Pyrazoles and C-Imidoylaziridines through [4+1] Annulation and [2+1] Cycloaddition of 1-Azabuta-1,3-dienes with a Synthetic Equivalent of Phthalimidonitrene

Article abstract of DOI:10.1002/ejoc.201700172

Oxidative addition of N-aminophthalimide to 1,2,4-triaryl-1-azabuta-1,3-dienes leads, in most cases, to the regiodefined formation of 1,3,5-triarylpyrazoles in moderate to good yields through [4+1] annulation. This transformation is supposed to proceed by nitrenoid attack onto a lone pair of electrons of the imine nitrogen atom to give the vinylazomethine imine, followed by its 1,5-electrocyclization into pyrazoline and further aromatization into pyrazole. Rare examples of 2-imidoyl-1-phthalimidoaziridines that are formed by competitive [2+1] cycloaddition onto the C=C bond were isolated in low yields for 1-azadienes with electron-deficient aryl substituents at the imine nitrogen atom.

Full text of DOI:10.1002/ejoc.201700172

A Journal of
Accepted Article
Title: Pyrazoles and C-imidoylaziridines via [4+1]-annulation and [2+1]-
cycloaddition of 1-azabuta-1,3-dienes with a synthetic equivalent
of phthalimidonitrene
Authors: Aleksandr Stukalov, Viktor Sokolov, Vitalii Suslonov, and
Mikhail Kuznetsov
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201700172
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10.1002/ejoc.201700172
European Journal of Organic Chemistry
FULL PAPER
Pyrazoles and C-imidoylaziridines via [4+1]-annulation and [2+1]-
cycloaddition of 1-azabuta-1,3-dienes with a synthetic equivalent
of phthalimidonitrene
Aleksandr Stukalov,[a] Viktor V. Sokolov,[a] Vitalii V. Suslonov[b] and Mikhail A. Kuznetsov *[a]
This paper is dedicated to Prof. I. Kalvinsh (LIOS, Riga) on the occasion of his 70th birthday.
Abstract: Oxidative addition of N-aminophthalimide to 1,2,4-triaryl-
1-azabuta-1,3-dienes leads, in most cases, to the regiodefined
formation of 1,3,5-triarylpyrazoles via [4+1]-annulation in moderate
to good yields. This transformation is supposed to proceed via a
nitrenoid attack onto a lone pair of the imine nitrogen atom giving the
vinyl-azomethine imine, followed by its 1,5-electrocyclization into
pyrazoline and further aromatization into pyrazole. Rare examples of
2-imidoyl-1-phthalimidoaziridines that are formed via competitive
[2+1]-cycloaddition onto the C=C bond were isolated in low yields for
1-azadienes with electron-deficient aryl substituents at the imine
nitrogen atom.
Introduction
A variety of nitrogen heterocycles can be conveniently
prepared via readily accessible building blocks with a 1-
azadiene (C=C–C=N) moiety. Such precursors are widely used
in [4+2]-annulation reactions utilizing a multitude of partners
Scheme 1. Synthesis of 2H-1,2,3-triazoles and pyrazoles
such as alkenes, alkynes, allenes, isocyanates, carbonyl
compounds, etc., leading to six-membered nitrogen
heterocycles.1 [4+1]-Annulations of 1-azabuta-1,3-dienes with
Since pyrazoles find numerous applications as pharmaceuticals
and for pest control, as dyes and ligands for transition metal
Fisher carbenes of chromium, in situ generated carbenes, sulfur
ylides, allylcarbonates, isonitriles, rhodium vinylidenes lead to
catalysts or luminophores,7 we studied this intriguing
pyrrolines and pyrroles.2 These diverse, well-known
transformation in details, as reported below.
transformations add a one-carbon fragment to the C=C–C=N
system. In contrast, reactions of 1-azadienes with aziridinating
Results and Discussion
reagents are scarce and include only copper-catalyzed
aziridination of N-substituted hydrazones of α,β-unsaturated
aldehydes3 as well as aminoaziridination of phthaloyl hydrazone
of cinnamic aldehyde.4 Because oxidative addition of N-
aminophthalimide to C=C bonds is a convenient approach to N-
phthalimidoaziridines with a different substitution pattern from
that highlighted above,5 we set about to explore if 2-imidoyl-1-
phthalimidoaziridines could be prepared from 1,2,4-triaryl-1-
azabuta-1,3-dienes (Scheme 1). Previously, we obtained
Starting imines 1a-n were obtained from chalcones and
arylamines in good yields in the presence of TiCl4/Et3N8
(Table 1) and were characterized by 1H, 13C NMR and
HRMS (ESI). According to the H and 13C NMR spectra,
1
these α,β-unsaturated imines exist as mixtures of (E/Z)-
isomers about the C=N bond in a ratio varying from 1.9:1 to
3.6:1. In most cases, these stereoisomers are
configurationally stable at room temperature on the NMR
time scale, with the exception of 1i that shows broad
signals in the 1H NMR spectrum that transform into two sets
of signals of (E/Z)-isomeric forms only at –20 °C. This is in
accord with lower barriers of isomerization for N-arylimines
with more electron-withdrawing substituents at the nitrogen
azoaziridines
and
2H-1,2,3-triazoles
from
conjugated
azoalkenes (1,2-diazabuta-1,3-dienes) via in situ oxidation of N-
aminophthalimide by lead tetraacetate.6 Now we have
unexpectedly found that it is mainly 1,3,5-triarylpyrazoles are
formed from 1-azadienes instead of imidoylaziridines under
similar conditions.
atom.9
Detailed
spectroscopic
analysis
of
the
[a]
[b]
Institute of Chemistry, Saint Petersburg State University,
Universitetskii pr. 26, 198504 Saint Petersburg, Russia.
E-mail: m.kuznetsov@spbu.ru
http://www.chem.spbu.ru/org/592-kuznetsov_scigroup
Center for X-ray Diffraction Studies, Saint Petersburg State
University, Universitetskii pr. 26, 198504 Saint Petersburg, Russia.
Supporting information for this article is available on the WWW
under http://dx.doi.org/
configurational assignment is given in the Supporting
Information.
The oxidative addition of N-aminophthalimide to N-arylimines
1 led to pyrazoles 2 in good yields (Table 1), except for imines
1h,i with electron withdrawing aryl groups on the nitrogen atom.
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10.1002/ejoc.201700172
European Journal of Organic Chemistry
FULL PAPER
Table 1. Synthesis of 1-azadienes (1a-n) and pyrazoles (2a-n)
Aziridines 3h,i provide broad NMR signals at room
temperature, but cooling their solutions down to –20 °C gives
three sets of signals with the ratio 0.14/0.16/1.00 for 3h and
0.13/0.13/1.00 for 3i. N-Phthalimidoaziridines have high barrier
of the pyramidal inversion of the aziridine nitrogen atom at room
temperature producing two sets of NMR signals for two
invertomers. Moreover, the coalescence of these signals does
not usually occur even upon heating of their solutions up to the
decomposition temperatures of aziridines.10 Therefore, we
speculate that the broadening of signals in NMR spectra of
aziridines 3h,i at room temperature is caused by the fast (E/Z)-
isomerization about the C=N bond, similar to what is observed in
the starting imines.
Yield
Yield
(%)a
1
R1
R2
R3
2
(%)a
61
1a
1b
1c
1d
1e
1f
H
H
H
Me
Me
OMe
Cl
2a
2b
2c
2d
2e
2f
75
72
58
55
46
67
59
31
24
68
70
63
54
50
91
67
56
66
54
53
67
76
69
64
77
88
70
H
Me
Given two stereogenic centers in 3h,i one would a priori
expect four sets of signals of stereoisomers in low temperature
NMR spectra. However, 1H NMR spectra of 3h,i at –20°C
feature three pairs of characteristic doublets assigned to the
protons of the aziridine ring at δ 3.97(3.98) (H2) and 4.80(4.80)
(H3) ppm for the major form of aziridines 3h(i), at 4.33(4.34) (H3),
4.94(4.95) (H2) ppm – for the first minor one and at 3.56(3.61)
(H3), 5.40(5.43) (H2) ppm – for the second minor isomer. Values
of the vicinal coupling constants 3J = 5.2-5.8 Hz indicate the
trans-arrangement of the protons in the aziridine ring11 in all
three forms of both compounds. It is consistent with the well-
known retention of the configuration of the double bond in the
oxidative aminoaziridination.5 The signals of the aziridine carbon
atoms in the 13C NMR spectra appear at δ 50.8(51.1) (C3),
52.3(52.2) (C2) ppm for the major form, at δ 47.2(47.2) (C2),
52.8(53.0) (C3) ppm – for the first minor one and at δ 42.6(42.8)
(C2), 51.7(51.7) (C3) ppm – for the second minor isomer. The
H
Me
Br
H
Me
CO2Me
Me
H
OMe
OMe
OMe
OMe
Cl
1g
1h
1i
H
Cl
2g
2h
2i
H
CN
H
NO2
OMe
Me
1j
H
2j
1k
1l
H
Cl
2k
2l
H
NO2
Me
OMe
OMe
OMe
1m
1n
OMe
NO2
2m
2n
Me
aIsolated yield.
The complete conversion of imines required a three-fold
excess of N-aminophthalimide and lead tetraacetate. Reactions
were completed in a few minutes at room temperature, and
pyrazoles 2a-n were isolated by column chromatography on
1
assignment of these signals was performed using COSY Н-1Н,
HMBC, HSQC 1H-13C spectra of compound 3i.
