Synthesis, characterization and crystal structure of (2Z)-3-[(4- methylphenyl)amino]-1-phenylbut-2-en-1-one

Article abstract of DOI:10.1007/s10870-012-0279-8

The compound (2Z)-3-[(4-methylphenyl)amino]- 1-phenylbut-2-en-1-one was synthesized by the condensation reaction of benzoylacetone with p-methylaniline and structurally characterized by ¹H NMR, ¹³C NMR, IR, mass spectrometry, element

Full text of DOI:10.1007/s10870-012-0279-8

J Chem Crystallogr (2012) 42:560–565
DOI 10.1007/s10870-012-0279-8
ORIGINAL PAPER
Synthesis, Characterization and Crystal Structure
of (2Z)-3-[(4-Methylphenyl)amino]-1-phenylbut-2-en-1-one
•
Siddappa A. Patil Diego Gonzalez-Flores Phillip A. Medina IV
•
•
•
•
•
Jason K. Vohs Seth Dever Joshua Popp Michael Stentzel
•
•
Leslie W. Pineda Mavis L. Montero Bradley D. Fahlman
•
Received: 11 August 2011 / Accepted: 27 January 2012 / Published online: 12 February 2012
Ó Springer Science+Business Media, LLC 2012
Abstract The compound (2Z)-3-[(4-methylphenyl)amino]-
1-phenylbut-2-en-1-one was synthesized by the condensation
reaction of benzoylacetone with p-methylaniline and structur-
Introduction
b-Enaminones have been widely used as key precursors
in organic synthesis [1–3], as well as synthons for dif-
ferent important heterocycles [4–6], antibacterial [7],
anticonvulsant, anti-inflammatory [8], antitumour agents
[9], and naturally occurring alkaloids [10]. Therefore,
development of new synthetic methods has received
considerable attention. In 1961, Martin [11] reported one
of the most important ways to prepare b-enaminones, via
the direct condensation of b-dicarbonyl compounds with
amines in a refluxing aromatic solvent. In recent years,
this reaction was investigated in depth and detail, mainly
focusing on improving the reaction conditions. This has
led to the development of interesting reaction systems,
such as those catalyzed by K-10 clay [12], NaAuCl4
[13], Zn(ClO4)2Á6H2O [14], ionic liquids [15],
CeCl3Á7H2O [16], ZrCl4 [17], and ytterbium triflate [18].
Nevertheless, the application of these systems suffers
from one or more disadvantages, such as using expensive
or less readily available reagents, toxic solvents, drastic
reaction conditions, long reaction times, unsatisfactory
yields and/or low selectivity. Therefore, the development
of facile and green synthetic methods is still in high
demand.
1
ally characterized by H NMR, 13C NMR, IR, mass spec-
trometry, elemental analysis, TGA/DSC and single crystal
X-ray diffraction. The title compound crystallizes in the ortho-
˚
rhombic space group Pccn (No. 56) with a = 17.0042(18) A,
3
˚
˚
˚
b = 11.5826(13) A, c = 14.0514(15) A, V = 2767.5(5) A
and Z = 8. Data collection on 223(2) K resulted its structure
with R1 = 0.0449, wR2 = 0.0980. The molecules in the unit
cell are arranged in layers. The intramolecular hydrogen bonds
of the type N–HÁÁÁO were observed in the structure. The com-
pound exhibits two distinct endothermic peaks at a temperature
94.70 °C and 232.60 °C corresponding to melting and boiling
points respectively.
Keywords Synthesis Á Spectroscopy Á Crystal structure Á
(2Z)-3-[(4-Methylphenyl)amino]-1-phenylbut-2-en-1-one Á
Thermogravimetric Analysis
S. A. Patil Á P. A. Medina IV Á S. Dever Á J. Popp Á
M. Stentzel Á B. D. Fahlman (&)
Formic acid or methanoic acid (HCOOH) is widely used
as acid catalyst in organic synthesis since it is relatively
inexpensive, and merits high volatility and easy work-up.
Accordingly, it has emerged as a key replacement for
conventional acidic catalysts in organic synthesis. In this
paper, we report the synthesis, characterization and crystal
structure of the product derived from 1:1 condensation of
benzoylacetone with p-methylaniline using formic acid as a
catalyst, where the keto- and amino- groups are aromatic
substituents.
