N′-[(E)-5-Oxopyrrolidin-2-yl­idene]pyridine-2-carbohydrazide

Bibik, Y.S.; Ivanova, H.V.; Khomenko, D.M.; Doroshchuk, R.O.; Stoica, A.-C.

doi:10.1107/S241431462500896X

organic compounds

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ISSN: 2414-3146

Volume 10| Part 10| October 2025| x250896

https://doi.org/10.1107/S241431462500896X

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N′-[(E)-5-Oxopyrrolidin-2-ylidene]pyridine-2-carbohydrazide

Yurii S. Bibik,^a ^* Hanna V. Ivanova,^a Dmytro M. Khomenko,^a,^b Roman O. Doroshchuk ^a,^b,^c and Alexandru-Constantin Stoica ^d

^aDepartment of Chemistry, Kyiv National Taras Shevchenko University, Hetman Pavlo Skoropadskyi Street 12, Kyiv 01033, Ukraine, ^bEnamine Ltd, Winston Churchil st. 78, Kyiv 02094, Ukraine, ^cChemBioCenter, Kyiv National Taras Shevchenko University, Hetman Pavlo Skoropadskyi Street 12, Kyiv 01601, Ukraine, and ^d`Petru Poni', Institute of Macromolecular Chemistry, Aleea Grigore Ghica Vodă 41A, Iaşi 700487, Romania
^*Correspondence e-mail: [email protected]

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 2 October 2025; accepted 14 October 2025; online 28 October 2025)

In the title compound, C₁₀H₁₀N₄O₂, the dihedral angle between the planes of the pyridine and oxopyrrolidine rings is 6.9 (2)°. In the crystal, inversion dimers linked by pairwise N—H⋯O hydrogen bonds generate R₂²(14) loops.

Keywords: crystal structure; X-ray crystallography; pyridine-2-carbohydrazide.

CCDC reference: 2495443

Structure description

Pyridine-2-carbohydrazides are organic compounds containing a pyridine ring substituted with a carbohydrazide (–CONHNH₂–) group at the 2-position. These compounds are valuable in organic and medicinal chemistry due to their diverse biological activities and reactivity. They have been studied extensively for their medicinal properties (e.g. Khan et al., 2022 ; Pitucha et al., 2020 ; Marinescu & Popa, 2022 ). As part of our work in this area, we now report the synthesis and structure of N′-[(E)-5-oxopyrrolidin-2-ylidene]pyridine-2-carbohydrazide.

The title compound crystallizes in the triclinic space group P $[\overline{1}]$ with one molecule in the asymmetric unit (Fig. 1). The molecule is not exactly planar, but can be divided into three almost planar fragments, viz. a pyridine ring, a carbohydrazide unit (O1/C6/N2/N3) and an oxopyrrolidine ring. The carbohydrazide unit forms dihedral angles of 3.9 (2) and 5.2 (2)° with the N1/C1–C5 pyridine and N4/C7–C10 oxopyrrolidine rings, respectively. The dihedral angle between the planes of the pyridine and oxopyrrolidine rings is 6.9 (2)°. Pyridine atom N1 and carbohydrazide atom N2 are cis with respect to each other [torsion angles N1—C5—C6—N2 and N1—C5—C6—O1 = −0.9 (3) and 177.6 (2)°, respectively]. Hydrazide atom H2 and oxopyrrolidine atom H4 are trans with respect to each other [torsion angle N2—N3—C7—N4 = 179.33 (18)°]. In addition, the C6—N2 bond length of 1.322 (3) Å agrees well with equivalent bonds in similar structures, being intermediate between a typical C—N single bond (∼1.47 Å) and a C=N double bond (∼1.29 Å). The N2—N3 bond length of 1.396 (2) Å also shows partial double-bond character, suggesting extensive delocalization in the compound (Singh et al., 2006 ).

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.

In the extended structure, the molecules forms dimers through pairwise N—H⋯O hydrogen bonds (Table 1 and Fig. 2), which generate R₂²(14) loops. These dimers are further connected into a two-dimensional framework via short C⋯C contacts (3.23–3.39 Å), which are likely of van der Waals nature and occur between symmetry-related C atoms of adjacent molecules (Fig. 3).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N4—H4⋯O1ⁱ	0.86	2.02	2.822 (2)	154
Symmetry code: (i) .

Figure 2
A dimer formed through pairwise N—H⋯O hydrogen bonds.

Figure 3
A view normal to the ab plane of the crystal structure of the title compound, showing the two-dimensional supramolecular network.

