Orthogonal π-Bridges in [2.2]Paracyclophanes

Abstract

Orthogonal π-bridges have been introduced into [2.2]paracyclophanes by the reaction of the pseudo-geminal bisacetylene with various monoacetylenes and nitriles. The reactions with bistrimethylsilylacetylene and dimethylacetylenedicarboxylate take place even in the absence of a catalyst. This procedure can incorporate not only aromatic but also heteroaromatic bridges, as in pyridine-annulated cyclophane.

Key words

[2.2]paracyclophane - cyclotrimerization - acetylenes - nitriles - aromatic bridges

References and Notes

• 1 Brown CJ. Farthing AC. Nature (London)  1949,  164:  915 
• 2 Cram DJ. Steinberg H. J. Am. Chem. Soc.  1951,  73:  5691 
• 3 Vögtle F. Neumann P. Synthesis  1973,  85 
• 4 Staab HA. Knaus GH. Henke H.-E. Krieger C. Chem. Ber.  1983,  116:  2785 
• 5 Boekelheide V. Top. Curr. Chem.  1983,  113:  87 
• 6 Hopf H. Marquard C. In Strain and its Implications in Organic Chemistry   de Meijere A. Blechert S. Kluwer; Dordrecht: 1983.  p.297 
• 7 Vögtle F. Cyclophane Chemistry, Synthesis, Structure and Reactions   Wiley; Chichester: 1993.  p.71 
• 8 Rozenberg VI. Sergeeva EV. Hopf H. In Modern Cyclophane Chemistry   Gleiter R. Hopf H. Wiley-VCH; Weinheim: 2004.  Chap. 17. p.435 
• 9 Greiving H. Hopf H. Jones PG. Bubenitschek P. Desvergne J.-P. Bouas-Laurent H. Eur. J. Org. Chem.  2005,  558 
• 10 Hopf H. Greiving H. Beck C. Dix I. Jones PG. Desvergne J.-P. Bouas-Laurent H. Eur. J. Org. Chem.  2005,  567 
• 11 For a review, see: Hopf H. Angew. Chem. Int. Ed.  2003,  42:  2822 ; Angew. Chem. 2003, 115, 2928
• 12 Bondarenko L. Dix I. Hinrich H. Hopf H. Synthesis  2004,  2751 
• 13 Mills WH. Nixon IG. J. Chem. Soc.  1930,  2510 
• 14 Vollhardt KPC. Acc. Chem. Res.  1977,  10:  1 
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• 19a

  Crystal Structure Determination of 3a - Crystal Data
  Orthorhombic, space group P2₁2₁2₁, a = 11.9328 (11), b = 12.6273 (12), c = 15.8769 (15) Å, Z = 4, T = 100 K.
  Data Collection
  A crystal ca. 0.3 × 0.2 × 0.17 mm^³ was used to record 89806 intensities to 2θ 63˚ on a Bruker APEX-2 diffractometer using Mo Kα radiation (λ = 0.71073 Å).
  Structure Refinement
  The structure was refined anisotropically on F ^² (program SHELXL-97)^¹7b to wR2 = 0.0861, R1 = 0.0320 for 277 parameters and 7929 unique reflexions. Data have been deposited in Cambridge under the number CCDC-796776.

• 19b Sheldrick GM. Acta Crystallogr., Sect. A.: Fundam. Crystallogr.  2008,  64:  112 

16

Typical Procedure for Cyclotrimerization
To a boiling solution of xylene (30 mL) a solution of bisacetylene 1 (0.5 mmol), acetylene 2a-c (2.5 mmol), and CpCo(CO)₂ (5 mol%) in xylene (20 mL) was added with a syringe pump over 16 h. The solvent was evaporated under vacuum, and the residue purified by column chromatography on silica gel.