Department of Chemistry, Central Michigan University,
Mount Pleasant, MI 48859, USA
e-mail: fahlm1b@cmich.edu
D. Gonzalez-Flores Á L. W. Pineda Á M. L. Montero
´
Centro de Electroquımica y Energıa Quımica (CELEQ); Escuela
de Quımica, Universidad de Costa Rica, San Jose, Costa Rica
´
´
´
´
J. K. Vohs
Department of Chemistry, Saint Vincent College,
300 Fraser Purchase Road, Latrobe, PA 15650, USA
123

J Chem Crystallogr (2012) 42:560–565
561
CH3
NH2
O
HN
O
O
HCOOH
CH3OH, 78oC
+
CH3
CH3
CH3
Scheme 1 Synthesis of (2Z)-3-[(4-methylphenyl)amino]-1-phenylbut-2-en-1-one
Experimental
methanol to get a pure compound. The synthetic pathway
described in this work is outlined in Scheme 1. Crystals
suitable for X-ray analysis were grown by the slow evap-
oration method using methanol as the solvent. Overall yield
95%; m.p. 93–95 °C. Compound was analyzed for
C17H17NO (calculated C 81.24, H 6.82, N 5.57, O 6.37%;
found C 81.19, H 6.79, N 5.59, O 6.35%). 1H NMR
(CDCl3, 300 MHz) d: 2.11 (s, 3H, CH3); 2.35 (s, 3H, CH3);
5.87 (s, 1H, CH); 7.09–7.05 (m, 2H, ArH); 7.18–7.14 (m,
2H, ArH); 7.46–7.40 (m, 3H, ArH); 7.93–7.89 (m, 2H,
ArH); 13.02 (s, 1H, NH). 13C NMR (CDCl3, 75 MHz) d:
20.3 (CH3), 20.9 (CH3), 93.8 (CH2), 124.8, 126.9, 128.2,
129.7, 130.7, 135.7, 135.9, 140.0 (ArC), 162.6 (C–N),
188.4 (C=O). Mass data (TOF MS EI?): calculated for
C17H17NO [M?] 251.1310, found: 251.1298. IR absorp-
tions (KBr, cm-1): 3445 (w), 3016 (w), 2921 (m), 1603 (s),
1506 (s), 1441 (s), 1323 (s), 1199 (s), 1155 (w), 1068 (s),
931 (m), 834 (s), 770 (s), 694 (m), 645 (w), 559 (m) 507
(s), 452 (w).
General Information on Reagents and Techniques
The reaction was carried out under aerobic conditions. All
reagents were of analytical grade; they were purchased and
used without further purification. Benzoylacetone,
p-methylaniline and formic acid were procured commercially
from Sigma-Aldrich Chemical Company and were used
without further purification. Nuclear magnetic resonance
(NMR) spectra were obtained using a 10 to 25% solution in
deuterochloroform (CDCl3). 1H and 13C NMR spectra were
recorded on a Varian Mercury 300 MHz spectrometer.
Proton and carbon chemical shifts are reported in parts-per-
million (d) with respect to tetramethylsilane (TMS) as
internal reference (d = 0.0 ppm). IR spectra were recorded
on a Perkin Elmer Paragon 1000 FT-IR Spectrometer
employing a KBr disc. Mass spectra were obtained on a
GC–MS instrument operating in TOF-MI? mode. CHN
analysis was performed by Atlantic Microlab using an
Exeter Analytical CE-440 Elemental Analyzer, and was
within 0.4% of the theoretical values. Thermogravimetric
analyses (TGA) and melting/boiling point determinations
were made using a TA Q600 simultaneous TGA/DSC
instrument. A heating rate of 5 °C min-1 was used, and
samples (5–10 mg) were contained in a platinum pan. The
sample compartment was purged with dry nitrogen at
50 mL min-1 during analysis. TA Thermal Advantage
software was used for data analysis. Single crystals suitable
for X-ray diffraction study were obtained from methanol
by slow evaporation at room temperature.
Crystal Structure Determination and Refinement
X-ray intensity data of 14993 reflections (of which 2535
unique) were collected at room temperature on a Rigaku
XtaLAB mini diffractometer equipped with graphite
˚
monochromated Mo Ka radiation (k = 0.71075 A) [19,
20]. The crystal used for data collection was of dimensions
0.32 9 0.18 9 0.08 mm. The intensities were measured
by / and x scan mode for h ranges 3.14–25.34°. Data were
corrected for Lorentz and polarization factors. The struc-
ture was solved by direct methods using SHELXS97 [21].
