Transformations of 5-(2-arylethynyl)-2-methyl-2H-tetrazoles under superelectrophilic activation

Article abstract of DOI:10.1016/j.tet.2018.02.050

Reaction of 5-arylethynyl-2-methyl-2H-tetrazoles (acetylene tetrazoles) with arenes under the action of Br?nsted superacid CF₃SO₃H or acidic zeolite HUSY CBV-720 gives rise to E-/Z-5-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles, as pro

Full text of DOI:10.1016/j.tet.2018.02.050

Accepted Manuscript
Transformations of 5-(2-arylethynyl)-2-methyl-2h-tetrazoles under superelectrophilic
activation
Dmitry S. Ryabukhin, Anna D. Lisakova, Anna S. Zalivatskaya, Irina A. Boyarskaya,
Galina L. Starova, Rostislav E. Trifonov, Vladimir A. Ostrovskii, Aleksander V.
Vasilyev
PII:
S0040-4020(18)30195-9
10.1016/j.tet.2018.02.050
TET 29321
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 26 December 2017
Revised Date: 18 February 2018
Accepted Date: 21 February 2018
Please cite this article as: Ryabukhin DS, Lisakova AD, Zalivatskaya AS, Boyarskaya IA, Starova GL,
Trifonov RE, Ostrovskii VA, Vasilyev AV, Transformations of 5-(2-arylethynyl)-2-methyl-2h-tetrazoles
under superelectrophilic activation, Tetrahedron (2018), doi: 10.1016/j.tet.2018.02.050.
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ACCEPTED MANUSCRIPT
TRANSFORMATIONS OF 5-(2-ARYLETHYNYL)-2-METHYL-2H-
TETRAZOLES UNDER SUPERELECTROPHILIC ACTIVATION
a
b
c
c
Dmitry S. Ryabukhin, Anna D. Lisakova, Anna S. Zalivatskaya, Irina A. Boyarskaya, Galina L.
c
b,c
b
a,c*
Starova, Rostislav E. Trifonov, Vladimir A. Ostrovskii and Aleksander V. Vasilyev
a
Department of Chemistry, Saint Petersburg State Forest Technical University, Institutsky per., 5,
Saint Petersburg, 194021, Russia.
b
Saint Petersburg State Institute of Technology (Technical University), Moskovsky pr., 26, Saint
Petersburg, 190013, Russia.
c
Institute of Chemistry, Saint Petersburg State University, Universitetskaya nab., 7/9, Saint
Petersburg, 199034, Russia.
*
Corresponding author
A.V. Vasilyev, tel.: 07 812 670 93 52; fax: 07 812 670 93 90, e-mail: aleksvasil@mail.ru,
a.vasilyev@spbu.ru
Keywords
acethylene tetrazoles, hydroarylation, ionic hydrogenation, Brønsted superacids, acidic zeolites
Graphical abstract
Me
Me
N
N
Ar'H
CF SO
zeolite CBV-720
N
N
N
N
N
N
N
N
3
H or
3
N
N
Ar
Ar
CF SO H Ar
3
3
Me
F CO SO
Ar'
3
2
E-/Z-
up to 98 %
E-/Z-
up to 98 %
Abstract
Reaction of 5-arylethynyl-2-methyl-2H-tetrazoles (acetylene tetrazoles) with arenes under the
action of Brønsted superacid CF SO H or acidic zeolite HUSY CBV-720 gives rise to E-/Z-5-(2,2-
3
3
diarylethenyl)-2-methyl-2H-tetrazoles, as products of hydroarylation of acetylene bond, in yields up
to 98 % with predominant formation of E-isomers. Cationic intermediates of these reactions have
been studied theoretically by DFT calculations. Addition of CF SO H to the triple bond of
3
3
acetylene tetrazoles leads to the corresponding E-/Z-vinyl triflates in high yields. Hydration of triple
bond in these tetrazoles in H SO results in the formation of 5-(2-aryl-2-oxoethyl)-2-methyl-2H-
2
4
tetrazoles. Tandem hydroarylation-ionic hydrogenation of acetylene tetrazoles in the systems
acid(CF SO H or AlCl )-arene-cyclohexane affords 5-(2,2-diarylethyl)-2-methyl-2H-tetrazoles.
3
3
3
1

ACCEPTED MANUSCRIPT
1
. Introduction
-Substituted tetrazoles have attracted a great attention of chemists for their multifaceted
pharmacological and medicinal applications, and also as a source for functional materials in many
5
1
-5
6-8
fields of material science. They are known as explosives in rocket propellants, chelating
9
,10
11
12
agents,
agricultural chemicals,
self-healing materials,
compounds for photophysics,
2
+
13
ratiometric sensors of Zn and sensibilizators of lanthanide luminescence. Tetrazoles are widely
used in pharmacology, for instance, such well known drugs, as valsartan, losartan, zolarsartan and
4
,14
5,15
candesartan. Tetrazole core has been often considered as a carboxylic acid fragment in drugs.
1
6-18
See also recent papers on tetrazole-based medicines.
Synthesis of 5-ethynyl-2-methyl- (or ethyl-) tetrazole (acetylene tetrazoles) is not trivial. For
1
9
the first time, it was investigated in 1980. Since that time, there have been only a few reports on 5-
ethynyl-substituted tetrazoles. These compounds are promising monomers for tetrazole-containing
2
0
21
chelating polymers,
precursors for synthesis of condensed systems,
and cores of
2
2
cyclopenta[def]phenanthrene and cyclopenta[jk]fluorine. Only one example of cross-coupling of
2
3
5
-ethynyltetrazole with haloarenes by Sonogashira reaction has been described. However,
acetylene tetrazoles are still remain a “white” spot in organic chemistry.
Thus, further development of chemistry of tetrazoles and synthesis of new tetrazole
derivatives are actual tasks in chemistry, medicine, and material science.
Based on our recent work on hydroarylation of side chain double bond in styryl substituted
2
4
25
tetrazoles and oxadiazoles under the action of Brønsted and Lewis superacids, we undertook this
research on investigation of transformation of 5-arylethynyl-2-methyl-2H-tetrazoles 1а-e (Figure 1)
under superelectrophilic activation.
The main goals of this work were study on hydroarylation of acetylene bond of tetrazoles 1a-e
in their reactions with arenes in Brønsted and Lewis superacids, or with acidic zeolites,
characterization of cationic intermediates of these reactions by quantum chemical theoretical
calculations, and investigation of other electrophilic reactions of compounds 1a-e.
N
N
N
N
N
N
N
N
R
Me
Me
1
a-d
1e
R = H (a), Me (b), MeO (c), CF (d)
3
Figure 1. 5-Arylethynyl-2-methyl-2H-tetrazoles 1а-d and 5-ethynyl-2-methyl-2H-tetrazole 1e used
in this study.
2

ACCEPTED MANUSCRIPT
2
. Results and discussion
As it has been shown previously the protonation of 5-styryltetrazoles in Brønsted acids
2
6
4
(
H SO , HClO , etc.) occurs at first at the nitrogen atom N of the tetrazole ring, then the second
2 4 4
α
β
α
protonation on the carbon C of the side chain styryl double bond (Ar–C H=C H–) takes place in
2
4
stronger superacids (CF SO H, FSO H) leading to the formation of reactive N,C-dications.
3
3
3
Analogously, protonation of acetylene tetrazoles 1a-e should proceed in the same steps.
In the beginning, using DFT calculations, we studied electronic characteristics of monocations
4
4
α
Aa-e (N -protonation) and dications Ba-e (N ,C -diprotonation) derived from tetrazoles 1a-e
correspondingly (Table 1). The energies of HOMO and LUMO, charges on atoms, contributions of
2
7
atomic orbitals into LUMO, and indexes of the global electrophilicity ω were calculated for the
estimation of electronic structure and reactivity of cations A, B. As it was expected, the
calculations have shown that N,C-diprotonated species B should be reactive electrophiles having
electrophilicity index values ω 5 – 8 eV, which are much higher compared to monocations A with ω
2
.7 – 3.0 eV (Table 1). Arylethynyl substituted dications Ba-d bear a large positive charge 0.38-
β
0
.47 e on the side chain carbon C . This carbon in these species gives a rather big contribution into
LUMO in 23.7 – 34.2 %. Among the species Ba-d, the CF -substituted cation Bd posses the highest
3
β
electropilic characteristics [ω 6.8 eV, q(C ) 0.47 e], due to the powerful electron-acceptor effect of
β
trifluoromethyl group. Thus, the carbon C in dications Ba-c should be reactive electrophilic center
form both charge and orbital points of views. The corresponding monocations Aa-c have much less
β
charge (0.15 – 0.18 e) and LUMO coefficient (8.8 – 14.2 %) on carbon C .
It must be specially mentioned that DFT calculations have clearly demonstrated that the
α
second protonation of ethynyl substituted cation Ae takes place at acetylene carbon C only, in anti-
Markovnikov way, affording dication Be, which has high energy. In this case, protonation of
β
acetylene bond on C is extremely unfavorable, due to the electron withdrawing character of the
protonated tetrazole ring. There are some experimental examples of anti-Markovnikov additions to
2
8
unsaturated bond in the superacids.
3

