Michael addition of phenylacetonitrile to the acrylonitrile group leading to diphenylpentanedinitrile. Structural data and theoretical calculations

Article abstract of DOI:10.2478/s11696-013-0503-9

Knoevenagel condensation of phenylacetonitrile with 4- diphenylaminophenylacetonitrile in the presence of piperidine was carried out to obtain a novel conjugated compound. In addition to the expected compound 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitr

Full text of DOI:10.2478/s11696-013-0503-9

Chemical Papers 68 (5) 668–680 (2014)
DOI: 10.2478/s11696-013-0503-9
ORIGINAL PAPER
Michael addition of phenylacetonitrile to the acrylonitrile group
leading to diphenylpentanedinitrile.
Structural data and theoretical calculations
a
a
aM. Judith Percino*, Margarita Cerón, Maria Eugenia Castro,
aGuillermo Soriano-Moro, Victor M. Chapela, Francisco J. Meléndez
a
b
aLaboratorio de Polímeros, Centro de Química, Instituto de Ciencias, Universidad Autónoma de Puebla, Complejo de Ciencias,
ICUAP, Edificio 103 H, 22 Sur y San Claudio, Ciudad Universitaria, Puebla, 72570, México
bLaboratorio de Química Teórica, Centro de Investigación, Dpto. de Fisicoquímica, Facultad de Ciencias Químicas,
Universidad Autónoma de Puebla, Edificio 105 I, 22 Sur y Avenida San Claudio, Ciudad Universitaria,
Colonia San Manuel, Puebla, 72570, México
Received 9 May 2013; Revised 10 September 2013; Accepted 13 September 2013
Knoevenagel condensation of phenylacetonitrile with 4-diphenylaminophenylacetonitrile in the
presence of piperidine was carried out to obtain a novel conjugated compound. In addi-
tion to the expected compound 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I ), the 3-((4-
diphenylamino)phenyl)-2,4-diphenylpentanedinitrile (II ) was also obtained with a good yield. Com-
pound II was obtained as a result of the Michael addition of phenylacetonitrile with 2-(phenyl)-
3-(4-diphenylaminophenyl)acrylonitrile (I ). Conversely, when the same reaction was performed in
the presence of KOH as catalyst, only the α,β-unsaturated nitrile (I ) was afforded with a 92 %
yield. The structures were confirmed with IR, EI-MS and NMR spectroscopy. Single crystals I and
II were formed and their structures were determined by X-ray single-crystal diffraction analysis.
Crystal I belongs to the monoclinic system with space group P21/n having unit cell parameters of
◦
˚
˚
˚
a = 16.8589(5) A, b = 6.68223(17) A, c = 19.8289(7) A, β = 111.133(4) and Z = 4. Crystal II
belongs to the same monoclinic system with space group P21/c, having unit cell parameters of a =
◦
˚
˚
˚
10.8597(4) A, b = 24.7533(10) A, c = 9.7832(4) A, β = 91.297(3) and Z = 4. In addition to the
structural data analysis, some theoretical calculations that reveal the nature of relevant structure–
property relationships are also reported.
c
ꢀ 2013 Institute of Chemistry, Slovak Academy of Sciences
Keywords: phenylacetonitrile, α,β-unsaturated nitrile, N-diphenylaminophenyl derivative, cyano-
substituted compound, Michael addition, crystal structure
Introduction
plant growth regulators in increasing the soybean crop
(Mori, 1976), and as inhibitors of prostaglandin syn-
thetase (Peat et al., 1981; Michel et al., 1984). The
traditional preparation of arylacrylonitriles involves
the reaction of aromatic aldehydes with arylacetoni-
triles (Knoevenagel reaction, as well as Meyer and
Frost reaction) (Knoevenagel, 1896; Frost, 1889). The
compounds can be obtained under basic conditions
in a polar solvent (NaOH, KOH, NaOEt, K2CO3
in MeOH, EtOH or THF) (D’sa et al., 1998; Guil-
Unsaturated nitriles play a key role in several path-
ways proposed for the pre-biotic synthesis of bio-
logical molecules (Guillemin et al., 1998). Arylacry-
lonitriles are important synthons for the synthesis
of several biologically active molecules used in the
preparation of perfumes (Fraysse, 1980), flavonoid pig-
ments (Fringuelli et al., 1994), sexual pheromones
and vitamin A, etc. They are directly involved as
*Corresponding author, e-mail: judith.percino@correo.buap.mx