Full-matrix least squares refinement was carried out using
SHELXL97 [21]. All the hydrogen atoms bound to carbon
atoms were placed at idealized positions and refined as
riding atoms. The only H atom which was located on the
electron density map is H1 (on N1). The final refinement
cycles converged to an R = 0.0449 and wR (F2) = 0.0980
for the observed data. Residual electron densities ranged
Synthesis of (2Z)-3-[(4-Methylphenyl)amino]-
1-phenylbut-2-en-1-one
Benzoylacetone (1.62 g; 10.0 mmol) was dissolved in
methanol (35 mL) and to this, p-methylaniline (1.07 g;
10.0 mmol) was added, followed by the addition of two
drops of formic acid and the solution was refluxed for
6–8 h and cooled. The yellow colored solid formed was
filtered and dried in air. The solid was recrystallized from
from -0.200 to 0.130 e A-3. The crystal data and the
˚
refinement results are given in Table 1. Selected bond
lengths and bond angles are summarized in Table 2.
123

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J Chem Crystallogr (2012) 42:560–565
˚
Table 1 Crystal data and structure refinement of (2Z)-3-[(4-methyl-
phenyl)amino]-1-phenylbut-2-en-1-one
Table 2 Selected bond lengths (A) and bond angles (°) of (2Z)-3-[(4-
methylphenyl)amino]-1-phenylbut-2-en-1-one
˚
Empirical formula
Formula weight
Temperature (K)
C17H17NO
251.32
Bond length
(A)
1.2598(19)
O(1)–C(11)
223 (2)
N(1)–C(9)
1.345(2)
1.415(2)
1.507(2)
1.504(2)
1.373(2)
1.425(2)
1.494(2)
˚
Wavelength (A)
˚
0.71075 A
N(1)–C(5)
Crystal system
Space group
Orthorhombic
Pccn (No.56)
C(1)–C(2)
C(8)–C(9)
Unit cell dimensions
C(9)–C(10)
˚
a (A)
17.0042 (18)
C(10)–C(11)
˚
b (A)
11.5826 (13)
C(11)–C(12)
˚
c (A)
14.0514 (15)
Bond angle
(°)
a (°)
b (°)
c (°)
90
C(9)–N(1)–C(5)
C(7)–C(2)–C(3)
C(7)–C(2)–C(1)
C(3)–C(2)–C(1)
C(6)–C(5)–C(4)
C(6)–C(5)–N(1)
C(4)–C(5)–N(1)
N(1)–C(9)–C(10)
N(1)–C(9)–C(8)
C(10)–C(9)–C(8)
C(9)–C(10)–C(11)
O(1)–C(11)–C(10)
O(1)–C(11)–C(12)
C(10)–C(11)–C(12)
C(13)–C(12)–C(17)
C(13)–C(12)–C(11)
C(17)–C(12)–C(11)
131.02(15)
117.22(17)
121.52(16)
121.24(16)
118.99(16)
124.45(16)
116.42(15)
119.63(16)
120.21(16)
120.13(16)
124.63(16)
123.14(16)
118.30(15)
118.53(15)
118.71(16)
122.06(15)
119.23(15)
90
90
3
˚
Volume (A )
2767.5 (5)
Z
8
Density (calculated) (Mg m-3
Absorption coefficient (mm-1
F000
)
1.206
)
0.075
1,072
0.32 9 0.18 9 0.08 mm3
3.14–25.34o
Crystal size
h range for data collection
Index ranges
-20 B h B 17, -13 B k B 13,
-15 B l B 16
Reflections collected
Independent reflections
Refinement method
14,993
2535[R(int) = 0.0586]
Full-matrix least-squares on F2
99.8%
Completeness to hmax
Max. and min. Transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I [ 2r(I)]
R indices (all data)
0.9941 and 0.9765
2535/0/180
1.033
R1 = 0.0449, wR2 = 0.0980
R1 = 0.0747, wR2 = 0.1087
0.130 and -0.200
amino]-1-phenylbut-2-en-1-one is displayed in Fig. 2. The
analysis of the crystal structure of (2Z)-3-[(4-methylphenyl)
amino]-1-phenylbut-2-en-1-one evidences that it is coplanar.