ACCEPTED MANUSCRIPT
Table 1. Selected calculated (DFT) electronic characteristics of species Aa-e and Ba-e generated on
protonation of tetrazoles 1a-e.
H
H
4
H
4
4
N
N3
H+
N
N3
H+
N
5
5
5
α
N
3
R
2
R
N2
α
β
α
N1 N
β
β
N1
N N
2
R
Me
R = Ar (a-d), H (e)
Me
1
1a-e
Aa-e
Ba-e
Me
a
β
b
β
с
4
b
Species
EHOMO
eV
,
ELUMO
eV
,
ω,
q(C ), k(C )LUMO,
q(N ),
e
eV
e
%
H
-7.13
-2.76
2.8
0.18
14.2
-0.28
4
5
N
3
N
Ph
N2
β
α
N1
Me
Aa
H
N
-8.63
-6.92
-8.63
-4.89
-2.72
-4.73
6.1
2.8
5.7
0.45
0.15
0.42
34.2
12.2
30.6
-0.27
-0.28
-0.27
H
4
5
α
β
N
3
N N 2
Ph
Ba 1
Me
H
4
5
N
3
N
Me
β
α
N2
N1
Me
Ab
4H
N
H
5
α
N
3
β
2
N N
1
Me
Bb
Me
H
-6.55
-8.44
-2.67
-4.36
2.7
5.0
0.18
0.38
8.8
-0.28
-0.28
4
5
N
3
N
MeO
N2
β
α
N1
Me
Ac
H
4
N
23.7
H
5
α
N
3
β
2
N N
1
Me
Bc
MeO
H
-7.45
-2.95
3.0
0.17
17.3
-0.28
4
5
N
3
N
F3C
N2
β
α
N1
Me
Ad
4

ACCEPTED MANUSCRIPT
H
N
-8.90
-5.25
6.8
0.47
32.0
-0.27
H
4
5
α
N
3
β
2
N N
1
Me
Bd
F3C
H
-8.70
-2.80
-6.36
2.8
8.0
-0.13
-0.33
2.9
2.6
-0.27
-0.18
4
5
N
3
N
β
α
N2
N1
Me
Ae
4H
N
-11.12
H
5
α
N
3
β
2
N N
1
Be
Me
a
2
Global electrophilicity index ω = (EHOMO + ELUMO) /8(E
- EHOMO).
LUMO
b
c
Natural charges.
Contribution of atomic orbital into the molecular orbital.
Calculations of Gibbs energies ∆G298 of reaction formation of species Aa-e and Ba-e in
+
reaction of 1a-e with H O have revealed that first protonation leading to cations Aa-e is
3
thermodynamically favorable (Table 2). Despite ∆G298 values of reaction formation of dications
Ba,b,d are positive, the formation of these dications from the corresponding tetrazoles 1a,b,d is
very possible (negative ∆G298 values in two steps), as well as species Bc. Contrary to that,
protonation of acetylene bond in cation Ae, having no aryl ring, and formation of dication Be are
thermodynamically very unfavorable (Table 2).
Table 2. Calculated Gibbs energies ∆G298 of reaction formation of species Aa-e and Ba-e from 1a-e
and Aa-e correspondingly.
H
H
R =
X
H
+
N
N
+
N
N
N
H O
3
N
N
H O
3
N
R
R
X = H (a),
Me (b),
N
N
N N
Me
Me
R
1
a-e
Aa-e
MeO (c),
Me
Ba-e
R = H (e)
CF (d)
3
Tetrazole Gibbs energies ∆G298 of formation of А
from 1, kJ/mol
Gibbs energies ∆G298 of formation of B
from A, kJ/mol
1
a
-74.2
-75.2
-77.1
-65.4
-69.1
16.6
1.3
-23.6
146
1
b
1
1
c
e
1
d
48.2
5

ACCEPTED MANUSCRIPT
Concluding data on the calculations (Tables 1, 2) and taking into account our previous
2
4
25
research on protonation of styryltetrazoles and styryloxadiazoles, one may state that dications
Ba-d are, the most probably, reactive species in transformations of tetrazoles 1a-d in superacids.
Then, we conducted reactions of phenylethynyl tetrazole 1a with benzene under the action of
various acidic reagents to achieve hydrophenylation of the triple bond (Table 3). This reaction in
H SO at room temperature took quite a long time, 120 h (entry 1, Table 3). The main reaction
2
4
product was ketone 4a, as a result of hydration of acetylene bond, yield of hydrophenylation
product 2a was very poor, only 6 %. In CF SO H at 0 °C for 1 h, two compounds were formed,
3
3
adducts of mono- (2a) and bis- (3a) hydrophenylation of the triple bond, respectively (entry 2, see
X-ray structure of 3a in Figure 2). At lower temperature -40 °C in CF SO H, this reaction gave only
3
3
2
a with no formation of 3a (entry 3). Lewis acid AlCl led to 2a in a moderate yield of 44 % (entry
3
4
). The use of AlBr gave complex mixture of unidentified products (entry 5). Good result was
3
obtained with acidic zeolite HUSY CBV-720, yield of 2a was 85 % (entry 6). Another kind of
zeolite, CBV-500, was not so efficient (entry 7). See also our recent work on acidic zeolite-
2
9
promoted reactions of arylacetylenes conjugated with electron withdrawing groups, and general
3
0
review on applications of zeolites in organic synthesis.
Table 3. Reactions of 2-methyl-5-phenylethynyl-2H-tetrazole 1a with benzene under the action of
various acidic reagents.
N
Me
+
N
N
N
N
N
Ph
Ph
N
N
N
acid
Ph
Ph
N
N
Ph
+
N
Ph
+ PhH
Me
N N
3a
N N
Ph
O
1a
2a
Me
Me
4a
Entry Reaction conditions
Reaction products, isolated yields, %
2
6
59
94
44
a
3a
-
27
-
4a
72
-
-
-
1
2
3
4
5
6
7
H SO , r.t., 120 h
2
4
CF SO H, 0°C, 1 h
3
3
CF SO H, -40°C, 1 h
3
3
AlCl , r.t., 1 h
-
3
AlBr , r.t., 1 h
mixture of unidentified products
3
zeolite HUSY, CBV-720, 130 °C, 15 h
zeolite HUSY, CBV-500, 130 °C, 15 h
85
30
-
-
-
-
6

ACCEPTED MANUSCRIPT
Figure 2. Molecular structures of 3a (ellipsoid contours of probability levels are 50 %, CCDC
1
588152).
Thus, based on data of Table 3, CF SO H and zeolite CBV-720 were chosen to obtain
3
3
hydroarylation products of acetylene bond in reactions of tetrazoles 1a-d with arenes through
intermediate formation of dications Ba-d (Table 4). These reactions led mainly to E-/Z-isomers of
5
-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles 2b-p in yields of 24- 98 % with predominant (entries
, 4, 6, 8, 10, 11-15, 18-20) or exclusive (entries 2, 3) formation of E-isomers. E-/Z-Configuration
1
of compounds 2 was determined by NOESY correlations between vinyl proton and ortho-protons of
neighbor aromatic ring (see SI). In some cases reactions were complicated by formation of other
compounds. For instance, acetylene bond hydration product 4a (entry 1), addition of two arene
molecules (3a,b in entries 18-20), or formation of compound 2a (entries 10, 11). In the latter case,
most probably, that compounds 2k,l lost benzene molecule, which then was added to the initial 1a
through intermediate formation of the corresponding vinyl cation. Various arenes, benzene, xylenes
(dimethylbenzenes), anisole (methoxybenzene), veratrole (1,2-dimethoxybenzene), 1,2-
dichlorobenzene, were involved in this reaction. Hydroarylation with anisole, veratrole, and 1,2-
dichlorobenzene did not take place with zeolite CBV-720 (entries 5, 7, 9). It may be caused by two
main factors: insufficient electrophilic activation of starting tetrazoles 1 by zeolites, and decreasing
of nucleophilicity of anisole, veratrole, and 1,2-dichlorobenzene, due to ythe interaction of their
heteroatoms with zeolite acidic sites.
Acidity of zeolite CBV-720 was not enough for electrophilic activation of tetrazole 1d
bearing trifluoromethyl acceptor group (entry 16). Complete conversion of this tetrazole was
achieved in CF SO H at room temperature for 72 h (compare reaction temperature and time in
3
3
entries 17-20), but reaction was accompanied by the formation of compounds 3a,b (entries 18-20).
Most probably, that 3a was formed from 3b by aryl group exchange.
7

ACCEPTED MANUSCRIPT
Ethynyl tetrazol 1e was absolutely nonreactive under superelectrophilic activation with
CF SO H or zeolite CBV-720 and gave no reaction product, due to unfavorable formation of the
3
3
corresponding dication Be (see data on DFT calculations in Tables 1, 2).
Concluding data from Table 4, one may state that both Brønsted superacid CF SO H and
3
3
acidic zeolite HUSY CBV-720 may be used for activation of acetylene tetrazoles 1 in
hydroarylation of their triple bond to obtain compounds 2.
Table 4. Reactions of 5-arylethynyl-2-methyl-2H-tetrazoles 1a-d with arenes under the action of
CF SO H or zeolite CBV-720.
3
3
H
N
R
H
CF SO H or
zeolite CBV-720
3
3
Me
+
N
N
N
N
N
N
ArH
- 2 H+
N
N
R
other
products
N N
N
Me
Me
1a-d
Ba-d
Ar
E-/Z-2b-p
R
R = H (a), Me (b), MeO (c), CF (d)
3
Entry
1
Starting
tetrazole
1a
Substituents Reaction
Reaction products, isolated yields, %
in Ar
conditions
N
Me
1,2-Me2
zeolite
N
N
Ph
CBV-720,
N
Ph
1
1
30 °C,
5 h
N
N
N
N
E-2b (38%)
Me
Me Me
Z-2c (22%)
Me
Me
E-/Z- ratio 1 : 0.6
N
N
N N
Ph
4
a (31%)
Me
O
Me
N
2
3
1a
1a
1,3-Me2
1,3-Me2
zeolite
CBV-720,
N
N
Ph
N
1
1
30 °C,
5 h
Me
Me
E-2d (81%)
N
Me
CF SO H,
3
3
N
N
0
1
°C,
h
Ph
N
Me
Me
E-2d (70%)
8

