Synthesis and structure of (Z)-2-(eth­oxy­methyl­idene)-8-methyl-2,3,4,9-tetra­hydro-1H-carbazol-1-one

Sridharan, M.; Thiruvalluvar, A.A.

doi:10.1107/S2056989026005049

research communications

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ISSN: 2056-9890

Volume 82| Part 6| June 2026| Pages 670-673

https://doi.org/10.1107/S2056989026005049

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Synthesis and structure of (Z)-2-(ethoxymethylidene)-8-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one

Makuteswaran Sridharan ^a ^* and Aravazhi Amalan Thiruvalluvar ^b ^*

^aDepartment of Chemistry, RV College of Engineering, Bangalore 560 059, Karnataka, India, and ^bPrincipal (Retired), 63 Shanthi Nagar, 5th Street, Nanjikottai Road, Thanjavur 613 006, Tamilnadu, India
^*Correspondence e-mail: [email protected], [email protected]

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 20 April 2026; accepted 12 May 2026; online 15 May 2026)

In the title compound, C₁₆H₁₇NO₂, the cyclohexene ring adopts an envelope conformation and the side chain is extended. In the extended structure, N—H⋯O hydrogen bonds connect the molecules into [100] chains and weak C—H⋯O interactions and pairwise C—H⋯π interactions consolidate the packing. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (57.6%), C⋯H/H⋯C (24.2%), and H⋯O/ O⋯H (13.8%) contacts. Evaluation of the electrostatic, dispersion and total energy frameworks indicates that the cohesion of the crystal largely depends on dispersion energy contributions.

Keywords: crystal structure; carbazol-1-one; Hirshfeld surface; energy framework analysis.

CCDC reference: 1540675

1. Chemical context

Carbazole derivatives represent a class of heteroaromatic compounds that continue to inspire extensive investigation in both organic synthesis and medicinal chemistry (Knölker & Reddy, 2002 ). Substitution at different positions of the carbazole ring system has yielded derivatives with enhanced reactivity and diverse biological properties, underscoring the versatility of this structural motif.

Within this context, 2,3,4,9-tetrahydrocarbazol-1-ones have proven to be valuable precursors, offering a convenient entry point to more elaborate heterocycles. Of particular interest is 2-(ethoxymethylene)-2,3,4,9-tetrahydrocarbazol-1-one, which has been reported as a versatile intermediate in heterocyclic synthesis (Sridharan & Thiruvalluar, 2026 ). The ethoxymethylene substituent (Dasgupta & Ghatak, 1985 ) at the 2-position introduces an electrophilic site amenable to condensation and cyclization, while the carbonyl group at the 1-position enhances synthetic flexibility. This dual functionality renders the compound an effective building block for the construction of complex heterocycles with potential pharmaceutical relevance.

As part of our studies in this area, we now describe the synthesis and structure of the title compound, C₁₆H₁₇NO₂ (I).

2. Structural commentary

As shown in Fig. 1, compound (I), which crystallizes in the orthorhombic space group Pbca with one molecule in the asymmetric unit, consists of indole and cyclohexene units fused via the C7—C12 bond. As expected, the pyrrole (N1/C1/C6/C7/C12) and benzene (C1–C6) rings are nearly co-planar, subtending a dihedral angle of 1.38 (6)°. A puckering analysis (Cremer & Pople, 1975 ) of the C7–C12 ring gave the parameters: q₂ = 0.3271 (13) Å, q₃ = −0.1784 (13) Å, Q_T = 0.3726 (13) Å, θ = 118.6 (2)° and φ = 280.9 (2)°, which corresponds to an envelope conformation, where atom C9 is at the flap position and displaced by −0.497 (2) Å from the best plane of the remaining tricyclic carbazole non-H atoms. The C7—C8—C9—C10 torsion angle is −42.40 (15)°. The ethoxymethylene side chain adopts an extended conformation, as indicated by the C10—C14—O1—C15 and C14—O1—C15—C16 torsion angles of 176.41 (11) and 174.05 (13)°, respectively.

