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DOI: 10.1055/s-2002-32981
Novel Synthesis of (E)-α-Fluorochalcones
Publication History
Publication Date:
25 July 2002 (online)
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Abstract
α-Fluorochalcones 4 can be synthesized by the Wittig reaction via α-fluoro substituted ylide 3, affoding a general method for the stereoselective synthesis of (E)-α-fluoro-α,β-unsaturated compounds 4.
Key words
α-fluorochalcones - Wittig reaction - synthesis
- 1
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References
General Procedure
for the Stereoseletive Synthesis ofα-Fluorochalcones
4 (Method B): To the solution of benzoylmethylene triphenylphosphorane 1 (0.92 g, 2.0 mmol) in THF (20 mL), was
added dropwise the solution of N-fluorodiphenylsulfonamide
(0.63 g, 2.0 mmol) in THF (20 mL) at -20 °C. The
mixture was stirred at r.t. for 3 h and a lot of precipitate was
formed. After LDA (2 mmol) was added dropwise and the reaction mixture
was stirred for 30 min, aldehyde (2 mmol) was added and the reaction
mixture was stirred at r.t. for 27-40 h (see Table
[1]
). After filtration, the
filtrate was concentrated and subjected to preparative TLC (silica
gel, hexane-ethyl acetate as eluent) to give
α-fluorochalcones 4a-e.
4a: Mp 100-101 °C. 1H
NMR: δ (ppm) = 8.29 (d, 2 H, J = 8 Hz),
8.04 (d, 2 H, J = 8
Hz), 7.83 (d, 1 H, J = 16
Hz), 7.68-7.60 (m, 3 H), 7.58-7.50 (m, 2 H). MS: m/z (%) = 271(1) [M+],
77(100). Compound 4b: mp 89-90 °C. 1H
NMR:
δ (ppm) = 8.03 (d, 2 H, J = 8 Hz),
7.83 (d, 1 H, J = 16
Hz), 7.70-7.61 (m, 2 H), 7.51-7.48 (m, 3 H), 7.45-7.40
(m, 2 H). MS: m/z (%) = 244(4) [M+],
57(100). 4c: Mp 79-80 °C
(Lit
[9]
77 °C). 1H
NMR: δ (ppm) = 8.01 (d, 2 H, J = 8
Hz), 7.76 (d, 1 H, J = 16
Hz), 7.60-7.56(m, 2 H), 7.51-7.46 (m, 3 H), 7.40 (d,
2 H, J = 8
Hz). MS m/z (%) = 260(2) [M+],
157(100). 4d: Mp 52-53 °C
(Lit
[9]
54 °C). 1H
NMR: δ (ppm) = 8.01 (d, 2 H, J = 8
Hz), 7.81 (d, 1 H, J = 16
Hz), 7.65-7.61 (m, 2 H), 7.53-7.49 (m, 3 H), 7.44-7.40
(m, 2 H). MS m/z (%) = 226(13) [M+],
57(100). 4e: Mp 69-70 °C
(Lit
[9]
69 °C). 1H NMR: δ (ppm) = 8.01(d,
2 H, J = 8
Hz), 7.79(d, 1 H, J = 16 Hz),
7.61-7.45 (m, 5 H), 7.23 (d, 1 H, J = 8
Hz), 2.40 (s, 3 H). MS m/z (%) = 240(2) [M+],
207(100).