Solvent-free, one-pot synthesis of pentasubstituted cyclopropanes in the presence of BrCN and EtONa by milling

Article abstract of DOI:10.1007/s00706-014-1180-2

A solvent-free, one-pot process for the preparation of pentasubstituted 3-arylcyclopropane-1,1,2,2-tetracarbonitriles in the presence of solid sodium ethoxide by milling was achieved. The one-pot reaction of aromatic aldehydes and dialdehydes with malonon

Full text of DOI:10.1007/s00706-014-1180-2

Monatsh Chem
DOI 10.1007/s00706-014-1180-2
ORIGINAL PAPER
Solvent-free, one-pot synthesis of pentasubstituted cyclopropanes
in the presence of BrCN and EtONa by milling
•
Nader Noroozi Pesyan Mohammad Rezaee
Received: 27 August 2013 / Accepted: 11 February 2014
Ó Springer-Verlag Wien 2014
Abstract A solvent-free, one-pot process for the prepa-
ration of pentasubstituted 3-arylcyclopropane-1,1,2,2-
tetracarbonitriles in the presence of solid sodium ethoxide
by milling was achieved. The one-pot reaction of aromatic
aldehydes and dialdehydes with malononitrile, cyanogen
bromide, and solid sodium ethoxide afforded pentasubsti-
tuted cyclopropanes in excellent yield under solvent-free
conditions. The structures were characterized and con-
K2CO3 [9], solvent-free stereoselective synthesis of cis-1-
carbomethoxy-2-aryl-3,3-dicyanocyclopropanes by grind-
ing [10], solvent-free reactions of C60 with active
methylene compounds in the presence of a base under
high-speed vibration grinding (HSVM) [11], and solvent-
free rhodium(II)-catalyzed enantioselective cyclopropana-
tion [12].
Ball milling has been extensively used as a solvent-
free technique in the development of new synthetic
routes, e.g., Suzuki–Miyaura coupling [13], Suzuki
reaction [14], aldol condensation [15], asymmetric or-
ganocatalytic aldol reaction [16], solid-phase synthesis of
2,20-dihydroxy-1,10-binaphthyl (BINOL) [17], and oxida-
tion reactions [18]. In addition, ball milling is also a
useful method to produce ferrite nanoparticles [19],
Chevrel phase superconductors [20], etc. Attrition or
mechanical milling is a typical top-down method in
preparing nanoparticles [21]. Therefore, this technique
should be considered as a potentially attractive solution
for solvent-free synthesis.
1
firmed by IR, H NMR, 13C NMR spectroscopy, and mass
spectrometry. Its advantages are easy workup, mild reac-
tion conditions, and excellent yields.
Keywords Cyanogen bromide ꢀ Malononitrile ꢀ
Milling ꢀ Solvent-free ꢀ Tetracyanocyclopropanes
Introduction
The cyclopropyl group is an important structure in many
herbal compounds displaying antifungal [1], antibacterial,
antiviral, and some enzyme inhibition activities [2–8].
Nowadays, the development of solvent-free reactions is
an important goal in organic synthesis. There are several
reports in the literature about cyclopropanation under sol-
vent-free conditions, e.g., microwave-assisted solvent-free
cyclopropanation of some b-dicarbonyls in the presence of
More recently, we reported the cyclopropanation of
some b-dicarbonyls such as malononitrile [22] and
Meldrum’s acid [23] in the reaction of aliphatic and
aromatic aldehydes and BrCN in the presence of trieth-
ylamine under solvent conditions. Nevertheless, the
reaction of (thio)barbituric acids (as a symmetrical bar-
bituric acid) with aldehydes [24] and ketones [25] gave
spiro-dihydrofurans in the presence of BrCN and trieth-
ylamine under the same conditions (solution case). There
is no report in the literature about the cyclopropanation
of b-dicarbonyls via BrCN under solvent-free conditions.