2D NOESY 1Н-1Н spectrum of 3i at –55 °C allows
establishing the spatial structure of these stereoisomeric
forms. The cross-peak between signals δ 6.48 ppm (HoC)
and 7.43-7.54 ppm (HoA, HoB) shows that the major form
has (E)-configuration about the C=N bond. The orientation
of the phthalimido substituent can be determined given that
the latter deshields protons located syn in N-
phthalimidoaziridines (and the lone pair of the endocyclic
nitrogen atom, on the contrary, shields these protons).11
Since the value of the chemical shift for the H2 proton (3.98
ppm) in the major form (syn-, (E)-N) 3i is far smaller and the
value of the chemical shift for the H3 proton (4.80 ppm) is
far greater than the corresponding values in both minor
forms (δ(H2) = 4.95 (anti-, (E)-N), 5.43 (anti-, (Z)-N) and
δ(H3) = 4.34 (anti-, (E)-N), 3.61 (anti-, (Z)-N) ppm), the
phthalimido substituent and Н3 proton are oriented syn- in
the major form and anti- in both minor forms (the same for
3h) (Scheme 3). As raising temperature from -55 °C to 25
°C hardly affects the shape of almost all signals of the
1
silica gel. H NMR spectra and melting points of compounds 2a
and 2g are in agreement with the literature data. All other
1
pyrazoles are previously unknown and were characterized by H,
13C NMR and HRMS (ESI).
Classical synthesis of pyrazoles from hydrazines and 1,3-
dicarbonyl compounds or their synthetic equivalents often yields
mixtures of regioisomers.7 In contrast, our [4+1]-annulation
protocol provides pyrazoles with the arrangement of substituents
unambiguously defined by the nature of the starting materials.
Observed side products are anticipated imidoylaziridines,
resulting from the [2+1]-addition of the nitrenoid onto the C=C
bond. In most cases these compounds are too unstable during
1
purification on silica gel and their formation can be proved by H
NMR spectra of reaction mixtures. Nevertheless, we were able
to isolate imidoylaziridines 3h,i (Scheme 2) by avoiding
chromatography and doing recrystallization of reaction mixtures
(see ESI for details).
1
major form (syn-, (E)-N) of 3i in H spectrum, it is obvious
that the (E/Z)-isomerization about the C=N bond is strongly
inhibited or doesn’t proceed at all in this form, most likely
because of the steric hindrance.
Scheme 2. Competitive formation of imidoylaziridines
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This is due to the secondary orbital interactions between
the C=O bonds of the phthalimido unit and the unsaturated
substrate, which stabilize the transition state and are
responsible for the preferable formation of the invertomer
with the syn-phthalimido and carbonyl groups at low
temperature. However, isomerization into a more stable
anti-invertomer occurs when the temperature is
increased.11b
Scheme 3. Stereoisomeric forms of aziridines 3h,i
In our case the secondary orbital interactions between
the C=O bond of phthalimide and the C=N bond of the
unsaturated imine appear to play the same role. As was
In order to determine the configuration about the C=N bond
in minor isomers, which are easily convertible into each
other, we used the observation that the cis-arrangement of
the neighbouring aryl substituents causes their mutual
shielding in 1H NMR spectrum. The ortho-protons of the
phenyl ring B (HoB) are most sensitive to this effect. For
(anti, (Z)-N) isomer of 3h,i, the signals of these ortho-
protons appear at δ 8.03-8.10 ppm, while for (anti, (E)-N)
they are shielded and appear as multiplets at 7.23-7.38
ppm. The fact that minor forms of 3h,i have opposite
configurations about the C=N bond follows from the room
already discussed, imines
1 exist as a mixture of (E/Z)-
isomers with s-trans conformation (see ESI for details);
however, the s-cis conformation, preferable for
aminoaziridination, is easily reached via an almost free
rotation around the single bond. At the same time, it’s
curious that for 3h,i the invertomer with the syn-
arrangement of the phthalimido and imidoyl substituents is
the major species also at room temperature. It is easy to
see (Fig. 1) that in this invertomer the imidoyl fragment
becomes more compact with the cis-aryl rings at the C=N
bond, so the (E/Z)-isomerization about the C=N bond
doesn’t occur.
1
temperature H NMR spectra. The spectra of the starting
imines feature the rapid isomerization of the C=N bond in
the NMR time scale that causes broadening of signals in
minor isomers with two signals of the OMe-group
coalescing into one. In addition, at –20 °C the 13C NMR
Formation of pyrazoles
of the nitrenoid on the C=C bond followed by the
isomerization of aziridines into pyrazolines including the
2 could be a result of an attack
1
spectra of 3h,i and at –55 °C the H NMR spectrum of the
3
5
3i feature broadened signals of the phthalimido substituent.
This indicates that another dynamic process, namely,
rotation around the N–N bond is slowed down at these
temperatures.
C–N bond cleavage (note that the 1,3-sigmatropic shift is
forbidden by the orbital symmetry) with the subsequent
aromatization (Scheme 4). However, maintaining the
reaction mixtures with aziridines for several hours didn’t
increase yields of the pyrazoles, and isolated
imidoylaziridines 3h,i didn’t transform into pyrazoles 2h,i
under the reaction conditions either. Therefore we
Finally, the structure of 3i was confirmed by X-ray
diffraction data, and it should be noted that its spatial
arrangement in the solid state corresponds to the major
form (syn-, (E)-N) in CDCl3 solution (Figure 1).12
speculate that the pathway to pyrazoles
attack of the nitrenoid onto a lone pair of the imine nitrogen
atom, giving the vinyl-azomethine imine (Scheme 4)
followed by its 1,5-electrocyclization into pyrazoline
which gives the final after elimination of the phthalimide.
2 begins with an
From the mechanistic standpoint, two things should be
noted. First, oxidation of N-aminophthalimide with lead
tetraacetate affords CH3COONHNPhth, which is a synthetic
equivalent of the phthalimidonitrene (nitrenoid), the most
likely reactive species in the aziridination reaction.13
Second, it was shown that s-cis conformation of the starting
compound is preferable for aminoaziridination of α,β-
unsaturated carbonyl compounds, and the nitrenoid attack
on the double bond occurs from the side of the carbonyl
group.
4
5
,
2
The proposed mechanism assumes that reducing the
nucleophility of the nitrogen atom makes it less reactive
than the C=C bond, allowing the aziridination to take place.
Scheme 4. A plausible mechanism for the formation of pyrazoles
2
Figure 1. X-ray crystal structure of aziridine 3i
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N-((2E)-1,3-Diphenylprop-2-en-1-ylidene)-4-methylaniline14 (1a). Pale
yellow crystals, 0.906 g (61%), mp 90 °C (lit. 94-95 °C)14. According to
the 1H NMR spectrum, imine 1a exists as a mixture of E/Z isomers about
the C=N bond in the ratio 2.7:1 at 23 °C. 1H NMR (400 MHz, CDCl3): δ =
2.23 (s, 3H, Me, minor); 2.39 (s, 3H, Me, major); 6.60 (d, J = 8.2 Hz, 2H,
This is in agreement with low yields of pyrazoles from
imines 1h,i possessing electron-poor aryl substituents at
the nitrogen atom. This makes isolation of aziridines 3h,i
possible.
HoC, minor); 6.83 (d, J = 16.4 Hz, 1H, H3, minor); 6.87-7.01 (m, 4H, HoC
H2,3, major; 2H, HmC, minor); 7.12-7.22 (m, 2H, HmC, major; 2H, HoB
,
,
minor); 7.27-7.40 (m, 5H, HA, major; 7H, Hm,pB, Hm,pA, H2, minor); 7.44-
7.54 (m, 3H, Hm,pB, major; 2H, HoA, minor); 7.71-7.79 (m, 2H, HoB, major)
ppm. 13C NMR (100 MHz, CDCl3): δ = 20.8 (Me, minor); 20.9 (Me,
major); 120.9 (CoC, major); 121.1 (CoC, minor); 122.1 (C2, major); 127.5;
128.0; 128.3; 128.7; 128.9; 129.0; 129.1; 129.27; 129.33; 129.4; 129.7;
131.9; 132.8; 133.4; 135.7; 135.8; 135.9; 139.6 (CiB, major); 140.9 (C3,
minor); 141.2; (C3, major); 148.0 (CiC, minor); 148.3 (CiC, major); 166.9
(C=N, major); 168.5 (C=N, minor) ppm. Signals of the major and minor
isomers partially overlap. HRMS (ESI), m/z: calcd for C22H19N [M+H]+
298.1590, found 298.1586.
Conclusions
We reported that the oxidative addition of the N-
aminophthalimide to the 1,2,4-triaryl-1-azabuta-1,3-dienes
in the most cases constitutes a convenient regiodefined
method for the synthesis of the 1,3,5-triarylpyrazoles. This
reaction is a rare example of a [4+1]-annulation reaction in
which the formation of a weak N–N bond is followed by 1,5-
electrocyclization of the vinyl-azomethine imine into a
pyrazoline and its further aromatization into a pyrazole.
Competing with this manifold is [2+1]-cycloaddition onto the
C=C bond that gives imidoylaziridines.
