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Synlett 2009(20): 3365-3367  
DOI: 10.1055/s-0029-1218376
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

The Highly Efficient 1,4-Addition of TMSCN to Aromatic Enones Catalyzed by CsF with Water as the Additive

Jingya Yanga,b, Yinxian Wanga, Shaoxiang Wua, Fu-Xue Chen*a
a Department of Applied Chemistry, School of Chemical Engineering & the Environment, Beijing Institute of Technology, No. 5 South Zhongguancun Street, Haidian District, Beijing 100081, P. R. of China
Fax: +86(10)68918296; e-Mail: fuxue.chen@bit.edu.cn;
b College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. of China
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Publication History

Received 10 September 2009
Publication Date:
18 November 2009 (online)

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Abstract

An efficient 1,4-addition of TMSCN to aromatic enones has been achieved in excellent yields (91-99%) by CsF (1 mol%) as the catalyst and H2O (4 equiv) as the additive in refluxing dioxane within 2-7 hours.

Key words

1,4-addition reaction - enones - nitriles - regioselectivity - CsF

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See Supporting Information.

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Preparation of 2a The solution of CsF (0.5 mg, 0.003 mmol, 1 mol%) and enone (1a, 62.5 mg, 0.3 mmol) in dioxane (1 mL) is added TMSCN (84 µL, 0.66 mmol, 2.2 equiv) and H2O (22 µL, 1.2 mmol, 4 equiv) subsequently in a dry Schlenk tube equipped with cold finger under argon. The reaction mixture is stirred at reflux temperature until the reaction is completed (monitored by TLC). 1 M HCl (0.3 mL) is added to quench the reaction with additional 20 min stirring at r.t. The resulting mixture is extracted with EtOAc (5 mL) (Caution! HCN generated in the reaction mixture is highly toxic. Those operations should be conducted in a well-ventilated hood). The extract is washed with H2O, brine, dried over anhyd Na2SO4, and concentrated. The crude product is purified by flash chromatography on silica gel (PE-EtOAc, 20:1) to afford 2a as white solid in 99% yield.
Nitrile 2a: mp 120-122 ˚C (lit.: 122-125 ˚C).¹¹ ¹H NMR (400 MHz, CDCl3): δ = 3.52 (dd, J = 6.0, 18.0 Hz, 1 H, NCCHCH A HBCO), 3.74 (dd, J = 8.0, 18.0 Hz, 1 H, NCCHCHA H B CO), 4.57 (dd, J = 6.0, 8.0 Hz, 1 H, NCCHCHAHBCO), 7.34-7.49 (m, 7 H, ArH), 7.58-7.62 (m, 1 H, ArH), 7.92-7.94 (m, 2 H, ArH) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 31.9, 44.5, 120.6, 127.5, 128.1, 128.4, 128.8, 129.3, 133.9, 135.3, 135.8, 194.6 ppm. IR (KBr): ν = 1681, 2236 cm-¹.