N-((E)-1-Benzyl-5-((E)-(4-nitrophenyl)triaz-2-en-1-ylidene)-
1H-1,2,4-triazol-4(5H)-yl)-4-methylbenzenesulfonamide (11a).
HCl (1 N) was added dropwise to the solution of 9a (0.10 g, 0.19
mmol) in MeOH (10 mL) until the formation of a yellow precipitate
stopped. The resulting precipitate was collected by filtration, washed
with water (10 mL), and dried to obtain pure 11a as yellow crystals
(0.079 g, 85%), mp 173 °C, dec; 1H NMR (DMSO-d6) δ 8.11 (s, 1H),
8.03 (d, J = 8.1 Hz, 2H), 7.46 (d, J = 7.8 Hz, 2H), 7.37−7.28 (m, 3H),
7.23 (d, J = 7.8 Hz, 2H), 7.07−6.99 (m, 4H), 5.35 (s, 2H), 2.16 (s,
3H); 13C NMR (DMSO-d6) δ 157.9, 153.9, 143.4, 142.7, 141.7, 139.7,
136.7, 128.6, 128.5, 127.5, 126.8, 126.5, 124.5, 120.7, 53.5, 20.9. Anal.
Calcd For C22H20N8O4S: C, 53.65; H, 4.09; N, 22.75. Found: C,
53.36; H, 3.80; N, 22.64.
(E)-1-Butyl-3-methyl-2-((E)-(4-nitrophenyl)triaz-2-en-1-yli-
dene)-2,3-dihydro-1H-benzo[d]imidazole (6g). Red crystals (0.19
1
g, 84%), mp 158−161 °C; H NMR (CDCl3) δ 8.24 (d, J = 12.0 Hz,
2H), 7.67 (d, J = 9.0 Hz, 2H), 7.38−7.28 (m, 4H), 4.36 (t, J = 7.5 Hz,
2H), 3.92 (s, 3H), 1.97−1.82 (m, 2H), 1.51−1.37 (m, 2H), 0.98 (t, J =
6.0 Hz, 3H); 13C NMR (CDCl3) δ 155.9, 153.6, 145.4, 131.6, 131.1,
124.8, 123.5, 123.5, 121.5, 109.5, 109.3, 44.8, 32.0, 30.9, 20.1, 13.9;
HRMS (+ESI-TOF) m/z for C18H21N6O2 [M + H]+ calcd 353.1721,
found 353.1731.
(E)-1-Butyl-3-methyl-2-((E)-(4-nitrophenyl)triaz-2-en-1-yli-
dene)-2,3-dihydro-1H-imidazole (6h). Red crystals (0.16 g, 83%),
1
mp 144−145 °C; H NMR (CDCl3) δ 8.20 (d, J = 9.0 Hz, 2H), 7.54
(d, J = 9.0 Hz, 2H), 6.67−6.56 (m, 2H), 4.12 (t, J = 7.5 Hz, 2H), 3.78
(s, 3H), 1.84−1.77 (m, 2H), 1.46−1.31 (m, 2H), 0.95 (t, J = 6.0 Hz,
3H); 13C NMR (CDCl3) δ 157.7, 125.6, 124.8, 120.6, 119.3, 117.6,
116.2, 47.8, 36.3, 31.7, 19.8, 13.7; HRMS (+ESI-TOF) m/z for
C14H19N6O2 [M + H]+ calcd 303.1564, found 303.1573.
General Method for the Preparation of 11b,c. A mixture of 9a
(0.1 g, 0.19 mmol) and alkyl halide (0.19 mmol, 1.9 mmol in the case
of methyl iodide) in acetonitrile (3 mL) was stirred under reflux. After
5 h, the precipitate was removed by filtration, and the filtrate was
concentrated under reduced pressure. The residue was recrystallized
from MeOH to obtain pure 11b,c.
General Method for the Preparation of Push-Pull Triazene
Salts 9a−d. Potassium tert-butoxide (0.063 g, 0.63 mmol) was added
to a mixture of 1-azido-4-nitrobenzene 5 (0.10 g, 0.63 mmol) and the
corresponding 1,2,4-triazolium N-imide 7a−d (0.63 mmol) in dry
THF (10 mL) at −78 °C. After 10 min, the reaction mixture was
warmed to room temperature and stirred. After 24 h the precipitate
was collected by filtration, washed with THF (5 mL), and dried to
obtain pure triazene salt 9a−d.