Figure 1
The molecular structure of (I), showing displacement ellipsoids drawn at the 50% probability level.

3. Supramolecular features

In the extended structure, strong N1—H1⋯O2 hydrogen bonds (Table 1) form C(7) chains of molecules propagating parallel to the a-axis direction as shown in Fig. 2. Weak C14—H14⋯O2 links generate double chains. The molecules are further linked by pairwise C13—H13B⋯Cg2 (where Cg2 is the centroid of the C1–C6 benzene ring) interactions that connect parallel chains with each other (Fig. 3). No significant π–π stacking interactions are observed in this structure.

Table 1
Hydrogen-bond geometry (Å, °)

Cg2 is the centroid of the benzene (C1–C6) ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O2ⁱ	0.919 (17)	2.034 (17)	2.9235 (14)	162.2 (15)
C14—H14⋯O2ⁱⁱ	0.95	2.52	3.2396 (15)	133
C13—H13B⋯Cg2ⁱⁱⁱ	0.98	2.76	3.5669 (15)	140
Symmetry codes: (i) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]$ ; (ii) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]$ ; (iii) .

Figure 2
Partial packing view of (I), viewed down the a-axis direction, showing the hydrogen bonds. Black dashed lines represent C—H⋯O and N—H⋯O hydrogen bonds.

Figure 3
Straw-style packing view of (I), showing the C—H⋯π contacts. Centroids are shown as green spheres and black dashed lines are H⋯π contacts.

4. Database survey

A search of the Cambridge Structural Database (CSD, Version 6.01, updated to February 2026; Groom et al., 2016 ) using the core structure of (I) gave zero hits.

5. Hirshfeld surface

A Hirshfeld surface (HS) analysis was carried out using CrystalExplorer version 21.5 (Spackman et al., 2021 ) to further quantify the intermolecular interactions in the crystal of (I). The HS plotted over d_norm is shown in Fig. 4, where the bright-red spots correspond to donor and/or acceptor sites. According to the two-dimensional fingerprint plots (Fig. 5), C⋯H/H⋯C, H⋯O/O⋯H and H⋯H contacts make the most important contributions to the HS, with values of 24.2%, 13.8%, and 57.6% respectively. All other contact types, including C⋯N/N⋯C, C⋯O/O⋯C, H⋯N/N⋯H, N⋯O/O⋯N, and C⋯C contribute less than 2.0% each to the total.

Figure 4
View of the three-dimensional Hirshfeld surface of (I), plotted over d_norm in the range from −0.51 to 1.22 a.u. with a neighbouring molecule.

Figure 5
Two-dimensional fingerprint plots for (I), showing (a) all interactions, and those showing (b) C⋯H/H⋯C, (c) H⋯O/O⋯H, and (d) H⋯H interactions. The d_i and d_e values are the closest internal and external distances (in Å) from given points on the Hirshfeld surface.

6. Interaction energy calculations and energy frameworks

The CE-B3LYP/6-31G(d,p) energy model available in CrystalExplorer was used to calculate the intermolecular interaction energies. Hydrogen-bonding interaction energies (in kJ mol⁻¹) were calculated to be −41.4 (E_ele), −13.9 (E_pol), −23.1 (E_dis), 45.3 (E_rep) and −46.3 (E_tot) for the collective hydrogen bonds N1—H1⋯O2 and C14—H14⋯O2. Values of −9.4 (E_ele), −1.8 (E_pol), −38.8 (E_dis), 21.6 (E_rep) and −31.7 (E_tot) arose for the C13—H13B⋯π interaction. Energy frameworks (Turner et al., 2015 ) were constructed for E_ele (red cylinders), E_dis (green cylinders) and E_tot (blue cylinders) [Fig. 6(a)–(c)], and their evaluation indicates that crystal cohesion largely depends on dispersion energy contributions in the crystal structure of (I).

