Dearomatizing Anionic Cyclization of 1-Lithio-4-naphthyl-1,3-butadienes Leading to the Formation of Spiro Cyclopentadiene Derivatives

Abstract

On treatment with t-BuLi, 1-iodo-4-naphthyl-1,3-buta­diene derivatives cyclize with dearomatization to give spiro compounds bearing a moiety of allyllithium, which reacts further with electrophiles to yield spiro tricyclic systems.

Key words

anionic cyclization - cyclopentadiene derivative - de­aromatization - 1-lithio-4-naphthyl-1,3-butadiene - organolithium

References and Notes

• 1a Clayden J. Organolithiums: Selectivity for Synthesis   Tetrahedron Organic Chemistry Series, Pergamon; Oxford: 2002.  Vol. 23:  p.282-335  ; and references cited therein
• 1b Varela JA. Saa C. Chem. Rev.  2003,  103:  3787 
• 1c Xi Z. Eur. J. Org. Chem.  2004,  2773 
• 1d Foubelo F. Yus M. Curr. Org. Chem.  2005,  9:  459 
• 2a Clayden J. Turnbull R. Pinto I. Tetrahedron: Asymmetry  2005,  16:  2235 
• 2b Clayden J. Turnbull R. Pinto I. Org. Lett.  2004,  6:  609 
• 2c Clayden J. Turnbull R. Helliwell M. Pinto I. Chem. Commun.  2004,  2430 
• 2d Clayden J. Kenworthy MN. Synthesis  2004,  1721 
• 2e Clayden J. Organolithiums: Selectivity for Synthesis   Tetrahedron Organic Chemistry Series, Pergamon; Oxford: 2002.  Vol. 23:  p.327-329  
• 2f For a recent application of dearomatizing cyclization in synthesis, see: Clayden J. Knowles FE. Baldwin IR. J. Am. Chem. Soc.  2005,  127:  2412 
• 3a Clayden J. Hamilton SD. Mohammed RT. Org. Lett.  2005,  7:  3673 
• See also:
• 3b Fraenkel G. Ho CC. Liang Y. Yu S. J. Am. Chem. Soc.  1972,  94:  4732 
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• 4 Chen J. Song Q. Wang C. Xi Z. J. Am. Chem. Soc.  2002,  124:  6238 
• 5 Song Q. Li Z. Chen J. Wang C. Xi Z. Org. Lett.  2002,  4:  4627 
• 6 Fang H. Song Q. Wang Z. Xi Z. Tetrahedron Lett.  2004,  45:  5159 
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• 9 Wang Z. Fang H. Xi Z. Tetrahedron Lett.  2005,  46:  499 

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Typical Procedure for the Formation of 7a.
A solution of t-BuLi (2.0 equiv of a 1.5 M solution in pentane) was added dropwise to a stirred solution of compound 1a (209 mg, 0.5 mmol) in Et₂O (5 mL) at -78 °C under N₂. The reaction was stirred at the same temperature for 1 h, then TMSCl (108 mg, 1.0 mmol) was added. After the reaction was stirred for another 1 h at -78 °C, aq NaHCO₃ was added. The layers were separated, and the aqueous phase was extracted with Et₂O (3 ×). The combined extracts were washed with brine and dried over MgSO₄. Evaporation under reduced pressure gave a crude product which was purified by flash chromatography to yield product 7a. Colorless liquid, isolated yield 73% (133 mg). ¹H NMR (CDCl₃): δ = 0.10 (s, 9 H), 0.64 (t, J = 7.5 Hz, 3 H), 0.85 (t, J = 7.8 Hz, 3 H), 1.06-1.15 (m, 6 H), 1.86-2.34 (m, 8 H), 3.18 (t, J = 3.3 Hz, 1 H), 4.85 (dd, J = 10.2, 2.4 Hz, 1 H), 5.96 (dd, J = 10.2, 3.6 Hz, 1 H), 6.55 (dd, J = 7.5, 1.2 Hz, 1 H), 6.82-6.87 (m, 1 H), 6.97-7.06 (m, 2 H). ¹³C NMR (CDCl₃): δ = -1.52, 14.78, 15.00, 15.18, 15.68, 18.84, 18.87, 19.26, 19.37, 33.00, 62.90, 124.56, 125.35, 125.54, 125.85, 127.61, 127.77, 133.38, 136.50, 139.97, 142.04, 151.73, 152.44. HRMS: m/z calcd for C₂₅H₃₆Si: 364.2586; found: 364.2589.

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The deposition number at the Cambridge Crystallographic Data Centre: CCDC 295391.