Potassium ((E)-1-Benzyl-5-((E)-(4-nitrophenyl)triaz-2-en-1-
ylidene)-1H-1,2,4-triazol-4(5H)-yl)(tosyl)amide (9a). Yellow-or-
ange crystals (0.29 g, 86%), mp 216−217 °C; 1H NMR (DMSO-d6) δ
8.11 (s, 1H), 8.03 (d, J = 8.7 Hz, 2H), 7.46 (d, J = 7.5 Hz, 2H), 7.36−
7.29 (m, 3H), 7.23 (d, J = 8.7 Hz, 2H), 7.10−6.97 (m, 4H), 5.35 (s,
2H), 2.16 (s, 3H); 13C NMR (DMSO-d6) δ 157.7, 153.7, 143.2, 142.5,
141.5, 139.6, 136.5, 128.4, 128.3, 127.4, 126.7, 126.3, 124.4, 120.5,
53.3, 20.7; HRMS (-ESI-TOF) m/z for C22H19N8O4S [M − K]− calcd
491.1255, found 491.1267.
Potassium ((E)-1-Butyl-5-((E)-(4-nitrophenyl)triaz-2-en-1-yli-
dene)-1H-1,2,4-triazol-4(5H)-yl)(tosyl)amide (9b). Orange crys-
tals (0.28 g, 94%), mp 215−216 °C; 1H NMR (DMSO-d6) δ 8.16 (d, J
= 9.0 Hz, 2H), 8.00 (s, 1H), 7.50−7.39 (m, 4H), 7.01 (d, J = 8.1 Hz,
2H), 4.08 (t, J = 7.1 Hz, 2H), 2.17 (s, 3H), 1.67−1.60 (m, 2H), 1.28−
1.14 (m, 2H), 0.84 (t, J = 7.4 Hz, 3H); 13C NMR (DMSO-d6) δ 158.4,
153.0, 143.0, 142.1, 142.0, 139.2, 128.2, 126.5, 124.5, 120.3, 49.6, 30.4,
20.7, 18.8, 13.4; HRMS (-ESI-TOF) m/z for C19H21N8O4S [M − K]−
calcd 457.1412, found 457.1430.
Potassium ((E)-1-Methyl-5-((E)-(4-nitrophenyl)triaz-2-en-1-
ylidene)-1H-1,2,4-triazol-4(5H)-yl)(tosyl)amide (9c). Yellow-or-
ange crystals (0.23 g, 79%), mp 202−203 °C; 1H NMR (DMSO-d6) δ
8.15 (d, J = 9.0 Hz, 2H), 7.94 (s, 1H), 7.49 (d, J = 8.1 Hz, 2H), 7.48
(d, J = 9.0 Hz, 2H), 7.05 (d, J = 7.8 Hz, 2H), 3.76 (s, 3H), 2.19 (s,
3H); 13C NMR (DMSO-d6) δ 158.3, 153.6, 143.1, 142.4, 141.8, 139.3,
128.3, 126.6, 124.7, 120.5, 39.0, 20.8; HRMS (-ESI-TOF) m/z for
C16H15N8O4S [M − K]− calcd 415.0942, found 415.0954.
N-((E)-1-Benzyl-5-((E)-(4-nitrophenyl)triaz-2-en-1-ylidene)-
1H-1,2,4-triazol-4(5H)-yl)-N,4-dimethylbenzenesulfonamide
1
(11b). Orange crystals (0.088 g, 92%), mp 174−175 °C; H NMR
(DMSO-d6) δ 8.82 (s, 1H), 8.11 (d, J = 8.1 Hz, 2H), 7.66 (d, J = 7.5
Hz, 2H), 7.45−7.33 (m, 3H), 7.28 (t, J = 7.7 Hz, 4H), 7.19 (d, J = 8.0
Hz, 2H), 5.40 (s, 2H), 3.47 (s, 3H), 2.22 (s, 3H); 13C NMR (DMSO-
d6) δ 155.7, 152.4, 145.1, 144.9, 140.4, 135.7, 132.4, 129.9, 128.5,
128.1, 127.6, 126.5, 124.4, 121.4, 53.5, 38.0, 21.0; HRMS (+ESI-TOF)
m/z for C23H23N8O4S [M + H]+ calcd 507.1557, found 507.1553.
N-Benzyl-N-((E)-1-benzyl-5-((E)-(4-nitrophenyl)triaz-2-en-1-
ylidene)-1H-1,2,4-triazol-4(5H)-yl)-4-methylbenzenesulfon-
amide (11c). Red crystals (0.097 g, 88%), mp 172−173 °C; 1H NMR
(DMSO-d6) δ 8.64 (s, 1H), 8.14 (d, J = 8.1 Hz, 2H), 7.80 (d, J = 7.3
Hz, 2H), 7.37−7.26 (m, 12H), 6.91 (d, J = 7.6 Hz, 2H), 5.41 (d, J =
16.8 Hz, 1H), 5.32 (d, J = 16.2 Hz, 1H), 5.04 (d, J = 13.8 Hz, 1H),
5.00 (d, J = 13.8 Hz, 1H), 2.26 (s, 3H).; 13C NMR (DMSO-d6) δ
155.6, 152.4, 145.3, 145.1, 140.8, 135.6, 132.9, 130.0, 129.0, 128.6,
128.5, 128.3, 127.5, 126.0, 124.4, 121.5, 53.8, 53.3, 21.0; HRMS
(+APCI-TOF) m/z for C29H27N8O4S [M + H]+ calcd 583.1870,
found 583.1861.