Synthesis and crystallization

A solution of pyridine-2-carbohydrazide in ethanol (2.05 g, 1.5 mmol in 125 ml) was added to a mixture of ethyl 4-ethoxy-4-iminobutanoate hydrochloride (3.46 g, 1.65 mmol) and DIPEA (N,N-diisopropylethylamine) (2.85 ml, 1.72 mmol) in ethanol (125 ml) (Fig. 4). The reaction mixture was then refluxed for 8 h. After cooling to room temperature, the solvent was removed under reduced pressure. The resulting suspension was diluted with water (250 ml) and stirred to yield a white solid. The solid was collected by filtration, dried and recrystallized from acetonitrile solution. Crystals suitable for X-ray analysis were obtained by recrystallization from dimethylformamide (DMF) solution (yield: 8%, 0.3 g). ¹H NMR (400 MHz, DMSO-d₆): δ 11.31 (s, 0.5H), 10.96 (s, 0.5H), 10.74 (s, 0.5H), 10.61 (s, 0.5H), 8.66 (d, J = 4.6 Hz, 1H), 8.06–7.98 (m, 2H), 7.61 (dd, J = 3.8, 1.9 Hz, 1H), 2.92 (t, J = 7.2 Hz, 1H), 2.78 (t, J = 7.6 Hz, 1H). IR (KBr, ν, cm⁻¹): 3443, 3315, 3112, 1759, 1681, 1655, 1592, 1538, 1432, 1227, 900, 818, 579, 428. LC/MS (ESI): m/z 219 [MH]⁺. Elemental analysis calculated (%) for C₁₀H₁₀N₄O₂: C 55.04, H 3.62, N 14.66; found: C 55.02, H 3.59, N 14.63.

Figure 4
Synthesis scheme for the title compound.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₀H₁₀N₄O₂
M_r	218.22
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	293
a, b, c (Å)	5.6332 (5), 7.6439 (7), 11.7293 (11)
α, β, γ (°)	95.859 (8), 96.353 (8), 99.682 (8)
V (Å³)	491.04 (8)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	0.11
Crystal size (mm)	0.18 × 0.12 × 0.04

Data collection
Diffractometer	Rigaku Xcalibur Eos
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2021 )
T_min, T_max	0.716, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	4130, 1734, 1120
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.049, 0.121, 1.01
No. of reflections	1734
No. of parameters	146
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.17, −0.17
Computer programs: CrysAlis PRO (Rigaku OD, 2021), SHELXT2018 (Sheldrick, 2015a ), SHELXL2018 (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Structural data

CCDC reference: 2495443

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S241431462500896X/hb4539sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S241431462500896X/hb4539Isup2.hkl

Supporting information containing IR and 1H-NMR spectra of the title compound. DOI: https://doi.org/10.1107/S241431462500896X/hb4539sup3.pdf

checkCIF report

Computing details top

N'-[(E)-5-Oxopyrrolidin-2-ylidene]pyridine-2-carbohydrazide top

Crystal data top

C₁₀H₁₀N₄O₂	Z = 2
M_r = 218.22	F(000) = 228
Triclinic, P1	D_x = 1.476 Mg m⁻³
a = 5.6332 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.6439 (7) Å	Cell parameters from 990 reflections
c = 11.7293 (11) Å	θ = 2.7–24.0°
α = 95.859 (8)°	µ = 0.11 mm⁻¹
β = 96.353 (8)°	T = 293 K
γ = 99.682 (8)°	Plate, colourless
V = 491.04 (8) Å³	0.18 × 0.12 × 0.04 mm

Data collection top

Rigaku Xcalibur Eos diffractometer	1734 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Mo) X-ray Source	1120 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.037
Detector resolution: 16.1593 pixels mm^-1	θ_max = 25.0°, θ_min = 2.7°
ω scans	h = −6→6
Absorption correction: multi-scan (CrysAlis PRO; Rigaku OD, 2021)	k = −9→8
T_min = 0.716, T_max = 1.000	l = −13→13
4130 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.049	w = 1/[σ²(F_o²) + (0.0489P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.121	(Δ/σ)_max < 0.001
S = 1.01	Δρ_max = 0.17 e Å⁻³
1734 reflections	Δρ_min = −0.17 e Å⁻³
146 parameters	Extinction correction: SHELXL2018 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.019 (4)
Primary atom site location: dual

