Synlett 2006(8): 1275-1277  
DOI: 10.1055/s-2006-939083
LETTER
© Georg Thieme Verlag Stuttgart · New York

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

Zhihui Wanga, Zhenfeng Xi*a,b
a Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, P. R. of China
Fax: +86(10)62759728; e-Mail: zfxi@pku.edu.cn;
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. of China
Further Information

Publication History

Received 22 December 2005
Publication Date:
05 May 2006 (online)

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.

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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.