Synthesis and crystal structures of methyl 3-(benzoylamino)-6-methyl-2-oxo- 2H-pyran-5-carboxylate and N-[5-(3,4-dimethoxyphenyl)-6-methyl-2-oxo-2H-pyran-3- yl]benzamide

Article abstract of DOI:10.1007/s10870-011-0266-5

The compounds methyl 3-(benzoylamino)-6-methyl-2-oxo-2H-pyran-5-carboxylate (1), C₁₅H₁₃NO₅, and N-[5-(3,4-dimethoxyphenyl) -6-methyl-2-oxo-2H-pyran-3-yl] benzamide (2), C₂₁H ₁₉NO₅, crystallize as a centrosymmetric hydrogen-bonded dimer facilitated by N-H...O interactions involving the amide and carbonyl moiety of the lactone group of adjacent molecules. Supramolecular aggregation in 1 is controlled by a combination of π...π interactions [centroid-centroid distance = 4.0745(11) A] and weak C-H...O hydrogen bonding between the phenyl ring of the benzoylamino group and the carbonyl atom of the methoxycarbonyl group and in 2 by a combination of π...π interactions [centroid-centroid distance = 4.0699(8) and 4.1556(10) A], weak C-H...O interactions between the methoxy substituents of the adjacent dimethoxyphenyl group and weak C-H... π interactions. Springer Science+Business Media, LLC 2012.

Full text of DOI:10.1007/s10870-011-0266-5

J Chem Crystallogr (2012) 42:443–449
DOI 10.1007/s10870-011-0266-5
ORIGINAL PAPER
Synthesis and Crystal Structures of Methyl 3-(Benzoylamino)-
6-methyl-2-oxo-2H-pyran-5-carboxylate and N-[5-(3,4-
Dimethoxyphenyl)-6-methyl-2-oxo-2H-pyran-3-yl]benzamide
•
Kristof Kranjc Amadej Juranovic
•
ˇ
Marijan Kocevar Franc Perdih
ˇ
•
ˇ
Received: 15 July 2011 / Accepted: 29 December 2011 / Published online: 10 January 2012
Ó Springer Science+Business Media, LLC 2012
Abstract The compounds methyl 3-(benzoylamino)-6-
methyl-2-oxo-2H-pyran-5-carboxylate (1), C15H13NO5, and
N-[5-(3,4-dimethoxyphenyl)-6-methyl-2-oxo-2H-pyran-3-yl]
benzamide (2), C21H19NO5, crystallize as a centrosymmetric
hydrogen-bonded dimer facilitated by N–HÁÁÁO interactions
involving the amide and carbonyl moiety of the lactone
group of adjacent molecules. Supramolecular aggregation in
1 is controlled by a combination of p–p interactions [cen-
trends in organic synthesis it is desirable to conduct
the transformations of 2H-pyran-2-ones according to the
principles of green chemistry [5], including the application
of microwaves as an efficient mean of supplying necessary
energy for the activation of reactants [4, 6, 7] and executing
reactions in water as a benign solvent [8] or even under
solvent-free (neat) conditions [9].
When for cycloadditions with 2H-pyran-2-ones alkynes
are used as dienophiles the initial step gives the 7-oxabi-
cyclo[2.2.2]octadiene adducts, which are, however, unsta-
ble and spontaneously eliminate carbon dioxide to yield the
final benzene derivatives [10]. On the other hand, when
alkenes are applied as dienophiles, the initially formed
7-oxabicyclo[2.2.2]octenes are more stable and can be in
some cases isolated [11, 12]. Nevertheless, under thermal
reaction conditions the carbon dioxide is also often elimi-
nated yielding cyclohexadiene systems, which can either
serve as another diene to produce bicyclo[2.2.2]octene
products (double cycloadducts) [13] or can be oxidized
(aromatized) into benzene derivatives (formally analogous
to those obtained with alkynes). These oxidations can
be facilitated by the application of a heterogeneous
dehydrogenation catalyst (such as Rh/C) [14, 15]. Bicy-
clo[2.2.2]octenes easily prepared from 2H-pyran-2-ones
according to this methodology represent a very interesting
set of compounds for further studies of desymmetrization
[16] and also as rewarding systems for the investigations of
steric effects exhibited by fused rings of different sizes on
the stereochemistry of cycloadditions of maleic anhydride
and N-substituted maleimides [17]. Additionally, 2H-
pyran-2-ones can be used as useful precursors for the
preparation of substituted indoles [18].