Figure 6
The energy frameworks for a cluster of molecules of (I) viewed down the a-axis direction, showing (a) electrostatic energy E_ele, (b) dispersion energy E_dis and (c) total energy E_tot diagrams. The cylindrical radius is proportional to the relative strength of the corresponding energies and they were adjusted to the same scale factor of 80 with a cut-off value of 5 kJ mol⁻¹ within 2 × 2 × 2 unit cells.

7. Synthesis and crystallization

8-Methyl-2,3,4,9-tetrahydrocarbazol-1-one (1) (1.00 g, 0.005 mol) in dichloromethane (15 ml) was added to an ice-cooled solution of diethoxycarbenium fluoroborate [prepared in situ from 1.65 ml of BF₃·Et₂O (0.01 mol) and 1.25 ml of HC(OEt₃) (0.01 mol)]. The reaction mixture (Fig. 7) was kept at 258 to 263 K. To this mixture, triethylamine (0.01 mol) was added dropwise and the stirring was continued over a period of five h. The reaction was monitored by TLC. After the completion of reaction, the excess solvent was removed and extracted using ethyl acetate dried over anhydrous sodium sulfate. The brown solid separated out was then separated by column chromatography over silica gel using petroleum ether: ethyl acetate as eluants (99:1) and (95:5) to yield (Z)-8-methyl-2,3,4,9-tetrahydro-2 (8′-methyl-2′,3′,4′,9′-tetrahydrocarbazol-1-ylidene)-carbazol 1-one (2) and (Z)-2-(ethoxymethylene)-8-methyl-2,3,4,9 tetrahydro-1H-carbazol-1-one (3), respectively. The chemical structure of the final products was confirmed by NMR spectroscopy and elementary analysis data. Compound (3) was recrystallized from ethanol solution as yellow prisms (0.842 g, 66%), m.p. 377–379 K. The reaction scheme is shown in Fig. 7.

Figure 7
The synthesis scheme for (I).

8. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The N-bound H atom was located in a difference-Fourier map and its position was freely refined with U_iso(H) = 1.2U_eq(N). All the other H atoms were placed in calculated positions and refined as riding atoms with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(methyl C). The methyl group was allowed to rotate, but not to tip, to best fit the experimental electron density.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₆H₁₇NO₂
M_r	255.30
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	100
a, b, c (Å)	6.9872 (5), 18.3913 (13), 20.3450 (15)
V (Å³)	2614.4 (3)
Z	8
Radiation type	Mo Kα
μ (mm⁻¹)	0.09
Crystal size (mm)	0.68 × 0.46 × 0.43

Data collection
Diffractometer	Bruker AXS SMART APEX CCD
Absorption correction	Multi-scan (SADABS2004; Krause et al., 2015 )
T_min, T_max	0.885, 0.964
No. of measured, independent and observed [I > 2σ(I)] reflections	18986, 3238, 2854
R_int	0.029
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.046, 0.124, 1.04
No. of reflections	3238
No. of parameters	177
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.35, −0.31
Computer programs: SMART (Bruker, 2002 ), SAINT-Plus (Bruker, 2003 ), SHELXS (Sheldrick, 2008 ), SHELXL2025/1 (Sheldrick, 2015 ), ORTEP-3 for Windows (Farrugia, 2012 ), PLATON (Spek, 2020 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1540675

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989026005049/hb8217sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026005049/hb8217Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989026005049/hb8217Isup3.cdx

Supporting information file. DOI: https://doi.org/10.1107/S2056989026005049/hb8217Isup4.cml

checkCIF report

Computing details top

(Z)-2-(Ethoxymethylidene)-8-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one top

Crystal data top

C₁₆H₁₇NO₂	D_x = 1.297 Mg m⁻³
M_r = 255.30	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 6074 reflections
a = 6.9872 (5) Å	θ = 2.4–30.4°
b = 18.3913 (13) Å	µ = 0.09 mm⁻¹
c = 20.3450 (15) Å	T = 100 K
V = 2614.4 (3) Å³	Block, yellow
Z = 8	0.68 × 0.46 × 0.43 mm
F(000) = 1088