On the basis of these concepts, herein, we report the
transformation of aldehydes and malononitrile to 3-aryl-
cyclopropane-1,1,2,2-tetracarbonitriles in the presence of
BrCN and solid EtONa by milling.
Electronic supplementary material The online version of this
article (doi:10.1007/s00706-014-1180-2) contains supplementary
material, which is available to authorized users.
N. Noroozi Pesyan (&) ꢀ M. Rezaee
Department of Chemistry, Faculty of Science,
Urmia University, 57159 Urmia, Iran
e-mail: n.noroozi@urmia.ac.ir; nnp403@gmail.com
123

N. Noroozi Pesyan, M. Rezaee
Results and discussion
Scheme 2
This paper describes the one-pot reaction of aldehydes 1a–
1l with malononitrile (2) and BrCN to afford 3-arylcyclo-
propane-1,1,2,2-tetracarbonitriles 3a–3l in the presence of
EtONa by milling in excellent yield (Scheme 1).
The salt of sodium bromodicyanomethanide (7) plays a
major role in the synthesis of 3. A proposed reaction
mechanism for the formation of 7 is shown in Scheme 2.
According to our search, there is no report about this
compound in the literature. The salt of 7 was isolated and
characterized by FTIR spectroscopy. The FTIR spectrum
of 7 shows CN and C–Br stretching vibrations at 2,167 and
565 cm-1, respectively. This salt is hygroscopic so it
shows the OH stretching vibration of water at 3,413 cm-1
(Fig. 1). Unfortunately, all attempts failed to separate or
characterize intermediates 5 and 6. Other evidence for the
formation and confirmation of 7 (i.e., the existence of a
sodium ion and bromine atom in this salt structure) was
obtained by flame and Beilstein tests (intense yellow color
and precipitate of pale yellow silver bromide, respectively).
We also examined and measured the sodium ion emission
of the salt of 7 by flame photometry (see ‘‘Experimental’’).
On the basis of the well-established chemistry of barbituric
acids [24, 25], malononitrile [22], and Meldrum’s acid [23]
in the reaction with BrCN in the presence of triethylamine
it is reasonable to assume that compound 2 reacts directly
with EtONa to form malononitrile sodium salt (4) which
then reacts with BrCN to form an intermediate 5.
Intramolecular rearrangement of this intermediate produces
2-bromomalononitrile (6) intermediate. Finally, EtONa as
a base captures the acidic proton from 6 to afford 7
(Scheme 2). We performed the reaction of 2 with BrCN in
the presence of EtONa and in the absence of aldehydes 1 so
compound 7 was isolated in excellent yield.
Other evidence for the formation and confirmation of 7
is the formation of reported salts of triethylammonium
5-bromo(thio)barbiturates 13a0–13c0 [24, 25], triethylam-
monium 1-bromo-4,4-dimethyl-2,6-dioxocyclohexan-1-ide
(14a0) [26], triethylammonium 5-bromo-2,2-dimethyl-4,6-
dioxo-1,3-dioxan-5-ide (14b0) [23], and triethylammonium
bromodicyanomethanide (15) [22]. As a representative
example, the reaction of 2 with BrCN in the presence of
triethylamine in ethanol afforded the salt of 15 [22]; we
recently described the reaction mechanism in the case of
malononitrile 2 [22], (thio)barbituric acids 11a0–11c0 [24,
25, 27, 28], 5,5-dimethylcyclohexane-1,3-dione (dime-
done, 12a0) [26], and Meldrum’s acid (12b0) [23] (Fig. 2).
As a representative example, the reaction mechanism for
the formation of 3b is shown in Scheme 3. First, the
reaction of aldehyde 1b with malononitrile afforded 2-(3-
nitrobenzylidene) malononitrile (8b). Nucleophilic attack
of 7 at the b-carbon of the a,b-unsaturated 8b then afforded
the intermediate sodium 3-bromo-1,1,3,3-tetracyano-2-(3-
nitrophenyl)propan-1-ide (9b). Intramolecular nucleophilic
C-attack of this carbanion at the carbon atom bearing the
bromine atom (path a) produced 3-(3-nitrophenyl)cyclo-
propane-1,1,2,2-tetracarbonitrile (3b). All attempts failed
to separate and characterize the intermediates 8b and 9b.
