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The title compound, C14H24N2O4, consists of two symmetric moieties related through a twofold axis. The whole mol­ecule has a cis conformation. Both the ionic enol form and the non-ionic keto form make comparable contributions to the structure. In the crystal structure, infinite supramolecular chains are formed through N—H...O hydrogen bonds.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104016130/dn1052sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104016130/dn1052Isup2.hkl
Contains datablock I

CCDC reference: 208720

Comment top

β-Enaminoesters represent an important class of functionalized synthetic blocks (Bartoli et al., 2004). Recently, the title compound, (I), has been synthesized for the first time in our laboratory. According to a model of synergetic mutual reinforcement of hydrogen bonding and π-delocalization within a heterodienic system (Gilli et al., 1989, 1993; Bertolasi et al., 1991), (I) may be regarded as containing both the ionic enolic and non-ionic keto forms (see scheme). The structure of (I) has been established by 1H and 13C NMR and IR spectroscopies, and has been fully confirmed by an X-ray structural analysis. \sch

As shown in Fig. 1, compound (I) is built up from two asymmetric units related through a twofold axis. The whole molecule is arranged in a cis conformation with respect to the C6—C6(1 − x, y, 3/2 − z) bond. The C3O1 bond [1.221 (2) Å] is shorter than a normal single C—O bond (ca 1.40 Å; Reference?), but longer than the double CO bonds found in some esters, such as in an Amadori compound [1.189 (5) Å; Kojić-Prodić et al., 1995], a benzoate [1.200 (4) Å; Huertas et al., 1997] and a glycine derivative [1.186 (2) Å; Zhao et al., 2002]. The NC5 bond in (I) [1.344 (2) Å] is longer than a typical double CN bond (ca 1.269 Å; Reference?) but shorter than the C—N single bond [N—C6 1.443 (4) Å]. The C3—C4 bond length [1.425 (2) Å] is intermediate between a single C—C bond (ca 1.50 Å; Reference?) and a CC double bond (ca 1.34 Å; Reference?). These features of the bond lengths in (I) indicate that both the ionic enolic and the non-ionic keto forms make comparable contributions to the structure. Please provide a reference for the standard bond lengths used in the above comparisons.

The 1H and 13C NMR spectra show the olefinic resonances of atom C4 and its attached H atom at noticeably higher magnetic fields, 4.93 and 83.83 p.p.m., respectively. This indicates the contribution of the non-ionic keto form, which undertakes π-delocalization. On the other hand, the NH signal appears at a much lower magnetic field (8.64 p.p.m.) in the 1HNMR spectrum and this is indicative of the contribution of the ionic enolic form. These two forms are also observed in the related compound with an ethylenediimine (Özkara et al., 2004), which shows almost the same deviations of the corresponding signals in the NMR spectra.

The IR spectroscopic data of (I) are consistent with the crystal structure. The absorption band centred at around 3297 cm−1 is readily ascribed to the NH group. The absorption band of CO stretching at 1604 cm−1 appears to be lower than that for a typical CO group (1712–1708 cm−1; Reference?) and is indicative of the ionic enolic form of the molecule.

The asymmetric unit of (I) is almost planar, with mean and maximum deviations of 0.0014 and 0.1330 Å, respectively, as the π-delocalization is reinforced by an N—H···O1 hydrogen bond. The sum of the angles around the N atom is close to 360°, indicating that the N atom is involved in the ionic enolic form. In the solid state, the two halves of (I) are skewed, with a dihedral angle of 46.3° between them. In the structure, an infinite zigzag chain of molecules of (I) running along the [001] direction (Fig. 2) is built up via an N—H···O1(1 − x, 1 − y, 1 − z) hydrogen bond. These intermolecular hydrogen bonds form a ring which may be described as graph set R22(4) (Etter, 1990). This ring is embedded in the chain. There are no hydrogen bonds between separate chains. Duplication of the chain forms layers of (I) parallel to the (010) plane.

Experimental top

Ethyl acetoacetate and ethylenediamine, in a molar ratio of 2:1, were mixed together and refluxed with stirring for 2 h. Crystals of (I) were formed by recrystallization of the resulting solid from ethanol, with a yield of approximately 65% based on ethyl-acetoacetate. Spectroscopic analysis: IR (KBr, ν, cm−1): 3297, 2984, 2953, 2898, 1604 (br), 1509, 1438, 1390, 1288, 1259, 1224, 1167 (br), 1115, 1092, 1067, 1021, 980, 784, 726, 566; 1H NMR (CDCl3, δ, p.p.m.): 8.64 (1H, NH), 4.48 (1H, s, C4—H), 4.07 (2H, q, C2—H2), 3.35 (2H, s, C6—H2), 1.90 (3H, s, C7—H3), 1.23 (3H, t, C1jaH3); 13C NMR (CDCl3, δ, p.p.m.): 170.86 (C5), 161.55 (C3), 83.83 (C4), 58.72 (CH2), 44.07 (CH2), 19.49 (CH3), 14.85 (CH3).