ACCEPTED MANUSCRIPT
N
Me
4
1a
1,4-Me2
zeolite
N
N
Ph
CBV-720,
Ph
N
Me
1
1
30 °C,
5 h
Me
N
N
N
N
Me
Me
E-2e (54%)
Z-2f (4%)
Me
E-/Z-ratio 1 : 0.06
5
6
1a
1a
MeO
MeO
zeolite
CBV-720,
quantitative recovery of unreacted starting 1a
1
1
30 °C,
5 h
N
Me
CF SO H,
3
3
N
N
Ph
r.t., 20 h
Ph
N
N
N
N
N
MeO
Me
Z-2h (33%)
E-2g (54%)
E-/Z- ratio 1 : 0.6
MeO
7
8
1a
1a
1,2-MeO2
1,2-MeO2
zeolite
CBV-720,
quantitative recovery of unreacted starting 1a
1
1
30 °C,
5 h
N
Me
CF SO H,
3
3
N
Ph
N
r.t., 4 h
Ph
N
N
MeO
N
N
N
MeO
MeO
MeO
Me
E-2i (44%)
E-/Z- ratio 1 : 0.6
Z-2j (25%)
9
1
1a
1a
1,2-Cl2
1,2-Cl2
zeolite
CBV-720,
quantitative recovery of unreacted starting 1a
1
1
30 °C,
5 h
N
Me
0
CF SO H,
3 3
N
N
r.t., 90 h
Ph
Ph
N
N
Cl
N
N
N
Cl
Me
Z-2l (18%)
Cl
Cl
E-2k (29%)
E-/Z-ratio
1
: 0.6
N
Ph
N
N N
Ph
Me
2a (29%)
9

ACCEPTED MANUSCRIPT
N
Me
1
1
1a
1,2-Cl2
CF SO H, 0
3
3
N
N
°
C, 1 h
Ph
Ph
N
N
Cl
N
N
N
E-/Z- ratio Cl
Me
Z-2l (15%)
Cl
Cl
1
: 0.3
E-2k (50%)
N
Ph
N
N N
Ph
Me
2a (25%)
N
Me
1
1
2
3
1b
1b
H
H
zeolite
CBV-720,
N
Ph
N
Ph
N
1
1
30 °C,
5 h
N
N
N
N
Me
Me
Me
E-2m (46%)
Z-2n (37%)
E-/Z- ratio 1 : 0.8
Me
N
CF SO H, 0
3
3
N
Ph
N
°
C, 1 h
Ph
N
N
N
N
Me
N
Me
E-2m (57%)
E-/Z- ratio 1 : 0.72
Me
Z-2n (41%)
Me
N
1
1
4
5
1c
1c
H
H
zeolite
CBV-720,
N
N
Ph
Ph
N
1
1
30 °C,
5 h
N
N
N
N
MeO
Me
Z-2h (24%)
E-2g (28%)
MeO
E-/Z- ratio 1 : 0.86
N
Me
CF SO H,
3
3
N
N
Ph
r.t., 24 h
Ph
N
N
N
N
N
MeO
Me
Z-2h (28%)
E-/Z-ratio 1 : 0.4
E-2g (70%)
MeO
1
1
6
7
1d
1d
H
H
zeolite
CBV-720,
quantitative recovery of unreacted starting 1d
quantitative recovery of unreacted starting 1d
1
1
30 °C,
5 h
CF SO H,
3
3
0
°C, 1 h
1
0

ACCEPTED MANUSCRIPT
1d (66%) +
1
8
1d
H
CF SO H,
3 3
r.t., 1 h
N
Me
N
N
Ph
Ph
N
N
N
N
N
F3C
Me
E-2o (19%)
E-/Z- ratio 1 : 0.6
F3C
F3C
Z-2p (11%)
Ph
N
N
N N
Me
Ph
3b (3%)
1
2
9
0
1d
1d
H
H
CF SO H,
r.t., 24 h
1d (10%) + E-2o (15%) + Z-2p (9%) + 3a
(12%) + 3b (49%)
E-2o (15%) + Z-2p (9%) + 3a (8%) + 3b (65%)
3
3
CF SO H,
3
3
r.t., 72 h
We also conducted tandem hydroarylation–ionic hydrogenation of tetrazole 1a with arenes
and cyclohexane under the action of CF SO H or AlCl (Table 5), analogously our previous work
3
3
3
3
1
on the same reaction of phenylpropynoic acid derivatives. In this reaction the initially formed 2
-
undergoes N,C-diprotonation with formation of dication C, which abstracts hydrid ion H from
cyclohexane molecule leading to 5-(2,2-diarylethyl)-2-methyl-2H-tetrazoles 5 (see Scheme in Table
5
). It should be specially emphasized that compounds 2 may afford very easily products of ionic
hydrogenation in the presence of alkanes and strong acids (CF SO H or AlCl ). Thus, admixtures of
3
3
3
hydrocarbons (alkanes) in solvents or reagents give rise immediately to compounds 5 under the
conditions of formation of the corresponding tetrazoles 2 shown in Table 4!
Table 5. Tandem hydroarylation-ionic hydrogenation of tetrazole 1a in the systems acid-arene-
cyclohexane.
N
Me
H
N
Me
N
Me
N
N
N
N
N
N
cyclohexane
(source of H )
-H+
N
N
Ph
Ar
Ph
Ar
N
-
Ph
Ar
N
N
N
N
acid
acid
Ph
+ ArH
Me
2
5
1a
C
+
-
C H
6 11
Entry Arene, ArH
benzene
Reaction conditions
CF SO H, cyclohexane, r.t., 1 h
Reaction product, isolated yield, %
1
N
Me
3
3
N
N
Ph
Ph
N
5a (98%)
1
1

ACCEPTED MANUSCRIPT
2
3
benzene
AlCl , cyclohexane, r.t., 15 h
N
Me
3
N
N
N
Ph
Ph
5a (78%)
1,3-dimethylbenzene CF SO H, cyclohexane, r.t., 1 h
N
Me
3
3
N
N
N
Ph
Me
Me
5b (61%)
Then reactions of tetrazoles 1a-d in Brønsted acids (H SO and CF SO H) without arenes
2
4
3
3
were carried out. Hydration of 1b-d in H SO furnished ketones 4b-d (Scheme 1, for 4a see Table
2
4
3
, entry 1).
N
N
R
N
N
H
2
SO
4
N
R
N
4, b (71%),
c (39%),
d (86%)
r.t., 4-24 h
N N
Me
O
1b-d
Me
R = Me (b), MeO (c), CF (d)
3
Scheme 1. Hydration of tetrazoles 1b-d in H SO .
2
4
Addition of triflic acid to the triple bond of 1a,b,d resulted in the formation of E-/Z-vinyl
triflates 6a,b,d in high yields at room temperature for 1 h (Scheme 2). Under these conditions,
tetrazole 1b, having donating 4-methylphenyl ring, gave only Z-isomer 6b, as product of anti-
addition of CF SO H to the acetylene bond. Phenyl-substituted compound 1a and tetrazole 1d,
3
3
bearing acceptor 4-CF -phenyl ring, afforded mixtures of E- and Z-isomers 6a,d. It has been
3
previously shown that reaction of triflic acid with various acetylene compounds proceeds with the
formation of products of syn- and anti- addition to the triple bond depending on structure of starting
32,33
alkynes and reaction conditions.
E-/Z-Configuration of compounds 6a,b,d was determined by
H–F NOESY correlations between vinyl proton and CF group (see SI). Tetrazole 1c, having 4-
3
methoxyphenyl substituent, gave complex mixture of products in CF SO H, probably, due to
3
3
Friedel-Crafts reactions of intermediate cationic species with donating 4-methoxyphenyl ring.
We also checked reaction of vinyl triflates 1 with benzene in CF SO H to obtain the
3
3
corresponding hydroarylation product 2. But, no reactions occurred, and unreacted starting
compounds 1 were quantitatively recovered.
34-36
It should be noted, that vinyl triflates are important substrates for organic synthesis.
1
2