4-Methoxy-N-((2E)-3-(4-methylphenyl)-1-phenylprop-2-en-1-ylidene)-
aniline (1b). Yellow oil, 1.487 g (91%). According to the 1H NMR
spectrum, imine 1b exists as a mixture of E/Z isomers about the C=N
bond in the ratio 2.7:1 at 23 °C. 1H NMR (400 MHz, CDCl3): δ = 2.35 (s,
3H, Me, major); 2.36 (s, 3H, Me, minor); 3.71 (s, 3H, OMe, minor); 3.85
(s, 3H, OMe, major); 6.59-6.70 (m, 4H, Hm,oC, minor); 6.79 (d, J = 16.3 Hz,
1H, H3, minor); 6.85-7.00 (m, 6H, Hm,oC, H2,3, major); 7.09-7.19 (m, 2H,
HmA, major; 4H, HmA, HoB, minor); 7.20-7.28 (m, 2H, HoA, major; 1H, H2,
minor; CHCl3); 7.29-7.34 (m, 3H, Hm,pB, minor); 7.38 (d, J = 8.0 Hz, 2H,
Experimental Section
HoA, minor); 7.42-7.53 (m, 3H, Hm,pB, major); 7.67-7.77 (m, 2H, HoB
major) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.3 (Me, both isomers);
55.2 (OMe, minor); 55.4 (OMe, major); 113.6 (CmC, minor); 114.0 (CmC
,
General: NMR spectroscopic data were recorded on the Bruker Avance
400 spectrometer (400.13 MHz for H, 100.61 MHz for 13C, respectively)
1
,
in CDCl3 and DMSO-d6. The signals are referenced to the residual
solvent proton (δH = 7.26 and 2.50 ppm, respectively) and carbon signals
(δC = 77.00 and 39.52 ppm, respectively). DEPT spectra were used for
the assignment of carbon signals. Melting points were determined with a
Stuart SMP30 instrument. High-resolution mass spectra were recorded
major); 121.3 (C2, major); 122.4 (CoC, major); 122.8 (CoC, minor); 127.38;
127.40; 128.1; 128.2; 129.0; 129.4; 129.5; 129.7; 131.0; 133.0; 133.2;
136.0 (CiB, minor); 139.3; 139.6; 139.8; 140.7 (C3, minor); 141.1 (C3,
major); 143.7 (CiC, minor); 144.3 (CiC, major); 155.9 (CpC, minor); 156.5
(CpC, major); 167.2 (C=N, major); 168.4 (C=N, minor) ppm. Signals of the
major and minor isomers partially overlap. HRMS (ESI), m/z: calcd for
C23H21NO [M+H]+ 328.1696, found 328.1697.
with
a Bruker Maxis HRMS-ESI-qTOF spectrometer (electrospray
ionization mode). Column chromatography was performed on silica gel
Merck 60. The composition of the reaction mixtures and fractions
obtained after their separation as well as the purity of the isolated
compounds were monitored by TLC on Alugram SIL G/UV254 plates
(Macherey-Nagel).
4-Chloro-N-((2E)-3-(4-methylphenyl)-1-phenylprop-2-en-1-ylidene)-
aniline (1c). Pale yellow crystals, 1.110 g (67%), mp 89 °C. According to
the 1H NMR spectrum, imine 1c exists as a mixture of E/Z isomers about
the C=N bond in the ratio 2.5:1 at 23 °C. 1H NMR (400 MHz, CDCl3): δ =
2.35 (s, 3H, Me, major); 2.37 (s, 3H, Me, minor); 6.58-6.64 (m, 2H, HoC
,
General procedure for the preparation of imines 1a-n: A solution of
TiCl4 in CH2Cl2 (5.0 mL, 1.0 М) was added dropwise to a stirred mixture
of ketone (5 mmol), Et3N (3.5 mL, 2.5 g, 25 mmol) and arylamine (5
mmol) in dry CH2Cl2 (30 mL) at 0 °C. The reaction mixture was warmed
to room temperature and stirred for another 4 hours. Water (1 mL) was
added, the resulting suspension filtered through Celite and the solid
residue washed with CH2Cl2 (30 mL). The solution was washed with
water (30 mL), the organic layer separated and the aqueous extracted
with CH2Cl2 (2×15 mL). The combined organic layers were washed with
water and brine and dried over Na2SO4. The solvent was evaporated
under reduced pressure and the residue purified by flash
chromatography on silica gel (hexane/EtOAc). The obtained viscous oil
was crystallized at about –20 °C from hexane/dichloromethane (10:1)
(compounds 1c,d,g,i-n) or petroleum ether/ethyl acetate (10:1)
(compounds 1a,e,f), the precipitate was quickly filtered and dried under
reduced pressure. Compounds 1b,h are viscous oils.
minor); 6.79-6.87 (m, 1H, =CH, major; 1H, H3, minor); 6.88-6.97 (m, 3H,
HoC, =CH, major); 7.05-7.10 (m, 2H, HmC, minor); 7.11-7.16 (m, 2H, HmA
major; 2H, HoB, minor); 7.18 (d, J = 8.1 Hz, 2H, HmA, minor); 7.20-7.25 (m,
2H, HoA, major; 1H, H2, minor); 7.29-7.36 (m, 2H, HmC, major; 3H, Hm,pB
minor); 7.39 (d, J = 8.1 Hz, 2H, HoA, minor); 7.45-7.55 (m, 3H, Hm,pB
,
,
,
major); 7.69-7.77 (m, 2H, HoB, major) ppm. 13C NMR (100 MHz, CDCl3):
δ = 21.3 (Me, both isomers); 120.5 (C2, major); 122.1 (CoC, major); 122.5
(CoC, minor); 127.50; 127.53; 128.2; 128.3; 128.4; 128.5 (CpC, major);
128.6; 128.87; 128.91; 129.1 (CpC, minor); 129.3; 129.54; 129.56; 130.0;
130.4; 132.7 (CiA, major); 132.9 (CiA, minor); 135.3 (CiB, minor); 139.2;
139.7; 140.0; 141.9 (C3, minor); 142.3 (C3, major); 149.3 (CiC, minor);
149.5 (CiC, major); 167.9 (C=N, major); 169.7 (C=N, minor) ppm. HRMS
(ESI), m/z: calcd for C22H18ClN [M+H]+ 332.1201, found 332.1191.
4-Bromo-N-((2E)-3-(4-methylphenyl)-1-phenylprop-2-en-1-ylidene)-
aniline (1d). Pale yellow crystals, 1.051 g (56%), mp 99-100 °C.
According to the 1H NMR spectrum, imine 1d exists as a mixture of E/Z
isomers about the C=N bond in the ratio 2.5:1 at 23 °C. 1H NMR (400
MHz, CDCl3): δ = 2.35 (s, 3H, Me, major); 2.37 (s, 3H, Me, minor); 6.55
(d, J = 8.6 Hz, 2H, HoC, minor); 6.78-6.89 (m, 3H, HoC, =CH, major; 1H,
H3, minor); 6.93 (d, J = 16.4 Hz, 1H, =CH, major); 7.08-7.25 (m, 4H, Hm,oA
major; 7H, HmA, HoB, HmC, H2, minor); 7.28-7.34 (m, 3H, Hm,pB, minor);
7.38 (d, J = 8.0 Hz, 2H, HoA, minor); 7.43-7.55 (m, 5H, Hm,pB, HmC, major);
7.68-7.76 (m, 2H, HoB, major) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.4
(Me, both isomers); 116.3 (CpC, minor); 116.8 (CpC, major); 120.5 (C2,
major); 122.6 (CoC, major); 122.9 (CoC, minor); 127.6; 128.2; 128.3;
128.6; 128.9; 129.3; 129.55; 129.57; 130.0; 130.4; 131.4; 131.9; 132.7
,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700172
European Journal of Organic Chemistry
FULL PAPER
(CiA, major); 132.9 (CiA, minor); 135.2 (CiB, minor); 139.2; 139.7; 140.0;
142.0 (C3, minor); 142.4 (C3, major); 149.8 (CiC, minor); 150.0 (CiC,
major); 167.9 (C=N, major); 169.6 (C=N, minor) ppm. Signals of the
major and minor isomers partially overlap. HRMS (ESI), m/z: calcd for
C22H18BrN [M+H]+ 376.0695, found 376.0698.
4-Cyano-N-((2E)-3-(4-methoxyphenyl)-1-phenylprop-2-en-1-ylidene)-
aniline (1h). Yellow oil, 1.127 g (67%). According to the 1H NMR
spectrum, imine 1h exists as a mixture of E/Z isomers about the C=N
bond in the ratio 2.7:1 at -20 °C. 1H NMR (400 MHz, CDCl3, 253 K): δ =
3.81 (s, 3H, OMe, major); 3.83 (s, 3H, OMe, minor); 6.58 (d, J = 16.2 Hz,
1H, H2, major); 6.72 (d, J = 8.4 Hz, 2H, HoC, minor); 6.79-6.88 (m, 2H,
HmA, major; 1H, H3, minor); 6.90 (d, J = 8.7 Hz, 2H, HmA, minor); 6.96 (d,
J = 16.2 Hz, 1H, H3, major); 7.02 (d, J = 8.4 Hz, 2H, HoC, major); 7.06-
7.11 (m, 2H, HoB, minor); 7.13 (d, J = 16.3 Hz, 1H, H2, minor); 7.23-7.36
4-(Methoxycarbonyl)-N-((2E)-3-(4-methylphenyl)-1-phenylprop-2-en-
1-ylidene)aniline (1e). Pale yellow crystals, 1.168 g (66%), mp 110 °C.