17

Analytical Data of Compound 3a Yield 134 mg (63%); mp 158-159 ˚C. IR (ATR): 3342, 1611, 1432, 1342, 1297, 1031, 771, 755 cm^-¹. ^¹H NMR (400 MHz, CDCl₃, TMS): δ = 0.36 (s, 18 H, 6 CH₃), 2.47 (m, 2 H, CH₂), 2.51 (m, 2 H, CH₂), 2.95 (m, 4 H, 2 CH₂), 6.24 (d, 2 H, ⁴ J = 2.0 Hz, 2 CH_ar), 6.33 (d, 2 H, ^³ J = 7.9 Hz, 2 CH_ar), 6.42 (dd, 2 H, ^³ J = 7.9 Hz, ⁴ J = 2.0 Hz, 2 CH_ar), 7.74 (s, 2 H, 2 CH_ar). ^¹³C NMR (100 MHz, CDCl₃, TMS): δ = 2.2 (q), 33.5 (t), 35.4 (t), 130.5 (d), 130.8 (d), 132.8 (d), 139.1 (d), 139.3 (s), 141.0 (s), 143.6 (s), 144.8 (s), 145.1 (s). MS (EI): m/z (%) = 426 (100)[M⁺], 398 (81), 338 (41), 279 (34), 184 (22), 167 (23), 149 (40). Anal. Calcd for C₂₈H₃₄Si₂: C, 78.81; H, 8.03. Found: C, 78.52; H, 7.89.

18

Analytical Data of Compound 3b Yield 145 mg (73%); mp 162-163 ˚C. IR (ATR): 2927, 1719, 1438, 1325, 1262, 1243, 1120, 1066, 952, 783, 614 cm^-¹. ^¹H NMR (200 MHz, CDCl₃, TMS): δ = 2.52 (m, 4 H, 2 CH₂), 3.05 (m, 4 H, 2 CH₂), 3.95 (s, 6 H, 2 CH₃), 6.20 (d, 2 H, ⁴ J = 2.0 Hz, 2 CH_ar), 6.39 (d, 2 H, ^³ J = 8.0 Hz, 2 CH_ar), 6.52 (dd, 2 H, ^³ J = 8.0 Hz, ⁴ J = 2.0 Hz, 2 CH_ar), 7.89 (s, 2 H, 2 CH_ar). ^¹³C NMR (50 MHz, CDCl₃, TMS): δ = 33.1 (t), 35.4 (t), 52.7 (q), 124.9 (d), 130.9 (s), 131.5 (d), 133.1 (d), 138.5 (d), 139.6 (s), 140.1 (s), 141.8 (s), 149.3 (s), 168.1 (s). MS (EI): m/z (%) = 398 (100)[M⁺], 370 (60), 339 (35), 279 (39), 265 (32), 252 (23). Anal. Calcd for C₂₆H₂₂O₄: C, 78.39; H, 5.52. Found: C, 78.61; H, 5.41.

20

Analytical Data of Compound 5a Yield 58 mg (29%); mp 133-134 ˚C. IR (ATR): 2930, 1595, 1517, 1460, 1336, 1317, 1105, 855, 721 cm^-¹. ^¹H NMR (600 MHz, CDCl₃, TMS): δ = 2.61-2.80 (m, 4 H, 2 CH₂), 3.03-3.13 (m, 4 H, 2 CH₂), 2.95 (m, 4 H, 2 CH₂), 6.26 (d, 1 H, ⁴ J = 1.9 Hz, CH_ar), 6.29 (d, 1 H, ⁴ J = 1.9 Hz, CH_ar), 6.46 (d, 1 H, ^³ J = 8.1 Hz, CH_ar), 6.48 (d, 1 H, ^³ J = 8.1 Hz, CH_ar), 6.57 (dd, 1 H, ^³ J = 8.1 Hz, ⁴ J = 1.9 Hz, CH_ar), 6.59 (dd, 1 H, ^³ J = 8.1 Hz, ⁴ J = 1.9 Hz, CH_ar), 8.03 (s, 1 H, CH_ar), 8.31 (d, 2 H, ^³ J = 8.0 Hz, 2 CH_ar), 8.39 (d, 2 H, ^³ J = 8.0 Hz, 2 CH_ar), 8.89 (s, 1 H, CH_ar). ^¹³C NMR (150 MHz, CDCl₃, TMS): δ = 33.0 (t), 33.3 (t), 35.3 (t), 35.4 (t), 117.1 (d), 124.1 (d), 127.8 (d), 131.7 (d), 131.8 (d), 133.3 (d), 133.5 (d), 137.7 (d), 139.2 (d), 139.6 (s), 139.7 (s), 140.0 (s), 140.3 (s), 140.5 (s), 141.3 (s), 141.9 (s), 144.9 (d), 145.3 (s), 148.2 (s), 154.1 (s), 155.9 (s). MS (EI): m/z (%) = 404 (100)[M⁺], 389 (15), 359 (45), 283 (12), 190 (86), 176 (31). Anal. Calcd for C₂₇H₂₀N₂O₂: C, 80.20; H, 4.95. Found: C, 80.34; H, 4.79.