M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
669
Fig. 1. In situ formation of 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I) mixed with 3-(4-diphenylamino)phenyl)-2,4-
diphenylpentanedinitrile (II).
lot et al., 2005). Recently, Loupy et al. (2005) ap-
plied solvent-free procedures, using powdered KOH
as the base at ambient temperature, in the reaction
of phenylacetonitrile with 4-methoxybenzaldehyde to
yield the Z and E acrylonitrile isomers, accompanied
by compounds resulting from the Michael addition.
Using non-catalysed solvent-free conditions for the re-
action of 4-methoxybenzaldehyde with phenylacetoni-
trile, these investigators obtained α,β-unsaturated ni-
trile (Z + E) as the main product; they also occa-
sionally observed, by GC-MS detection, a product
from the Michael addition. The reaction of pheny-
lacetonitrile with aromatic and aliphatic aldehydes at
ambient temperature in the presence of KOH using
4-trifluoromethanophenyl afforded the compound 3-
(4-F3C(phenyl)-2,4-diphenylpentanedinitrile) with 8–
13 % yield. However, when a highly hindered aromatic
aldehyde, such as mesitaldehyde, was used, the reac-
tion afforded an almost quantitative yield (98 %) of
the α,β-unsaturated nitrile.
The present group has reported several studies on
syntheses of α,β-unsaturated nitriles by Knoevenagel
condensation without catalyst and under solvent-
free conditions (Percino et al., 2010, 2011, 2012;
Pérez-Gutiérrez et al., 2011), as well as the prepa-
ration of conjugated pyridine-(N-diphenylamino) or
N-dimethylamino carbazole)acrylonitrile derivatives.
Good yields were obtained by following the Kno-
evenagel method in the presence of piperidine or
KOH as the catalyst. The present work reports on
the in situ synthesis of 2,4-diphenyldinitrile, as a
side reaction of the Michael addition when the Kno-
evenagel condensation of phenylacetonitrile and N-
diphenylaminophenyaldehyde was carried out using
piperidine as the catalyst. The compounds 2-(phenyl)-
3-(4-diphenylaminophenyl)acrylonitrile (I ) and 3-(4-
diphenylamino) phenyl)-2,4-diphenylpentanedinitrile
(II ) were isolated even though the aldehyde is highly
hindered. The compounds were characterised using
IR, 1H-NMR, MS techniques and single crystal X-
ray analysis. Theoretical calculations were also per-
formed in order to evaluate the nature of the rele-
vant structure-property relationships, such as π-de-
localisation on the whole molecule of I as contrasted
with molecule II.
Experimental
Phenylacetonitrile and 4-diphenylaminophenyl-
acetonitrile were obtained from Aldrich (Mexico) and
purified prior to use. Melting points were measured
with an SEV (Systems and Equipments of Glass, SEV
Mexico) (0–300◦C) apparatus and are reported as un-
corrected values. The IR spectra of the products were
recorded on a Vertex (model 70, Bruker Optics, Ger-
many) 750 FT-IR spectrophotometer by attenuated
total reflectance (ATR). The 1H NMR spectra were
obtained using compounds dissolved in CDCl3 on a
Varian 400 MHz NMR spectrometer (Varian NMR,
Walnut Creek, CA, USA). The electron ionisation (EI)
spectra were acquired on a Jeol MStation 700-D mass
spectrometer (Jeol USA, Peabody, MA, USA).
The synthesis of compounds I and II was per-
formed by mixing 1 : 1 : 1 (molar ratios) of pheny-
lacetonitrile, 4-diphenylaminophenylacetonitrile and
piperidine, as shown in Fig. 1. Piperidine acted as

670
M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
Table 1. Crystallography data for I and II compounds
I
II
Empirical formula
Crystal system
Colour, Habit
Formula mass
Space group
T/K
C27H20N2
C35H27N3
Monoclinic
Pale yellow, plate
489.60
Monoclinic
Yellow, rod
372.45
P21/n
110(2)
P21/c
110(2)
˚
a/A
16.8589(5)
6.68223(17)
19.8289(7)
90.00
111.133(4)
90.00
10.8597(4)
24.7533(10)
9.7832(4)
90.00
91.297(3)
90.00
˚
b/A
˚
c/A
α/◦
β/◦
γ/◦
3
˚
V/A
2083.59(11)
4
2629.18(18)
4
Z
Dc/(g cm−3
F/(000)
µ/mm−1
)
1.187
784
0.070
1.237
1032
0.073
˚
λ/A
0.71073
0.62 × 0.19 × 0.15
25.00
0.71073
0.75 × 0.32 × 0.07
24.35
Crystal◦size/(mm3)
2θmax
/
N
15652
3074
3.30
13551
3619
5.85
N◦ (I > 2.0σ(I))
R1
wR2
8.24
14
Goodness-of-fit
Largest diff peak
1.036
–0.17 and 0.13
1.150
–0.31 and 0.42
−3
˚
and hole/(e A
)
Fig. 2. Reaction to obtain 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I).
both catalyst and solvent. The reaction mixture was
refluxed at 100◦C for 36 h. During the reaction,
the mixture appeared to be oily with a brownish-
red colour. The mixture was neutralised with a HCl
(2 M) solution to precipitate the products in pow-
der form and which were subsequently washed with
H2O. The products were purified by recrystallisation
with a solvent mixture of ethylacetate : hexane (4 : 1
vol.). The compound was characterised by IR, 1H-
NMR and EI mass spectrometry. The compound (II )
was obtained in the form of single crystals using the
following procedure: the 3-(4-diphenylamino)phenyl)-
2,4-diphenylpentanedinitrile (16.8 mg, 0.034 mmol)
was dissolved in 6.5 mL of ethanol and set aside at
4◦C for 4 days.
in accordance with the following procedure: pheny-
lacetonitrile (0.15 mL, 1.28 mmol) was added to a so-
lution of p-(diphenylaminophenyl) aldehyde (0.35 g,
1.28 mmol) in ethanol (10 mL) at 60◦C and at am-
bient temperature. The mixture was stirred and then
KOH powder (0.072 g, 1.28 mmol) was added. After
30 min. a yellow precipitate was formed, which was
filtered and washed with H2O. The product was pu-
rified by recrystallisation with methanol. Crystals of
(I ) were obtained with 10 mg of (I ) dissolved in 15
mL of cyclohexane and kept at ambient temperature;
after 72 h the yellow crystals were formed.
All reflection intensities were measured at 110(2)
K using a KM4/Xcalibur (detector: Sapphire3) with
enhanced graphite-monochromated Mo Kα radiation
˚
The reaction conditions to obtain 2-(phenyl)-3-(4-
diphenylaminophenyl)acrylonitrile (I ) were as shown
in Fig. 2. Compound I was obtained with a 92 % yield,
(λ = 0.71073 A) using the CrysAlisPro program
(Version 1.171.35.11, Oxford Diffraction, 2011). The
CrysAlisPro This program was used to refine the cell