The title compound (2Z)-3-[(4-methylphenyl)amino]-1-
phenylbut-2-en-1-one has two aromatic rings and a central
linkage. The crystal structure analysis shows that the angle
between ring A [C(12)–C(13)–C(14)–C(15)–C(16)–C(17)]
and ring B [C(4)–C(5)–C(6)–C(7)–C(2)–C(3)] is 1.73° (almost
coplanar), the angle of ring A and central linkage [O(1)–C(11)–
C(10)–C(9)–N(1)] is 32.75° and the angle between ring B and
central linkage is 33.44°. The O(1)–C(11) and C(9)–C(10) bond
Largest diff. peak
-3
˚
and hole (e A
)
Results and Discussion
Description of the Crystal Structure
The title compound (2Z)-3-[(4-methylphenyl)amino]-
1-phenylbut-2-en-1-one has been shown by 1H NMR spec-
troscopy to exist in solution in the enamino-ketone and not
the enol-imine form [22, 23]. IR spectroscopy shows only
the enamino-ketone form in the solid state; this has been
further confirmed in this study of its crystal structure.
Compound (2Z)-3-[(4-methylphenyl)amino]-1-phenylbut-
2-en-1-one crystallizes in the orthorhombic space group
Pccn (No. 56) and the structure with the correspond-
ing atomic numbering scheme is shown in Fig. 1. The
molecular packing diagram of (2Z)-3-[(4-methylphenyl)
˚
distances [1.2598(19) and 1.373(2) A, respectively] confirm
the existence of the enamino-ketone [24]. The O=C–C=C–N
linkage of the molecule (2Z)-3-[(4-methylphenyl)amino]-
1-phenylbut-2-en-1-one is planar; the bond lengths [C(9)–
˚
C(10) = 1.2598(19) and N(1)–C(9) = 1.345(2) A] indicate
electron delocalization. The C–C bond distances in both phenyl
˚
rings are in the normal range of 1.38–1.41 A, which is char-
acteristic of delocalized phenyl rings. The C–C–C bond angles
are around 120°, with the variation being less than 2°, which
A strong
is characteristic of sp2-hybridized carbons.
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J Chem Crystallogr (2012) 42:560–565
563
Fig. 3 1H NMR spectrum of (2Z)-3-[(4-methylphenyl)amino]-
1-phenylbut-2-en-1-one
Fig. 1 ORTEP diagram of (2Z)-3-[(4-methylphenyl)amino]-1-phe-
nylbut-2-en-1-one showing atom labeling scheme. 50% probability
amplitude displacement ellipsoids are shown. Hydrogen atoms are
omitted for clarity
the (2Z)-3-[(4-methylphenyl)amino]-1-phenylbut-2-en-1-one
exhibits four singlets at 13.02, 5.87, 2.35 and 2.11 ppm,
which are due to NH, CH2, CH3 (benzoylacetone) and CH3
(p-methylaniline) protons respectively. Four multiplets at
7.09–7.05, 7.18–7.14, 7.46–7.40 and 7.93–7.89 ppm are
attributed to the nine aromatic protons.
In 13C-NMR spectrum of the (2Z)-3-[(4-methylphenyl)-
amino]-1-phenylbut-2-en-1-one, the carbonyl (C=O) car-
bon is observed at 188.4 ppm. Peaks at 162.6 and 93.8 ppm
are due to carbons of the C–NH and CH groups, respec-
tively. The methyl (CH3) carbons of benzoylacetone and
p-methylaniline appear at 20.9 and 20.34 ppm, respectively.
Peaks at 124.8, 126.9, 128.2, 129.7, 130.7, 135.7, 135.9 and
140.0 ppm are attributed to the aromatic carbons.
Fig. 2 Perspective view of the molecular packing of (2Z)-
3-[(4-methylphenyl)amino]-1-phenylbut-2-en-1-one (hydrogen atoms
not involved in H-bonds have been omitted)
intramolecular hydrogen bond between the enamine N atom
and carbonyl O atom stabilizes the enamino-ketone. The
molecular packing diagram (Fig. 2) shows three layers of
molecules, which are independently arranged in the unit cell. In
each layer, the molecules are alternatively parallel and per-
pendicular to each other in a zig-zag array.