ACCEPTED MANUSCRIPT
R
Me
N
N
N
N
N
N
N
CF SO H
E-/Z-6, a (96%), E-/Z- 1 : 0.9;
3
3
N
R
b (85%), E-/Z- 0 : 1;
d (98%), E-/Z- 1 : 0.6
r.t., 1 h
Me
1a,b,d
F CO SO
3
2
R = H (a), Me (b), CF (d)
3
Scheme 2. Addition of CF SO H to tetrazoles 1a,b,d.
3
3
3
. Conclusions
We have developed novel and efficient methods for the synthesis of tetrazole derivatives
based on various transformations (hydroarylation, ionic hydrogenation, addition of acid, hydration)
of acetylene bond in 5-arylethynyl-2-methyl-2H-tetrazoles under the action of Brønsted (CF SO H,
3
3
H SO ) or Lewis (AlCl ) acids, and acidic zeolite HUSY CBV-720. These reactions proceed with
2
4
3
good yields of target products.
4
. Experimental part
General
The NMR spectra of solutions of compounds in CDCl were recorded on a Bruker AM-500
3
1
19
13
spectrometer at 25°C (at 500, 470 and 125 MHz for H, F, and C NMR spectra respectively) or
1
19
13
on Briker-400 spectrometer (at 400, 376 and 101 MHz for H, F and C NMR respectively). The
1
residual proton-solvent peak CDCl (δ 7.26 ppm) for H NMR spectra and the carbon signal of
3
1
3
19
CDCl (δ 77.16 ppm) for C NMR spectra were used as references. F NMR spectra were
3
indirectly referred to the signal of CFCl (δ 0.0 ppm). HRMS was carried out at an instrument
3
Bruker MicroTOF (ESI). GC-MS data were obtained at a machine G2570A GC/MSD Agilent
Technologies 6850c with a column HP-5MS (3m×0.25mm), a thickness of the stationary phase
0
.25ꢀm. The preparative reactions were monitored by thin-layer chromatography on silica gel plates
(Silufol UV-254) using UV light for detection. Column chromatography was performed on silica
gel Merck-60 with petroleum ether–ethylacetate mixture eluation.
DFT calculations
All computations has been carried out at the DFT/HF hybrid level of theory using Becke’s
three-parameter hybrid exchange functional in combination with the gradient-corrected correlation
3
7
functional of Lee, Yang, and Parr (B3LYP) by using GAUSSIAN 2003 program packages. The
1
3

ACCEPTED MANUSCRIPT
geometries optimization were performed using the 6-311+G(2d,2p) basis set. The Hessian matrix
was calculated analytically for the optimized structures in order to prove the location of correct
minima (no imaginary frequencies) and to estimate the thermodynamic parameters. Solvent (water)
was taken into account by using polarized continuum method (PCM).
X-ray analysis.
A suitable crystals were selected and studied on the Bruker diffractometer for X-ray analysis.
3
8
The crystals were kept at 100(2) K during data collection. Using Olex2 the structure was solved
3
9
with the ShelXS structure solution program using Direct Methods and refined with the ShelXL
refinement package using Least Squares minimization. 1588152 – (3a) contain the supplementary
crystallographic
www.ccdc.cam.ac.uk/conts/retrieving.htmL or from the Cambridge Crystallographic Data Centre,
2 Union Road, Cambridge CB2 1EZ, UK; Fax: (internat.)+44-1223-336-033; E-mail:
data,
which
can
be
obtained
free
of
charge
at
1
deposit@ccdc.cam.ac.uk.
Synthesis and characterization of starting tetrazoles 1a-e.
Synthesis and characterization of tetrazoles 1a-c.
Solution of bromine (6.3 mmol, 1.1. eq.) in 10 ml of CHCl was added dropwise to solution of
3
5
-(2-arylethenyl)-2-methyl-2H-tetrazoles (5.7 mmol) in 10 ml of CHCl . Reaction mixture was
3
stirred at room temperature for 2 h, then solvent was evaporated under vacuo to give quantitatively
the corresponding 5-(2-aryl-1,2-dibromoethyl)-2-methyl-2H-tetrazoles (dibromotetrazoles) 1a'-c',
as white solids, which were used in the next step without any purification.
Dibromotetrazole, t-BuOK (2.5 eq.) and anhydrous THF (10 mL) were loaded in 15 mL glass
high pressure tube (ACE). The resulting suspension was magnetically stirred at 100 °C for 5 h.
After cooling, reaction mixture was poured into water and extracted with EtOAc (3 × 30 ml).
Extracts were combined and dried over Na SO . Solvent was evaporated under vacuo and residue
2
4
was recrystallized from ethanol to give the corresponding 5-arylethynyl-2-methyl-2H-tetrazoles 1a-
c.
5-(1,2-Dibromo-2-phenylethyl)-2-methyl-2H-tetrazole (1a'). M. p. 164-166 °C. White
1
solid. Н NMR [500 МHz, CDCl ], δ, ppm: , ppm: 4.42 (s, 3H, CH ), 5.79 (AB-system, d + d, 2H,
3
3
1
3
J = 11.8 Hz), 7.38-7.45 (m, 3Harom.), 7.51-7.53 (m, 2Harom.). С NMR [125 МHz, CDCl ], δ, ppm:
3
+
3
2
9.8, 41.9, 52.8, 127.9, 128.9, 129.3, 138.7, 165.7. GC-MS (I ,%): 346 M (1), 314 (1), 265 (15),
rel.
37 (7), 224 (1), 208 (1), 185 (35), 171 (7), 158 (100).
1
2
-Methyl-5-phenylethynyl-2H-tetrazole (1a). Yield 86 %. M. p. 95-97 °C. White solid. Н
NMR [500 МHz, CDCl ], δ, ppm: 4.38 (s, 3H, N-CH ), 7.37-7.42 (m, 3Harom.), 7.61-7.63 (m,
3
3
1
4

ACCEPTED MANUSCRIPT
1
3
2
Harom.). С NMR [125 МHz, CDCl ], δ, ppm: 39.7, 75.8, 93.8, 120.9, 128.5, 129.7, 132.1, 160.7.
3
+
GC-MS (I ,%): 184 M (5), 156 (100), 127 (30), 114 (27), 102 (12). IR (CHCl ): 2239 (C≡C).
rel.
3
HRMS: calcd. for C H N [M+H] 185.0822; found 185.0830.
1
0
8
4
5-(1,2-Dibromo-2-(4-methylphenyl)ethyl)-2-methyl-2H-tetrazole (1b'). M. p. 159-161 °C.
1
White solid. Н NMR [500 МHz, CDCl ], δ, ppm: 4.41 (s, 3H, CH ), 5.79 (AB-system, d + d, 2H,
3
3
1
3
J = 11.8 Hz), 7.23 (d, 2Harom., J = 8.0 Hz), 7.40 (d, 2Harom., J = 8.0 Hz). С NMR [125 МHz,
CDCl ], δ, ppm: 21.3, 39.7, 42.1, 53.0, 122.8, 129.6, 135.8, 139.4, 165.8.
3
2-Methyl-5-(4-methylphenylethynyl)-2H-tetrazole (1b). Yield 65 %. M. p. 120-122 °C.
1
White solid. Н NMR [500 МHz, CDCl ], δ, ppm: 2.37 (s, 3H, CH ), 4.37 (s, 3H, N-CH ), 7.18 (d,
3
3
3
1
3
2
Harom., J = 8.0 Hz), 7.50 (d, 2Harom., J = 8.0 Hz). С NMR [125 МHz, CDCl ], δ, ppm: 21.6, 39.7,
3
+
7
5.3, 94.2, 117.9, 129.3, 132.0, 151.4, 160.7. GC-MS (I ,%): 198 M (10), 170 (100), 141 (40),
rel.
1
28 (37), 115 (12). IR (CHCl ): 2231 (C≡C). HRMS: calcd. for C C H N [M+H] 199.0978;
3
11 10
4
found 199.0979.
5-(1,2-Dibromo-2-(4-methoxyphenyl)ethyl)-2-methyl-2H-tetrazole (1c'). M. p. 143-145
1
°
C. White solid. Н NMR [500 МHz, CDCl ], δ, ppm: 3.85 (s, 3H, OCH ), 4.41 (s, 3H, N-CH ),
3
3
3
1
3
5
.78 (ABq, 2H, J = 11.8 Hz), 6.95 (d, 2Harom., J = 8.6 Hz), 7.44 (d, 2Harom., J = 8.6 Hz). С NMR
[
(
[
125 МHz, CDCl ], δ, ppm: 39.8, 42.4, 53.3, 55.3, 114.3, 129.3, 130.8, 160.2, 165.9. GC-MS
3
+
I ,%): 375 M (1), 268 (2), 243 (100), 215 (43), 108 (30). HRMS: calcd. for C H Br N O
rel.
11 12
2
4
M+H] 374.9451; found 374.9451.
5-(4-Methoxyphenylethynyl)-2-methyl-2H-tetrazole (1c). Yield 65 %. M. p. 105-107 °C.
1
White solid. Н NMR [500 МHz, CDCl ], δ, ppm: 3.83 (s, 3H, OCH ), 4.37 (s, 3H, N-CH ), 6.89
3
3
3
13
(
d, 2Harom., J = 8.8 Hz), 7.55 (d, 2Harom., J = 8.8 Hz). С NMR [125 МHz, CDCl ], δ, ppm: 39.7,
3
+
5
5.3, 74.8, 94.2, 112.9, 114.2, 133.8, 151.5, 160.8. GC-MS (I ,%): 214 M (15), 186 (100), 171
rel.
(
5), 157 (60), 143 (50). IR (CHCl ): 2259 (C≡C). HRMS: calcd. for C H N O [M+H] 215.0927;
3 11 10 4
found 215.0930.
Synthesis and characterization of tetrazole 1d.
-Iodo-4-trifluoromethylbenzene (6.9 mmol, 1.5 eq.), 5-ethynyl-2-methyl-2H-tetrazole (4.6
1
mmol) 1e, CuI (0.046 mmol, 0.01 eq.), PdCl (0.12 mmol, 0.025 eq.) were dissolved in DMF and
2
stirred at 80 °C for 5 h under the argon atmosphere. The reaction control was carried out by TLC.
Reaction mixture was poured into water and extracted with EtOAc (3 × 30 mL), washed with water
(
2 ×50 mL), brine (50 mL), dried over Na SO , evaporated under vacuo to give dark brown oil.
2 4
Recrystallization from EtOH gave brown solid.
1
5