Data collection top

Bruker AXS SMART APEX CCD diffractometer	3238 independent reflections
Radiation source: fine-focus sealed tube	2854 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.029
ω scans	θ_max = 28.3°, θ_min = 2.2°
Absorption correction: multi-scan (SADABS2004; Krause et al., 2015)	h = −9→9
T_min = 0.885, T_max = 0.964	k = −23→24
18986 measured reflections	l = −23→27

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.046	Hydrogen site location: mixed
wR(F²) = 0.124	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ²(F_o²) + (0.0659P)² + 1.1726P] where P = (F_o² + 2F_c²)/3
3238 reflections	(Δ/σ)_max < 0.001
177 parameters	Δρ_max = 0.35 e Å⁻³
0 restraints	Δρ_min = −0.31 e Å⁻³

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.

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

	x	y	z	U_iso*/U_eq
C1	0.98167 (17)	0.08476 (6)	0.42264 (6)	0.0194 (2)
C2	1.14974 (18)	0.05163 (7)	0.44576 (6)	0.0225 (3)
C3	1.20971 (19)	−0.00928 (7)	0.41145 (7)	0.0264 (3)
H3	1.321352	−0.034028	0.425941	0.032*
C4	1.11146 (19)	−0.03616 (7)	0.35569 (6)	0.0264 (3)
H4	1.159354	−0.077761	0.333422	0.032*
C5	0.94764 (18)	−0.00293 (6)	0.33325 (6)	0.0229 (3)
H5	0.882376	−0.020940	0.295664	0.027*
C6	0.87898 (17)	0.05835 (6)	0.36728 (6)	0.0198 (2)
C7	0.71601 (17)	0.10427 (6)	0.35948 (6)	0.0197 (2)
C8	0.55199 (18)	0.10052 (7)	0.31249 (6)	0.0235 (3)
H8A	0.457131	0.064632	0.328424	0.028*
H8B	0.598480	0.084221	0.268949	0.028*
C9	0.45628 (18)	0.17532 (7)	0.30579 (6)	0.0258 (3)
H9A	0.534229	0.205797	0.275922	0.031*
H9B	0.328899	0.168899	0.285286	0.031*
C10	0.43179 (17)	0.21508 (7)	0.37046 (6)	0.0215 (3)
C11	0.57990 (17)	0.20979 (7)	0.42188 (6)	0.0201 (2)
C12	0.72546 (16)	0.15533 (6)	0.40907 (6)	0.0198 (2)
C13	1.2535 (2)	0.08035 (7)	0.50504 (7)	0.0276 (3)
H13A	1.369795	0.051699	0.512380	0.041*
H13B	1.170246	0.076726	0.543665	0.041*
H13C	1.288073	0.131352	0.497714	0.041*
C14	0.28156 (17)	0.25820 (7)	0.38372 (6)	0.0222 (3)
H14	0.273853	0.280696	0.425672	0.027*
C15	−0.01415 (17)	0.31500 (7)	0.36423 (7)	0.0251 (3)
H15A	0.036691	0.360927	0.382643	0.030*
H15B	−0.082869	0.288797	0.399579	0.030*
C16	−0.1470 (3)	0.33099 (11)	0.30927 (8)	0.0480 (5)
H16A	−0.081211	0.360702	0.276282	0.072*
H16B	−0.258376	0.357541	0.326052	0.072*
H16C	−0.189264	0.285313	0.289162	0.072*
N1	0.88530 (14)	0.14364 (6)	0.44784 (5)	0.0202 (2)
O1	0.14156 (13)	0.27071 (5)	0.33973 (4)	0.0259 (2)
O2	0.58335 (13)	0.24760 (5)	0.47242 (4)	0.0253 (2)
H1	0.929 (2)	0.1750 (9)	0.4797 (8)	0.030*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0206 (5)	0.0199 (5)	0.0178 (5)	−0.0011 (4)	0.0012 (4)	0.0003 (4)
C2	0.0223 (6)	0.0235 (6)	0.0216 (6)	0.0001 (4)	−0.0012 (5)	0.0012 (5)
C3	0.0254 (6)	0.0258 (6)	0.0278 (6)	0.0049 (5)	−0.0019 (5)	−0.0001 (5)
C4	0.0314 (7)	0.0223 (6)	0.0254 (6)	0.0038 (5)	0.0011 (5)	−0.0024 (5)
C5	0.0289 (6)	0.0201 (6)	0.0196 (6)	−0.0011 (5)	−0.0001 (5)	−0.0008 (4)
C6	0.0207 (5)	0.0204 (5)	0.0181 (5)	−0.0021 (4)	0.0004 (4)	0.0017 (4)
C7	0.0200 (5)	0.0214 (5)	0.0178 (5)	−0.0016 (4)	0.0004 (4)	0.0004 (4)
C8	0.0221 (6)	0.0281 (6)	0.0202 (6)	0.0002 (5)	−0.0034 (5)	−0.0041 (5)
C9	0.0241 (6)	0.0340 (7)	0.0192 (6)	0.0062 (5)	−0.0035 (5)	−0.0039 (5)
C10	0.0194 (5)	0.0267 (6)	0.0184 (5)	−0.0006 (4)	−0.0009 (4)	−0.0007 (4)
C11	0.0179 (5)	0.0231 (6)	0.0192 (5)	−0.0020 (4)	0.0013 (4)	−0.0006 (4)
C12	0.0182 (5)	0.0229 (6)	0.0184 (5)	−0.0014 (4)	−0.0012 (4)	0.0003 (4)
C13	0.0254 (6)	0.0305 (6)	0.0269 (6)	0.0028 (5)	−0.0066 (5)	−0.0022 (5)
C14	0.0201 (6)	0.0280 (6)	0.0185 (5)	−0.0006 (5)	−0.0004 (4)	−0.0006 (4)
C15	0.0196 (6)	0.0263 (6)	0.0293 (7)	0.0030 (5)	0.0029 (5)	−0.0009 (5)
C16	0.0433 (9)	0.0655 (11)	0.0353 (8)	0.0311 (8)	−0.0068 (7)	−0.0040 (8)
N1	0.0193 (5)	0.0219 (5)	0.0195 (5)	0.0009 (4)	−0.0025 (4)	−0.0026 (4)
O1	0.0207 (4)	0.0350 (5)	0.0221 (4)	0.0076 (4)	−0.0023 (3)	−0.0034 (4)
O2	0.0229 (4)	0.0302 (5)	0.0227 (4)	0.0031 (4)	−0.0023 (3)	−0.0075 (4)