M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
671
dimensions and for data reduction. The structures
were solved with the SHELXS-97 program (Sheldrick,
1998) and were refined on F2 with SHELXL-97
(Sheldrick, 1998). Analytical numeric absorption cor-
rections based on a multi-faceted crystal model were
applied using CrysAlisPro. The temperature of the
data collection was controlled using the Cryojet sys-
tem (manufactured by Oxford Instruments). The H
atoms (except for specified atoms) were located at
calculated positions using the instructions AFIX 13
or AFIX 43 with isotropic displacement parameters
having values 1.2 times Ueq of the attached C atoms.
The crystallography data for I and II compounds are
presented in Table 1.
Fig. 3. Baylis–Hillman reaction (Lubineau & Augé, 1999; Augé
et al., 1994).
Results and discussion
Reactions with acrylonitriles
alyst (Fig. 2). The use of piperidine as a catalyst made
it possible to obtain both compounds: II with a yield
of 21 % mixed with I with a 42 % yield. Product II is
characterised in anti configuration in two enantiomeric
forms, anti (2R,4R) and anti (2S,4S). Recent stud-
ies of the Michael addition of some aldehydes to mal-
onates in the presence of organic catalysts have been
reported using different solvents; here the reactions
were found to be highly enantioselective (Saidalimu
et al., 2013). However, in this case, in the presence of
piperidine, the reaction does not proceed enantioselec-
tively. By contrast, with the use of KOH as a catalyst
at ambient temperature (Fig. 2), the primary product
was the α,β-unsaturated nitrile (I ) (92 %). This out-
come could be explained by the low reactivity of the
—COH group through the —N(Ph)2 moiety, which is
a strong electron-donating group with a greater influ-
ence than the highly hindered aromatic aldehyde. It is
suggested that both catalyst and solvent play a deter-
minant role in the diastereo- and enantioselectivity of
the Michael addition reaction (Saidalimu et al., 2013).
According to a report by Jenner, the amines can
react via Michael addition under aqueous conditions
(Jenner, 1996), especially with α,β-unsaturated ni-
triles, using a combination of pressure and cataly-
sis by ytterbium triflate which strongly promotes the
addition of amines to α,β-ethylenic compounds (Lu-
bineau & Augé, 1999). Physicochemical activation by
water is highly efficient except when the substituent is
—OOCH3 due to the rapid retro-Michael reactions. A
related reaction is the Baylis–Hilman reaction, which
proceeds readily in water with a good rate enhance-
ment (Fig. 3) (Lubineau & Augé, 1999).
There have been several recent approaches to the
preparation of arylacrylonitriles with aromatic alde-
hydes. Solvent-free methods at various temperatures
were used successfully to synthesise different α,β-
unsaturated nitriles as well as for a series of iso-
mers of 3-(4-substituted phenyl)-2-arylacrylonitriles
(aryl, phenyl or pyridyl) with chloro-, fluoro- sub-
stituents (Percino et al., 2010, 2011, 2012; Pérez-
Gutiérrez et al. 2011). Procedures using piperi-
dine and elevated temperature afforded compounds
with dimethylamino-, diphenylamino- and N-ethyl-3-
carbazole- substituents. These reports did not indicate
any secondary reactions.
Lorente et al. (1995) reported the isolation of sub-
stituted 1-aminocyclohexene-2,4-dicarbonitriles obtai-
ned by the reaction of α,β-unsaturated nitriles (two
equivalents) with benzyl cyanide making use of a
stronger base than piperidine, such as sodium methox-
ide or sodium 2-propoxide in methanol. The out-
come of this reaction is attributed to the depen-
dence of the reaction on the catalyst and of the mo-
lar ratios of the reactants, because when l-amino-
3,4,5-triphenylcyclohexene-2,4-dicarbonitrile was used
with another equivalent of cinnamonitrile in a sodium
methoxide-methanol solution, the cyclohexene
l-amino-3,4,5-triphenylcyclohexene-2,4-dicarbonitrile
was obtained. However, Guillot et al. (2005) compared
two synthetic methods: one using KOH as a cata-
lyst at ambient temperature and another performed
at a higher temperature (110◦C) under microwave
(MW) irradiation. These authors reported that using
KOH at ambient temperature led to the preparation of
3-phenyl-2,4-diphenylpentanedinitrile, as detected by
GC-MS. The presence and the yield of this compound
depended on the steric hindrance of the aldehyde re-
actant.
Sa˘gırli and co-workers recently reported a number
of poly-substituted cyclopentenes obtained by a multi-
component catalyst-free reaction using a combina-
tion of β-nitrostyrene, benzylidenemalononitriles and
2-morpholinoethyl isocyanide (Sag˘ırli et al., 2013).
These authors proposed the mechanism shown in
Fig. 4. Both of these mechanisms were helpful in ex-
plaining the formation of (II ) as shown in Fig. 5.
In the current work, the compound II is formed in
situ under reaction conditions that include piperidine
(Fig. 1), because II was not present with the KOH cat-

