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Synthesis 2007(12): 1797-1806  
DOI: 10.1055/s-2007-983707
PAPER
© Georg Thieme Verlag Stuttgart · New York

Intermolecular Reductive Cyclodimerization of Cyclic α,β-Unsaturated Ketones­ Promoted by a Low-Valent Titanium Reagent: A Facile Synthesis of Some New Spiro Compounds

Da-Qing Shi*a,b, Guo-Lan Doub, Zheng-Yi Lib, Chun-Ling Shib, Xiao-Yue Lib, Hong Jiangc, Sai-Nan Nib, Shun-Jun Jia
a College of Chemistry and Chemical Engineering, Key Laboratory of Organic Synthesis of Jiangsu Province, Suzhou University, Suzhou 215123, P. R. of China
e-Mail: dqshi@263.net;
b Department of Chemistry, Xuzhou Normal University, Xuzhou 221116, P. R. of China
c The Key Laboratory of Biotechnology for Medical Plants of Jiangsu Province, Xuzhou 221116, P. R. of China
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Publication History

Received 5 March 2007
Publication Date:
08 June 2007 (online)

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Abstract

The intermolecular reductive cyclodimerization reactions of cyclic α,β-unsaturated ketones such as 2-benzylideneindan-1-ones, 2-benzylidene-1-tetralones, 3-benzylidenechroman-4-ones, and 3-benzylidenethiochroman-4-ones induced by a low-valent titanium reagent were studied. Some new spiro compounds were prepared in good yields under neutral and mild conditions. High stereoselectivity was achieved and the stereochemistry of the products was confirmed by X-ray diffraction analysis.

Key words

low-valent titanium - cyclic α,β-unsaturated ketones - spiro compounds - stereochemistry

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Crystal data for 7a: C34H30O4; M = 502.58, colorless block crystal, 0.35 × 0.16 × 0.11 mm, monoclinic, space group P21/c, a = 12.209 (5), b = 10.889 (4), c = 20.087 (8) Å, β = 95.577 (7)°, V = 2657.6 (19) Å3, Z = 4, D c = 1.256 g·cm-3, F(000) = 1064, µ(Mo Kα) = 0.081 mm-1. Intensity data were collected on a Smart-1000 diffractometer with graphite monochromated Mo Kα radiation (λ = 0.71073 Å) using the ω scan mode with 2.04° < θ < 25.01°; 4637 unique reflec­-tions were measured and 1921 reflections with I > 2σ(I) were used in the Fourier techniques. The final refinement was converged to R = 0.0570 and wR = 0.1140.

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Crystal data for 9a: C32H26Br2O2S2 CH3COCH3; M = 724.55, colorless block crystal, 0.29 × 0.26 × 0.10 mm, triclinic, space group P-1, a = 11.476 (2), b = 12.064 (3), c = 13.002 (3) Å, α = 77.283 (3), β = 67.200(3), γ = 80.305 (4)°, V = 1611.7 (6) Å3, Z = 2, D c = 1.493 g.cm-3, F(000) = 736, µ(Mo Kα) = 2.678 mm-1. Intensity data were collected on a Smart-1000 diffractometer with graphite monochro­-mated Mo Kα radiation (λ = 0.71073 Å) using the ω scan mode with 1.93° < θ < 25.01°; 5625 unique reflections were measured and 2927 reflections with I > 2σ(I) were used in the Fourier techniques. The final refinement was converged to R = 0.0500 and wR = 0.1026.