Refinement top

All H atoms were positioned geometrically and allowed to ride on their parent atoms, with an N—H distance of 0.86 Å and C—H distances in the range 0.93–0.97 Å, and with Uiso(H) = 1.5Ueq(C) for methyl H atoms and 1.2Ueq(C,N) for others. Please check amended text.

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SMART; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The formula unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. Hydrogen bonds are illustrated by dashed lines.
[Figure 2] Fig. 2. Part of the crystal structure of (I), showing the infinite hydrogen-bonded chains running along the [001] direction. H atoms have been omitted for clarity, except those involved in hydrogen bonds. Hydrogen bonds are illustrated by dashed lines.
Diethyl 3,8-dimethyl-4,7-diazadec-2,8-dienedioate top
Crystal data top
C14H24N2O4F(000) = 616
Mr = 284.35Dx = 1.220 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 850 reflections
a = 11.734 (3) Åθ = 2.7–20.2°
b = 10.566 (2) ŵ = 0.09 mm1
c = 13.418 (3) ÅT = 293 K
β = 111.44 (1)°Prism, colourless
V = 1548.5 (6) Å30.25 × 0.15 × 0.15 mm
Z = 4
Data collection top
Bruker SMART Apex CCD area-detector
diffractometer
1520 independent reflections
Radiation source: fine-focus sealed tube946 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.071
ϕ and ω scansθmax = 26.0°, θmin = 2.7°
Absorption correction: multi-scan
(SADABS; Bruker, 2000)
h = 1414
Tmin = 0.98, Tmax = 0.99k = 128
4031 measured reflectionsl = 1614
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.047Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.112H-atom parameters constrained
S = 0.91 w = 1/[σ2(Fo2) + (0.0455P)2]
where P = (Fo2 + 2Fc2)/3
1520 reflections(Δ/σ)max < 0.001
93 parametersΔρmax = 0.11 e Å3
0 restraintsΔρmin = 0.15 e Å3
Crystal data top
C14H24N2O4V = 1548.5 (6) Å3
Mr = 284.35Z = 4
Monoclinic, C2/cMo Kα radiation
a = 11.734 (3) ŵ = 0.09 mm1
b = 10.566 (2) ÅT = 293 K
c = 13.418 (3) Å0.25 × 0.15 × 0.15 mm
β = 111.44 (1)°
Data collection top
Bruker SMART Apex CCD area-detector
diffractometer
1520 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2000)
946 reflections with I > 2σ(I)
Tmin = 0.98, Tmax = 0.99Rint = 0.071
4031 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0470 restraints
wR(F2) = 0.112H-atom parameters constrained
S = 0.91Δρmax = 0.11 e Å3
1520 reflectionsΔρmin = 0.15 e Å3
93 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.63346 (19)0.99298 (19)0.38556 (14)0.0799 (7)
H1A0.59791.06270.40980.120*
H1B0.61411.00030.30980.120*
H1C0.72070.99410.42200.120*
C20.58367 (19)0.87270 (18)0.40878 (14)0.0722 (6)
H2A0.49500.87300.37630.087*
H2B0.61430.80200.37980.087*
C30.59892 (15)0.74921 (19)0.56145 (14)0.0559 (5)
C40.64768 (14)0.74732 (17)0.67556 (13)0.0543 (5)
H40.68580.82040.71080.065*
C50.64255 (15)0.64664 (17)0.73649 (13)0.0516 (5)
C60.56509 (14)0.43002 (17)0.75074 (13)0.0531 (5)
H6A0.62190.43180.82440.064*
H6B0.57900.35220.71850.064*
C70.70155 (17)0.65551 (18)0.85594 (12)0.0661 (6)
H7A0.63970.65100.88690.099*
H7B0.74450.73450.87510.099*
H7C0.75810.58680.88230.099*
N0.58968 (12)0.53648 (14)0.69409 (10)0.0536 (4)
H0.56820.52850.62590.064*
O10.54318 (12)0.66427 (13)0.50176 (9)0.0680 (4)