Special details top

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

Refinement. All H atoms were placed geometrically (C—H = 0.93–0.97 Å and N—H = 0.86 Å) and refined as riding atoms, with U_iso(H) = 1.2U_eq(carrier).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O1	−0.2261 (3)	0.2881 (3)	0.25651 (14)	0.0656 (6)
O2	0.6944 (3)	0.9414 (2)	0.63831 (14)	0.0578 (6)
N1	0.1853 (4)	0.3516 (3)	0.05028 (15)	0.0402 (5)
N2	0.1546 (4)	0.4460 (3)	0.26871 (15)	0.0416 (6)
H2	0.278937	0.471361	0.233005	0.050*
N3	0.1655 (4)	0.5201 (3)	0.38345 (15)	0.0392 (5)
N4	0.4061 (3)	0.7230 (2)	0.52866 (14)	0.0372 (5)
H4	0.308537	0.706286	0.579587	0.045*
C1	0.2008 (5)	0.3059 (3)	−0.0616 (2)	0.0467 (7)
H1	0.341810	0.352645	−0.090781	0.056*
C2	0.0195 (5)	0.1935 (3)	−0.1359 (2)	0.0482 (7)
H2A	0.039786	0.164612	−0.212720	0.058*
C3	−0.1905 (5)	0.1248 (3)	−0.0955 (2)	0.0470 (7)
H3	−0.315240	0.048043	−0.143784	0.056*
C4	−0.2127 (5)	0.1729 (3)	0.01988 (19)	0.0422 (6)
H4A	−0.354490	0.130957	0.049950	0.051*
C5	−0.0224 (4)	0.2831 (3)	0.08845 (18)	0.0341 (6)
C6	−0.0415 (4)	0.3380 (3)	0.21342 (19)	0.0380 (6)
C7	0.3606 (4)	0.6329 (3)	0.41794 (18)	0.0320 (6)
C8	0.5706 (4)	0.6949 (3)	0.35502 (19)	0.0410 (6)
H8A	0.518851	0.753902	0.289671	0.049*
H8B	0.643339	0.595005	0.327358	0.049*
C9	0.7488 (4)	0.8250 (3)	0.44387 (19)	0.0456 (7)
H9A	0.897665	0.779229	0.460945	0.055*
H9B	0.788117	0.940108	0.415897	0.055*
C10	0.6218 (4)	0.8415 (3)	0.5493 (2)	0.0401 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0498 (12)	0.0928 (15)	0.0417 (11)	−0.0198 (11)	0.0219 (10)	−0.0139 (10)
O2	0.0616 (13)	0.0639 (13)	0.0365 (10)	−0.0063 (10)	0.0007 (9)	−0.0121 (9)
N1	0.0406 (13)	0.0460 (13)	0.0325 (11)	0.0000 (10)	0.0127 (10)	0.0017 (9)
N2	0.0420 (13)	0.0517 (13)	0.0267 (11)	−0.0043 (10)	0.0146 (10)	−0.0063 (9)
N3	0.0419 (13)	0.0470 (13)	0.0267 (11)	0.0031 (11)	0.0104 (10)	−0.0025 (9)
N4	0.0370 (12)	0.0481 (12)	0.0249 (10)	0.0038 (10)	0.0097 (9)	−0.0022 (9)
C1	0.0459 (16)	0.0586 (17)	0.0343 (15)	−0.0001 (14)	0.0166 (13)	0.0024 (12)
C2	0.0614 (19)	0.0546 (17)	0.0277 (13)	0.0075 (15)	0.0103 (13)	0.0003 (12)
C3	0.0514 (17)	0.0502 (16)	0.0336 (14)	0.0000 (13)	0.0004 (13)	−0.0014 (12)
C4	0.0383 (15)	0.0499 (15)	0.0340 (14)	−0.0036 (12)	0.0080 (11)	−0.0005 (11)
C5	0.0362 (14)	0.0373 (14)	0.0274 (12)	0.0026 (11)	0.0070 (11)	0.0018 (10)
C6	0.0393 (15)	0.0387 (14)	0.0336 (14)	−0.0013 (12)	0.0106 (12)	0.0003 (11)
C7	0.0353 (14)	0.0339 (13)	0.0279 (12)	0.0081 (11)	0.0073 (11)	0.0021 (10)
C8	0.0437 (15)	0.0448 (15)	0.0342 (14)	0.0054 (12)	0.0123 (12)	−0.0001 (11)
C9	0.0374 (15)	0.0535 (16)	0.0424 (15)	0.0006 (13)	0.0081 (12)	−0.0014 (12)
C10	0.0407 (16)	0.0423 (15)	0.0354 (14)	0.0064 (13)	0.0019 (12)	0.0005 (12)