ACCEPTED MANUSCRIPT
2
-Methyl-5-[4-(trifluoromethylphenyl)ethynyl]-2H-tetrazole (1d). Yield 62 %. Mp. 136-
1
1
38 °C. Brown solid. Н NMR [500 МHz, CDCl ], δ, ppm: 4.41 (s, 3H, N-Me), 7.65 (d, 2Harom., J
3
13
=
8.2 Hz), 7.73 (d, 2Harom., J = 8.2 Hz). С NMR [125 МHz, CDCl ], δ, ppm: 39.8, 78.0, 92.1,
3
1
9
1
23.6 (q, J = 271 Hz), 124.7, 125.5 (q, J = 3.8 Hz), 131.3, 132.4, 160.7. F NMR [470 МHz,
+
CDCl ], δ, ppm: – 64.85 (s, CF ). GC-MS (I ,%): 252 M (2), 224 (100), 205 (8), 196 (52), 182
3
3
rel.
(
21). IR (CHCl ): 2282 (C≡C). HRMS: calcd. for C H F N [M+H] 253.0696; found 253.0707.
3 11 7 3 4
Synthesis and characterization of tetrazole 1e.
Solution of bromine (38.1 mmol, 1.05 eq.) in 20 mL of CHCl was added dropwise to solution
3
of 1-vinyltetrazole (36.3 mmol) шт 20 mL of CHCl . Reaction mixture was stirred at room
3
temperature for 2 h. Then solvent was evaporated under vacuo to give the corresponding 5-(1,2-
dibromoethyl)-2-methyl-2H-tetrazole, as yellow oil, which was used in the next step without any
purification. Solution of 5-(1,2-dibromoethyl)-2-methyl-2H-tetrazole in 10 mL of anhydrous THF
was added dropwise to solution of t-BuOK (91mmol, 2.5 eq.) in 40 mL of anhydrous THF at 0 °C.
Reaction mixture was stirred at 0 °C for 30 min, then at room temperature overnight. Solution was
poured into water and extracted with EtOAc (3×50 mL), washed with water (2 × 50 mL), brine (50
mL), dried over Na SO . Solvent was evaporated under vacuo to give brown oil, which was distilled
2
4
-2
in vacuo at 10 mbar (b.p. 83 °C) and collected as colorless oil with
1
9
1
5
-Ethynyl-2-methyl-2H-tetrazole (1e). Colorless oil, yield 64%. Н NMR [400 МHz,
13
CDCl ], δ, ppm: 3.33 (s, 1H, HC≡C), 4.37 (s, 3H, CH ). С NMR [100 МHz, CDCl ], δ, ppm:
3
3
3
3
9.7, 70.5, 82.5, 150.2. IR (CHCl ): 3269 (≡C–H), 2139 (C≡C).
3
General procedure for synthesis of E-/Z-5-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles 2
from tetrazoles 1 and arenes in CF SO H (Tables 3, 4).
3
3
A solution of tetrazole 1 (0.3 mmol) in TfOH (1 mL) and arene (0.9 mmol, 3 eq.) was stirred
at –40 ÷ 20°C for the time as indicated in Tables 3, 4. The mixture was poured into ice water (30
mL) and extracted with CHCl (3 × 30 mL). The extracts were combined, washed with water, a
3
saturated aqueous solution of NaHCO , water again, and dried over Na SO , the solvent was
3
2
4
evaporated under vacuo, and the residue was subjected to chromatographic separation on silica gel
using hexane–ethyl acetate as an eluent.
Yields of compounds 2a-p are given in Tables 3, 4.
General procedure for synthesis of E-/Z-5-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles 2
from tetrazoles 1 and arenes under the action of acidic zeolite HUSY CBV-720 (Tables 3, 4).
Zeolite HUSY CBV-720 (obtained from Zeolyst Int.) was activated at 550 °C under air for 4
h. The activated zeolite (0.45 g), tetrazoles 1 (0.3 mmol) and arene (3 ml) were loaded in a 15 mL
glass high pressure tube (ACE). The resulting suspension was stirred magnetically at 130 °C for the
1
6

ACCEPTED MANUSCRIPT
time indicated in Tables 3, 4. After cooling, the reaction mixture was filtered to remove the zeolite
catalyst. The zeolite was subsequently boiled with several portions of MeOH (3 × 10 ml) and
filtered off each time. The combined organic phases (arene and methanol solutions) were
concentrated in vacuo to provide a residue, which was subjected to chromatographic separation on
silica gel using hexane–ethyl acetate as an eluent.
Yields of compounds 2a-p are given in Tables 3, 4.
General procedures for tandem hydroarylation-ionic hydrogenation of tetrazoles 1.
Synthesis of 5-(2,2-diarylethyl)-2-methyl-2H-tetrazoles 5 (Table 5).
Method A. A solution of tetrazole 1 (0.3 mmol) in TfOH (1 mL), arene (0.1 mL) and
cyclohexane (0.1 mL) was stirred at room temperature for 1 h. The mixture was poured into ice
water (30 mL) and extracted with CHCl (3 × 30 mL). The extracts were combined, washed with
3
water, a saturated aqueous solution of NaHCO , water again, and dried over Na SO , the solvent
3
2
4
was distilled off under reduced pressure, and the residue was subjected to chromatographic
separation on silica gel using hexane–ethyl acetate as an eluent.
Method B. Tetrazole 1 (0.3 mmol) was added to solution of AlCl (5.0 mmol) in benzene (3
3
mL) and cyclohexane (0.5 mL). Reaction mixture was stirred at room temperature for 15 h. The
mixture was quenched with ice water (50 mL) extracted and worked-up as described above.
Yields of compounds 5a-b are given in Table 5.
General procedure for synthesis of 5-(2-aryl-2-oxoethyl)-2-methyl-2H-tetrazoles 4 from
tetrazoles 1 in H SO (Scheme 1).
2
4
A solution of tetrazole 1 (0.3 mmol) in H SO (3mL) was stirred at room temperature for 4-24
2
4
h. Reaction was controlled by TLC. The mixture was poured into ice water (30 mL) and extracted
with CHCl (3 × 30 mL). The extracts were combined, washed with water, a saturated aqueous
3
solution of NaHCO , water again, and dried over Na SO . The solvent was distilled off under
3
2
4
reduced pressure, and the residue was subjected to chromatographic separation on silica gel using
hexane–ethyl acetate as an eluent.
General procedure for synthesis of vinyl triflates 6 from tetrazoles 1 in CF SO H
3
3
(Scheme 2).
A solution of tetrazoles 1 (0.3 mmol) in TfOH (1 mL) was stirred at room temperature for 1h.
The mixture was poured into ice water (30 mL) and extracted with CHCl (3 × 30 mL). The extracts
3
were combined, washed with water and dried over Na SO , the solvent was distilled off under
2
4
reduced pressure to give yellow oily compounds.
Characterization of compounds 2, 3, 4, 5, 6.
1
7

