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Synlett 2006(20): 3504-3506  
DOI: 10.1055/s-2006-956478
LETTER
© Georg Thieme Verlag Stuttgart · New York

GaCl3-Catalyzed Chloroacylation of Alkynes: A Simple, Convenient and Efficient Method to β-Chlorovinyl Ketones

Hongwei Zhou*a, Changying Zenga, Lianjun Rena, Wenhui Liaoa, Xian Huang*a,b
a Department of Chemistry, Zhejiang University (Campus Xixi), Hangzhou 310028, P. R. of China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. of China
Fax: +86(571)88212531; e-Mail: zhouhw@zju.edu.cn;
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Publication History

Received 27 August 2006
Publication Date:
08 December 2006 (online)

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Abstract

Gallium chloride catalyzed acylation of alkynes was studied to afford one of the most atom-economic and efficient methodologies for the preparation of β-chlorovinyl ketones. In contrast to the Friedel-Crafts acylation, only a catalytic amount of GaCl3 was needed to produce the target products in high stereoselectivity.

Key words

gallium trichloride - acylation - alkyne - β-chlorovinyl ketone

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All reagents were obtained commercially except GaCl3. The GaCl3 used was prepared as follows: Gallium (3.5 g) was dissolved in concd HCl (100 mL) under reflux and excessive HCl was removed under reduced pressure. To the reaction mixture was added SOCl2 (35 mL) and excessive SOCl2 was removed under reduced pressure (ca. 20 mm Hg by rotary evaporation then 5 mm Hg by a pump). The residue was used directly for our reaction with 80% purity. GaCl 3 -Catalyzed Acylation of Alkynes; General Procedure: To a solution of GaCl3 (20 mol%) and acid chloride (0.6 mmol) in CH2Cl2 (5 mL) was added alkyne (0.5 mmol) under nitrogen. The reaction was stirred at r.t. and filtered through a short celite pad, washed with Et2O, concentrated by vacuo, and purified by chromatography on silica gel with n-hexane-EtOAc (10:1) as the eluent.
( Z )-1-Chloro-1-phenyloct-1-en-3-one (3a): 1H NMR (400 MHz, CDCl3): δ = 7.66-7.69 (m, 2 H), 7.38-7.44 (m, 3 H), 6.79 (s, 1 H), 2.67-2.71 (t, J = 7.2 Hz, 2 H), 1.66-1.70 (t, J = 7.4 Hz, 2 H), 1.31-1.37 (m, 4 H), 0.89-0.92 (m, 3 H). 13C NMR (100 MHz, CDCl3): δ = 199.0, 142.3, 137.4, 130.5, 128.6, 127.2, 123.8, 44.4, 31.3, 23.6, 22.4, 13.9. MS (EI): m/z = 239 (7.2) [M + 3], 238 (4.6) [M + 2], 237 (21.6) [M + 1], 236 (3.85) [M+]. IR (neat): 1695, 1591 cm-1.
( Z )-4-Chloronon-3-en-2-one ( Z-3f): 1H NMR (400 MHz, CDCl3): δ = 6.24 (s, 1 H), 2.42-2.45 (t, J = 7.8 Hz, 2 H), 2.37 (s, 3 H), 1.61-1.64 (m, 2 H), 1.30-1.35 (m, 4 H), 0.89-0.92 (m, 3 H). 13C NMR (100 MHz, CDCl3): δ = 196.6, 147.4, 125.0, 41.2, 31.4, 30.6, 26.9, 22.2, 13.8. MS (EI): m/z = 176 (1.25) [M + 2], 174 (2.68) [M+]. IR (neat): 1710, 1610 cm-1.
( E )-4-Chloronon-3-en-2-one ( E-3f): 1H NMR (400 MHz, CDCl3): δ = 6.44 (s, 1 H), 2.90-2.94 (t, J = 7.8 Hz, 2 H), 2.20 (s, 3 H), 1.59-1.62 (m, 2 H), 1.30-1.34 (m, 4 H), 0.87-0.91 (m, 3 H). 13C NMR (100 MHz, CDCl3): δ = 195.5, 157.0, 125.7, 35.8, 31.9, 30.9, 27.3, 22.3, 13.9. MS (EI): m/z = 176 (0.96) [M + 2], 174 (1.33) [M+]. IR (neat): 1697, 1600 cm-1.