No 20b was observed. This observation indicated that no
C-attack of the carbanion occurred at the nitrile group
(Scheme 3, path b). The reaction of 1b and 2 exclusively
yielded 8b in the presence of EtONa and absence of BrCN.
It has been shown that the salt of 7 plays a major role in
these reactions. First, it is a nucleophile in the reaction with
8b and then it has electrophile character (carbon atom
bearing bromine) in the intermediate 9b to form 3b
(Scheme 3). The reaction conditions, time, and yields are
outlined in Table 1.
Scheme 1
1
As a representative example, the H NMR spectrum of
3b shows a singlet at d = 5.44 ppm corresponding to the
123

Solvent-free, one-pot synthesis of pentasubstituted cyclopropanes
Fig. 1 Comparison of the FTIR spectra of 2 (blue), 4 (green), and 7 (red) (color figure online)
different chemical shifts. The FTIR spectrum shows two
peaks at 2,258 and 2,193 cm-1 that confirm the existence
of cyano groups in the molecule. The stretching vibrations
of the sole CH of cyclopropane and the CHs of the phenyl
ring appeared at 3,005 and 3,083 cm-1, respectively. These
data are in good agreement with the structure of 3b (see
‘‘Experimental’’).
To explore the generality of these reactions, we per-
formed the reaction of some liquid aldehydes with 2 and
BrCN in the presence of solid sodium ethoxide by stir-
ring under solvent-free conditions (Scheme 4). The
results of these reactions are summarized in Table 1
(entries 13–17; for more information, see Supplementary
Material).
The reaction of bulky aldehydes such as 9-anthracene-
carbaldehyde (1h) and aldehydes containing exchangeable
protons such as hydroxyl groups (1i–1l) with 2 and BrCN
in the presence of EtONa afforded Knoevenagel adducts
8h–8l instead of cyclopropane products 3h–3l. Presumably,
the steric hindrance in 1h led to formation of 8h. Com-
pound 7 acted as a base to capture the acidic proton of the
OH group (path a) more rapidly than it underwent Michael
addition to the b-carbon position of Knoevenagel adducts
8i–8l (path b) (Scheme 5). Therefore, path a is favored
over path b. It seems that the presence of exchangeable
acidic protons on the Knoevenagel adducts prevented the
Michael addition of 7, thereby favoring path a (Scheme 5).
Another possible pathway could be path c. Sodium eth-
oxide as a base can deprotonate the phenol derivative, e.g.,
4-hydroxybenzaldehyde (1i), to afford sodium 4-formyl-
phenolate (21i, Scheme 5, path c). Our attempts failed to
separate and characterize 8i, 10i, and 21i. These results
Fig. 2 Structural formulas of (thio)barbituric acids (11a0–11c0),
dimedone (12a0), Meldrum’s acid (12b0), triethylammonium
5-bromo(thio)barbiturates (13a0–13c0) [24, 25], triethylammonium
1-bromo-4,4-dimethyl-2,6-dioxocyclohexan-1-ide (14a0) [26], trieth-
ylammonium 5-bromo-2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ide (14b0)
[23], and triethylammonium bromodicyanomethanide (15) [22]
cyclopropyl C–H proton and two multiplets at 7.79 and
8.34 ppm and a singlet at 9.01 ppm for the m-nitrophenyl
ring. The 13C NMR spectrum of this compound shows ten
distinct peaks. The peaks at d = 109.9 and 111.3 ppm
correspond to the cyano groups. Two peaks at 46.2 and
24.1 ppm correspond to cyclopropane carbons with
123

N. Noroozi Pesyan, M. Rezaee
Scheme 3