General Method for the Preparation of 12a,b. A mixture of 7a
(0.5 g, 1.5 mmol) and alkyl halide (1.5 mmol, 15.0 mmol in the case of
methyl iodide) in acetonitrile (15 mL) was stirred under reflux. After 5
h, the reaction mixture was concentrated under reduced pressure to
afford pure 12a,b.
1-Benzyl-4-(N,4-dimethylphenylsulfonamido)-1H-1,2,4-tria-
zol-4-ium Iodide (12a). White crystals (0.71 g, >99%), mp 168−170
1
°C; H NMR (DMSO-d6) δ 10.89 (s, 1H), 9.61 (s, 1H), 7.69 (d, J =
8.1 Hz, 2H), 7.57 (d, J = 8.1 Hz, 2H), 7.51−7.41 (m, 5H), 5.66 (s,
2H), 3.43 (s, 3H), 2.50 (s, 3H); 13C NMR (DMSO-d6) δ 147.2, 143.7,
143.3, 132.2, 130.9, 129.2, 129.0, 128.9, 127.0, 55.9, 39.2, 21.4. Anal.
Calcd For C17H19IN4O2S: C, 43.41; H, 4.07; N, 11.91. Found: C,
43.39; H, 3.78; N, 11.93.
1-Benzyl-4-(N-benzyl-4-methylphenylsulfonamido)-1H-
1,2,4-triazol-4-ium Bromide (12b). White crystals (0.76 g, >99%),
mp 137−139 °C; 1H NMR (DMSO-d6) δ 11.21 (s, 1H), 9.69 (s, 1H),
7.85 (d, J = 8.1 Hz, 2H), 7.60 (d, J = 8.1 Hz, 2H), 7.45−7.37 (m, 3H),
7.36−7.27 (m, 5H), 7.25−7.13 (m, 2H), 5.64 (s, 2H), 4.98 (s, 2H),
2.50 (s, 3H); 13C NMR (DMSO-d6) δ 147.2, 144.9, 143.8, 132.3,
131.6, 131.0, 129.1, 128.9, 128.9, 128.6, 128.4, 55.9, 55.2, 21.4. Anal.
Calcd For C23H23BrN4O2S: C, 55.31; H, 4.64; N, 11.22. Found: C,
55.40; H, 4.44; N, 11.28.
Potassium ((E)-1-Butyl-5-((E)-(4-nitrophenyl)triaz-2-en-1-yli-
dene)-1H-1,2,4-triazol-4(5H)-yl)((4-nitrophenyl)sulfonyl)amide
(9d). Orange crystals (0.32 g, 95%), mp 245−246 °C; 1H NMR
(DMSO-d6) δ 8.18 (s, 1H), 8.12 (d, J = 9.3 Hz, 2H), 8.00 (d, J = 8.7
Hz, 2H), 7.68 (d, J = 8.7 Hz, 2H), 7.32 (d, J = 9.3 Hz, 2H), 4.05 (t, J =
7.1 Hz, 2H), 1.70−1.58 (m, 2H), 1.31−1.12 (m, 2H), 0.84 (t, J = 7.4
Hz, 3H); 13C NMR (DMSO-d6) δ 158.0, 153.0, 151.2, 147.5, 143.2,
142.5, 127.8, 124.6, 123.1, 120.2, 49.7, 30.5, 19.0, 13.5; HRMS (-ESI-
TOF) m/z for C18H18N9O6S [M − K]− calcd 488.1106, found
488.1125.
(E)-3-(1,3-Dibenzyl-1H-benzo[d]imidazol-2(3H)-ylidene)-1-
methyl-1-(4-nitrophenyl)triaz-1-en-1-ium Iodide (10). Methyl
iodide (0.15g, 1.1 mmol) was added to a solution of 6f (0.10 g, 0.22
E
dx.doi.org/10.1021/jo302697q | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Note
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ASSOCIATED CONTENT
■
S
* Supporting Information
1H and 13C spectra for 2a,b, 3a,b, 6a−h, 9a−d, 10, 11a−c, and
12a,b. X-ray CIF files for 6e, 6f, and 10. This material is
available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
■
Corresponding Author
*E-mail: katritzky@chem.ufl.edu.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors acknowledge the U.S. Navy, Kenan Foundation
(University of Florida), and the King Abdulaziz University
(Saudi Arabia) for their financial support. The authors also
thank Dr. Mirna El Khatib for her help in TGA analysis.
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