According to the 1H NMR spectrum, imine 1e exists as a mixture of E/Z
isomers about the C=N bond in the ratio 2.5:1 at 23 °C. 1H NMR (400
MHz, CDCl3): δ = 2.33 (s, 3H, Me, major); 2.37 (s, 3H, Me, minor); 3.84
(s, 3H, CO2Me, minor); 3.93 (s, 3H, CO2Me, major); 6.70 (d, J = 8.4 Hz,
2H, HoC, minor); 6.75 (d, J = 16.4 Hz, 1H, H2, major); 6.86 (d, J = 16.3 Hz,
1H, H3, minor); 6.94 (d, J = 16.4 Hz, 1H, H3, major); 6.99 (d, J = 8.4 Hz,
2H, HoC, major); 7.07-7.14 (m, 2H, HmA, major; 2H, HoB, minor); 7.15-7.31
(m, 2H, HoA, major; 6H, HmA, Hm,pB, H2, minor; CHCl3); 7.39 (d, J = 7.9 Hz,
(m, 2H, HoA, major; 3H, Hm,pB, minor; CHCl3); 7.40 (d, J = 8.4 Hz, 2H, HmC
minor); 7.44 (d, J = 8.7 Hz, 2H, HoA, minor); 7.47-7.58 (m, 3H, Hm,pB
,
,
major); 7.66 (d, J = 8.4 Hz, 2H, HmC, major); 7.69-7.76 (m, 2H, HoB
,
major) ppm. 13C NMR (100 MHz, CDCl3): δ = 55.3 (OMe, both isomers);
105.8 (CpC, minor); 106.4 (CpC, major); 114.1 (CmA, both isomers); 118.3
(C2, major); 119.46 (C≡N, minor); 119.54 (C≡N, major); 121.3 (CoC
,
2H, HoA, minor); 7.44-7.56 (m, 3H, Hm,pB, major); 7.70-7.77 (m, 2H, HoB
major); 7.81 (d, J = 8.4 Hz, 2H, HmC, minor); 8.06 (d, J = 8.4 Hz, 2H, HmC
,
,
major); 121.5 (CoC, minor); 127.4; 127.6; 128.0; 128.2; 128.4; 128.7;
128.9; 129.2; 130.3 (CpB, major); 132.6 (CmC, minor); 133.1 (CmC, major);
134.2 (CiB, minor); 138.2 (CiB, major); 143.1 (C3, minor); 143.4 (C3,
major); 154.9 (CiC, minor); 155.0 (CiC, major); 160.6 (CpA, minor); 160.8
(CpA, major); 168.3 (C=N, major); 170.5 (C=N, minor) ppm. Signals of the
major and minor isomers partially overlap. HRMS (ESI), m/z: calcd for
C23H18N2O [M+H]+ 339.1492, found 339.1484.
major) ppm. 13C NMR (100 MHz, CDCl3) of the (E)-isomer: δ = 21.4 (Me);
51.9 (CO2Me); 120.3 (C2); 120.3 (CoC); 125.4 (CpC); 127.56 (CoA); 128.4
(CmB); 129.3 (CoB); 129.6 (CmA); 130.1 (CpB); 130.7 (CmC); 132.6 (CiA);
138.8 (CiB); 140.1 (CpA); 142.8 (C3); 155.5 (CiC); 167.0 (CO2Me); 167.6
(C=N) ppm. 13C NMR (100 MHz, CDCl3) of the (Z)-isomer: δ = 21.4 (Me);
51.8 (CO2Me); 120.6 (CoC); 124.7 (CpC); 127.60 (CoA); 128.1 (CmB); 128.7
(CpB); 128.8 (CoB); 129.6 (CmA); 130.0 (C2); 130.2 (CmC); 132.8 (CiA);
135.1 (CiB); 139.8 (CpA); 142.4 (C3); 155.3 (CiC); 166.9 (CO2Me); 169.6
(C=N) ppm. The assignment of signals was performed using 2D NMR
N-((2E)-3-(4-Methoxyphenyl)-1-phenylprop-2-en-1-ylidene)-4-nitro-
aniline (1i). Orange crystals, 1.364 g (76%), mp 90 °C. According to the
1H NMR spectrum, imine 1i exists as a mixture of E/Z isomers about the
C=N bond in the ratio 2.7:1 at -20 °C. 1H NMR (400 MHz, CDCl3, 253 K):
δ = 3.81 (s, 3H, OMe, major); 3.84 (s, 3H, OMe, minor); 6.59 (d, J = 16.2
Hz, 1H, H2, major); 6.74 (d, J = 8.9 Hz, 2H, HoC, minor); 6.81-6.88 (m, 2H,
HmA, major; 1H, H3, minor); 6.90 (d, J = 8.7 Hz, 2H, HmA, minor); 6.99 (d,
J = 16.2 Hz, 1H, H3, major); 7.05 (d, J = 8.8 Hz, 2H, HoC, major); 7.09-
1
including H-13C and 15N-1H HMBC, 1H-13C HSQC spectra. HRMS (ESI),
m/z: calcd for C24H21NO2 [M+H]+ 356.1645, found 356.1643.
N-((2E)-3-(4-Methoxyphenyl)-1-phenylprop-2-en-1-ylidene)-4-methyl-
aniline (1f). Pale yellow crystals, 0.885 g (54%), mp 96 °C. According to
the 1H NMR spectrum, imine 1f exists as a mixture of E/Z isomers about
the C=N bond in the ratio 2.9:1 at 23 °C. 1H NMR (400 MHz, CDCl3): δ =
2.22 (s, 3H, Me, minor); 2.38 (s, 3H, Me, major); 3.80 (s, 3H, OMe,
major); 3.83 (s, 3H, OMe, minor); 6.58 (d, J = 8.0 Hz, 2H, HoC, minor);
7.18 (m, 3H, HoB, H2, minor); 7.23-7.36 (m, 2H, HoA, major; 3H, Hm,pB
minor; CHCl3); 7.45 (d, J = 8.7 Hz, 2H, HoA, minor); 7.48-7.60 (m, 3H,
Hm,pB, major); 7.66-7.80 (m, 2H, HoB, major); 8.01 (d, J = 8.9 Hz, 2H, HmC
,
,
minor); 8.27 (d, J = 8.8 Hz, 2H, HmC, major) ppm. 13C NMR (100 MHz,
CDCl3): δ = 55.3 (OMe, both isomers); 114.1 (CmA, both isomers); 118.2
(C2, major); 120.9 (CoC, major); 121.1 (CoC, minor); 124.5 (CmC, minor);
125.1 (CmC, major); 127.3; 127.6; 127.8; 128.2; 128.5; 128.6; 129.0;
129.26; 129.30; 129.32; 130.4 (CpB, major); 134.2 (CiB, minor); 138.1 (CiB,
major); 142.8 (CpC, minor); 143.4 (C3, minor); 143.5 (CpC, major); 143.9
(C3, major); 157.12 (CiC, minor); 157.14 (CiC, major); 160.7 (CpA, minor);
160.9 (CpA, major); 168.4 (C=N, major); 170.6 (C=N, minor) ppm. HRMS
(ESI), m/z: calcd for C22H18N2O3 [M+H]+ 359.1390, found 359.1389.
N-((2E)-3-(4-Chlorophenyl)-1-phenylprop-2-en-1-ylidene)-4-methoxy-
aniline15 (1j). Yellow crystals, 1.207 g (69%), mp 113 °C (lit. 113-
115 °C)15. According to the 1H NMR spectrum, imine 1j exists as a
mixture of E/Z isomers about the C=N bond in the ratio 2.3:1 at 23 °C. 1H
NMR (400 MHz, CDCl3): δ = 3.71 (s, 3H, OMe, minor); 3.85 (s, 3H, OMe,
major); 6.60-6.70 (m, 4H, Hm,oC, minor); 6.75 (d, J = 16.3 Hz, 1H, H3,
minor); 6.86 (d, J = 16.4 Hz, 1H, H3, major); 6.90-6.98 (m, 5H, Hm,oC, H2,
major); 7.10-7.17 (m, 2H, HoB, minor); 7.20-7.35 (m, 4H, Hm,oA, major; 6H,
Hm,pB, HmA, H2, minor; CHCl3); 7.40 (d, J = 8.5 Hz, 2H, HoA, minor); 7.43-
7.53 (m, 3H, Hm,pB, major); 7.67-7.75 (m, 2H, HoB, major) ppm. 13C NMR
(100 MHz, CDCl3) of the (E)-isomer: δ = 55.4 (OMe); 114.1 (CmC); 122.4
(CoC); 122.7 (C2); 128.3 (CmB); 128.5 (CoA); 129.00 (CmA); 129.3 (CoB);
129.8 (CpB); 134.3 (CiA); 135.1 (CpA); 139.5 (CiB); 139.6 (C3); 144.1 (CiC);
156.6 (CpC); 166.6 (C=N) ppm. 13C NMR (100 MHz, CDCl3) of the (Z)-
isomer: δ = 55.2 (OMe); 113.6 (CmC); 122.8 (CoC); 128.3 (CmB); 128.4
(CpB); 128.5 (CoA); 128.9 (CoB); 128.98 (CmA); 132.6 (C2); 134.5 (CiA);
134.8 (CpA); 135.7 (CiB); 139.1 (C3); 143.5 (CiC); 156.1 (CpC); 167.9 (C=N)
ppm. The assignment of signals was performed using 2D NMR including
1H-13C and 15N-1H HMBC, 1H-13C HSQC, and NOESY spectra. HRMS
(ESI), m/z: calcd for C22H18ClNO [M+H]+ 348.1150, found 348.1142.