Table 1 Synthesis of cyclopropanes 3 from aldehydes 1 (Schemes 1, 4)
Entry
R
Product
Time/min
Yielda/%
M.p. (lit. m.p.)/°C
1
2-NO2-C6H4
3-NO2-C6H4
4-Br-C6H4
3a
30
38
30
30
30
45
30
94
217–219 (215–216 [22])
215–217 (214–216 [22])
219–221 (218–219 [22])
239–241 (240–243 [22])
227–229 (227–229 [22])
223–224 (225–226 [22])
248–251 (249–252 [22], 257–259 [29])
208–210 (207–209 [22])
185–186 (185–186 [30])
92 (91 [31])
2
3b
95
3
3c
95
4
4-Cl-C6H4
3d
100
90
5
3,4,5-(MeO)3-C6H2
4-CN-C6H4
1-Naphthalenyl
9-Anthracenyl
4-OH-C6H4
3-OH-C6H4
4-OH-3-MeO-C6H3
3-OH-4-MeO-C6H4
C6H5
3e
6
3f
100
95
7
3g
8
8hb
8ib
8jb
8kb
8lb
3md
3nd
3od,e
3pd,e
3qd,e
(85c)
(80c)
(75c)
(80c)
(80c)
100
90
9
10
11
12
13
14
15
16
17
a
134–136 (135–136 [31])
251–253 (250 [32])
0.2
0.2
0.2
0.2
0.3
226–228 (225–227 [22], 229–230 [33])
207–209 (209–211 [22], 208–210 [33])
172–174 (173–175 [22])
201–205 (203–208 [34])
180–182 (194–196 [29], 197 [35])
4-MeO-C6H4
2-Pyridinyl
90f
2-Furanyl
100
80
C2H5
Yield refer to isolated product
b
c
d
e
f
Knoevenagel adducts were obtained
Yield of conversion to Knoevenagel adducts
Reaction was done under solvent-free conditions with stirring
Freshly distilled before reaction
No zwitterionic salt of Knoevenagel adduct of pyridine 1o [36, 37] was observed
demonstrated the reason for the unsuccessful cyclopropa-
nation of aromatic aldehydes possessing an exchangeable
proton.
(16c00) with 2 in the presence of BrCN and EtONa by
milling under the same conditions (Scheme 6). The reac-
tion of 16a00 with 2 and BrCN in the presence of EtONa
afforded 3-(2-formylphenyl) cyclopropane-1,1,2,2-tetra-
carbonitrile (17a00) as a result of the ortho hindrance effect.
We also performed the reaction of phthalaldehyde
(16a00), isophthalaldehyde (16b00), and terphthalaldehyde
123

Solvent-free, one-pot synthesis of pentasubstituted cyclopropanes
In respect to 16b00 and 16c00, both aldehyde groups in each
(18b00) and 3,30-(1,4-phenylene)bis(cyclopropane-1,1,2,2-
tetracarbonitrile) (18c00), respectively. The reaction condi-
tions and yields of aromatic dialdehydes 16a00–16c00 are
outlined in Table 2.
compound reacted with 2
(1,3-phenylene)bis(cyclopropane-1,1,2,2-tetracarbonitrile)
and afforded 3,30-
1
Scheme 4
As a representative example, the H NMR spectrum of
17a00 shows a singlet at d = 5.08 ppm corresponding to the
cyclopropyl C–H proton and three multiplets at 7.95, 8.20,
and 8.30 ppm for the phenyl ring and a singlet at 10.27
corresponding to the aldehyde proton. The 13C NMR
spectrum of this compound shows 11 distinct peaks. The
peaks at d = 109.2 and 110.7 ppm correspond to the cyano
Scheme 5
Scheme 6
123

N. Noroozi Pesyan, M. Rezaee
General procedure for the preparation
Table 2 Reactions of dialdehydes 16 (Scheme 6)
of 3-arylcyclopropane-1,1,2,2-tetracarbonitriles
under solvent-free conditions by milling
Entry Dialdehyde Product Time/
min
Yielda/ M.p. (lit. m.p.)/°C
%
As a representative example, in a 10-cm3 Teflon-faced
screw cap tube cooled in an ice bath 0.15 g m-nitro-
benzaldehyde (1b, 1.0 mmol), 0.14 g malononitrile (2,
2.0 mmol), 0.13 g cyanogen bromide (1.2 mmol), and
0.14 g solid sodium ethoxide (2.0 mmol) were mixed,
milled with a magnetic stirrer, and homogenized at 0 °C
to room temperature. The Teflon-faced screw cap tube
prevents the evaporation of cyanogen bromide (Caution!