ACCEPTED MANUSCRIPT
1
5
-(2,2-Diphenylethenyl)-2-methyl-2H-tetrazole (2a). Oil. Н NMR [500 МHz, CDCl ], δ,
3
1
3
ppm: 4.17 (s, 3H, N-CH ), 7.08 (s, 1H, =CH), 7.23-7.24 (m, 2Harom.), 7.33-7.38 (m, 8Harom.). С
3
NMR [125 МHz, CDCl ], δ, ppm: 39.2, 112.7, 127.93, 127.95, 128.2, 128.4, 128.6, 129.8, 139.3,
3
+
1
41.7, 149.6, 163.6. GC-MS (I ,%): 262 M (5), 234 (35), 204 (15), 191 (100), 176 (10). HRMS:
rel.
calcd. for C H N [M+H] 263.1291; found 263.1296.
1
6
14
4
(E)-5-(2-(3,4-Dimethylphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2b) and (Z)-5-(2-
(3,4-dimethylphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2c) were obtained as inseparable
oily mixture of isomers with ratio ~ 1 : 0.6. (E)-5-(2-(3,4-Dimethylphenyl)-2-phenylethenyl)-2-
1
methyl-2H-tetrazole (2b) Н NMR [500 МHz, CDCl , from the spectrum of the mixture of
3
isomers], δ, ppm: 2.25 (s, 3H, CH ), 2.28 (s, 3H, CH ), 4.16 (s, 3H, N-CH ), 6.98-7.37 (m, 8Harom.),
3
3
3
+
7
.04 (s, 1H, =CH). GC-MS (I ,%, for 2b): 290 [M] (10), 275 (21), 262 (74), 219 (100), 203 (85).
rel.
1
(
Z)-5-(2-(3,4-Dimethylphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2c). Н NMR [500
МHz, CDCl , from the spectrum of the mixture of isomers], δ, ppm: 2.22 (s, 3H, CH ), 2.30 (s, 3H,
3
3
CH ), 4.20 (s, 3H, N-CH ), 6.98 (s, 1H, =CH), 6.98-7.37 (m, 8H
). GC-MS (I ,%, for 2c): 290
3
3
arom.
rel.
+
13
M (5), 275 (12), 262 (65), 247 (15), 234 (30), 219 (80), 203 (100). С NMR [125 МHz, CDCl ,
3
data for the mixture of isomers 2b and 2c], δ, ppm: 19.5, 19.6, 19.7, 19.8, 39.1, 39.2, 111.7, 112.3,
1
1
25.5, 127.4, 127.8, 128.0, 128.1, 128.2, 128.4 129.0, 129.3, 129.6, 129.7, 130.9, 136.1, 136.3,
36.47, 136.49, 137.3, 139.3, 139.4, 142.3, 149.7, 149.9, 163.8. HRMS (for mixture of isomers):
calcd. for C H N [M+H] 291.1604; found 291.1605.
1
8
18
4
1
(E)-5-(2-(2,4-Dimethylphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2d). Oil.
Н
NMR [400 МHz, CDCl ], δ, ppm: 2.01 (s, 3H, CH ), 2.38 (s, 3H, CH ), 4.16 (s, 3H, N-CH ), 6.96-
3
3
3
3
7
2
1
.03 (m, 2Harom.), 7.07 (br.s, 1Harom.), 7.22 (s, 1H, =CH), 7.31-7.33 (m, 3Harom.), 7.37-7.39 (m,
1
3
Harom.). С NMR [101 МHz, CDCl ], δ, ppm: 19.5, 21.3, 39.2, 113.0, 126.4, 127.0, 128.4, 128.5,
3
+
29.2, 130.9, 135.8, 136.0, 137.3, 140.6, 148.5, 163.7. GC-MS (I ,%): 290 M (5), 275 (22), 262
rel.
(
45), 247 (8), 219 (100), 203 (80). HRMS: calcd. for C H N [M+H] 291.1604; found 291.1605.
18 18 4
(E)-5-(2-(2,5-Dimethylphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2e) and (Z)-5-(2-
(2,5-dimethylphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2f) were obtained as inseparable
oily mixture of isomers with ratio ~1:0.06. (E)-5-(2-(2,5-Dimethylphenyl)-2-phenylethenyl)-2-
1
methyl-2H-tetrazole (2e). Н NMR [500 МHz, CDCl , from the spectrum of the mixture of
3
isomers], δ, ppm: 2.02 (s, 3H, CH ), 2.30 (s, 3H, CH ), 4.15 (s, 3H, N-CH ), 6.89 (s, 1H, =CH),
3
3
3
1
3
7
.08-7.15 (m, 2Harom.), 7.24 (s, 1Harom.), 7.33-7.40 (m, 5Harom.). С NMR [125 МHz, CDCl , from
3
the spectrum of the mixture of isomers], δ, ppm: 19.1, 21.0, 39.2, 112.8, 127.0, 128.48, 128.52,
+
1
29.7, 129.9, 133.0, 135.0, 138.6, 140.5, 148.4, 163.6. GC-MS (I ,%, for 2e): 290 M (3), 275
rel.
(45), 262 (27), 247 (78), 233 (38), 219 (72), 203 (100). (Z)-5-(2-(2,5-Dimethylphenyl)-2-
1
8

ACCEPTED MANUSCRIPT
1
phenylethenyl)-2-methyl-2H-tetrazole (2f). Н NMR [500 МHz, CDCl , from the spectrum of the
3
mixture of isomers], δ, ppm: 2.05 (s, 3H, CH ), 2.35 (s, 3H, CH ), 4.24 (s, 3H, N-CH ), 6.67 (s, 1H,
3
3
3
+
=
CH), 7.08-7.40 (m, 8Harom.). GC-MS (I ,%, for 2f): 290 M (2), 275 (25), 262 (27), 247 (45), 233
rel.
(
15), 219 (51), 203 (100). HRMS (for mixture of isomers): calcd. for C H N [M+H] 291.1604;
18 18 4
found 291.1605.
(E)-5-(2-(4-Methoxyphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2g) and (Z)-5-(2-(4-
methoxyphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2h) were obtained as inseparable oily
mixture of isomers with ratio ~1:0.6. (E)-5-(2-(4-Methoxyphenyl)-2-phenylethenyl)-2-methyl-
1
2
H-tetrazole (2g). Н NMR [400 МHz, CDCl , from the spectrum of the mixture of isomers], δ,
3
ppm: 3.82 (s, 3H, OCH ), 4.16 (s, 3H, N-CH ), 6.87 (d, 2Harom., J = 8.8. Hz), 7.01 (s, 1H, =CH),
3
3
13
7
.20-7.22 (m, 2Harom.), 7.31 (d, 2Harom., J = 8.8. Hz), 7.35-7.37 (m, 3Harom.). С NMR [101 МHz,
CDCl , from the spectrum of the mixture of isomers], δ, ppm: 39.2, 55.3, 110.9, 113.8, 127.9,
3
+
1
28.1, 129.2, 129.7, 131.3, 134.2, 139.5, 149.1, 160.1. GC-MS (I ,%, for 2g): 292 M (12), 280
rel.
(5), 264 (25), 249 (3), 236 (21), 221 (100), 206 (15). (Z)-5-(2-(4-Methoxyphenyl)-2-
1
phenylethenyl)-2-methyl-2H-tetrazole (2h). Н NMR [400 МHz, CDCl , , from the spectrum of
3
the mixture of isomers], δ, ppm: 3.85 (s, 3H, OCH ), 4.20 (s, 3H, N-CH ), 6.86-7.37 (m, 9Harom.),
3
3
1
3
6
.98 (s, 1H, =CH). С NMR [101 МHz, CDCl , from the spectrum of the mixture of isomers], δ,
3
ppm: 39.3, 55.2, 112.3, 113.5, 128.2, 128.3, 128.6, 131.3, 131.4, 142.3, 149.5, 159.4, 163.9. GC-
+
MS (I ,%, for 2h): 292 M (10), 264 (30), 249 (5), 235 (12), 221 (100), 206 (13). HRMS (for
rel.
mixture of isomers): calcd. for C H N O [M+H] 293.1397; found 293.1401.
1
7
16
4
(E)-5-(2-(3,4-Dimethoxyphenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2i) and (Z)-5-
(2-(3,4-dimethoxyphenyl)-2-phenylethyl)-2-methyl-2H-tetrazole (2j) were obtained as
inseparable oily mixture of isomers with ratio ~1:0.6. (E)-5-(2-(3,4-Dimethoxyphenyl)-2-
1
phenylethenyl)-2-methyl-2H-tetrazole (2i). Н NMR [500 МHz, CDCl , from the spectrum of the
3
mixture of isomers], δ, ppm: 3.84 (s, 3H, OCH ), 3.89 (s, 3H, OCH ), 4.16 (s, 3H, N-CH ), 6.80-
3
3
3
6
3
1
.86 (m, 2Harom.), 6.95-6.97 (m, 1Harom.), 7.02 (s, =CH), 7.22-7.24 (m, 2Harom.), 7.36-7.37 (m,
13
Harom.). С NMR [125 МHz, CDCl , from mixture of compounds], δ, ppm: 39.2. 55.9, 55.95,
3
10.6, 110.7, 111.1, 121.3, 128.0, 128.1, 129.8, 134.4, 139.3, 148.7, 149.3, 149.7, 163.8. (Z)-5-(2-
1
(
3,4-Dimethoxyphenyl)-2-phenylethyl)-2-methyl-2H-tetrazole (2j). Н NMR [500 МHz CDCl ,
3
from the spectrum of the mixture of isomers], δ, ppm: 3.51 (s, 3H, OCH ), 3.89 (s, 3H, OCH ),
3
3
4
7
.16 (s, 3H, N-CH ), 6.71 (dd, 1Harom., J = 1.4, 7.6 Hz), 6.95-6.97 (m, 1Harom.), 7.07 (t, 1Harom., J =
3
1
3
.6 Hz), 7.20 (s, =CH), 7.32-7.33 (m, 3Harom.), 7.42-7.44 (m, 2Harom.). С NMR [125 МHz, CDCl ,
3
from the spectrum of the mixture of isomers], δ, ppm: 39.2, 55.7, 60.4, 112.2, 113.5, 122.5, 123.9,
1
9