672
M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
Table 2. IR, 1H-NMR and EI mass spectrometry data of I and II compounds
(2-(Phenyl)-3-(4-diphenylaminophenyl)acrylonitrile) I:
Yellow powder solid, (yield, 42 % section 3.2.1 and 92 % section 3.2.2); M.p.: 162–164 ◦C
IR (KBr), ν˜/cm−1: 3033 (w), 2216 (s, C—N), 1586 (broad, C
C
and C C), 1492 (s, ν(C—H) double bond), 829 (s,
Ar
—
—
—
—
—
—
—
C—H, CR1R2—CR3H)
1H NMR (400 MHz, CDCl3), δ: 7.795–7.766 (dd, 2H), 7.658–7637 (dd, 2H), 7.446–7.407 (m, 3H), 7.373–7.297 (m, 5H),
7.258 (s, 1H), 7.173–7.104 (m, 5H), 7.070–7.042 (dd, 2H) EI, m/z (Ir/%): 372 (100) (M), 371 (10) (M+
)
(3-(4-Diphenylamino)phenyl)-2,4-diphenylpentanedinitrile) II:
Pale yellow powder (21 %) M.p.: 116–118◦C
IR (KBr), ν˜/cm−1: 3033 (w), 2209 (s, C—N), and 2238 (w, C—N), 1586 (broad, C
CAr), 1492 (s, ν(C—H) aliphatic),
—
—
—
—
—
—
—
829 (s, C—H, CR1R2—CR3H)
1H NMR (400 MHz, CDCl3), δ: 7.793–7.772 (dd, 2H), 7.663–7.634(dd, 2H), 7.448–6.9387 (m, 20H), 6.809–735 (q, 4H),
4.77–4.764 (dd, 1H), 4.407–4.381 (dd, 1H), 3.425–385, (dd, 1H)
EI, m/z (Ir/%): 488 (15) (M+), 372 (100) (M)
pound II. The band at 2216 cm−1 was assigned to the
—
—C—N group and is an indication that, even with
—
—
the —C—N attached to the alkene double bond, the
—
presence of the —N(Ph)2 in the p-position induced
a strong conjugation. For II, the band at 2209 cm−1
and one with smaller intensity at 2238 cm−1 could be
—
indicative of two —C— N groups in the 2 and 4 po-
—
sitions, due to the asymmetry of the molecule. The
band at 2890 cm−1 is due to the stretching ν(C—H).
1
The H-NMR data in the CD3Cl solution showed
the general de-shielding effect of the protons of the
α,β-unsaturated nitrile compounds. Thus, the proton
H(3) in compound I appeared at 7.258 ppm, (7.540
ppm corresponds to the chemical shift of a proton in
a double bond) (Williams & Fleming, 1980). The same
protons associated with the —N(CH3)2 substituent
were reported at 7.41 ppm for the respective phenyl
groups. Compound II is of an asymmetrical structure,
1
hence the H-NMR results showed three different me-
thine carbon atoms, which appeared at 4.77–4.764 (J
= 5.2 Hz, dd, 1H, H(2)), 4.407–4.381 (J = 10.4 Hz, dd,
1H, H(4)), and 3.399–3.411 (J = 5.6 Hz, J = 10.4 Hz,
dd, 1H, H(3)), clearly indicating the formation of 2,4-
diphenylpentanedinitrile.
Fig. 4. Proposed mechanism for formation of poly-substituted
cyclopentenes (Sa˘gırli et al., 2013).
Crystallography studies
The synthesised compounds I and II were charac-
1
terised by IR, H-NMR, EI MS data, X-ray crystal-
The data and structure refinements obtained from
single crystals of I and II are given in the Supple-
mentary Information. For both compounds, the data
were collected at 110(2) K after the crystals were flash-
cooled from ambient temperature. The I and II struc-
tures derived from X-ray studies indicated that struc-
tures I and II were ordered, solved and refined in the
space group monoclinic, with P21/c and P21/n, re-
spectively, having 4 molecules per cell for both struc-
tures. The ORTEP structures of I and II are shown
in Fig. 6. The X-ray investigation showed that com-
pound I had the Z-geometry about the ethylene bridge
which links the aromatic rings. Table 3 gives the se-
lected bond lengths with estimated standard devia-
tions for compounds I and II, as well as the dihe-
dral angles between the acrylonitrile linkage and the
lography and physical characterisation. These results
are given in Tables 2 and 3. For α,β-conjugated−n1itrile
—
—
I, the double bond ν(—C C—) at ≈ 1625 cm was
not observed (Bellamy, 1975; Nakanishi & Solomon,
1977) as identified in compounds containing N(CH3)2
at 1613–1610 cm−1 and this behaviour could be at-
tributed to the overlap of the signals arising from the
—
—
ν(—C C—) from the aromatic and pyridine rings.
This result provided evidence that the electrons in the
compounds exhibited a higher extent of delocalisation
(Percino et al., 2011). The electrons from the π bonds
are delocalised or distributed over the whole system
(acting as a group of interacting conjugated atoms).
The out-of-plane C—H deformation in I appeared at
829 cm−1. This signal disappeared completely in com-

M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
673
Fig. 5. Proposed mechanisms for formation of compounds I and II in the presence of piperidine (a) and I in KOH (b).

674
M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
Table 3. Selected bond lengths, bond and torsion angles for I and II
˚
Bond length/A
I
II
C(13)—C(14)
C(13)—C(18)
C(13)—N(1)
C(14)—C(15)
C(15)—C(16)
C(16)—C(17)
C(16)—C(19)
C(17)—C(18)
C(19)—C(20)
C(20)—C(22)
1.3973(16)
C(19)—C(20)
C(19)—C(28)
C(20)—C(22)
C(21)—N(2)
C(20)—C(21)
C(28)—C(29)
C(28)—C(30)
C(29)—N(3)
1.556(4)
1.560(4)
1.517(4)
1.151(3)
1.479(4)
1.469(4)
1.518(4)
1.161(4)
1.3980(16)
1.3997(15)
1.3792(16)
1.4010(16)
1.4011(15)
1.4557(15)
1.3797(16)
1.3495(16)
1.4839(15)
Bond angles/◦
C(19)—C(20)—C(22)
C(19)—C(20)—C(21)
C(16)—C(19)—C(20)
C(17)—C(16)—C(19)
C(15)—C(16)—C(19)
C(19)—C(20)—C(22)
123.96(10)
120.50(10)
129.59(10)
124.12(10)
118.51(10)
123.96(10)
C(7)—N(1)—C(13)
C(1)—N(1)—C(13)
118.25(19)
118.2(2)
119.0(2)
122.6(2)
113.7(2)
118.8(2)
122.2(2)
120.8(2)
119.7(2)
C(15)—C(16)—C(19)
C(17)—C(16)—C(19)
C(20)—C(19)—C(28)
C(12)—C(7)—N(1)
C(8)—C(7)—N(1)
C(2)—C(1)—N(1)
C(6)—C(1)—N(1)
Torsion angles/◦
C(17)—C(16)—C(19)—C(20)
C(16)—C(19)—C(20)—C(21)
C(19)—C(20)—C(22)—C(23)
C(19)—C(20)—C(22)—C(27)
C(18)—C(13)—N(1)—C(1)
C(14)—C(13)—N(1)—C(7)
29.69(17)
6.53(17)
–154.21(11)
26.45(16)
29.75(16)
27.92(17)
C(16)—C(19)—C(20)—C(22)
C(6)—C(1)—N(1)—C(13)
C(2)—C(1)—N(1)—C(13)
C(12)—C(7)—N(1)—C(13)
C(8)—C(7)—N(1)—C(1)
C(16)—C(19)—C(28)—C(30)
55.8(3)
–147.2(2)
32.4(4)
41.1(3)
21.9(4)
–47.2(3)
Fig. 6. Molecular structure of compounds I and II; displacement ellipsoids are drawn at the 30 % probability level and H atoms
are shown as small spheres of arbitrary radii.
phenyl ring and with the p-diphenylaminophenyl moi-
ety.
that the phenyl ring was Z-located to the dipheny-
laminophenyl ring in relation to the double bond.
The C(sp2)—C(sp2) conjugated bond length between
From the molecular structure of I, it was observed