Cyanogen bromide is toxic. The milling should be car-
ried out in a well-ventilated hood). After 5 min the
homogenized mixture was perturbed by milling (indi-
cating the release of EtOH). The reaction progression
was monitored by thin-layer chromatography (TLC,
acetone/n-hexane 3:7) every 10 min. Initially, the reac-
tion mixture was extracted with water (2 9 5 cm3)
twice to remove the residue of EtONa and sodium
bromodicyanomethanide (7), and then residue m-nitro-
benzaldehyde and malononitrile were removed by
extraction with fresh ethanol (2 9 5 cm3). The spectro-
scopic data and physical properties of the obtained
3-(3-nitrophenyl)cyclopropane-1,1,2,2-tetracarbonitrile (3b)
were compared with those reported in Ref. [22] (0.26 g,
100 % yield).
1
2
3
16a00
16b00
16c00
17a00
18b00
18c00
45b
80
286–288 (287–289
[22])
45
98
97
256–258 (255–257
[22])
45
235–237 (236–239
[22])
a
Yield refer to isolated product
Maximum reaction time
b
groups with different chemical shifts and a peak at
193.8 ppm related to the carbonyl group. The FTIR spec-
trum shows two peaks at 2,259 and 1,682 cm-1 that
confirm the existence of cyano and carbonyl groups in the
1
molecule. The H NMR spectrum of 18b00 shows a singlet
at 5.24 ppm, a triplet at 7.81 (J = 8.1 Hz), a doublet at
8.14 (J = 7.8 Hz), and a singlet at 8.44 ppm corresponding
to cyclopropyl C–H and phenyl protons, respectively. The
13C NMR spectrum of this compound shows eight distinct
peaks. The FTIR spectrum show a peak at 2,262 cm-1 and
no carbonyl frequency absorption was observed in this
spectrum. These data are in good agreement with the
structural formula of 17a00 and 18b00, respectively (see
‘‘Experimental’’).
Experimental
General procedure for the preparation
of 3-arylcyclopropane-1,1,2,2-tetracarbonitriles
from liquid aldehydes under solvent-free conditions
by stirring
All melting points were measured with a digital melting
1
point apparatus (Electrothermal). The H and 13C NMR
spectra of 3a–3p were recorded on a Bruker 300 FT-NMR
at 300 and 75 MHz, respectively (Urmia University, Urmia,
Iran) and spectra of 3q were recorded at Shahid Beheshti
As a representative example, in a 10-cm3 Teflon-faced
screw cap tube cooled in an ice-bath 0.11 g benzalde-
hyde (1m, 1.0 mmol), 0.13 g malononitrile (2,
2.0 mmol), 0.13 g cyanogen bromide (1.2 mmol), and
0.14 g solid sodium ethoxide (2.0 mmol) were mixed,
stirred by a magnetic stirrer, and homogenized at 0 °C to
room temperature. The Teflon-faced screw cap tube
prevents the evaporation of cyanogen bromide. The
reaction progression was monitored by TLC (acetone/n-
hexane 3:7). After completion of the reaction, similar to
the milling reaction workup initially, the reaction mixture
was extracted with water (2 9 5 cm3) to remove the
residue of EtONa and 7, and then residue benzaldehyde
and malononitrile were removed by extraction with fresh
ethanol (2 9 5 cm3). The spectroscopic data and physical
properties of the obtained 3-phenylcyclopropane-1,1,2,2-
tetracarbonitrile (3m) were compared with those reported
in Ref. [22] (0.23 g, 100 % yield).