N-((2E)-3-(4-Chlorophenyl)-1-phenylprop-2-en-1-ylidene)-4-methyl-
aniline16 (1k). Beige crystals, 1.059 g (64%), mp 116 °C (lit. 118-
120 °C)16. According to the 1H NMR spectrum, imine 1k exists as a
mixture of E/Z isomers about the C=N bond in the ratio 2.5:1 at 23 °C. 1H
NMR (400 MHz, CDCl3): δ = 2.22 (s, 3H, Me, minor); 2.39 (s, 3H, Me,
6.77 (d, J = 16.3 Hz, 1H, H3, minor); 6.80-6.94 (m, 6H, HmA, HoC, H2,3
,
major; 4H, HmA, HmC, minor); 7.11-7.21 (m, 2H, HmC, major; 3H, HoB, H2,
minor); 7.23-7.33 (m, 2H, HoA, major; 3H, Hm,pB, minor; CHCl3); 7.43 (d, J
= 8.7 Hz, 2H, HoA, minor); 7.45-7.52 (m, 3H, Hm,pB, major); 7.68-7.77 (m,
2H, HoB, major) ppm. 13C NMR (100 MHz, CDCl3): δ = 20.8 (Me, minor);
20.9 (Me, major); 55.3 (OMe, both isomers); 114.2 (CmA, both isomers);
119.9 (CoC, minor); 120.9 (CoC, major); 121.2 (C2, major); 128.0; 128.19;
128.23; 128.5 (CiA, major); 128.6 (CiA, minor); 128.89; 128.93; 128.96;
129.00; 129.3; 129.4; 129.6; 129.8; 132.6 (CpC, minor); 133.2 (CpC
,
major); 135.9 (CiB, minor); 139.8 (CiB, major); 140.6 (C3, minor); 141.0 (C3,
major); 148.1 (CiC, minor); 148.5 (CiC, major); 160.5 (CpA, minor); 160.6
(CpA, major); 167.3 (C=N, major); 168.8 (C=N, minor) ppm. Signals of the
major and minor isomers partially overlap. HRMS (ESI), m/z: calcd for
C23H21NO [M+H]+ 328.1696, found 328.1695.
4-Chloro-N-((2E)-3-(4-methoxyphenyl)-1-phenylprop-2-en-1-ylidene)-
aniline (1g). Yellow crystals, 0.926 g (53%), mp 89 °C. According to the
1H NMR spectrum, imine 1g exists as a mixture of E/Z isomers about the
C=N bond in the ratio 2.5:1 at 23 °C. 1H NMR (400 MHz, CDCl3): δ =
3.81 (s, 3H, OMe, major); 3.83 (s, 3H, OMe, minor); 6.60 (d, J = 8.6 Hz,
2H, HoC, minor); 6.74 (d, J = 16.3 Hz, 1H, =CH, major); 6.80 (d, J = 16.3
Hz, 1H, H3, minor); 6.83-6.95 (m, 5H, HmA, HoC, =CH, major; 2H, HmA
,
minor); 7.07 (d, J = 8.6 Hz, 2H, HmC, minor); 7.09-7.19 (m, 3H, HoB, H2,
minor); 7.22-7.37 (m, 4H, HoA, HmC, major; 3H, Hm,pB, minor; CHCl3); 7.43
(d, J = 8.7 Hz, 2H, HoA, minor); 7.45-7.55 (m, 3H, Hm,pB, major); 7.66-7.76
(m, 2H, HoB, major) ppm. 13C NMR (100 MHz, CDCl3): δ = 55.3 (OMe,
both isomers); 114.26 (CmA, minor); 114.29 (CmA, major); 119.3 (C2,
major); 122.2 (CoC, major); 122.5 (CoC, minor); 128.1; 128.3; 128.4;
128.5; 128.88; 128.91; 129.0; 129.1; 129.2; 129.3; 129.9; 135.3 (CiB,
minor); 139.3 (CiB, major); 141.6 (C3, minor); 142.0 (C3, major); 149.3
(CiC, minor); 149.6 (CiC, major); 160.7 (CpA, minor); 160.9 (CpA, major);
168.0 (C=N, major); 169.8 (C=N, minor) ppm. Signals of the major and
minor isomers partially overlap. HRMS (ESI), m/z: calcd for C22H18ClNO
[M+H]+ 348.1150, found 348.1159.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700172
European Journal of Organic Chemistry
FULL PAPER
major); 6.58 (d, J = 8.2 Hz, 2H, HoC, minor); 6.76 (d, J = 16.4 Hz, 1H, H3,
minor); 6.83-6.96 (m, 4H, HoC, H2,3, major; 2H, HmC, minor); 7.11-7.15 (m,
2H, HoB, minor); 7.18 (d, J = 8.0 Hz, 2H, HmC, major); 7.21-7.35 (m, 4H,
Hm,oA, major; 6H, Hm,pB, HmA, H2, minor; CHCl3); 7.40 (d, J = 8.6 Hz, 2H,
(CmB, major); 127.5; 129.6; 130.00; 130.04; 130.3; 132.5 (CiA, major);
132.6 (CiA, minor); 139.9 (CpA, minor); 140.2 (CpA, major); 141.3 (C3,
minor); 141.6 (C3, major); 142.96, 142.99 (CiB, CiC, minor); 143.5 (CiC,
major); 145.9 (CiB, major); 147.5 (CpB, minor); 148.5 (CpB, major); 156.4
(CpC, minor); 157.0 (CpC, major); 165.0 (C=N, major); 166.2 (C=N, minor)
ppm. Signals of the major and minor isomers partially overlap. HRMS
(ESI), m/z: calcd for C23H20N2O3 [M+H]+ 373.1547, found 373.1546.
General procedure for the preparation of pyrazoles 2a-n: N-
Aminophthalimide (0.486 g, 3 mmol) was added to a stirred suspension
of K2CO3 (2.5 g, 18 mmol) in a solution of imine 1a-n (1 mmol) in dry
CH2Cl2 (30 mL) at room temperature followed by addition of Pb(OAc)4
(1.329 g, 3 mmol) in small portions within 5 min. Reaction mixture was
stirred for 10 min and the inorganic precipitate was filtered off. The solid
was washed with CH2Cl2 and combined filtrates concentrated under
reduced pressure. The residue was purified by column chromatography
(hexane/ethylacetate from 14:1 to 9:1) on silica gel. Aziridines 3h,i could
be obtained in addition to pyrazoles 2h,i by avoiding column
chromatography. (See General procedure for the preparation of
pyrazoles, 2 mmol scale). The residue after solvent evaporation was
grinded with 12 mL Et2O/CH2Cl2/hexane 4:1:1. The precipitate was
filtered and recrystallized from ethyl acetate with a little ethanol to give
aziridines 3h,i. The filtrate was evaporated under reduced pressure, and
pyrazole 2h,i was isolated by column chromatography on silica gel
(hexane/ethyl acetate from 14:1 to 9:1).
HoA, minor); 7.44-7.53 (m, 3H, Hm,pB, major); 7.68-7.76 (m, 2H, HoB
,
major) ppm. 13C NMR (100 MHz, CDCl3): δ = 20.8 (Me, minor); 20.9 (Me,
major); 120.8 (CoC, major); 121.1, 122.6 (CoC, minor; C2, major); 128.1;
128.3; 128.4; 128.6; 128.9; 128.96; 128.98; 129.3; 129.4; 129.8; 132.5;
133.0; 133.6; 134.3; 134.4; 134.9; 135.1; 135.6; 139.3 (C3, minor); 139.4
(CiB, major); 139.8 (C3, major); 147.8 (CiC, minor); 148.2 (CiC, major);
166.6 (C=N, major); 168.2 (C=N, minor) ppm. Signals of the major and
minor isomers partially overlap. HRMS (ESI), m/z: calcd for C22H18ClN
[M+H]+ 332.1201, found 332.1207.
4-Methoxy-N-((2E)-3-(4-nitrophenyl)-1-phenylprop-2-en-1-ylidene)-
aniline (1l). Orange crystals, 1.375 g (77%), mp 121 °C. According to the
1H NMR spectrum, imine 1l exists as a mixture of E/Z isomers about the
C=N bond in the ratio 1.9:1 at 23 °C. 1H NMR (400 MHz, CDCl3): δ =
3.72 (s, 3H, OMe, minor); 3.84 (s, 3H, OMe, major); 6.61-6.71 (m, 4H,
Hm,oC, minor); 6.84 (d, J = 16.4 Hz, 1H, H3, minor); 6.89-6.99 (m, 5H,
Hm,oC, H3, major); 7.10 (d, J = 16.5 Hz, 1H, H2, major); 7.13-7.18 (m, 2H,
HoB, minor); 7.31-7.41 (m, 4H, Hm,pB, H2, minor); 7.43-7.54 (m, 5H, HoA
Hm,pB, major); 7.60 (d, J = 8.8 Hz, 2H, HoA, minor); 7.68-7.76 (m, 2H, HoB
,
,
major); 8.13-8.23 (m, 2H, HmA, major; 2H, HmA, minor) ppm. 13C NMR
(100 MHz, CDCl3): δ = 55.2 (OMe, minor); 55.4 (OMe, major); 113.7 (CmC
minor); 114.1 (CmC, major); 122.5 (CoC, major); 123.0 (CoC, minor); 124.1
(CmA, both isomers); 126.2 (C2, major); 127.8; 128.4; 128.7 (CpB, minor);
128.8; 129.2; 130.1; 135.4 (CiB, minor); 136.3; 137.3; 137.9 (C3, major);
139.1 (CiB, major); 142.1 (CiA, major); 142.3 (CiA, minor); 143.1 (CiC,
minor); 143.8 (CiC, major); 147.6 (CpA, minor); 147.8 (CpA, major); 156.5
(CpC, minor); 156.9 (CpC, major); 165.8 (C=N, major); 167.0 (C=N, minor)
ppm. Signals of the major and minor isomers partially overlap. HRMS
(ESI), m/z: calcd for C22H18N2O3 [M+H]+ 359.1390, found 359.1393.