M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
675
˚
C(19)—C(20) was 1.3495(6) A, which is slightly longer
than a typical bond length for C(sp2)—C(sp2)2 con-
—
—
—
jugated (C C—C C, subst.), usually found to be
—
2
2
˚
1.330 A (Allen et al., 1987). The C(sp )—C(sp )
C(16)—C(19) was 1.4557(15) A and C(20)—C(22)
was 1.4839(15) A, lengths that deviated slightly from
the standard values for C(sp )—C(Ar) of 1.470 A (Ta-
˚
˚
2
˚
ble 3), indicating a delocalisation of the π-electrons
at the junction of the two rings through the C(20)—
C(19) bond. Also, the distances of C(15)—C(16) equal
˚
to 1.410(16) and C(16)—C(17) equal to 1.4011(15) A
were slightly longer than for typical C(Ar)≈≈ C(Ar)
˚
C (overall), generally reported to be 1.384 A.
—
—
C
This value was closer to that for the bond lengths
of C(15)—C(14), C(17)—C(18), C(18)—C(13) and
Fig. 7. Resonance structure of 2-(phenyl)-3-(4-diphenylamino-
phenyl)acrylonitrile (I).
˚
˚
C(14)—C(13) which were 1.379(16) A, 1.3797(16) A,
˚
˚
1.3980(16) A and 1.3973(16) A, respectively.
It was also observed that the C(13)—N(1) bond
˚
length was 1.3997(15) A which is larger higher than
through the π-conjugated units, as they provide an
effective pathway for the efficient push–pull charge
transfer for the donor and acceptor groups. The molec-
ular packing does not present non-planar molecules for
the phenyl, double bond and diphenylamine moieties
(Fig. 8). The diphenylamino group forms a dihedral
angle of C(14)—C(13)—N(1)—C(7) = –27.92(17)◦
a standard bond for C(sp2)—N(3) with N(sp2) pla-
˚
nar, at 1.355 A. The information accords well with
the variation of the resonance structure depicted in
Fig. 7.
The 2-(phenyl)-3-(4-diphenylaminophenyl)acrylo-
nitrile electron density is appropriately delocalised
Fig. 8. Projection of crystal packing of I along b axis (a), II along a axis (b) and diastereoisomers (2R,4R) and (2S,4S) with
stereocentric atoms (c).

676
M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
Fig. 9. Stereoisomers of 3-((4-diphenylamino)phenyl)-2,4-diphenylpentanedinitrile (II).
and C(18)—C(13)—N(1)—C(1) = 29.75(16)◦ in re-
spect of its phenyl rings. The phenyl rings are twisted
out of the ethylene bond plane of C(17)—C(16)—
also be identified as D and L forms, respectively: see
Fig. 9.
Selected bond lengths, bond angles and torsion
˚
—
—
C(19) C(20) for 29.69(17) A, C(19) C(20)—C(22)
angles are given in Table 3. All lengths and angles
have normal values. The molecule consists of a central
chain of five C atoms including two phenyl rings, with
two cyano groups attached to positions 2 and 4 and
the diphenylaminophenyl attached to the central atom
in position 3 of the —PhCH—CH—CHPh— moiety:
see Fig. 9. The —PhCH—CH—CHPh— moiety of
the molecule revealed bond lengths for C(20)—C(22)
—
—
—
—C(23) for –154.21(11); the —C—N group is not co-
planar with the aromatic ring, with a torsion angle
C(16)—C(19) C(20)—C(21) of 6.53(17) . Also, the
—
◦
—
—
area between the planes of the rings is defined by
the torsion angle for molecule I, showing a torsion
◦
—
angle of C(19) C(20)—C(22)—C(27) = 26.45(16) .
—
Deviations from the ideal bond-angle geometry for
C(sp2) atoms of the double bond are lower for C(16)—
= 1.517(4) A, C(19)—C(20) = 1.556(4) A; C(19)—
˚
˚
◦
˚
˚
—
—
C(19) C(20) = 129.59(10) while C(19) C(20)—
C(28) = 1.560(4) A and C(28)—C(30) = 1.518(4) A.
—
—
C(22) = 123.96(10)◦ is closer to 120◦, indicating a
small repulsion between the aromatic rings.
The typical distance for a single C(Ar)—C(sp3),
˚
C*—C(Ar) (overall) bond is 1.513 A and for
The X-ray structural refinement showed that
molecule II possessed two stereogenic carbon atoms,
C(20)* and C(28)*, indicating four possible stereoiso-
mers of (II ), two enantiomers and two equivalent di-
astereoisomers of a meso form: see Fig. 9. In this
case, the crystal structure belongs to a centrosym-
metric space group, P21/c, revealing that it is a
racemic mixture, as was expected for stereomeric
racemates. The assignment of relative configurations
to the racemates (2R,4R) and (2S,4S), as enan-
tiomeric forms, was performed by X-ray diffraction of
monocrystal, while meso forms of II were not found
in the crystalline structure. Figs. 8a and 8b show
that the crystal packing containing four molecules
of II, denoted as IIa–IId, IIa and IIc corresponds
to the (2R,4R) relative configuration, while IIb and
IId have (2S,4S) relative configuration. Fig. 8c dis-
plays a view of the molecules with stereocentric
atomic numbering, which are a couple of enantiomers
(2R,4R) and (2S,4S) in their anti forms, which can
C(sp3)—C(sp3) C*—C* (overall) is 1.530, as previ-
ously reported in the literature (Nakanishi & Solomon,
3
1
—
1977). For C(sp )—C(sp ), C*—C—N, a bond length
of 1.470 A has been reported while for C C—C—N
= 1.427 A, as observed for molecule (I ). The dis-
—
˚
˚
—
—
—
—
˚
tances of C(21)—N(2) = 1.151(3) A and C(29)—N(3)
˚
˚
= 1.161(4) A, as well as, C(28)—C(29) = 1.469(4) A
˚
and C(20)—C(21) = 1.479(4) A were values closer to
those reported for Csp *N(1) and C*—C—N.
—
1
—
On the other hand, the benzene ring composed of
atoms C(13)—C(14)—C(15)—C(16)—C(17)—C(18)
is co-planar with the carbon C(19) and with the
N(1) with bond angles between C(1)—N(1)—C(13)
= 118.2(2)◦ and C(7)—N(1)—C(13) = 118.25(19)◦.
In addition, C(15)—C(16)—C(19) = 119.0(2)◦ and
C(17)—C(16)—C(19) = 122.6(2)◦ are angles with val-
ues of almost 120◦. For torsion angles around C(28)—
C(19)—C(20) are C(16)—C(19)—C(20)—C(22) =
55.8(3)◦ while C(16)—C(19)—C(28)—C(30)
–47.2(3)◦. For the rest of the molecule, the planes de-
=