˚
troid–centroid distance = 4.0745(11) A] and weak C–HÁÁÁO
hydrogen bonding between the phenyl ring of the benzoyla-
mino group and the carbonyl atom of the methoxycarbonyl
groupandin 2 bya combinationofp–p interactions [centroid–
˚
centroid distance = 4.0699(8) and 4.1556(10) A], weak
C–HÁÁÁO interactions between the methoxy substituents of
the adjacent dimethoxyphenyl group and weak C–HÁÁÁ p
interactions.
Keywords 2H-Pyran-2-ones Á Crystal structure Á
Hydrogen bonds Á C–HÁÁÁp interaction Á p–p interaction
Introduction
2H-Pyran-2-ones represent an important class of com-
pounds useful for various ring transformations [1, 2],
especially for those including nucleophiles [3] and as
dienes in Diels–Alder reactions [4]. Considering the recent
ˇ
ˇ
K. Kranjc Á A. Juranovic Á M. Kocevar Á F. Perdih (&)
Faculty of Chemistry and Chemical Technology, University
ˇ
of Ljubljana, Askerceva cesta 5, 1000 Ljubljana, Slovenia
e-mail: franc.perdih@fkkt.uni-lj.si
ˇ
Due to the wide applicability of 2H-pyran-2-ones, a
straightforward one-pot synthesis starting from the simple
commercially available compounds was desired [19–21].
F. Perdih
CO EN-FIST, Dunajska 156, 1000 Ljubljana, Slovenia
123

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J Chem Crystallogr (2012) 42:443–449
Examples given here include such a transformation
between a molecule containing an activated CH2 group,
a C1-synthon N,N-dimethylformamide dimethyl acetal
(DMFDMA) and hippuric acid as an N-acylglycine deriv-
ative taking place in acetic anhydride (or in a mixture
with acetic acid) as the solvent yielding methyl 3-(ben-
zoylamino)-6-methyl-2-oxo-2H-pyran-5-carboxylate (1) and
N-[5-(3,4-dimethoxyphenyl)-6-methyl-2-oxo-2H-pyran-3-yl]
benzamide (2) (Scheme 1).
4.49; N, 4.93. IR (KBr) 3370, 1735, 1711, 1674, 1638, 1600,
1580, 1531, 1492 cm-1. 1H NMR (300 MHz, CDCl3) d 2.69
(s, 3H, Me), 3.90 (s, 3H, CO2Me), 7.54 (m, 3H, Ph), 7.88
(m, 2H, Ph), 8.54 (s, 1H, NH), 8.87 (s, 1H, 4-H). 13C NMR
(75.5 MHz, CDCl3) d 19.3, 52.2, 109.5, 122.1, 123.6, 126.9,
128.7, 132.3, 133.2, 158.5, 162.8, 164.1, 165.6.
Synthesis of N-[5-(3,4-Dimethoxyphenyl)-6-methyl-2-
oxo-2H-pyran-3-yl]benzamide (2)
A mixture of (3,4-dimethoxyphenyl)acetone (16.68 g,
0.086 mol) and DMFDMA (21.46 g, 0.18 mol) was heated
on reflux for 4 h. The volatile components were removed
under reduced pressure, thereafter hippuric acid (15.81 g,
0.088 mol) and acetic anhydride (111 mL) were added and
the mixture heated on an oil bath at 90 °C for further 4 h.
After the removal of the volatile components the residue
was treated with ethanol (55 mL) and, after cooling, the
precipitate was filtered off and washed with a small amount
of ethanol (5 mL) to afford 18.384 g (59%) of the title
product 2. M.p. 161–162 °C (EtOH). [21].
Experimental
Materials and Measurements
Melting points were determined on a micro hot stage
apparatus and are uncorrected. 1H NMR spectra were
recorded with a Bruker Avance DPX 300 spectrometer at
29 °C and 300 MHz using Me4Si as an internal standard.