Geometric parameters (Å, º) top

C1—N1	1.3744 (15)	C9—H9B	0.9900
C1—C2	1.4041 (17)	C10—C14	1.3430 (17)
C1—C6	1.4211 (16)	C10—C11	1.4747 (17)
C2—C3	1.3848 (18)	C11—O2	1.2416 (15)
C2—C13	1.5030 (17)	C11—C12	1.4510 (16)
C3—C4	1.4152 (18)	C12—N1	1.3841 (15)
C3—H3	0.9500	C13—H13A	0.9800
C4—C5	1.3755 (18)	C13—H13B	0.9800
C4—H4	0.9500	C13—H13C	0.9800
C5—C6	1.4069 (17)	C14—O1	1.3457 (15)
C5—H5	0.9500	C14—H14	0.9500
C6—C7	1.4266 (16)	C15—O1	1.4476 (15)
C7—C12	1.3799 (16)	C15—C16	1.483 (2)
C7—C8	1.4940 (16)	C15—H15A	0.9900
C8—C9	1.5356 (18)	C15—H15B	0.9900
C8—H8A	0.9900	C16—H16A	0.9800
C8—H8B	0.9900	C16—H16B	0.9800
C9—C10	1.5150 (17)	C16—H16C	0.9800
C9—H9A	0.9900	N1—H1	0.919 (17)