M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
677
Fig. 10. Comparison between geometrical structures of X-ray (red) and optimised structures (blue) calculated at B3LYP/6-
31+G(d) level for compounds I and II.
Fig. 11. Total electronic density distribution was mapped onto the electrostatic potential surface throughout compounds I and
II calculated at B3LYP/6-31+G(d) level. Red regions indicate negative charge and blue regions indicate positive charge.
Yellow regions correspond to an intermediate value between extremes of red and blue.
fined by C(6)—C(1)—N(1), C(2)—C(1)—N(1), C(12)
—C(7)—N(1) and C(8)—C(7)—N(1) were related to
the amine geometry and were all perfectly planar, in-
dicating that the nitrogen atoms are of sp2 hybridis-
ation. The ring systems were non-co-planar. The di-
hedral angles between the planes of three substituted
groups attached to the atoms of N1 are C(12)—C(7)—
N(1)—C(13) = 41.1(3)◦, C(8)—C(7)—N(1)—C(1) =
21.9(4)◦, C(6)—C(1)—N(1)—C(13) = 147.2(2)◦ and
C(2)—C(1)—N(1)—C(13) = 32.4(4)◦. Accordingly,
such arrangements have little steric crowding. All
bond lengths in the compound are within the nor-
mal range. In the cell projection along the c axis, the
connected molecular units of I are located along the
border and for units II at the centre. The two molec-
ular units differed substantially in their packing.
Theoretical calculations
On the other hand, theoretical calculations of the

678
M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
Fig. 12. Isosurfaces of frontier molecular orbitals HOMO and LUMO of compounds I and II calculated at B3LYP/6-31+G(d)
level. Red regions correspond to regions of high electron density.
fully optimised compounds I and II were carried out
using the B3LYP hybrid functional (Becke, 1993) with
6-31+G(d) basis set (Ditchfield et al., 1971) in the
Gaussian 09 package (Frisch et al., 2009). For mod-
elling, the initial designs of the molecules were ob-
tained from X-ray coordinate data and transformed
using the Mercury program (The Cambridge Crys-
tallographic Data Centre, 2012) into the Gaussian
Z-matrix format. Fig. 10 shows that the optimised
geometries (shown in blue) for compounds I and II
did not differ significantly from the X-ray structures
(shown in red).
culated for the torsion of the phenyl ring in respect of
the acrylonitrile moiety was 7.4◦ with regard to the
X-ray data. The dihedral angle formed by C(21)—
C(20)—C(22)—C(23) was 21.51(14)◦ while the opti-
mised structure of the angle was calculated as having
a value of 28.87◦. For compound II, the maximum
structural variations were located in one of the phenyl
rings bonded to the acrylonitrile moiety at the chi-
ral carbon C(20) and in one of the phenyl rings of the
diphenylaminophenyl group. These variations are best
evaluated by the dihedral values of C(16)—C(19)—
C(20)—C(22) of 55.8(3)◦ and 56.36◦ and for C(12)—
C(7)—N(1)—C(13), 41.1(3)◦ and 43.96◦ for the X-ray
and the optimised structures, respectively. Hence, the
results of the structural analysis of the theoretical cal-
It was observed that, for compound I, the maxi-
mum variation was located on the part of the phenyl
ring and the acrylonitrile linkage. The variation cal-

