Ethyl 2,6-bis­(4-chloro­phen­yl)-1-iso­cyano-4-oxo­cyclo­hexa­necarboxyl­ate

Dawei Zhang; Peng Yang; Wei Liu; Jing Li

doi:10.1107/S160053681401383X

. 2014 Jun 21;70(Pt 7):o802. doi: 10.1107/S160053681401383X

Ethyl 2,6-bis(4-chlorophenyl)-1-isocyano-4-oxocyclohexanecarboxylate

Dawei Zhang ^a, Peng Yang ^a, Wei Liu ^a, Jing Li ^b,^*

PMCID: PMC4120570 PMID: 25161583

Abstract

In the title compound, C₂₂H₁₉Cl₂NO₃, the central six-membered ring is in a twist-boat conformation. The two aryl groups are in equatorial positions, trans to each other and with a dihedral angle of 77.50 (2)° between them. One of the least hindered –CH₂– groups and one of the aryl-substituted C atoms, with its axial H atom, are in the flagpole positions. The ethoxycarbonyl group is in an equatorial position and is cis to the second aryl group. In the crystal, molecules are linked via weak C—H⋯O hydrogen bonds, forming chains along [010].

Keywords: crystal structure

Related literature

For the synthesis, see: Zhang et al. (2010 ▶); Tan et al. (2009 ▶). For related structures, see: Rowland & Gill (1988 ▶); Aleman et al. (2009 ▶); Wu et al. (2011 ▶); Li et al. (2011 ▶). For other [5 + 1] annulation reactions, see: Bi et al. (2005 ▶); Zhao et al. (2006 ▶); Fu et al. (2009 ▶); Xu et al. (2012 ▶). graphic file with name e-70-0o802-scheme1.jpg

Experimental

Crystal data

C₂₂H₁₉Cl₂NO₃
M _r = 416.28
Monoclinic,
a = 21.6980 (17) Å
b = 11.0770 (19) Å
c = 17.515 (3) Å
β = 104.535 (2)°
V = 4075.0 (10) Å³
Z = 8
Mo Kα radiation
μ = 0.34 mm⁻¹
T = 293 K
0.21 × 0.19 × 0.15 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.932, T _max = 0.951
9983 measured reflections
3602 independent reflections
2584 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.117
S = 1.01
3602 reflections
253 parameters
H-atom parameters constrained
Δρ_max = 0.37 e Å⁻³
Δρ_min = −0.35 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S160053681401383X/lr2127sup1.cif

e-70-0o802-sup1.cif^{(21.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681401383X/lr2127Isup2.hkl

e-70-0o802-Isup2.hkl^{(173.1KB, hkl)}

Click here for additional data file.^{(7.1KB, cml)}

Supporting information file. DOI: 10.1107/S160053681401383X/lr2127Isup3.cml

CCDC reference: 1008201

Additional supporting information: crystallographic information; 3D view; checkCIF report

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C11—H11⋯O1ⁱ	0.98	2.57	3.218 (3)	123

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Symmetry code: (i) Inline graphic .

Acknowledgments

Financial support of this research by the Science and Technology Development Program Foundation of Jilin Province (No. 20140204022NY) and the Interdisciplinary Innovation Fund of Jilin University (No. 450060481143) is gratefully acknowledged.

supplementary crystallographic information

S1. Introduction

S2. Experimental

S2.1. Synthesis and crystallization

To the mixture of 1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (303 mg, 1.0 mmol) and ethyl isocyanoacetate (0.132 mL, 1.2 mmol) in DMF (5 mL) was added 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) (0.015 mL, 0.1 mmol) in one portion at room temperature. The reaction mixture was stirred at room temperature, and the reaction mixture was monitored by TLC. After the substrate 1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one was consumed, the resulting mixture was poured into ice-water (30 mL) under stirring. The precipitated solid was collected by filtration, washed with water (3 × 10 mL), and dried under vacuum to afford the crude product, which was purified by flash chromatography (silica gel, petroleum ether : diethyl ether = 3:1, V/V) to give ethyl 2,6-bis(4-chlorophenyl)-1-isocyano-4-oxocyclohexanecarboxylate (387 mg, 93%). The material was recrystallized from a mixture of petroleum ether and diethyl ether to provide a crystalline solid.

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.Hydrogen atoms were generated in idealized positions (according to the sp2 or sp3 geometries of their parent carbon), and then refined using a riding model with fixed C—H distances (C—H = 0.95–1.00 Å) and with Uiso(H) = 1.2Ueq(C).

S3. Results and discussion

[5+1] annulation is a novel strategy for the construction of six-membered cyclic compounds and total synthesis of natural products (Rowland & Gill, 1988; Wu et al., 2011; Li et al., 2011). The regiospecific [5+1] annulation reactions have drawn much attentions and both the five-carbon 1,5-bielectrophiles and the one-atom nucleophiles been explored extensively (Bi et al., 2005; Zhao et al., 2006; Fu et al., 2009; Xu et al., 2012). We have been dealing with functionalized ketene dithioacetals for several years and have succeeded in the preparation of six-membered aromatic and heterocyclic compounds based on [5C+1X] annulations (Zhang et al., 2010; Tan et al., 2009). The aromatic cyclic compounds are analogues of phenylalanine (Phe) which are potential moieties for the synthesis of peptide analogues with controlled fold in the backbone. The constrained ring systems play important roles in restricting torsional angle χ1 and in peptide receptor recognition processes (Aleman et al., 2009).

The crystal structure of title compound, a phenyl substituted highly constrained cyclohexane analogue of Ph, is reported in this paper. Due to the steric hindrance, the oxocyclohexane is in a twist-boat conformation (Fig. 1). The ethoxyl carbonyl and the two aryl groups are located in equatorial positions. The dihedral angle between two aromatic rings is 77.495 (20)°. The C7 axial hydrogen and the CH₂ bonded to C10 are on the flagpole positions of the boat conformation, which give the least torsional strain. The equatorial ethoxyl carbonyl on C18 and the equatorial aryl group on C11 also lead the formation of a comparable stable boat conformation of this compound.