1H NMR and 13C NMR Spectroscopy
1H NMR and 13C NMR spectra of the title compound (2Z)-
3-[(4-methylphenyl)amino]-1-phenylbut-2-en-1-one was
recorded in CDCl3 solvent and the spectra are presented
Fig. 4 13C NMR spectrum of (2Z)-3-[(4-methylphenyl)amino]-1-
phenylbut-2-en-1-one
1
in Figs. 3 and 4, respectively. The H-NMR spectrum of
123

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J Chem Crystallogr (2012) 42:560–565
250.1228
Fig. 5 Mass spectrum of (2Z)-
3-[(4-methylphenyl)amino]-
1-phenylbut-2-en-1-one
100
251.1298
105.0338
146.0959
174.0918
77.0388
91.0551
236.1071
252.1324
131.0721
106.0599
65.0385
0
m/z
60
80
100
120
140
160
180
200
220
240
260
280
Fig. 6 TGA/DSC of (2Z)-
3-[(4-methylphenyl)amino]-
1-phenylbut-2-en-1-one
FT-IR Spectrum
The thermal behavior of title compound (2Z)-3-
[(4-methylphenyl)amino]-1-phenylbut-2-en-1-one has been
investigated using thermogravimetric techniques in the
temperature range from 0 to 1000 °C at a heating rate of
10 °C min-1. We observed a sharp endothermic peak at a
temperature 94.70 °C from the temperature difference
curve; it indicates that the compound melts at 94.70 °C as
was expected from the melting point analysis (93–95 °C) of
the compound. One additional endothermic peak occurred at
a temperature of 232.60 °C, corresponding to boiling point
of the compound. Onset of mass loss in the compound
occurred at 137.47 °C and terminated at 248.34 °C as
observed by weight loss curve of the TGA data in Fig. 6.
The FT-IR spectrum for the compound (2Z)-3-[(4-meth-
ylphenyl)amino]-1-phenylbut-2-en-1-one is recorded in the
region from 400 to 4000 cm-1. It shows strong character-
istic absorptions near 1603 (mas) and 1545 cm-1 (ms) for the
carbonyl group (C=O) and the weak absorption at
3445 cm-1 (m) is typical of the NH group. Weak to med-
ium absorptions around 3100–3000 cm-1 observed, cor-
responding to the =C–H stretch of aromatic ring.
Mass Spectrum and Thermogravimetric Analysis
The mass spectrum of title compound (2Z)-3-[(4-methyl-
phenyl)amino]-1-phenylbut-2-en-1-one was analyzed by GC–MS.
The peak observed at m/z 251.1298 suggested the molec-
ular formula C17H17NO of the title compound. The mass
spectrum of the compound is shown in Fig. 5.
Supplementary Material
Crystallographic data for the structure reported in this
article have been deposited with the Cambridge
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J Chem Crystallogr (2012) 42:560–565
565
8. Michael JP, Koning CB, Hosken GD, Stanbury TV (2001) Tet-
rahedron 57:9635
Crystallographic Data Center with the deposition number
862748. Copy of the data can be obtained free of charge
from the Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK [Fax: ?44-1223-336-033; E-mail: depos-
it@ccdc.cam. ac.uk or www.ccdc.cam.ac.uk].
9. Boger DL, Ishizaki T, Wysocki JRJ, Munk SA, Kitos PA, Sun-
tornwat O (1989) J Am Chem Soc 111:6461
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Sambri L (2004) Synlett 11:239
Acknowledgments The authors would like to thank the National
Science Foundation (CHE-0911061) for financial support. We also
´
acknowledge the Ministerio de Ciencia y Tecnologıa de Costa Rica
(MICIT), Consejo Nacional para Investigaciones Cientıficas y Tec-
´
´
´
´
nologicas (CONICIT), and the Centro de Electroquımica y Energıa
Quımica (CELEQ) at the Universidad de Costa Rica for providing
´
15. Bhosale RS, Suryawanshi PA, Ingle SA, Lokhande MN, More
SP, Mane SB, Bhosale SV, Pawar RP (2006) Synlett 6:933
16. Khodaei MM, Khosropour AR, Kookhazadeh M (2004) Synlett
11:1980
partial financial support for an internship for Diego Gonzalez-Flores
at Central Michigan University.
17. Lin J, Zhang LF (2007) Monatsh Chem 138:77
18. Epifano F, Genovese S, Curini M (2007) Tetrahedron Lett
48:2717
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