M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
679
culations on these compounds were consistent with
those observed in the crystal diffraction analysis.
The total electron density distribution was mapped
onto the electrostatic potential surface through the
whole molecules (isoval = 0.003) in Fig. 11. In com-
pound I, the distribution of the electron density
indicated a charge distribution delocalised for the
π-electrons throughout the phenyl rings and the cen-
tral bond substituted with the cyano group. A high
electron density on the cyano group was clearly ob-
served. The continuous distribution throughout the
molecule is lost in the N-atom of the diphenylamine
moiety due to a twist of the phenyl rings. A similar de-
localised distribution was observed in previous studies,
even though the structure was not completely planar
(Improta & Santoro, 2005; Mabrouk et al., 2010; Lin et
al., 2010). In stilbene-like compounds, a range of 0–60◦
for the torsion angle of the phenyl rings in the photoi-
somerisation process was evaluated (Mabrouk et al.,
2010). The dihedral angles of the ethylenic bridge of
the trans isomers were closer to planarity than the
cis isomers. In benzothiazole derivatives, non-planar
structures were found with dihedral angles with sig-
nificant twists between the bonds linking aromatic
rings, with the average angles being circa 37◦ and
47◦ (Mabrouk et al., 2010). In naphthylacrylonitrile
derivatives, the electronic resonances were evaluated
according to the electronic nature of the amino group
(Lin et al., 2010). In these compounds, the phenyl
rings are twisted out of the plane with dihedral an-
gles of 30◦ and 55◦.
nyl)-2,4-diphenylpentanedinitrile (II ), resulting from
the Michael addition of phenylacetonitrile to the
expected α,β-unsaturated nitrile. The reaction con-
ducted at ambient temperature using neat powdered
KOH afforded 2-(phenyl)-3-(4-diphenylaminophenyl)
acrylonitrile (I ) with a yield of almost 100 %. This
outcome is an indication that the reaction depends on
the strong base used to avoid side reactions such as
the Michael addition or the Baylis–Hillman reaction.
Acknowledgements. The authors wish to express their
thanks to VIEP-BUAP (PEZM-NAT13-G and CHCV-NAT13-
G), PROMEP-SEP (Thematic network collaboration) and
CONACYT (157552 and 183833).
Supplementary data
The crystallographic data (excluding structure fac-
tors) reported in this paper have been deposited with
the Cambridge Crystallographic Data Centre as sup-
plementary publication no. 920122 CCDC and no.
920123 CCDC. Copies of available material can be
obtained, free of charge, on application to the CCDC,
12 Union Road. Cambridge CB2 IEZ, UK, (fax: +44-
(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk).
References
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Or-
pen, A. G., & Taylor, R. (1987). Tables of bond lengths de-
termined by X-ray and neutron diffraction. Part 1. Bond
lengths in organic compounds. Journal of the Chemi-
cal Society, Perkin Transactions 2, 1987, S1–S19. DOI:
10.1039/p298700000s1.
Fig. 12 shows the isosurfaces of the frontier molec-
ular orbitals HOMO and LUMO for both molecules.
For compound I, the orbital HOMO was localised over
the entire molecule while the orbital LUMO was not
localised on the phenyl rings of the diphenylamine
group, but only on the N-atom. On the other hand,
for compound II, the distribution of the electron den-
sity did not show the distribution delocalised as for
compound I. This outcome was expected due to the
change in the sp2 to sp3 configuration of C(3) ac-
cepting another phenylacetonitrile for the formation of
2,4-diphenylpentanedinitrile. Fig. 12 shows the regions
with high electronic density (in red) for the cyano
group, phenyl rings and the N-atom of the dipheny-
lamine group. The isosurfaces of the orbitals HOMO
and LUMO show that the distributions for both or-
bitals are localised mainly in the diphenylamine group
and the phenyl ring attached to it. In the case of or-
bital LUMO, its distribution is extended to the pheny-
lacetonitrile substituted in the α position.
Augé, J., Lubin, N., & Lubineau, A. (1994). Acceleration in
water of the Baylis–Hillman reaction. Tetrahedron Letters,
35, 7947–7948. DOI: 10.1016/0040-4039(94)80018-9.
Becke, A. D. (1993). Density-functional thermochemistry. III.
The role of exact exchange. The Journal of Chemical
Physics, 98, 5648–5652. DOI: 10.1063/1.464913.
Bellamy, L. J. (1975). The infra-red spectra of complex
molecules. New York, NY, USA: Wiley.
Ditchfield, R., Hehre, W. J., & Pople, J. A. (1971). Self-
consistent molecular-orbital methods. IX. An extended
Gaussian-type basis for molecular-orbital studies of organic
molecules. The Journal of Chemical Physics, 54, 724–728.
DOI: 10.1063/1.1674902.
D’Sa, B. A., Kisanga, P., & Verkade, J. G. (1998). Direct syn-
thesis of α,β-unsaturated nitriles catalyzed by nonionic su-
perbases. The Journal of Organic Chemistry, 63, 3961–3967.
DOI: 10.1021/jo972343u.
Fraysse, M. J. (1980). Nitriles: their application in perfumery.
Perfumer & Flavorist, 4, 11–12.
Fringuelli, F., Pani, G., Piermatti, O., & Pizzo, F. (1994). Con-
densation reactions in water of active methylene compounds
with arylaldehydes. One-pot synthesis of flavonols. Tetrahe-
dron, 50, 11499–11508. DOI: 10.1016/s0040-4020(01)89287-5.
Frisch, M. J., Trucks, G. W., Schlegel, H. B., Scuseria, G. E.,
Robb, M. A., Cheeseman, J. R., Scalmani, G., Barone, V.,
Mennucci, B., Petersson, G. A., Nakatsuji, H., Caricato, M.,
Li, X., Hratchian, H. P., Izmaylov, A. F., Bloino, J., Zheng,
G., Sonnenberg, J. L., Hada, M., Ehara, M., Toyota, K.,
Fukuda, R., Hasegawa, J., Ishida, M., Nakajima, T., Honda,
Y., Kitao, O., Nakai, H., Vreven, T., Montgomery, J. A.,
Conclusions
It has been shown that, under piperidine condi-
tions, the condensation reaction of 4-diphenylamino-
phenylacetonitrile with phenylacetonitrile under con-
ventional heating afforded 3-(4-diphenylamino)phe-