4-Methoxy-N-((2E)-1-(4-methoxyphenyl)-3-(4-methylphenyl)prop-2-
en-1-ylidene)aniline (1m). Yellow crystals, 1.572 g (88%), mp 123 °C.
According to the 1H NMR spectrum, imine 1m exists as a mixture of E/Z
isomers about the C=N bond in the ratio 3.3:1 at 23 °C. 1H NMR (400
MHz, CDCl3): δ = 2.35 (s, 3H, Me, major); 2.36 (s, 3H, Me, minor); 3.73
(s, 3H, OMe, minor); 3.81 (s, 3H, OMe, minor); 3.84 (s, 3H, OMe, major);
3.88 (s, 3H, OMe, major); 6.61-6.72 (m, 4H, Hm,oC, minor); 6.80-6.96 (m,
,
Possible transformation of imidoylaziridines 3h,i into pyrazoles 2h,i:
Pb(OAc)4 (44 mg, 0.1 mmol) was added to a stirred suspension of K2CO3
(83 mg, 0.6 mmol) in solution of aziridine 3h,i (0.1 mmol) and N-
aminophthalimide (16 mg, 0.1 mmol) in dry CH2Cl2 (2 mL) at room
temperature and the reaction mixture was kept for 2 hours. According to
the TLC analysis, pyrazole 2h,i did not form. According to 1H NMR
spectra of the substances obtained after solvent removal, only starting
aziridines 3h,i and small amounts of unidentified impurities, but not
pyrazoles 2h,i were present in the reaction mixture.
6H, Hm,oC, H2,3, major; 3H, HmB, H3, minor); 6.98 (d, J = 8.7 Hz, 2H, HmB
major); 7.08 (d, J = 8.6 Hz, 2H, HoB, minor); 7.11-7.28 (m, 4H, Hm,oA
,
,
major; 3H, HmA, H2, minor; CHCl3); 7.38 (d, J = 8.0 Hz, 2H, HoA, minor);
7.71 (d, J = 8.7 Hz, 2H, HoB, major) ppm. 13C NMR (100 MHz, CDCl3): δ
= 21.3 (Me, both isomers); 55.1 (OMe, minor); 55.2 (OMe, minor); 55.35
(OMe, major); 55.41 (OMe, major); 113.5, 113.60 (CmB, CmC, minor);
113.64, 114.0 (CmB, CmC, major); 121.8 (C2, major); 122.6 (CoC, major);
122.8 (CoC, minor); 127.3; 127.4; 128.0; 129.5; 130.6; 130.9; 131.2 (C2,
minor); 132.3; 133.1; 133.2; 139.2 (CpA, minor); 139.4 (CpA, major); 140.4
(C3, minor); 140.6 (C3, major); 144.0 (CiC, minor); 144.5 (CiC, major);
1-(4-Methylphenyl)-3,5-diphenylpyrazole17 (2a). Colorless crystals, 232
mg (75%), mp 107 °C (lit. 106-108 °C)17. 1H NMR (400 MHz, CDCl3): δ =
2.37 (s, 3H, Me); 6.83 (s, 1H, H4); 7.16 (d, J = 8.2 Hz, 2H, HmA); 7.24-
7.38 (m, 8H, HoA, HpB, HC; CHCl3); 7.40-7.48 (m, 2H, HmB); 7.90-7.98 (m,
2H, HoB) ppm.
1-(4-Methoxyphenyl)-3-(4-methylphenyl)-5-phenylpyrazole
(2b).
Cream crystals, 246 mg (72%), mp 160 °C. 1H NMR (400 MHz, CDCl3): δ
= 2.39 (s, 3H, Me); 3.82 (s, 3H, OMe); 6.79 (s, 1H, H4); 6.87 (d, J = 8.8
Hz, 2H, HmA); 7.20-7.36 (m, 9H, HoA, HmB, HC; CHCl3); 7.82 (d, J = 8.8 Hz,
2H, HoB) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.3 (Me); 55.5 (OMe);
104.5 (C4); 114.1 (CmA); 125.6, 126.7 (CoB, CoA); 128.1 (CpC); 128.4;
128.7; 129.3; 130.3, 130.7 (CiB, CiC); 133.5 (CiA); 137.6 (CpB); 144.2 (C5);
151.7 (C3); 158.8 (CpA) ppm. HRMS (ESI), m/z: calcd for C23H20N2O
[M+H]+ 341.1648, found 341.1636.
155.8 (CpC, minor); 156.3 (CpC, major); 159.4 (CpB, minor); 161.0 (CpB
,
major); 166.4 (C=N, major); 168.0 (C=N, minor) ppm. Signals of the
major and minor isomers partially overlap. HRMS (ESI), m/z: calcd for
C24H23NO2 [M+H]+ 358.1802, found 358.1802.
4-Methoxy-N-((2E)-1-(4-nitrophenyl)-3-(4-methylphenyl)prop-2-en-1-
ylidene)aniline (1n). Orange crystals, 1.303 g (70%), mp 150-151 °C.
According to the 1H NMR spectrum, imine 1n exists as a mixture of E/Z
isomers about the C=N bond in the ratio 3.3:1 at 23 °C. 1H NMR (400
MHz, CDCl3): δ = 2.36 (s, 3H, Me, major); 2.37 (s, 3H, Me, minor); 3.71
(s, 3H, OMe, minor); 3.85 (s, 3H, OMe, major); 6.56-6.61 (m, 2H, HC,
minor); 6.63-6.70 (m, 3H, HC, H3, minor); 6.81 (d, J = 16.6 Hz, 1H, H3,
major); 6.91-7.01 (m, 5H, Hm,oC, H2, major); 7.12-7.20 (m, 2H, HmA, major;
2H, HmA, minor); 7.22-7.28 (m, 2H, HoA, major; 1H, H2, minor; CHCl3);
1-(4-Chlorophenyl)-3-(4-methylphenyl)-5-phenylpyrazole (2c). Yellow
crystals, 201 mg (58%), mp 144 °C. 1H NMR (400 MHz, CDCl3): δ = 2.40
(s, 3H, Me); 6.79 (s, 1H, H4); 7.23-7.32 (m, 8H, HA, HmB, HoC; CHCl3);
7.33-7.38 (m, 3H, Hm,pC); 7.81 (d, J = 8.1 Hz, 2H, HoB) ppm. 13C NMR
(100 MHz, CDCl3): δ = 21.3 (Me); 105.4 (C4); 125.7, 126.3 (CoB, CoA);
128.5 (CpC); 128.6; 128.7; 129.0; 129.4; 130.0, 130.4 (CiB, CiC); 132.9
(CpA); 137.9 (CpB); 138.7 (CiA); 144.3 (C5); 152.3 (C3) ppm. HRMS (ESI),
m/z: calcd for C22H17ClN2 [M+H]+ 345.1153, found 345.1155.
7.31-7.34 (m, 2H, HoB, minor); 7.36 (d, J = 8.1 Hz, 2H, HoA, minor); 7.86-
7.92 (m, 2H, HoB, major); 8.16-8.21 (m, 2H, HmB, minor); 8.28-8.35 (m, 2H,
HmB, major) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.4 (Me, both
isomers); 55.2 (OMe, minor); 55.4 (OMe, major); 113.9 (CmC, minor);
114.2 (CmC, major); 120.5 (C2, major); 122.5 (CoC, major); 123.46; 123.49
1-(4-Bromophenyl)-3-(4-methylphenyl)-5-phenylpyrazole (2d). Beige
crystals, 214 mg (55%), mp 154 °C. 1H NMR (400 MHz, CDCl3): δ = 2.40
(s, 3H, Me); 6.79 (s, 1H, H4); 7.22-7.31 (m, 6H, HoA, HmB, HoC; CHCl3);
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700172
European Journal of Organic Chemistry
FULL PAPER
7.32-7.38 (m, 3H, Hm,pC); 7.43-7.49 (m, 2H, HmA); 7.81 (d, J = 8.1 Hz, 2H,
HoB) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.3 (Me); 105.5 (C4); 120.8
(CpA); 125.7, 126.5 (CoB, CoA); 128.5 (CpC); 128.6; 128.7; 129.4; 130.0,
130.4 (CiB, CiC); 132.0 (CmA); 137.9 (CpB); 139.2 (CiA); 144.3 (C5); 152.4
(C3) ppm. HRMS (ESI), m/z: calcd for C22H17BrN2 [M+H]+ 389.0648,
found 389.0639.
1-(4-(Methoxycarbonyl)phenyl)-3-(4-methylphenyl)-5-phenylpyrazole
(2e). Colorless crystals, 169 mg (46%), mp 160 °C. 1H NMR (400 MHz,
CDCl3): δ = 2.40 (s, 3H, Me); 3.91 (s, 3H, CO2Me); 6.81 (s, 1H, H4); 7.21-
7.39 (m, 7H, HmB, HC; CHCl3); 7.45 (d, J = 8.6 Hz, 2H, HoA); 7.82 (d, J =
8.0 Hz, 2H, HoB); 8.01 (d, J = 8.6 Hz, 2H, HmA) ppm. 13C NMR (100 MHz,
CDCl3): δ = 21.3 (Me); 52.2 (CO2Me); 106.1 (C4); 124.4 (CoA); 125.7
(CoB); 128.4 (CpA); 128.60 (CpC); 128.64; 128.8; 129.4; 129.9 (CiB); 130.3
(CmA); 130.4 (CiC); 138.1 (CpB); 143.7 (CiA); 144.5 (C5); 152.7 (C3); 166.4
(CO2Me) ppm. HRMS (ESI), m/z: calcd for C24H20N2O2 [M+H]+ 369.1598,
found 369.1591.