N1—C1—C2	128.81 (11)	C14—C10—C9	123.21 (11)
N1—C1—C6	108.52 (10)	C11—C10—C9	120.33 (11)
C2—C1—C6	122.65 (11)	O2—C11—C12	121.45 (11)
C3—C2—C1	115.81 (11)	O2—C11—C10	124.35 (11)
C3—C2—C13	122.87 (11)	C12—C11—C10	114.20 (10)
C1—C2—C13	121.31 (11)	C7—C12—N1	110.46 (10)
C2—C3—C4	122.67 (12)	C7—C12—C11	124.58 (11)
C2—C3—H3	118.7	N1—C12—C11	124.78 (11)
C4—C3—H3	118.7	C2—C13—H13A	109.5
C5—C4—C3	120.96 (12)	C2—C13—H13B	109.5
C5—C4—H4	119.5	H13A—C13—H13B	109.5
C3—C4—H4	119.5	C2—C13—H13C	109.5
C4—C5—C6	118.45 (12)	H13A—C13—H13C	109.5
C4—C5—H5	120.8	H13B—C13—H13C	109.5
C6—C5—H5	120.8	C10—C14—O1	122.38 (11)
C5—C6—C1	119.45 (11)	C10—C14—H14	118.8
C5—C6—C7	133.76 (11)	O1—C14—H14	118.8
C1—C6—C7	106.79 (10)	O1—C15—C16	108.82 (11)
C12—C7—C6	106.46 (10)	O1—C15—H15A	109.9
C12—C7—C8	122.41 (11)	C16—C15—H15A	109.9
C6—C7—C8	131.01 (11)	O1—C15—H15B	109.9
C7—C8—C9	110.46 (10)	C16—C15—H15B	109.9
C7—C8—H8A	109.6	H15A—C15—H15B	108.3
C9—C8—H8A	109.6	C15—C16—H16A	109.5
C7—C8—H8B	109.6	C15—C16—H16B	109.5
C9—C8—H8B	109.6	H16A—C16—H16B	109.5
H8A—C8—H8B	108.1	C15—C16—H16C	109.5
C10—C9—C8	113.86 (10)	H16A—C16—H16C	109.5
C10—C9—H9A	108.8	H16B—C16—H16C	109.5
C8—C9—H9A	108.8	C1—N1—C12	107.77 (10)
C10—C9—H9B	108.8	C1—N1—H1	126.4 (10)
C8—C9—H9B	108.8	C12—N1—H1	124.9 (10)
H9A—C9—H9B	107.7	C14—O1—C15	114.43 (10)
C14—C10—C11	116.42 (11)

N1—C1—C2—C3	177.44 (12)	C8—C9—C10—C11	36.83 (16)
C6—C1—C2—C3	−0.47 (18)	C14—C10—C11—O2	−7.56 (19)
N1—C1—C2—C13	−1.2 (2)	C9—C10—C11—O2	170.33 (12)
C6—C1—C2—C13	−179.16 (11)	C14—C10—C11—C12	172.13 (11)
C1—C2—C3—C4	1.28 (19)	C9—C10—C11—C12	−9.99 (16)
C13—C2—C3—C4	179.95 (13)	C6—C7—C12—N1	−0.32 (13)
C2—C3—C4—C5	−0.9 (2)	C8—C7—C12—N1	176.05 (11)
C3—C4—C5—C6	−0.35 (19)	C6—C7—C12—C11	−175.65 (11)
C4—C5—C6—C1	1.11 (17)	C8—C7—C12—C11	0.72 (19)
C4—C5—C6—C7	−178.20 (13)	O2—C11—C12—C7	169.91 (12)
N1—C1—C6—C5	−179.00 (10)	C10—C11—C12—C7	−9.78 (17)
C2—C1—C6—C5	−0.72 (18)	O2—C11—C12—N1	−4.76 (19)
N1—C1—C6—C7	0.48 (13)	C10—C11—C12—N1	175.55 (11)
C2—C1—C6—C7	178.76 (11)	C11—C10—C14—O1	176.51 (11)
C5—C6—C7—C12	179.28 (13)	C9—C10—C14—O1	−1.3 (2)
C1—C6—C7—C12	−0.09 (13)	C2—C1—N1—C12	−178.82 (12)
C5—C6—C7—C8	3.3 (2)	C6—C1—N1—C12	−0.68 (13)
C1—C6—C7—C8	−176.04 (12)	C7—C12—N1—C1	0.63 (13)
C12—C7—C8—C9	25.96 (16)	C11—C12—N1—C1	175.94 (11)
C6—C7—C8—C9	−158.65 (12)	C10—C14—O1—C15	176.41 (11)
C7—C8—C9—C10	−42.40 (15)	C16—C15—O1—C14	174.05 (13)
C8—C9—C10—C14	−145.43 (12)