13C NMR spectra were recorded on the same instrument at
75.5 MHz and are referenced against the central line of the
solvent signal (CDCl3 triplet at 77.0 ppm). IR spectra were
obtained with a Bio-Rad FTS 3000MX as KBr pellets. MS
spectra were recorded with a VG-Analytical AutoSpec Q
instrument. Elemental analyses (C, H, N) were performed
with a Perkin Elmer 2400 Series II CHNS/O Analyzer.
TLC was carried out on Fluka silica-gel TLC-cards. All
reagents and solvents were used as received from com-
mercial suppliers.
Crystallography
Single-crystal X-ray diffraction data were collected at
room temperature on a Nonius Kappa CCD diffractometer
with the graphite monochromated Mo-Ka radiation
˚
(k = 0.71073 A). The data were processed by DENZO
[22]. Structures were solved by direct methods imple-
mented in SHELXS-97 and refined by a full-matrix least-
squares procedure based on F2 with SHELXL-97 [23]. All
non-hydrogen atoms were refined anisotropically. All
hydrogen atoms were readily located in a difference Fou-
rier maps and were subsequently treated as riding atoms in
geometrically idealized positions, with C–H = 0.93 (aro-
Synthesis of Methyl 3-(benzoylamino)-6-methyl-2-oxo-
2H-pyran-5-carboxylate (1)
A mixture of methyl acetoacetate (23.22 g, 0.2 mol),
DMFDMA (23.83 g, 0.2 mol), acetic anhydride (200 mL)
and glacial acetic acid (50 mL) was heated on an oil bath at
80 °C for 150 min. Thereafter, hippuric acid (35.84 g,
0.2 mol) was added and heated on an oil bath at 80 °C for
further 4 h. After the removal of the volatile components the
residue was treated with ethanol (125 mL) and, after cooling,
the precipitate was filtered off and washed with a small
amount of ethanol (10 mL) to afford 35.93 g (63%) of the
title product 1. M.p. 164–167.5 °C (EtOH). Anal. calcd. for
C15H13NO5: C, 62.72; H, 4.56; N, 4.88. Found: C, 63.00; H,
˚
˚
matic and alkenyl) or 0.96 A (CH3), N–H = 0.86 A and
with Uiso(H) = kUeq(C or N), where k = 1.5 for NH and
methyl groups, which were permitted to rotate but not to
tilt, and 1.2 for all other H atoms. Crystallographic data are
listed in Table 1. Selected bond lengths and bond angles
are listed in Table 2. All the bond lengths of compounds 1
and 2 are within normal ranges [24]. Hydrogen bonding
interactions are listed in Table 3.
Me
O
O
Me
O
O
Results and Discussion
O
NH
NH
In both compounds 1 and 2 the central 2H-pyran-2-one ring
is planar (Fig. 1). The maximum deviation from the
OMe
O
MeO
O
˚
mean plane described by the ring atoms is 0.040(2) A for
˚
atom C1 in 1 and -0.017(1) A in 2, again for atom C1. In
OMe
1
2
Scheme 1 Molecular structures of 1 and 2
both crystal structures weak intramolecular C3–H3ÁÁÁO3
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J Chem Crystallogr (2012) 42:443–449
445
˚
Table 1 Crystal data and refinement parameters for the compounds 1
and 2
Table 2 Selected bond lengths [A] and angles [°] for 1 and 2
1
Compound
1
2
O1–C1
O1–C5
O2–C1
O3–C7
O4–C14
O5–C14
O5–C15
N1–C7
N1–C2
1.3786(15)
1.3653(16)
1.2055(16)
1.2173(17)
1.2019(17)
1.3316(17)
1.4476(17)
1.3661(17)
1.4017(16)
C5–O1–C1
O2–C1–O1
O2–C1–C2
C7–N1–C2
C3–C2–N1
N1–C2–C1
O3–C7–N1
O3–C7–C8
124.25(10)
117.48(11)