Geometric parameters (Å, º) top

O1—C6	1.226 (2)	C2—C3	1.366 (3)
O2—C10	1.216 (3)	C3—H3	0.9300
N1—C1	1.340 (3)	C3—C4	1.390 (3)
N1—C5	1.342 (3)	C4—H4A	0.9300
N2—H2	0.8600	C4—C5	1.368 (3)
N2—N3	1.396 (2)	C5—C6	1.504 (3)
N2—C6	1.322 (3)	C7—C8	1.498 (3)
N3—C7	1.276 (3)	C8—H8A	0.9700
N4—H4	0.8600	C8—H8B	0.9700
N4—C7	1.382 (3)	C8—C9	1.518 (3)
N4—C10	1.370 (3)	C9—H9A	0.9700
C1—H1	0.9300	C9—H9B	0.9700
C1—C2	1.376 (3)	C9—C10	1.500 (3)
C2—H2A	0.9300

C1—N1—C5	116.3 (2)	C4—C5—C6	120.1 (2)
N3—N2—H2	119.1	O1—C6—N2	124.8 (2)
C6—N2—H2	119.1	O1—C6—C5	121.7 (2)
C6—N2—N3	121.87 (19)	N2—C6—C5	113.48 (19)
C7—N3—N2	112.39 (18)	N3—C7—N4	121.6 (2)
C7—N4—H4	123.3	N3—C7—C8	130.20 (19)
C10—N4—H4	123.3	N4—C7—C8	108.2 (2)
C10—N4—C7	113.35 (19)	C7—C8—H8A	110.8
N1—C1—H1	118.2	C7—C8—H8B	110.8
N1—C1—C2	123.6 (2)	C7—C8—C9	104.83 (17)
C2—C1—H1	118.2	H8A—C8—H8B	108.9
C1—C2—H2A	120.4	C9—C8—H8A	110.8
C3—C2—C1	119.3 (2)	C9—C8—H8B	110.8
C3—C2—H2A	120.4	C8—C9—H9A	110.7
C2—C3—H3	120.9	C8—C9—H9B	110.7
C2—C3—C4	118.2 (2)	H9A—C9—H9B	108.8
C4—C3—H3	120.9	C10—C9—C8	105.28 (18)
C3—C4—H4A	120.5	C10—C9—H9A	110.7
C5—C4—C3	118.9 (2)	C10—C9—H9B	110.7
C5—C4—H4A	120.5	O2—C10—N4	125.0 (2)
N1—C5—C4	123.7 (2)	O2—C10—C9	126.9 (2)
N1—C5—C6	116.2 (2)	N4—C10—C9	108.08 (19)

N1—C1—C2—C3	0.8 (4)	C3—C4—C5—N1	1.5 (4)
N1—C5—C6—O1	177.6 (2)	C3—C4—C5—C6	179.7 (2)
N1—C5—C6—N2	−0.9 (3)	C4—C5—C6—O1	−0.8 (4)
N2—N3—C7—N4	179.33 (18)	C4—C5—C6—N2	−179.3 (2)
N2—N3—C7—C8	0.2 (3)	C5—N1—C1—C2	−0.8 (4)
N3—N2—C6—O1	−2.4 (4)	C6—N2—N3—C7	−174.0 (2)
N3—N2—C6—C5	176.01 (18)	C7—N4—C10—O2	176.4 (2)
N3—C7—C8—C9	−178.2 (2)	C7—N4—C10—C9	−3.8 (3)
N4—C7—C8—C9	2.6 (2)	C7—C8—C9—C10	−4.6 (2)
C1—N1—C5—C4	−0.3 (3)	C8—C9—C10—O2	−175.0 (2)
C1—N1—C5—C6	−178.6 (2)	C8—C9—C10—N4	5.2 (3)
C1—C2—C3—C4	0.4 (4)	C10—N4—C7—N3	−178.6 (2)
C2—C3—C4—C5	−1.5 (4)	C10—N4—C7—C8	0.7 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N4—H4···O1ⁱ	0.86	2.02	2.822 (2)	154

Symmetry code: (i) −x, −y+1, −z+1.

Acknowledgements

We are grateful to the Ministry of Education and Science of Ukraine for financial support. We thank Drs Oleksandr V. Vaschenko and Ilona V. Raspertova for fruitful discussion regrading some chemical concepts of this work, and Professor Rostyslav D. Lampeka for the general management of the present contribution. Funding for this research was provided by the Ministry of Education and Science of Ukraine and a grant for the perspective development of the scientific direction `Mathematical sciences and natural sciences' at Taras Shevchenko National University of Kyiv.

Funding information

Funding for this research was provided by: Ministry of Education and Science of Ukraine (award No. 25BF037-02).

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