CpA); 144.5 (C5); 150.6 (C3) ppm. HRMS (ESI), m/z: calcd for C22H17ClN2
[M+H]+ 345.1153, found 345.1158.
3-(4-Nitrophenyl)-1-(4-methoxyphenyl)-5-phenylpyrazole
(2l).
Colorless crystals, 234 mg (63%), mp 146 °C. 1H NMR (400 MHz,
CDCl3): δ = 3.83 (s, 3H, OMe); 6.85-6.93 (m, 3H, H4, HmA); 7.24-7.37 (m,
7H, HoA, HC; CHCl3); 8.07 (d, J = 8.9 Hz, 2H, HoB); 8.28 (d, J = 8.9 Hz, 2H,
HmB) ppm. 13C NMR (100 MHz, CDCl3): δ = 55.5 (OMe); 105.3 (C4);
114.2 (CmA); 124.1 (CmB); 126.1, 126.6 (CoB, CoA); 128.5 (CpC); 128.6;
128.7; 130.0 (CiC); 133.0 (CiA); 139.5 (CiB); 145.0 (C5); 147.2 (CpB); 149.2
(C3); 159.2 (CpA) ppm. HRMS (ESI), m/z: calcd for C22H17N3O3 [M+H]+
372.1343, found 372.1341.
1,5-Bis(4-methoxyphenyl)-3-(4-methylphenyl)pyrazole (2m). Beige
crystals, 201 mg (54%), mp 119 °C. 1H NMR (400 MHz, CDCl3): δ = 2.39
(s, 3H, Me); 3.81 (s, 3H, OMe); 3.82 (s, 3H, OMe); 6.72 (s, 1H, H4); 6.81-
6.91 (m, 4H, HmA, HmC); 7.17-7.25 (m, 4H, HmB, HoC); 7.27-7.32 (m, 2H,
HoA); 7.81 (d, J = 8.1 Hz, 2H, HoB) ppm. 13C NMR (100 MHz, CDCl3): δ =
21.3 (Me); 55.2 (OMe); 55.4 (OMe); 103.9 (C4); 113.8, 114.0 (CmA, CmC);
123.1 (CiC); 125.6 (CoA); 126.7 (CoB); 129.3, 129.9 (CmB, CoC); 130.4 (CiB);
3-(4-Methoxyphenyl)-1-(4-methylphenyl)-5-phenylpyrazole
(2f).
Colorless crystals, 228 mg (67%), mp 119 °C. 1H NMR (400 MHz,
CDCl3): δ = 2.36 (s, 3H, Me); 3.86 (s, 3H, OMe); 6.75 (s, 1H, H4); 6.97 (d,
133.6 (CiA); 137.5 (CpB); 144.0 (C5); 151.5 (C3); 158.7, 159.4 (CpA, CpC
)
J = 8.7 Hz, 2H, HmB); 7.14 (d, J = 8.2 Hz, 2H, HmA); 7.21-7.36 (m, 7H, HoA
HC; CHCl3); 7.86 (d, J = 8.7 Hz, 2H, HoB) ppm. 13C NMR (100 MHz,
CDCl3): δ = 21.1 (Me); 55.3 (OMe); 104.5 (C4); 114.0 (CmB); 125.1 (CoA);
126.0 (CiB); 127.0; 128.1 (CpC); 128.4; 128.7; 129.4; 130.8 (CiC); 137.2,
137.8 (CiA, CpA); 144.2 (C5); 151.6 (C3); 159.5 (CpB) ppm. HRMS (ESI),
m/z: calcd for C23H20N2O [M+H]+ 341.1648, found 341.1645.
,
ppm. HRMS (ESI), m/z: calcd for C24H22N2O2 [M+H]+ 371.1754, found
371.1749.
1-(4-Methoxyphenyl)-3-(4-methylphenyl)-5-(4-nitrophenyl)pyrazole
(2n). Beige crystals, 193 mg (50%), mp 183 °C. 1H NMR (400 MHz,
CDCl3): δ = 2.40 (s, 3H, Me); 3.84 (s, 3H, OMe); 6.87-6.94 (m, 3H, H4,
HmA); 7.21-7.30 (m, 4H, HoA, HmB; CHCl3); 7.39-7.46 (m, 2H, HoC); 7.80 (d,
J = 8.1 Hz, 2H, HoB); 8.13-8.20 (m, 2H, HmC) ppm. 13C NMR (100 MHz,
CDCl3): δ = 21.3 (Me); 55.5 (OMe); 105.5 (C4); 114.4 (CmA); 123.7 (CmC);
125.7 (CoA); 126.9 (CoB); 129.1, 129.4 (CmB, CoC); 129.7 (CiB); 132.8 (CiA);
1-(4-Chlorophenyl)-3-(4-methoxyphenyl)-5-phenylpyrazole18
(2g).
1H
Colorless crystals, 214 mg (59%), mp 123-124 °C (lit. 124-125 °C)18
.
NMR (400 MHz, CDCl3): δ = 3.86 (s, 3H, OMe); 6.75 (s, 1H, H4); 6.97 (d,
J = 8.7 Hz, 2H, HmB); 7.25-7.32 (m, 6H, HA, HoC; CHCl3); 7.33-7.38 (m,
3H, Hm,pC); 7.84 (d, J = 8.7 Hz, 2H, HoB) ppm.
136.8 (CiC); 138.1 (CpB); 141.8 (C5); 147.1 (CpC); 152.1 (C3); 159.3 (CpA
)
ppm. HRMS (ESI), m/z: calcd for C23H19N3O3 [M+H]+ 386.1499, found
1-(4-Cyanophenyl)-3-(4-methoxyphenyl)-5-phenylpyrazole
(2h).
386.1501.
Cream crystals, 218 mg (31%) (2 mmol scale), mp 132-133 °C. 1H NMR
(400 MHz, CDCl3): δ = 3.86 (s, 3H, OMe); 6.77 (s, 1H, H4); 6.95-7.01 (m,
2H, HmB); 7.27-7.32 (m, 2H, HoC); 7.35-7.43 (m, 3H, Hm,pC); 7.46-7.51 (m,
2H, HoA); 7.57-7.63 (m, 2H, HmA); 7.81-7.88 (m, 2H, HoB) ppm. 13C NMR
(100 MHz, CDCl3): δ = 55.3 (OMe); 106.5 (C4); 110.1 (CpA); 114.1 (CmB);
118.3 (C≡N); 124.6 (CoA); 125.1 (CiB); 127.1; 128.76; 128.82; 128.9 (CpC);
130.2 (CiC); 132.8 (CmA); 143.4 (CiA); 144.6 (C5); 152.9 (C3); 160.0 (CpB
)
ppm. HRMS (ESI), m/z: calcd for C23H17N3O [M+H]+ 352.1444, found
352.1444.
4-{[[rel-(2S,3R)-1-(1,3-Dioxo-1,5-dihydro-2H-isoindol-2-yl)-3-(4-
methoxyphenyl)-aziridin-2-yl](phenyl)methylene]amino}benzonitrile
(3h). Pale yellow crystals, 328 mg (33%), mp 164 °C. According to the 1H
NMR spectrum at -20 °C it exists as a mixture of three forms in the ratio
of 1:0.16:0.14. 1H NMR (400 MHz, CDCl3, 253 K): δ = 3.56 (d, J = 5.8 Hz,
1H, H3, minor II); 3.69 (s, 3H, OMe, minor II); 3.72 (s, 3H, OMe, minor I);
3.81 (s, 3H, OMe, major); 3.97 (d, J = 5.2 Hz, 1H, H2, major); 4.34 (d, J =
5.4 Hz, 1H, H3, minor I); 4.80 (d, J = 5.2 Hz, 1H, H3, major); 4.94 (d, J =
5.4 Hz, 1H, H2, minor I); 5.40 (d, J = 5.8 Hz, 1H, H2, minor II); 6.45 (d, J =
8.5 Hz, 2H, HoC, major); 6.68 (d, J = 8.7 Hz, 2H, HmA, minor II); 6.77 (d, J
= 8.7 Hz, 2H, HmA, minor I); 6.81 (d, J = 8.5 Hz, 2H, HoC, minor I); 6.90-
1-(4-Nitrophenyl)-3-(4-methoxyphenyl)-5-phenylpyrazole (2i). Yellow
crystals, 179 mg (24%) (2 mmol scale), mp 134-135 °C. 1H NMR (400
MHz, CDCl3): δ = 3.87 (s, 3H, OMe); 6.79 (s, 1H, H4); 6.99 (d, J = 8.8 Hz,
2H, HmB); 7.28-7.34 (m, 2H, HoC); 7.36-7.45 (m, 3H, Hm,pC); 7.50-7.57 (m,
2H, HoA); 7.86 (d, J = 8.8 Hz, 2H, HoB); 8.14-8.22 (m, 2H, HmA) ppm. 13C
NMR (100 MHz, CDCl3): δ = 55.3 (OMe); 106.9 (C4); 114.2 (CmB); 124.3,
124.4 (CmA, CoA); 125.0 (CiB); 127.2; 128.8; 128.9; 129.0 (CpC); 130.2
(CiC); 144.8, 145.0 (C5, CiA); 145.6 (CpA); 153.1 (C3); 160.0 (CpB) ppm.