126.53(12)
125.25(11)
127.05(12)
113.14(11)
122.00(12)
121.66(12)
CCDC
834643
C15H13NO5
287.26
834644
C21H19NO5
365.37
Molecular formula
Molecular weight
Crystal system
Space group
Triclinic
P -1
Triclinic
P -1
Temperature (K)
293(2)
293(2)
˚
a (A)
8.4667(3)
8.4753(3)
10.9239(4)
86.481(2)
72.282(2)
64.194(2)
669.91(4)
2
8.1480(2)
9.5704(3)
12.2802(4)
83.255(2)
73.079(2)
77.758(2)
893.72(5)
2
˚
b (A)
2
˚
c (A)
O1–C1
O1–C5
O2–C1
O3–C7
O4–C16
O5–C17
N1–C7
N1–C2
1.3645(16)
1.3800(16)
1.2091(17)
1.2206(18)
1.3636(16)
1.3605(16)
1.3616(18)
1.4015(17)
C1–O1–C5
O2–C1–O1
O2–C1–C2
C7–N1–C2
C3–C2–N1
N1–C2–C1
O3–C7–N1
O3–C7–C8
123.45(11)
118.32(12)
125.14(12)
126.00(12)
127.63(13)
112.59(12)
121.39(13)
121.71(13)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
Dcalc (g cm-3
Absorption coefficient
(mm-1
F(000)
)
1.424
1.358
0.108
0.097
)
300
384
Crystal dimensions (mm)
0.50 9
0.25 9 0.25
0.40 9
0.20 9 0.13
structures it is much smaller, 4.17° [26] and 4.95° [27]. The
dihedral angle between the 2H-pyran-2-one and phenyl
ring of the benzoylamino group are in all three known
structures markedly smaller, ranging from 6.09° to 7.80°
[25–27].
Theta range (°)
Range/indices (h, k, l)
5.47–27.47
3.55–27.46
-10, 10; -10,
10; -14, 14
-10, 10; -12,
12; -15, 15
Reflections collected
5390
6954
Independent reflections
3008
4030
The methoxycarbonyl group (C15/O5/O4/C14/C4) in 1
is nearly planar with the central 2H-pyran-2-one ring, the
dihedral angle is 9.09(8)°. Such small deviations of car-
boxylic group (either as an acid or ester functionality) from
the planarity of 2H-pyran-2-one [28–34] or benzene ring
[35–43] are often observed. When a bulky substituent is
present in the ortho position to the carboxylic group much
larger twist angles ranging from *20° up to *80° are
observed in the cases of 2H-pyran-2-one [44–48] or ben-
zene ring [49–58].
[Rint = 0.0193]
[Rint = 0.0158]
Completeness
98.2%
98.4%
Tmax/Tmin
0.9734/0.9478
0.9874/0.9621
4030/0/248
0.0464, 0.1193
0.0608, 0.1337
1.017
Data/restraints/parameters 3008/0/193
R1, wR2 [I [ 2r(I)]a
0.0446, 0.1187
R1, wR2 (all data)b
Goodness of fit on F2, Sc
Largest diff. peak
0.0551, 0.1297
1.037
0.222 and -0.213 0.156 and -0.188
-3
)
˚
and hole (e A
P
P
P
P
aR = ||Fo| - |Fc||/ Fo|, wR2 = { [w(Fo2 - F2c)2]/ [w(Fo2)2]}1/2
,
b
P
In the compound 2 a dimethoxyphenyl group is attached
to the central 2H-pyran-2-one ring instead of methoxy-
carbonyl group. The dihedral angle between the 2H-pyran-
2-one and phenyl ring (C14–C19) is 55.99(7)°. In CSD we
found no structure similar to 2 that would incorporate a
dimethoxyphenyl group at the position 5 of pyran-2-one
ring (as in 2) and neither at the positions 3 or 4. However, a
few structures that possess a dimethoxyphenyl group
attached at the position 6 of pyran-2-one ring were found
[59–62]. Wide variety of dihedral angles can be observed
in these cases, being either small (4.56° [59], 8.83° [60]) or
large (19.58° [61], 42.54° [62]).
S = { [(F2o - Fc2)2]/(n/p}1/2 where nis the number of reflections and
p is the total number of parameters refined
c
hydrogen bonding is present. Furthermore, in compound 1
additional C6–H6CÁÁÁO4 hydrogen bonding is present
(Table 3).
