4,12-Bis(2,2-dibromo­vinyl)[2.2]paracyclo­phane

Sébastien Clément; Laurent Guyard; Michael Knorr; Christian Däschlein; Carsten Strohmann

doi:10.1107/S1600536809002475

. 2009 Feb 13;65(Pt 3):o528. doi: 10.1107/S1600536809002475

4,12-Bis(2,2-dibromovinyl)[2.2]paracyclophane

Sébastien Clément ^a, Laurent Guyard ^a, Michael Knorr ^a, Christian Däschlein ^b, Carsten Strohmann ^b,^*

PMCID: PMC2968423 PMID: 21582189

Abstract

In the title compound, C₂₀H₁₆Br₄, both vinylic substituents were introduced by a Corey–Fuchs reaction using 4,12-diformyl[2.2]paracyclophane as starting material. The title compound may be used as a valuable precursor for the synthesis of diethynyl[2.2]paracyclophane. The title molecule is centrosymmetric with a crystallographic center of inversion between the centers of the two phenyl rings. A strong tilting is observed with an interplanar angle between the best aromatic plane and the vinyl plane of 49.4 (5)°. No significant intermolecular interactions are found in the crystal.

Related literature

For related structures of halovinyl compounds, see: Clément et al. (2007a ▶,b ▶); Jones et al. (1993 ▶); Hua et al. (2006 ▶). For ethynyl-functionalized[2.2]paracyclophanes, see: Jones et al. (2007 ▶). For the Corey–Fuchs reaction, see: Corey et al. (1972 ▶). For applications of [2.2]paracyclophanes, see: Hopf et al. (2008 ▶). For an alternative to the classical Sonogashira synthesis, see: Morisaki et al. (2003 ▶).

Experimental

Crystal data

C₂₀H₁₆Br₄
M _r = 575.97
Orthorhombic,
a = 12.155 (1) Å
b = 8.3819 (9) Å
c = 18.335 (2) Å
V = 1867.9 (3) Å³
Z = 4
Mo Kα radiation
μ = 8.62 mm⁻¹
T = 173 (2) K
0.30 × 0.20 × 0.10 mm

Data collection

Bruker APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 1999 ▶) T _min = 0.141, T _max = 0.418
16030 measured reflections
2043 independent reflections
1766 reflections with I > 2σ(I)
R _int = 0.045

Refinement

R[F ² > 2σ(F ²)] = 0.032
wR(F ²) = 0.073
S = 1.08
2043 reflections
109 parameters
H-atom parameters constrained
Δρ_max = 0.84 e Å⁻³
Δρ_min = −0.60 e Å⁻³

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809002475/im2094sup1.cif

e-65-0o528-sup1.cif^{(13.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809002475/im2094Isup2.hkl

e-65-0o528-Isup2.hkl^{(98.5KB, hkl)}

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

Acknowledgments

We are grateful to the French Ministère de la Recherche et Technologie for a PhD grant for SC. The CNRS is acknowledged for financial support. CS thanks the DFG for financial support. CD thanks the Studienstiftung des deutschen Volkes for a doctoral scholarship.

supplementary crystallographic information

Comment

In the context of our research in developing novel π-conjugated functionalized [2.2]paracyclophanes and ferrocenes (Clément et al., 2007a) for potential applications in coordination chemistry, we have recently reported an alternative to the classical Sonogashira synthesis (Morisaki et al., 2003) for the synthesis of ethynyl functionalized [2.2]paracyclophanes (Scheme 2). Our route involves a Corey-Fuchs reaction (Clément et al., 2007b) and subsequent dehydobromation induced by a strong base. In the first step, an ylide species, formed in situ by the interaction of zinc dust, CBr₄ and PPh₃, reacts with the formyl derivative 1a or 1b leading to the dibromoolefin derivatives 2a or 2b. The molecular structure of the vinylic intermediate 2b was elucidated by an single-crystal X-ray diffraction study (Figure 1).

2 b possesses a crystallographic center of inversion in the middle of the cyclophane framework. Bond lengths and angles may be considered as normal. Distortions typical of [2.2]paracyclophane systems, e.g. lengthened C—C bonds and widened angles in the bridges, narrowed ring bond angles at the bridgehead atoms, and boat-like distortion of the rings (the bridgehead atoms lie significantly out of the plane of the other four ring atoms) are observed. As previously noticed for the monodibromoolefin compound 2a, the alkenyl unit of 2b is strongly tilted. The two best planes of the arene (C3, C4, C5, C6, C7, C8; plane 1) and the vinyl-group (Br1, Br2, C1, C2; plane 2) possess a cutting angle of the normals of 49.4 (5)°

Contrary to a recently published, related system, no significant intermolecular interactions are observed for 2b due to inproper orientation of the molecules relative to each other (Hopf et al., 2007).

In the light of our recent work on the reactivity of (2,2-dibromovinyl)ferrocene towards thiolates (Clément et al., 2007b), the vinylic intermediates 2a and 2b should be promising starting materials for building new ligand systems. Synthesis, reactivity and photochemical properties of these new compounds will be reported in due course.

Experimental

PPh₃ (4.20 g, 16.0 mmol), CBr₄ (5.31 g, 16.0 mmol) and zinc dust (1.05 g, 16.0 mmol) are placed in a Schlenk tube and CH₂Cl₂ (45 ml) is added slowly. The mixture is stirred at room temperature for 28 h. Then, 1 b (1.05 g, 4.00 mmol), dissolved in CH₂Cl₂ (20 ml), is added and stirring is continued for 2 h. The reaction mixture is extracted with three 50 ml portions of pentane. CH₂Cl₂ is added when the reaction mixture became too viscous for further extractions. The extracts are filtered and evaporated under reduced pressure. The crude product was purified by column chromatography on silica gel with CH₂Cl₂/petroleum ether (1:1). Slow evaporation afforded white crystals of 2 b (Yield: 94%). mp 183°C, ¹H NMR (CDCl₃): 3.00 (m, 7H, CH₂), 3.24 (m, 1H, CH₂), 6.43 (d,2H, J = 8.2 Hz, H_aromatic), 6.59 (d, 2H, J = 2.1 Hz, H_aromatic), 6.65 (dd, 2H, J = 8.2 Hz, J = 2.1 Hz, H_aromatic), 7.43(s, 2H, CH=CBr₂) p.p.m.. ¹³C{¹H}NMR (CDCl₃): 34.9, 35.4 (C-1, C-2, C-9, C-10), 90.5 (C-18,C-20), 130.5, 134.0, 135.7, 135.8 (C-5, C-7, C-8, C-12, C-13, C-15, C-16,C-17), 136.2 (C-4, C-16), 138.1, 139.3 (C-3, C-6, C-11, C-14) p.p.m.. UV-vis (CH₂Cl₂)[l_maxnm (e)]: 229 (57544 M^-1.cm^-1),266 (20417 M^-1.cm^-1). Anal. Calcd for C₂₀H₁₆Br₄:C, 41.71, H, 2.80, Found: C, 41.63, H, 2.71.(Clément et al., 2007b).