HRMS (ESI), m/z: calcd for C22H17N3O3 [M+Na]+ 394.1162, found
394.1157.
3-(4-Chlorophenyl)-1-(4-methoxyphenyl)-5-phenylpyrazole
(2j).
6.98 (m, 2H, HmA, major; 2H, HoA, minor II); 7.02 (d, J = 8.5 Hz, 2H, HoC
,
Cream crystals, 245 mg (68%), mp 174 °C. 1H NMR (400 MHz, CDCl3): δ
minor II); 7.23-7.37 (m, 5H, Hm,pB, HmC, major; 4H, HoA, HoB, minor I;
CHCl3); 7.41-7.53 (m, 4H, HoA, HoB, major; 10H, Hm,pB, HmC, minor I and
II); 7.58-7.73 (m, 4H, PhthN, major, 8H, PhthN, minor I and II); 8.05-8.10
(m, 2H, HoB, minor II) ppm. 13C NMR (100 MHz, CDCl3, 253 K): δ = 42.6
(C2, minor II); 47.2 (C2, minor I); 50.8 (C3, major); 51.7 (C3, minor II); 52.3
(C2, major); 52.8 (C3, minor I); 55.06, 55.08 (OMe, minor I and II); 55.2
(OMe, major); 106.07 (CpC, major); 106.14, 106.4 (CpC, minor I and II);
113.5, 113.6 (CmA, minor I and II); 113.8 (CmA, major); 119.1 (C≡N,
major); 119.9 (CoC, minor); 120.1 (C≡N, minor I or II); 120.6 (CoC, major);
121.2 (CoC, minor); 121.3 (C≡N, minor I or II); 122.8 (Cb, br); 123.0; 127.1
(CiA, major); 128.2; 128.3; 128.4; 128.50; 128.52; 129.1; 129.5 (Ca, br);
129.8 (CpB, major); 130.1; 130.2; 130.6; 131.4; 132.78 (CmC, major);
132.85 (CmC, minor); 134.1 (Cc, minor); 134.16 (Cc, major); 134.24 (Cc,
minor); 134.3 (CiB, minor); 135.4 (CiB, major); 135.6 (CiB, minor); 153.5
(CiC, major); 153.9, 154.3 (CiC, minor I and II); 159.4 (CpA, major); 159.7,
= 3.82 (s, 3H, OMe); 6.78 (s, 1H, H4); 6.84-6.91 (m, 2H, HmA); 7.24-7.35
(m, 7H, HoA, HC; CHCl3); 7.36-7.42 (m, 2H, HmB); 7.82-7.88 (m, 2H, HoB
)
ppm. 13C NMR (100 MHz, CDCl3): δ = 55.5 (OMe); 104.5 (C4); 114.1
(CmA); 126.7, 127.0 (CoB, CoA); 128.3 (CpC); 128.5; 128.7; 128.8; 130.4
(CiC); 131.7 (CiB); 133.3, 133.6 (CiA, CpB); 144.5 (C5); 150.5 (C3); 158.9
(CpA) ppm. HRMS (ESI), m/z: calcd for C22H17ClN2O [M+H]+ 361.1102,
found 361.1108.
3-(4-Chlorophenyl)-1-(4-methylphenyl)-5-phenylpyrazole
(2k).
Colorless crystals, 242 mg (70%), mp 160 °C. 1H NMR (400 MHz,
CDCl3): δ = 2.37 (s, 3H, Me); 6.78 (s, 1H, H4); 7.15 (d, J = 8.2 Hz, 2H,
HmA); 7.21-7.36 (m, 7H, HoA, HC; CHCl3); 7.40 (d, J = 8.5 Hz, 2H, HmB);
7.86 (d, J = 8.5 Hz, 2H, HoB) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.1
(Me); 104.8 (C4); 125.1 (CoA); 127.0 (CoB); 128.3 (CpC); 128.5; 128.7;
128.8; 129.5 (CmA); 130.5 (CiC); 131.7 (CiB); 133.6 (CpB); 137.5, 137.6 (CiA,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700172
European Journal of Organic Chemistry
FULL PAPER
159.8 (CpA, minor I and II); 164.0 (C=N, major); 164.2 (C=N, minor II);
165.2 (CON, br, all forms); 167.4 (C=N, minor I) ppm. Signals of the
major and minor isomers partially overlap. HRMS (ESI), m/z: calcd for
C31H22N4O3 [M+H]+ 499.1765, found 499.1745.
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methoxyphenyl)-aziridin-2-yl](phenyl)methylene]-4-nitroaniline (3i).
Pale yellow crystals, 425 mg (41%), mp 164 °C. According to the 1H
NMR spectrum at -20 °C it exists as a mixture of three forms in the ratio
of 1:0.13:0.13. 1H NMR (400 MHz, CDCl3, 253 K): δ = 3.61 (d, J = 5.8 Hz,
1H, H3, minor II); 3.69 (s, 3H, OMe, minor II); 3.74 (s, 3H, OMe, minor I);
3.83 (s, 3H, OMe, major); 3.98 (d, J = 5.2 Hz, 1H, H2, major); 4.34 (d, J =
5.4 Hz, 1H, H3, minor I); 4.80 (d, J = 5.2 Hz, 1H, H3, major); 4.95 (d, J =
5.4 Hz, 1H, H2, minor I); 5.43 (d, J = 5.8 Hz, 1H, H2, minor II); 6.48 (d, J =
8.9 Hz, 2H, HoC, major); 6.67 (d, J = 8.6 Hz, 2H, HmA, minor II); 6.78 (d, J
= 8.6 Hz, 2H, HmA, minor I); 6.85 (d, J = 8.8 Hz, 2H, HoC, minor I); 6.94 (d,
J = 8.6 Hz, 2H, HmA, major); 6.99 (d, J = 8.6 Hz, 2H, HoA, minor II); 7.05
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2005, 41, 1321–1326; (d) M. A. Kuznetsov, V. N. Belov, S. N. Buchaka,
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(d, J = 8.8 Hz, 2H, HoC, minor II); 7.27-7.38 (m, 3H, Hm,pB, major, 4H, HoA
,
HoB, minor I); 7.43-7.54 (m, 4H, HoA, HoB, major, 6H, Hm,pB, minor I and II);
7.59-7.74 (m, 4H, PhthN, major, 8H, PhthN, minor I and II); 7.87 (d, J =
8.9 Hz, 2H, HmC, major); 8.03-8.10 (m, 6H, HoB, minor II, HmC, minor I and
II) ppm. 13C NMR (100 MHz, CDCl3, 253 K): δ = 42.8 (C2, minor II); 47.2
(C2, minor I); 51.1 (C3, major); 51.7 (C3, minor II); 52.2 (C2, major); 53.0
(C3, minor I); 55.11, 55.14 (OMe, minor I and II); 55.3 (OMe, major);
113.5 (CmA, minor I); 113.7 (CmA, minor II); 113.9 (CmA, major); 119.6 (CoC
minor II); 120.1 (CiA, minor II); 120.2 (CoC, major), 120.8 (CoC, minor I);
121.3 (CiA, minor I); 122.8 (Cb, br); 123.1 (Cb); 124.6 (CmC, minor I or II);
124.7 (CmC, major); 124.8 (CmC, minor I or II); 127.1 (CiA, major); 128.2
(CoB, minor II); 128.4 (CoA, major); 128.45 (CmB, major); 128.53; 128.55;
128.6; 129.2 (CoB, major); 129.6 (Ca, br, all forms); 130.1 (CpB, major);
130.2 (CoA, minor II); 130.3; 130.6 (CoA, minor I); 131.6 (CpB, minor II);
134.2 (Cc, minor I or II or both); 134.3 (Cc, major); 135.37 (CiB, major);
,
135.42 (CiB, minor I or II or both); 143.0 (CpC, major); 143.2 (CpC, minor II),
143.3 (CpC, minor I); 155.6 (CiC, major); 156.0, 156.5 (CiC, minor I and II);
159.5 (CpA, major); 159.8, 159.9 (CpA, minor I and II); 163.9 (C=N, minor
II); 164.4 (C=N, major); 165.2 (CON, br, all forms); 167.7 (C=N, minor I)
ppm. Signals of the major and minor isomers partially overlap. The
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The authors thank Dr. Alexey Fedorov (ETH Zurich) for his help
in the preparation of this manuscript and acknowledge the
Russian Science Foundation (Research Grant 14-13-00126) for
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Keywords: [4+1]-annulation • [2+1]-cycloaddition • regiodefined
synthesis • pyrazoles • aziridines
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10.1002/ejoc.201700172
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
FULL PAPER
Cycloaddition, [4+1]-Annulation
Aleksandr Stukalov,[a] Viktor V.
Sokolov,[a] Vitalii V. Suslonov[b] and
Mikhail A. Kuznetsov *[a]
Page No. – Page No.
Oxidative addition of N-aminophthalimide to 1,2,4-triaryl-1-azabuta-1,3-dienes
leads, in most cases, to the regiodefined formation of 1,3,5-triarylpyrazoles via
[4+1]-annulation in moderate to good yields. Rare examples of 2-imidoyl-1-
phthalimidoaziridines that are formed via competitive [2+1]-cycloaddition onto the
C=C bond were isolated in low yields for 1-azadienes with electron-deficient aryl
substituents at the imine nitrogen atom.
Pyrazoles and C-imidoylaziridines via
[4+1]-annulation and [2+1]-
cycloaddition of 1-azabuta-1,3-dienes
with a synthetic equivalent of
phthalimidonitrene
This article is protected by copyright. All rights reserved.