O20.62179 (11)0.86080 (12)0.52292 (9)0.0667 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0989 (16)0.0766 (16)0.0645 (13)0.0110 (12)0.0303 (12)0.0107 (11)
C20.0907 (14)0.0717 (15)0.0516 (12)0.0127 (11)0.0228 (10)0.0043 (10)
C30.0626 (11)0.0541 (12)0.0554 (12)0.0057 (9)0.0265 (9)0.0007 (10)
C40.0587 (11)0.0551 (12)0.0503 (10)0.0089 (9)0.0214 (8)0.0062 (9)
C50.0536 (10)0.0556 (12)0.0486 (10)0.0050 (9)0.0223 (8)0.0066 (9)
C60.0628 (10)0.0487 (11)0.0496 (10)0.0032 (8)0.0227 (8)0.0003 (8)
C70.0736 (12)0.0700 (14)0.0492 (11)0.0074 (10)0.0158 (9)0.0031 (9)
N0.0667 (9)0.0553 (10)0.0424 (8)0.0074 (7)0.0241 (7)0.0048 (7)
O10.0880 (9)0.0632 (9)0.0513 (8)0.0215 (7)0.0237 (6)0.0062 (7)
O20.0905 (9)0.0578 (9)0.0509 (8)0.0148 (7)0.0249 (6)0.0011 (6)
Geometric parameters (Å, º) top
C1—C21.479 (2)C4—H40.9300
C1—H1A0.9600C5—N1.344 (2)
C1—H1B0.9600C5—C71.499 (2)
C1—H1C0.9600C6—N1.445 (2)
C2—O21.436 (2)C6—C6i1.520 (3)
C2—H2A0.9700C6—H6A0.9700
C2—H2B0.9700C6—H6B0.9700
C3—O11.221 (2)C7—H7A0.9600
C3—O21.353 (2)C7—H7B0.9600
C3—C41.425 (2)C7—H7C0.9600
C4—C51.356 (2)N—H0.8600
C2—C1—H1A109.5N—C5—C7117.93 (16)
C2—C1—H1B109.5C4—C5—C7119.38 (16)
H1A—C1—H1B109.5N—C6—C6i112.71 (11)
C2—C1—H1C109.5N—C6—H6A109.0
H1A—C1—H1C109.5C6i—C6—H6A109.0
H1B—C1—H1C109.5N—C6—H6B109.0
O2—C2—C1107.88 (15)C6i—C6—H6B109.0
O2—C2—H2A110.1H6A—C6—H6B107.8
C1—C2—H2A110.1C5—C7—H7A109.5
O2—C2—H2B110.1C5—C7—H7B109.5
C1—C2—H2B110.1H7A—C7—H7B109.5
H2A—C2—H2B108.4C5—C7—H7C109.5
O1—C3—O2121.54 (16)H7A—C7—H7C109.5
O1—C3—C4127.05 (17)H7B—C7—H7C109.5
O2—C3—C4111.40 (16)C5—N—C6127.00 (14)
C5—C4—C3124.73 (17)C5—N—H116.5
C5—C4—H4117.6C6—N—H116.5
C3—C4—H4117.6C3—O2—C2117.13 (13)
N—C5—C4122.65 (15)
O1—C3—C4—C52.2 (3)C7—C5—N—C610.9 (2)
O2—C3—C4—C5177.66 (16)C6i—C6—N—C596.2 (2)
C3—C4—C5—N0.1 (3)O1—C3—O2—C23.3 (3)
C3—C4—C5—C7177.78 (15)C4—C3—O2—C2176.53 (14)
C4—C5—N—C6171.27 (16)C1—C2—O2—C3171.74 (16)
Symmetry code: (i) x+1, y, z+3/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N—H···O10.862.142.7841 (18)132
N—H···O1ii0.862.673.292 (2)130
Symmetry code: (ii) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC14H24N2O4
Mr284.35
Crystal system, space groupMonoclinic, C2/c
Temperature (K)293
a, b, c (Å)11.734 (3), 10.566 (2), 13.418 (3)
β (°) 111.44 (1)
V3)1548.5 (6)
Z4
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.25 × 0.15 × 0.15
Data collection
DiffractometerBruker SMART Apex CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2000)
Tmin, Tmax0.98, 0.99
No. of measured, independent and
observed [I > 2σ(I)] reflections
4031, 1520, 946
Rint0.071
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.047, 0.112, 0.91
No. of reflections1520
No. of parameters93
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.11, 0.15

Computer programs: SMART (Bruker, 2000), SMART, SAINT (Bruker, 2000), SHELXTL (Bruker, 2000), SHELXTL, ORTEP-3 for Windows (Farrugia, 1997).

Selected bond lengths (Å) top
C1—C21.479 (2)C4—C51.356 (2)
C2—O21.436 (2)C5—N1.344 (2)
C3—O11.221 (2)C5—C71.499 (2)
C3—O21.353 (2)C6—N1.445 (2)
C3—C41.425 (2)C6—C6i1.520 (3)
Symmetry code: (i) x+1, y, z+3/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N—H···O10.862.142.7841 (18)132
N—H···O1ii0.862.673.292 (2)130
Symmetry code: (ii) x+1, y+1, z+1.
 

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