Hydrogen-bond geometry (Å, º) top

Cg2 is the centroid of the benzene (C1–C6) ring.

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2ⁱ	0.919 (17)	2.034 (17)	2.9235 (14)	162.2 (15)
C14—H14···O2ⁱⁱ	0.95	2.52	3.2396 (15)	133
C13—H13B···Cg2ⁱⁱⁱ	0.98	2.76	3.5669 (15)	140

Symmetry codes: (i) x+1/2, −y+1/2, −z+1; (ii) x−1/2, −y+1/2, −z+1; (iii) −x+2, −y, −z+1.

Acknowledgements

Authors contributions are as follows: conceptualization, synthesis, methodology and writing original draft, MS; crystallographic analysis, Hirshfeld surface analysis, software, validation, review and editing, AAT. AAT acknowledge the Cambridge Crystallographic Data Centre (CCDC) for providing access to the Cambridge Structural Database (CSD, version 6.01). Database searches were performed using CONQUEST, and structural analyses were carried out using Mercury. MS thanks academic and administrative authorities of RV College of Engineering for their support and encouragement. The authors thank Dr Matthias Zeller for the X-ray data collection. The X-ray diffractometer was funded by NSF Grant CHE 0087210, Ohio Board of Regents Grant CAP-491, and by Youngstown State University.

References

Bruker (2002). SMART. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2003). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358. CrossRef CAS Web of Science Google Scholar
Dasgupta, R. & Ranjan Ghatak, U. (1985). Tetrahedron Lett. 26, 1581–1584. CrossRef CAS Web of Science Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CrossRef IUCr Journals Google Scholar
Knölker, H.-J. & Reddy, K. R. (2002). Chem. Rev. 102, 4303–4427. Web of Science PubMed Google Scholar
Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3–10. Web of Science CSD CrossRef ICSD CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Spackman, P. R., Turner, M. J., McKinnon, J. J., Wolff, S. K., Grimwood, D. J., Jayatilaka, D. & Spackman, M. A. (2021). J. Appl. Cryst. 54, 1006–1011. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2020). Acta Cryst. E76, 1–11. Web of Science CrossRef IUCr Journals Google Scholar
Sridharan, M. & Thiruvalluvar, A. A. (2026). Acta Cryst. E82, 450–453. CrossRef IUCr Journals Google Scholar
Turner, M. J., Thomas, S. P., Shi, M. W., Jayatilaka, D. & Spackman, M. A. (2015). Chem. Commun. 51, 3735–3738. Web of Science CrossRef CAS Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar

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research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Synthesis and structure of (Z)-2-(eth­­oxy­methyl­­idene)-8-methyl-2,3,4,9-tetra­hydro-1H-carbazol-1-one

1. Chemical context

2. Structural commentary

3. Supra­molecular features

4. Database survey

5. Hirshfeld surface

6. Inter­action energy calculations and energy frameworks

7. Synthesis and crystallization

8. Refinement

Supporting information

Acknowledgements

References

research communications

Synthesis and structure of (Z)-2-(ethoxymethylidene)-8-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one

3. Supramolecular features

6. Interaction energy calculations and energy frameworks