ACCEPTED MANUSCRIPT
1
27.1, 128.36, 128.42, 133.8, 140.9, 145.6, 146.8, 153.0, 163.7. HRMS (for mixture of isomers):
calcd. for C H N O [M+H] 323.1503; found 323.1508.
1
8
18
4
2
(E)-5-(2-(3,4-Dichlorophenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2k) and (Z)-5-(2-
(3,4-dichlorophenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2l) were obtained as inseparable
oily mixture of isomers with ratio ~1:0.3. (E)-5-(2-(3,4-Dichlorophenyl)-2-phenylethenyl)-2-
1
methyl-2H-tetrazole (2k). Н NMR [400 МHz, CDCl , from the spectrum of the mixture of
3
isomers], δ, ppm: 4.18 (s, 3H, N-CH ), 7.05 (s, 1H, =CH), 7.21-7.24 (m, 3Harom.), 7.40-7.44 (m,
3
1
3
5
1
Harom.). С NMR [101 МHz, CDCl , from the spectrum of the mixture of isomers], δ, ppm: 39.3,
3
14.1, 126.8, 127.1, 128.4, 128.7, 129.6, 129.7, 130.3, 132.7, 138.1, 141.8, 147.2, 163.1. (Z)-5-(2-
1
(
3,4-Dichlorophenyl)-2-phenylethenyl)-2-methyl-2H-tetrazole (2l). Н NMR [400 МHz, CDCl ,
3
from the spectrum of the mixture of isomers], δ, ppm: 4.17 (s, 3H, N-CH ), 7.18-7.44 (m, 8Harom.),
3
7
3
.30 (s, 1H, =CH). HRMS (for mixture of isomers): calcd. for C H Cl N [M+H] 331.0512; found
16 12 2 4
31.0522.
E)-2-Methyl-5-(2-phenyl-2-(4-methylphenyl)ethenyl)-2H-tetrazole (2m) and (Z)-2-
(
methyl-5-(2-phenyl-2-(4-methylphenyl)ethenyl)-2H-tetrazole (2n) were obtained as inseparable
oily mixture of isomers. (E)-2-Methyl-5-(2-phenyl-2-(4-methylphenyl)ethenyl)-2H-tetrazole
1
(
2m). Н NMR [400 МHz, CDCl , from the spectrum of the mixture of isomers], δ, ppm: 2.34 (s,
3
3
2
H, CH ), 4.19 (s, 3H, N-CH ), 7.04 (s, 1H, =CH), 7.06-7.37 (m, 9H
). GC-MS (I ,%, for 2m):
3
3
arom. rel.
+
76 M (4), 248 (42), 219 (18), 205 (100), 189 (55). (Z)-2-methyl-5-(2-phenyl-2-(4-
1
methylphenyl)ethenyl)-2H-tetrazole (2n). Н NMR [400 МHz, CDCl , from the spectrum of the
3
mixture of isomers], δ, ppm: 2.36 (s, 3H, CH ), 4.22 (s, 3H, N-CH ), 7.02 (s, 1H, =CH), 7.06-7.37
3
3
+
13
(
m, 9Harom.). GC-MS (I ,%, for 2n): 276 M (3), 248 (35), 219 (12), 205 (100), 189 (51). С NMR
rel.
[
101 МHz, CDCl , data for the mixture of isomers 2m and 2n], δ, ppm: 21.1, 21.3, 39.4, 39.5,
3
1
12.9, 113.5, 128.5, 128.53, 128.7, 128.9, 129.2, 129.3, 129.5, 129.9, 130.5, 130.6, 137.3, 138.3,
39.3, 139.9, 140.5, 143.0, 149.9, 150.1, 164.1 164.15. HRMS (for mixture of isomers): calcd. for
1
C H N [M+Na] 299.1273; found 299.1279.
17
16
4
(E)-2-Methyl-5-[2-phenyl-2-(4-(trifluoromethyl)phenyl)ethenyl]-2H-tetrazole (2o) and
(Z)-2-methyl-5-[2-phenyl-2-(4-(trifluoromethyl)phenyl)ethenyl]-2H-tetrazole (2p) were
obtained as inseparable oily mixture of isomers with ratio ~1:0.6. (E)-2-Methyl-5-[2-phenyl-2-(4-
1
(
trifluoromethyl)phenyl)ethenyl]-2H-tetrazole (2o). Н NMR [500 МHz, CDCl , from mixture of
3
compounds], δ, ppm: 4.20 (s, 3H, N-CH ), 7.18 (s, 1H, =CH), 7.24-7.25 (m, 2Harom.), 7.39-7.82 (m,
3
13
7
Harom.). С NMR [125 МHz, CDCl , from the spectrum of the mixture of isomers], δ, ppm: 39.3,
3
1
14.5, 127.8, 128.3, 128.4, 130.0, 130.1 (q, J = 283.3 Hz), 130.2, 132.5, 138.6, 145.6, 148.5, 163.3.
1
9
F NMR [470 МHz, CDCl , from mixture of compounds], δ, ppm: – 73.40 (s, CF ). (Z)-2-Methyl-
3
3
2
0

ACCEPTED MANUSCRIPT
1
5
-[2-phenyl-2-(4-(trifluoromethyl)phenyl)ethenyl]-2H-tetrazole (2p). Н NMR [500 МHz,
CDCl , from mixture of compounds], δ, ppm: 4.21 (s, 3H, N-CH ), 7.15 (s, 1H, =CH), 7.39-7.82
3
3
1
9
(
m, 9Harom.). F NMR [470 МHz, CDCl , from mixture of compounds], δ, ppm: – 73.53 (s, CF ).
3
3
HRMS (for mixture of isomers): calcd. for C H F N [M+H] 331.1165; found 331.1178.
1
7
13
3
4
1
2
-Methyl-5-(2,2,2-triphenylethyl)-2H-tetrazole (3a). White solid, mp. 163-165 °C. Н
NMR [500 МHz, CDCl ], δ, ppm: 4.06 (s, 3H, N-CH ), 4.25 (s, 2H, CH ), 7.15-7.29 (m, 15Harom.).
3
3
2
1
3
С NMR [125 МHz, CDCl ], δ, ppm: 37.1, 39.0, 57.3, 126.2, 127.7, 129.4, 146.3, 164.3. GCMS
3
+
(
I, %): 340 [M] (6), 312 (6), 283 (5), 243 (100), 165 (55). HRMS: calcd. for C H N [M+H]
2
2
20
4
3
41.1761; found 341.1767.
-(2,2-diphenyl-2-[4-(trifluoromethyl)phenyl]ethyl)-2-methyl-2H-tetrazole (3b). Oil. Н
NMR [500 МHz, CDCl ] 4.01 (s, 3H, N-CH ), 4.22 (s, 2H, CH ), 7.11-7.14 (m, 2Harom.), 7.17-7.21
1
5
3
3
2
(m, 2Harom.), 7.37-7.40 (m, 4Harom.), 7.49 (t, 2Harom., J = 7.4 Hz), 7.63 (t, 2Harom., J = 8.5 Hz), 7.71-
1
3
7
1
.72 (m, 2Harom.). С NMR [125 МHz, CDCl ], δ, ppm: 37.0, 39.1, 57.5, 126.6, 128.0, 128.3,
3
19
29.4, 129.5, 129.6 (q, J = 221 Hz), 129.7, 130.0, 132.4, 135.4, 137.6, 145.7, 151.1, 164.0. F
NMR [470 МHz, CDCl ], δ, ppm: – 73.42 (s, CF ).
3
3
1
2
-(2-Methyl-2H-tetrazol-5-yl)-1-phenylethanone (4a). White solid, mp 71-73 °C. Н NMR
[
500 МHz, CDCl ], δ, ppm: 4.34 (s, 3H, N-CH ), 4.60 (a, 2H, CH ), 7.49 (t, 2Harom., J = 7.4 Hz),
3
3
2
1
3
7
.60 (t, 1Harom., J = 7.4 Hz), 8.03 (d, 2Harom., J = 7.4 Hz). С NMR [125 МHz, CDCl ], δ, ppm:
3
+
3
5.9, 39.4, 128.5, 128.8, 133.7, 135.8, 160.7, 193.6. GC-MS (I ,%): 202 M (2), 174 (7), 105
rel.
(
100), 77 (32). HRMS: calcd. for C H N O [M+H] 203.0927; found 203.0934.
10 10 4
2-(2-Methyl-2H-tetrazol-5-yl)-1-(4-methylphenyl)ethanone (4b). White solid, mp 117-119
1
°
C. Н NMR [500 МHz, CDCl ], δ, ppm: 2.42 (s, 3H, CH ), 4.34 (s, 3H, N-CH ), 4.57 (s, 2H,
3 3 3
1
3
CH ), 7.28 (d, 2Harom., J = 8.2 Hz), 7.93 (d, 2Harom., J = 8.2 Hz). С NMR [125 МHz, CDCl ], δ,
2
3
+
ppm: 21.6, 35.9, 39.4, 128.6, 129.5, 133.4, 144.6, 160.9, 193.2. GC-MS (I ,%): 216 M (2), 188
rel.
(
4), 119 (100), 103 (2), 91 (28). HRMS: calcd. for C H N O [M+H] 217.1084; found 217.1083.
11 12 4
2-(2-Methyl-2H-tetrazol-5-yl)-1-(4-methoxyphenyl)ethanone (4c). White solid, mp 102-
1
1
04 °C. Н NMR [500 МHz, CDCl ], δ, ppm: 3.88 (s, 3H, OCH ), 4.34 (s, 3H, N-CH ), 4.55 (s,
3
3
3
1
3
2
H, CH ), 6.95 (d, 2Harom., J = 8.8 Hz), 8.01-8.03 (m, 2Harom.). С NMR [125 МHz, CDCl ], δ,
2
3
ppm: 35.7, 39.4, 55.5, 113.9, 128.9, 130.88, 130.91, 164.0, 192.1. HRMS: calcd. for C H N O
2
1
1
12
4
[
M+H] 233.1033; found 233.1029.
2-(2-Methyl-2H-tetrazol-5-yl)-1-[4-(trifluoromethyl)phenyl]ethanone (4d). Brown solid,
1
mp 102-104 °C. Н NMR [500 МHz, CDCl ], δ, ppm: 4.35 (s, 3H, N-CH ), 4.55 (s, 2H, CH ), 7.76
3
3
2
13
(
d, 2Harom., J = 8.1 Hz), 8.13 (d, 2Harom., J = 8.1 Hz). С NMR [125 МHz, CDCl ], δ, ppm: 36.3,
3
3
9.5, 123.4 (q, J = 272 Hz), 125.9 (d, J = 2.7 Hz), 128.9, 135.0 (d, J = 32.6 Hz), 138.4. 160.2,
2
1

