2-[(2Z)-Azepan-2-yl­idene]-1-(4-nitro­phen­yl)ethanone

Siyanda T Mthembu; Lee G Madeley; Charles B de Koning; Joseph P Michael

doi:10.1107/S1600536812032035

. 2012 Jul 18;68(Pt 8):o2479. doi: 10.1107/S1600536812032035

2-[(2Z)-Azepan-2-ylidene]-1-(4-nitrophenyl)ethanone

Siyanda T Mthembu ^a, Lee G Madeley ^a, Charles B de Koning ^a, Joseph P Michael ^a,^*

PMCID: PMC3414934 PMID: 22904921

Abstract

The title compound, C₁₄H₁₆N₂O₃, is an NH-vinylogous amide (enaminone) produced by the reaction of 4-nitrophenacyl bromide with azepane-2-thione. The conformation about the C=C bond [1.3927 (14) Å] is Z, which allows for the formation of an intramolecular N—H⋯O hydrogen bond that leads to an S(6) loop. Inversion-related molecules associate via N—H⋯O hydrogen bonds to form a 12-membered {⋯OC₃NH}₂ synthon.

Related literature

For uses and reactions of enaminones, see: Roth et al. (1971 ▶); Paulvannan & Stille (1994 ▶); Michael et al. (1999 ▶). For related structures, see: Balderson et al. (2007 ▶). For graph-set notation, see: Bernstein et al. (1995 ▶).

Experimental

Crystal data

C₁₄H₁₆N₂O₃
M _r = 260.29
Triclinic,
a = 6.7963 (3) Å
b = 8.4054 (3) Å
c = 11.6649 (5) Å
α = 76.508 (2)°
β = 81.134 (2)°
γ = 80.596 (2)°
V = 634.58 (5) Å³
Z = 2
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 173 K
0.56 × 0.5 × 0.42 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.905, T _max = 0.955
10354 measured reflections
3041 independent reflections
2732 reflections with I > 2σ(I)
R _int = 0.048

Refinement

R[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 0.116
S = 1.06
3041 reflections
177 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.30 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT-Plus (Bruker, 2004 ▶); data reduction: SAINT-Plus and XPREP (Bruker 2004 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶) and DIAMOND (Brandenburg, 1999 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶) and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812032035/tk5129sup1.cif

e-68-o2479-sup1.cif^{(21.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812032035/tk5129Isup2.hkl

e-68-o2479-Isup2.hkl^{(146.2KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812032035/tk5129Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O1	0.897 (16)	1.998 (15)	2.7041 (11)	134.6 (13)
N1—H1⋯O1ⁱ	0.897 (16)	2.392 (15)	3.0303 (12)	128.2 (12)

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Symmetry code: (i) Inline graphic .

Acknowledgments

This work was supported by the University of the Witwatersrand, which is thanked for providing the required infrastructure.

supplementary crystallographic information

Comment

The title compound was prepared as part of an ongoing methodological investigation into the use of enaminones in the synthesis of azabicyclic alkaloids (Michael et al., 1999). For example, its reaction with acryloyl chloride, according to the method of Paulvannan & Stille (1994), produced a 2,3,6,7-tetrahydro-5(1H)-indolizinone related to numerous natural products. The crystal structures of analogous 4-bromophenyl enaminones with 5-, 6- and 7-membered rings have been reported (Balderson et al., 2007).

The asymmetric unit of (I) consists of one molecule of 2-[(2Z)-azepan-2-ylidene]-1-(4-nitrophenyl)ethan-1-one (Fig. 1). The hydrogen bonding consists of an intramolecular N—H···O═C hydrogen bond, and an intermolecular N—H···O═C hydrogen bond (Table 1). The combination of these two hydrogen bonds results in an R²₂(4) ring (Fig. 2) as described by graph set notation (Bernstein et al., 1995).

Experimental

The employed synthesis followed the Eschenmoser procedure (Roth et al., 1971). p-Nitrophenacyl bromide (995 mg, 4.08 mmol) was added to a solution of azepane-2-thione (502 mg, 3.88 mmol) in dry acetonitrile (30 ml). The resulting solution was stirred at room temperature for 4 h, after which S-alkylation was complete as shown by the precipitation of the thioiminium salt. This was then followed by the addition of triphenylphosphine (1.069 g, 4.08 mmol) and triethylamine (413 mg, 4.08 mmol) to induce sulfur extrusion. The reaction mixture was poured into water and the organic components were extracted with diethyl ether (3 × 30 ml). The resulting organic layer was dried over MgSO₄, filtered and the solvent removed in vacuo. The resulting residue was purified by column chromatography on silica gel with hexane:ethyl acetate (19:1 v/v) as eluent to yield 2-[(2Z)-azepan-2-ylidene]-1-(4-nitrophenyl)ethan-1-one (829 mg, 82%) as yellow crystals, m.p. 398–400 K.