1
University, Tehran, Iran. H and 13C NMR spectra were
obtained from solutions in acetone-d6 and/or DMSO-d6 as
solvent using TMS as internal standard. The data are
reported as s = singlet, d = doublet, t = triplet,
q = quartet, m = multiplet or unresolved, bs = broad
singlet, coupling constant(s) in Hz, integration. FTIR
spectra were determined using KBr pellets in the region
4,000–400 cm-1 on a Nexus 670 FTIR spectrophotometer.
Cyanogen bromide was synthesized on the basis of reported
methods [38]. The flame photometry analysis of Na? in 7
was recorded on a Corning 410 flame photometer (Urmia
University, Urmia, Iran). EtONa was obtained by dissolving
the fresh metal sodium in an appropriate volume of absolute
EtOH and then evaporating the solvent. Aromatic mono-
and dialdehydes, propanal, and malononitrile were pur-
chased from Merck and used without further purification.
123

Solvent-free, one-pot synthesis of pentasubstituted cyclopropanes
14. Nielsen SF, Axelsson O (2000) Synth Commun 30:3501
15. Rodriguez B (2006) Angew Chem Int Ed 45:6924
16. Rodriguez B, Bruckmann A, Bolm C (2007) Chem Eur J 13:4710
17. Rasmussen MO, Axelsson O, Tanner D (1997) Synth Commun
27:4027
Sodium bromodicyanomethanide (7)
In a 10-cm3 Teflon-faced screw cap tube cooled in an ice
bath 0.14 g malononitrile (2, 1.0 mmol), 0.13 g cyanogen
bromide (1.2 mmol), and 0.14 g solid sodium ethoxide
(2.0 mmol) were mixed, milled with a magnetic stirrer, and
homogenized at 0 °C for 30 min. After 5 min the homog-
enized mixture was perturbed by milling (indicating the
release of EtOH), washed with dichloromethane, and dried.
To demonstrate the presence of sodium ions, the flame
photometry instrument was first calibrated with a standard
solution of 0.02 mol dm-3 sodium chloride and the emis-
18. Wang G-W (2008) J Org Chem 73:7088
19. Goya GF, Rechenberg HR (1999) J Magn Magn Mater 203:141
20. Niu HJ, Hampshire DP (2002) Phys C 372–376:1145
21. Verma A, Biswas K, Tiwary CS, Mondal AK, Chattopadhyay K
(2011) Metall Mater Trans A 42:1127
22. Noroozi Pesyan N, Kimia MA, Jalilzadeh M, S¸ahin E (2013) J
Chin Chem Soc 60:35
23. Noroozi Pesyan N, Gharib A, Behroozi M, Shokr A (2013) Arab J
Chem. doi:10.1016/j.arabjc.2013.05.024
24. Jalilzadeh M, Noroozi Pesyan N, Rezaee F, Rastgar S, Hosseini
Y, S¸ahin E (2011) Mol Divers 15:721
sion was set to 50 %. Then a solution of 7 (0.02 mol dm-3
)
¨
25. Hosseini Y, Rastgar S, Heren Z, Bu¨yu¨kgu¨ngor O, Noroozi Pesyan
N (2011) J Chin Chem Soc 58:309
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was prepared and showed 48 % emission. Olive green
solid; m.p.: 238–240 °C (dec.); FTIR (KBr) = 3,413,
2,241, 2,175, 1,638, 1,619, 1,480, 1,247, 568 cm-1
.
27. Jalilzadeh M, Noroozi Pesyan N (2011) Bull Korean Chem Soc
32:3382
28. Jalilzadeh M, Noroozi Pesyan N (2011) J Korean Chem Soc
55:940
Acknowledgments We gratefully acknowledge financial support by
the Research Council of Urmia University.
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Vorontsov AY, Nikishin GI (2009) Tetrahedron 65:6057
30. Bhuiyan MMH, Hossain MI, Ashraful Alam M, Mahmud MM
(2012) Chem J 2:30
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