ACCEPTED MANUSCRIPT
19
+
1
92.7. F NMR [470 МHz, CDCl ], δ, ppm: – 61.96 (s, CF ). GC-MS (I ,%): 270 M (1), 252
3 3 rel.
(
4), 242 (12), 13 (100), 145 (52). HRMS: calcd. for C H F N O [M+Na] 293.0626; found
11 9 3 4
2
93.0607.
-(2,2-Diphenylethyl)-2-methyl-2H-tetrazole (5a). Oil. Н NMR [500 МHz, CDCl ], δ,
1
5
3
ppm: 3.61 (d, 2H, CH , J = 8.2 Hz), 4.19 (s, 3H, N-CH ), 4.68 (t, 1H, CH, J = 8.2 Hz), 7.13-7.17
2
3
13
(
m, 2Harom.), 7.23-7.26 (m, 8Harom.). С NMR [125 МHz, CDCl ], δ, ppm: 31.6, 39.2, 49.6, 126.5,
3
+
1
27.8, 128.5, 143.3, 165.2. GC-MS (I ,%): 264 M (15), 167 (100), 152 (13). HRMS: calcd. for
rel.
C H N [M+Na] 287.1273; found 287.1275.
16
16
4
1
5
-[2-(2,4-Dimethylphenyl)-2-phenylethyl]-2-methyl-2H-tetrazole (5b). Oil. Н NMR [500
МHz, CDCl ], δ, ppm: 2.26 (s, 3H, OCH ), 2.29 (s, 3H, OCH ), 3.40-3.64 (m, 2H, CH ), 4.20 (s,
3
3
3
2
+
3
H, N-CH ), 4.61-4.70 (m, 2H, CH), 6.90-7.27 (m, 8H
). GC-MS (I ,%): 292 M (12), 264
arom. rel.
3
(
25), 249 (3), 236 (21), 221 (100), 206 (13).
E)-5-[2-Phenyl-2-trifluoromethylsulfonyloxyethenyl]-2-methyl-2H-tetrazole (6a) and
Z)-5-[2-phenyl-2-trifluoromethylsulfonyloxyethenyl]-2-methyl-2H-tetrazole (6a) were
(
(
obtained as inseparable oily mixture of isomers with ratio ~1:0.9. (E)-5-[2-Phenyl-2-
1
trifluoromethylsulfonyloxyethenyl]-2-methyl-2H-tetrazole (6a). H NMR [500 MHz, CDCl ,
3
from the spectrum of the mixture of isomers], δ, ppm: 4.41 (s, 3H N-CH ), 6.94 (s, 1H, =CH),
,
3
1
9
7
.43-7.65 (m, 5Harom.). F NMR [470 МHz, CDCl , from the spectrum of the mixture of isomers],
3
δ, ppm: – 73.61 (s, OSO CF ). (Z)-5-[2-Phenyl-2-trifluoromethylsulfonyloxyethenyl]-2-methyl-
2
3
1
2
H-tetrazole (6a). H NMR [500 MHz, CDCl , from the spectrum of the mixture of isomers], δ,
3
19
ppm: 4.26 (s, 3H N-CH ), 6.89 (s, 1H, =CH), 7.43-7.65 (m, 5H
). F NMR [470 МHz, CDCl ,
3
,
3
arom.
1
3
from the spectrum of the mixture of isomers], δ, ppm: – 73.78 (s, OSO CF ). С NMR [125 МHz,
2
3
CDCl , data for the mixture of isomers E-/Z-6a], δ, ppm: 39.5, 39.6, 107.8, 109.4, 118.2 (q, J = 319
3
Hz, OSO CF ), 118.4 (q, J = 319 Hz, OSO CF ), 126.3, 128.3, 129.0 (2 peaks), 129.2, 130.9, 131.2,
2
3
2
3
1
3
32.6, 150.5, 152.9, 159.4, 159.6. HRMS (for mixture of isomers): calcd. for C H F N O S [M+H]
11 9 3 4 3
35.0420; found 335.0418.
(Z)-5-[2-(4-Methylphenyl)-2-trifluoromethylsulfonyloxyethenyl]-2-methyl-2H-tetrazole
1
(
6b). Oil. H NMR [400 MHz, CDCl ], δ, ppm: 2.44 (s, 3H, Me), 4.43 (s, 3H, N-CH ), 6.92 (s, 1H,
3
3
1
3
=
CH), 7.30 (d, 2Harom., J = 8.3 Hz), 7.56 (d, 2Harom., J = 8.3 Hz). С NMR [125 МHz, CDCl ], δ,
3
ppm: 21.6, 39.8, 107.1, 118.4 (q, J = 321 Hz, OSO CF ), 126.42, 129.84, 130.03, 141.64, 150.94,
2
3
1
9
1
59.88. F NMR [376 MHz, CDCl ], δ, ppm: – 73.57 (s, OSO CF ). HRMS: calcd. for
3 2 3
C H F N O S [M+H] 349.0577; found 349.0544.
12
11
3
4
3
(E)-5-[2-(4-Trifluoromethylphenyl)-2-trifluoromethylsulfonyloxyethenyl]-2-methyl-2H-
tetrazole (6d) and (Z)-5-[2-(4-trifluoromethylphenyl)-2-trifluoromethylsulfonyloxyethenyl]-2-
2
2

ACCEPTED MANUSCRIPT
methyl-2H-tetrazole (6d) were obtained as inseparable oily mixture of isomers with ratio ~1:0.6.
(E)-5-[2-(4-Trifluoromethylphenyl)-2-trifluoromethylsulfonyloxyethenyl]-2-methyl-2H-
1
tetrazole (6d). H NMR [500 MHz, CDCl , from the spectrum of the mixture of isomers], δ, ppm:
3
1
9
4
.29 (s, 3H N-CH ), 6.99 (s, 1H, =CH), 7.65-7.78 (m, 4H
). F NMR [470 МHz, CDCl , from
,
3
arom. 3
the spectrum of the mixture of isomers], δ, ppm: – 73.59 (s, OSO CF ), – 63.09 (s, CF ). (Z)-5-[2-
2
3
3
(4-Trifluoromethylphenyl)-2-trifluoromethylsulfonyloxyethenyl]-2-methyl-2H-tetrazole (6d).
1
H NMR [500 MHz, CDCl , from the spectrum of the mixture of isomers], δ, ppm: 4.43 (s, 3H N-
3
,
1
9
CH ), 7.03 (s, 1H, =CH), 7.65-7.78 (m, 4H
). F NMR [470 МHz, CDCl , from the spectrum of
3
3
arom.
1
3
the mixture of isomers], δ, ppm: – 73.49 (s, OSO CF ), – 63.04 (s, CF ). С NMR [125 МHz,
2
3
3
CDCl , data for the mixture of isomers E-/Z-6d], δ, ppm: 39.6, 39.7, 109.8, 111.0, 118.2 (q, J = 319
3
Hz, OSO CF ), 118.3 (q, J = 319 Hz, OSO CF ), 123.5 (q, J = 271 Hz, CF ), 123.54 (q, J = 271 Hz,
2
3
2
3
3
CF ), 125.4, 126.1, 126.6, 129.7, 132.4, 133.0, 134.5, 136.1, 148.7, 150.9, 159.0, 159.2. HRMS (for
3
mixture of isomers): calcd. for C H F N O S [M+Ag] 508.9272; found 508.9272.
1
2
8
6
4
3
Acknowledgements
This work was supported by Russian Science Foundation (grant no. 17-73-10087) (synthesis of
tetrazoles 3-6), and Russian Foundation for Basic Research (grant no. 15-03-02936-a) (synthesis of
tetrazoles 1, 2). Spectral studies were performed at Center for Magnetic Resonance, Center for
Chemical Analysis and Materials, Research Center for X-ray Diffraction Studies of Saint
Petersburg University (Saint Petersburg, Russia).
Supplementary data
1
13
19
These data include H, C, F NMR spectra of the obtained compounds, details of DFT
calculations, X-ray data.
References and notes
1
. Ostrovskii, V.A.; Popova, E.A.; Trifonov, R.E. Developments in Tetrazole Chemistry
2009-16). In: Advances in Heterocyclic Chemistry. Eds: Scriven, C.F.V.; Ramsden, Ch. A.
Academic Press (An imprint of Elsevier), 2017, v.123, p.1-62.
(
2. Yet. L. Progress in Heterocyclic Chemistry, 2016, 28, 275.
3. Butler, R. N. In Comprehensive Heterocyclic Chemistry II, vol. 4; Katritzky, A. R.; Rees,
C. W.; Scriven, E. F. V., eds.; Pergamon: Oxford, 1996, p. 897.
2
3

ACCEPTED MANUSCRIPT
4
. Ostrovskii, V. A.; Koldobskii, G. I.; Trifonov, R. E. In Comprehensive Heterocyclic
Chemistry III, vol. 6; Katritzky, A. R.; Ramsden, C. A.; Scriven, E. F. V.; Taylor, R. J. K., eds.;
Elsevier: Oxford, 2008, p. 257.
5. Wei, C.-X.; Bian, M.; Gong, C.-H. Molecules 2015, 20, 5528.
6. Hammerl, A.; Hiskey, M. A.; Holl, M.; Klapötke, T. M.; Polborn, K.; Stierstorfer, J.;
Weigand, J. J. Chem. Mater. 2005, 17, 3784.
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Highlights
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Synthesis of acetylene tetrazoles
Hydroarylation of the triple bond of acetylene tetrazoles under superelectrophilic activation
Hydroarylation-ionic hydrogenation of the triple bond of acetylene tetrazoles under
superelectrophilic activation
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Addition of acids to the triple bond of acetylene tetrazoles
DFT calculation of cations derived under protonation of acetylene tetrazoles