The mean plane through the amide group (O3–C7–N1–
C2–C8) in 1 is inclined to the 2H-pyran-2-one ring by
20.38(8)° and the dihedral angle between the 2H-pyran-2-
one and phenyl ring (C8–C13) is 33.35(9)° while these
angles in 2 are 12.15(8)° and 23.54(8)°, respectively. This
deviation of the amide group from planarity is similar also
in 3-benzoylamino-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-
coumarin being 12.95° [25], while in the other two known
Both compounds 1 and 2 crystallize as centrosymmetric
hydrogen-bonded dimers facilitated by the amide and car-
bonyl moiety of the lactone group of adjacent molecules
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J Chem Crystallogr (2012) 42:443–449
Table 3 Hydrogen bond
˚
˚
D–H (A)
˚
˚
D–HÁÁÁA
HÁÁÁA (A)
DÁÁÁA (A)
D–HÁÁÁA (°)
Symmetry code
geometry of 1 and 2 (A and °)
1
N1–H1ÁÁÁO2
C3–H3ÁÁÁO3
C6–H6CÁÁÁO4
C11–H11ÁÁÁO4
C13–H13ÁÁÁO2
2
0.86
0.93
0.96
0.93
0.93
2.42
2.31
2.20
2.54
2.43
3.2517(15)
2.843(2)
162.8
115.7
128.0
161.1
167.6
1 - x, 1 - y, 1 - z
2.890(2)
3.4321(19)
3.3458(18)
x, 1 ? y, 1 ? z
1 - x, 1 - y, 1 - z
N1–H1ÁÁÁO2
C3–H3ÁÁÁO3
C13–H13ÁÁÁO2
C21–H21BÁÁÁO4
C20–H20CÁÁÁCg3
0.86
0.93
0.93
0.96
0.96
2.52
2.26
2.38
2.54
2.94
3.3303(17)
2.8286(18)
3.312(2)
156.5
118.8
176.5
153.1
141.0
-x, 1 - y, 2 - z
-x, 1 - y, 2 - z
-x, -1 - y, 1 - z
-x, -y, 1 - z
3.423(2)
3.738(2)
the position 3 [25, 26] and in one structure at the position 6
[27]. Similar dimer formation is present only in 3-ben-
zoylamino-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydrocoumarin
with the separation of mean planes through the 2H-pyran-
˚
2-one ring of adjacent molecules of 1.595 A [25]. In other
two compounds dimer formation is not present because
N–H group is either not involved in the hydrogen bonding
[26] or is hydrogen-bonded to a 1,4-dioxane solvate mol-
ecule [27].
Dimers of 1 form ribbons by weak C11–H11ÁÁÁO4
(x, 1 ? y, 1 ? z) hydrogen bonding between the phenyl
ring of the benzoylamino group and the carbonyl atom of
the methoxycarbonyl group parallel to [011] (Fig. 2;
Table 3). Supramolecular aggregation is stabilized by p–p
interactions between two parallel C8–C13 rings (centroid
Cg1), with a Cg1ÁÁÁCg1(1 - x, 2 - y, 1 - z) centroid-to-
˚
centroid distance of 4.0745(11) A, a perpendicular distance
from the centroid Cg1 to the plane of the other ring of
˚
˚
3.7354(8) A and a centroid offset of 1.627 A (Fig. 4).
Dimers of 2 also form ribbons by weak C21–H21BÁÁÁO4
(-x, -1 - y, 1 - z) hydrogen bonding, but in this case
between the methoxy substituents of the adjacent dime-
thoxyphenyl group parallel to [011] (Fig. 3; Table 3).