680
M. J. Percino et al./Chemical Papers 68 (5) 668–680 (2014)
Jr., Peralta, J. E., Ogliaro, F., Bearpark, M., Heyd, J. J.,
Michel, F., Mecklein, L., Crastes de Paulet, A., Doré, J. C.,
Gilbert, J., & Miquel, J. F. (1984). The effect of vari-
ous acrylonitriles and related compounds on prostaglandin
biosynthesis. Prostaglandins, 27, 69–84. DOI: 10.1016/0090-
6980(84)90221-1.
Mori, K. (1976). Synthetic chemistry of insect pheromones and
juvenile hormones (Recent developments in the chemistry of
natural carbon compounds). Budapest, Hungary: Akadémiai
Kiadó.
Brothers, E., Kudin, K. N., Staroverov, V. N., Kobayashi,
R., Normand, J., Raghavachari, K., Rendell, A., Burant, J.
C., Iyengar, S. S., Tomasi, J., Cossi, M., Rega, N., Millam, N.
J., Klene, M., Knox, J. E., Cross, J. B., Bakken, V., Adamo,
C., Jaramillo, J., Gomperts, R., Stratmann, R. E., Yazyev,
O., Austin, A. J., Cammi, R., Pomelli, C., Ochterski, J. W.,
Martin, R. L., Morokuma, K., Zakrzewski, V. G., Voth, G.
A., Salvador, P., Dannenberg, J. J., Dapprich, S., Daniels,
¨
A. D., Farkas, O., Foresman, J. B., Ortiz, J. V., Cioslowski,
Nakanishi, K., & Solomon, P. H. (1977). Infrared absorption
spectroscopy. Oakland, CA, USA: Holden-Day.
J., & Fox, D. J. (2009). Gaussian 09 Revision A.1 [computer
software]. Wallingford, CT, USA: Gaussian.
Peat, J. R., Minchin, F. R., Jeffcoat, B., & Summerfield, R.
J. (1981). Young reproductive structures promote nitrogen
fixation in soya bean. Annals of Botany, 48, 177–182.
Percino, M. J., Chapela, V. M., Montiel, L. F., Pérez-Gutiérrez,
E., & Maldonado, J. L. (2010). Spectroscopic characteriza-
tion of halogen- and cyano-substituted pyridinevinylenes syn-
thesized without catalyst or solvent. Chemical Papers, 64,
360–367. DOI: 10.2478/s11696-010-0012-z.
Percino, M. J., Chapela, V. M., Pérez-Gutiérrez, E., Cerón, M.,
& Soriano, G. (2011). Synthesis, optical and spectroscopic
characterisation of substituted 3-phenyl-2-arylacrylonitriles
Chemical Papers, 65, 42–51. DOI: 10.2478/s11696-010-0075-
x.
Frost, H. V. (1889). Ueber die Kondensation von Benzylcyanid
und seinen Substitutionsproducten mit Aldehyden und mit
Amylnitrit. Justus Liebigs Annalen der Chemie, 250, 156–
166. DOI: 10.1002/jlac.18892500106. (in German)
Guillemin, J. C., Breneman, C. M., Joseph, J. C., & Ferris, J.
P. (1998). Regioselectivity of the photochemical addition of
ammonia, phosphine, and silane to olefinic and acetylenic ni-
triles. Chemistry – A European Journal, 4, 1074–1082. DOI:
10.1002/(sici)1521-3765(19980615)4:6<1074::aid-chem1074>
3.0.co;2-b.
Guillot, R., Loupy, A., Meddour, A., Pellet, M.,
& Pe-
tit, A. (2005). Solvent-free condensation of arylacetoni-
trile with aldehydes. Tetrahedron, 61, 10129–10137. DOI:
10.1016/j.tet.2005.07.040.
Percino, M. J., Chapela, V. M., Cerón, M., Castro, M.
E., Soriano-Moro, G., Pérez-Gutiérrez, E.,
& Meléndez-
Improta, R., & Santoro, F. (2005). Excited-state behavior of
trans and cis isomers of stilbene and stiff stilbene: A TD-DFT
study. The Journal of Physical Chemistry A, 109, 10058–
10067. DOI: 10.1021/jp054250j.
Jenner, G. (1996). Comparative study of physical and chem-
ical activation modes. The case of the synthesis of β-
amino derivatives. Tetrahedron, 52, 13557–13568. DOI:
10.1016/0040-4020(96)00831-9.
Knoevenagel, E. (1896). Ueber eine Darstellungsweise des Ben-
zylidenacetessigesters. Berichte der Deutschen Chemischen
Gesellschaft, 29, 172–174. DOI: 10.1002/cber.18960290133.
(in German)
Lin, R., Horng, H. C., Lin, H. M., Lin, S. Y., Hon, Y. S., & Chow,
T. J. (2010). 2-Amino-3-naphthylacrylonitrile derivatives as
green luminance dyes. Journal of the Chinese Chemical So-
ciety, 57, 805–810.
Lorente, A., Galan, C., Fonseca, I., & Sanz-Aparicio, J. (1995).
1-Aminocyclohexene-2,4-dicarbonitrile derivatives. Synthe-
ses and structural study. Canadian Journal of Chemistry,
73, 1546–1555. DOI: 10.1139/v95-192.
Loupy, A., Pellet, M., Petit, A., & Vo-Thanh, G. (2005).
Solvent-free condensation of phenylacetonitrile and nonanen-
itrile with 4-methoxybenzaldehyde: Optimization and mech-
anistic studies. Organic & Biomolecular Chemistry, 3, 1534–
1540. DOI: 10.1039/b418156e.
Lubineau, A., & Augé, J. (1999). Water as solvent in or-
ganic synthesis. In P. Knochel (Ed.), Modern solvents in or-
ganic synthesis (pp. 1–39). Berlin, Germany: Springer. DOI:
10.1007/3-540-48664-x 1.
Bustamante, F. (2012). Synthesis and characterization of
conjugated pyridine-(N-diphenylamino) acrylonitrile deriva-
tives: Photophysical properties. Journal of Materials Science
Research, 1, 181–192. DOI: 10.5539/jmsr.v1n2p181.
Pérez-Gutiérrez, E., Percino, M. J., Chapela, V. M., Cerón,
M., Maldonado, J. L., & Ramos-Ortiz, G. (2011). Synthesis,
characterization and photophysical properties of pyridine-
carbazole acrylonitrile derivatives. Materials, 4, 562–574.
DOI: 10.3390/ma4030562.
Saidalimu, I., Fang, X., Lv, W. W., Yang, X. Y., He, X. P.,
Zhang, J. Y., Wu, F. H., & Pizzo, F. (2013). Organocat-
alytic asymmetric Michael addition/carbon–carbon bond
cleavage of trifluoromethyl α-fluorinated gem-diols to ni-
troolefins. Advanced Synthesis & Catalysis, 355, 857–863.
DOI: 10.1002/adsc.201200757.
Sa˘gırli, A., Du¨ru¨st, Y., Kariuki, B., & Knight, D. W. (2013).
A practical isocyanide-based multicomponent synthesis of
polysubstituted cyclopentenes. Tetrahedron, 69, 69–72. DOI:
10.1016/j.tet.2012.10.065.
Sheldrick, G. M. (1998). SHELXL 97 [computer software].
Go¨ttingen, Germany: University of G¨ottingen.
The Cambridge Crystallographic Data Centre (2012). Mercury
3.0 [computer software]. Cambridge, UK: The Cambridge
Crystallographic Data Centre.
Williams, D. H., & Fleming, I. (1980). Spectroscopic methods
in organic chemistry (3rd ed.). London, UK: MacGraw-Hill.
Mabrouk, A., Azazi, A., & Alimi, K. (2010). On the properties
of new benzothiazole derivatives for organic light emitting
diodes (OLEDs): A comprehensive theoretical study. Jour-
nal of Physics and Chemistry of Solids, 71, 1225–1235. DOI:
10.1016/j.jpcs.2010.04.020.