Supramolecular aggregation is stabilized by weak C20–
H20CÁÁÁCg3(-x, -y, 1 - z) interactions (Cg3 is the cen-
troid of the C14–C19 ring) (Fig. 5) and p–p interactions
parallel to [100] between two parallel O1/C1–C5 rings
(centroid Cg1), with a Cg1ÁÁÁCg1(-x, -y, 2 - z) centroid-
Fig. 1 The molecular structure of 1 and 2, showing the atom-
labelling scheme. Displacement ellipsoids are drawn at the 50%
probability level
(Figs. 2,3; Table 3). The dimers in 1 and 2 can be descri-
bed by the graph-set motif R22(10) [63]. Dimers in both
crystal structures are further stabilized by weak C13–
H13ÁÁÁO2 interactions. In both compounds the two
2H-pyran-2-one rings involved in the dimer formation are
not coplanar. The separation of mean planes, which are
described by the atoms of each 2H-pyran-2-one ring in a
˚
to-centroid distance of 4.0699(8) A, a perpendicular dis-
tance from the centroid Cg1 to the plane of the other ring of
˚
˚
3.5648(6) A and a centroid offset of 1.964 A. Supramolec-
ular aggregation is further stabilized by p–p interactions
between O1/C1–C5 ring (centroid Cg1) and C8–C13 ring
(centroid Cg2), with a Cg1ÁÁÁCg2(-1 ? x, y, z) centroid-to-
˚
˚
dimer is 1.431 A in 1 and 1.569 A in 2. In the Cambridge
Structural Database (CSD) [64] we found only three
structures with benzoylamino moiety attached to the 2H-
pyran-2-one ring, in two of them this moiety is attached at
˚
centroid distance of 4.1556(10) A, a dihedral angle between
the rings of 23.54(8)°, a perpendicular distance from the
˚
centroid Cg1 to the plane of the other ring of 2.8300(6) A
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J Chem Crystallogr (2012) 42:443–449
447
Fig. 2 1D framework
formation of dimers in 1.
Dashed lines indicate hydrogen
bonds, dimers are connected via
C11–H11ÁÁÁO4 hydrogen-
bonding
Fig. 3 1D framework formation of dimers in 2. Dashed lines indicate hydrogen bonds, dimers are connected via C21–H21BÁÁÁO4 hydrogen-
bonding
Fig. 4 A packing diagram for 1. Dashed lines indicate p–p interactions and C11–H11ÁÁÁO4 hydrogen bonds. For the sake of clarity, H atoms not
involved in the motif shown have been omitted
and the angle between the intercentroid vector and the nor-
mal to the second ring of 23.54° (consequently the perpen-
dicular distance from the centroid Cg2 to the plane of the
˚
first ring is 3.8096(7) A and the angle between the inter-
centroid vector and the normal to the first ring is 47.08°)
(Fig. 6). These p–p interactions are consistent with well
defined p–p stacking interactions [65–68]. According to
Janiak [69], they can be regarded as medium strong, since
strong interactions exhibit rather short centroid–centroid
˚
contacts (CgÁÁÁCg \ 3.8 A), small slip angles (\25°) and
˚
small vertical displacements (\1.5 A), which translate into a
sizeable overlap of the aromatic planes. In comparison,
medium-to-weak interactions exhibit rather long centroid–
˚
centroid distances ([4.0 A) together with large slip angles
([30°) and large vertical displacements ([2.0 A) [69–71].
Fig. 5 A packing diagram for 2. Dashed lines indicate C20–
H20CÁÁÁCg3 hydrogen-bonding
˚
123

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J Chem Crystallogr (2012) 42:443–449
Fig. 6 A packing diagram for
2. Dashed lines indicate p–p
interactions. For the sake of
clarity, H atoms have been
omitted
ˇ
16. Hren J, Perdih F, Polanc S, Kocevar M (2011) Eur J Org Chem
3368–3374
17. Kranjc K, Perdih F, Kocevar M (2009) J Org Chem 74:
Supplementary Material
ˇ
Crystallographic data of 1 and 2 were deposited in the
Cambridge Crystallographic Data Center under the number
CCDC 834643-834644. CIF files containing complete
information on the studied structures may be obtained free
of charge from the Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK, fax ?44-1223-336033; e-mail:
data_request@ccdc.cam.ac.uk or from the following web
site: www.ccdc.cam.ac.uk/data_request/cif.
6303–6306
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ˇ
ˇ
ˇ ˇ
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Tetrahedron 46:2081–2088
ˇ
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ˇ
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Acknowledgement The authors thank the Ministry of Higher
Education, Science and Technology of the Republic of Slovenia and
the Slovenian Research Agency for financial support (grant Nos. P1-
0230-0103 and P1-0230-0175) and grant packet X-2000 for Kap-
paCCD Nonius diffractometer. This work was also partially supported
with infrastructure of the EN-FIST, Center of Excellence, Ljubljana,
Slovenia.
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