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Synlett 2008(1): 137-141  
DOI: 10.1055/s-2007-1000840
LETTER
© Georg Thieme Verlag Stuttgart · New York

Efficient Solvent-Free Synthesis of Homoallylic Alcohols Mediated by Zinc-Copper Couple

Wenjun Zhoua, Wenjun Yana, Jin-Xian Wang*a,b, Kehu Wanga
a Institute of Chemistry, Department of Chemistry, Northwest Normal University, 967 An Ning Road (E.), Lanzhou 730070, P. R. of China
Fax: +86(931)7768159; e-Mail: Wangjx@nwnu.edu.cn;
b State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. of China
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Publikationsverlauf

Received 17 September 2007
Publikationsdatum:
11. Dezember 2007 (online)

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Abstract

Under solvent-free conditions, it was found that zinc-copper couple could efficiently mediate the Barbier-type reaction of ketones and allyl bromide to give the corresponding homoallylic alcohols in high to excellent yields at room temperature.

Key words

solvent-free - zinc-copper couple - ketones - allylation - homoallylic alcohols

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Preparation of the Zinc-Copper Couple: Zinc powder (11.6 g) and distilled H2O (80 mL) were placed into a 100-mL round-bottom flask equipped with a stir bar. With stirring, HCl acid (37%, 2 × 1 mL) was added over 10 min. Then the CuSO4 solution (20%, 20 mL) was added dropwise with stirring and the stirring was continued for about 15 min. Finally, the mixture was filtered and the solid was washed with H2O (3 × 30 mL), acetone (3 × 10 mL), and Et2O (2 × 10 mL). Then the solid was transferred into a flask equipped with vacuum take-off and dried under vacuum for 3 h at 100 °C. Other M-Cu couples were also prepared in this way.Preparation of the Homoallylic Alcohols: Zinc-copper couple (0.24 g), allyl bromide (2.5 mmol) and ketones (2 mmol) were placed in a dried round-bottom flask, and the mixture was stirred at r.t. and the reaction was monitored by TLC. After reaction completed, sat. brine (10 mL) was poured into the mixture, the mixture was extracted with Et2O (3 × 10 mL) and the organic layer was separated, dried over anhyd MgSO4, filtered, and evaporated. The pure products were obtained by flash chromatography over silica gel, and characterized by IR, 1H NMR, 13C NMR and MS.

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Representative Spectroscopic Data for Compounds 3. Compound 3i: IR: 3475, 2976, 1670, 1456, 1269, 1101, 920, 771, 738 cm-1. 1H NMR (400 MHz, CDCl3): δ = 7.24-7.84 (m, 7 H), 5.60-5.70 (m, 1 H), 5.09-5.19 (m, 2 H), 3.88 (q, J = 6.4 Hz, 2 H), 2.65-2.76 (m, 1 H), 2.52-2.63 (m, 1 H), 2.14 (s, 1 H), 1.61 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 146.4, 143.3, 143.3, 141.4, 140.2, 133.7, 126.7, 126.5, 125.0, 123.4, 121.5, 119.8, 119.4, 73.8, 48.6, 37.0, 30.1, 26.8. EI-MS: m/z (%) = 250 (2.4) [M+], 209 (64.9), 193 (16.8), 165 (37.7), 43 (100), 39 (17.2). Anal. Calcd for C18H18O: C, 86.36; H, 7.25. Found: C, 86.36; H, 7.36. Compound 3p: IR: 3406, 3077, 2977, 1644, 1439, 1372, 1114, 923, 796 cm-1. 1H NMR (400 MHz, CDCl3): δ = 6.88 (d, J = 3.6 Hz, 1 H), 6.63 (d, J = 3.6 Hz, 1 H), 5.67-5.78 (m, 1 H), 5.12-5.19 (m, 2 H), 2.57-2.67 (m, 1 H), 2.48-2.54 (m, 1 H), 2.34 (s, 1 H), 1.57 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 154.6, 132.8, 129.5, 122.5, 120.2, 110.5, 73.0, 48.7, 30.1. EI-MS: m/z (%) = 248 (0.3) [M+ + 2], 246 (0.2) [M+], 231 (0.3) [M+ - Me], 229 (0.3) [M+ - OH], 207 (33.7), 43 (100), 39 (21.7). Anal. Calcd for C9H11BrOS: C, 43.74; H, 4.49. Found: C, 43.29; H, 3.93. Compound 3q: IR: 3439, 3072, 2922, 1662, 1445, 1369, 1142, 917, 829 cm-1. 1H NMR (400 MHz, CDCl3): δ = 6.54 (s, 1 H), 5.67-5.78 (m, 1 H), 5.12-5.17 (m, 2 H), 2.15-2.50 (m, 8 H), 2.04 (s, 1 H), 1.51 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 142.1, 134.2, 133.9, 131.3, 125.3, 119.2, 73.6, 47.7, 30.9, 29.3, 15.0. EI-MS: m/z (%) = 196 (2.37) [M+], 181 (0.04) [M+ - OH], 155 (24.9), 139 (10.5), 113 (5.7), 59 (9.3), 43 (100), 41 (16.2), 39 (16.9). Anal. Calcd for C11H16OS: C, 67.30; H, 8.22. Found: C, 66.92; H, 8.07. Compound 3r: IR: 3411, 3077, 2981, 1684, 1373, 1097, 921, 786 cm-1. 1H NMR (400 MHz, CDCl3): δ = 6.05 (s, 1 H), 5.87 (s, 1 H), 5.68-5.72 (m, 1 H), 5.11-5.15 (m, 2 H), 2.64-2.69 (m, 1 H), 2.51-2.56 (m, 1 H), 2.28 (s, 3 H), 2.14 (s, 1 H), 1.51 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 157.3, 151.2, 133.5, 119.0, 105.8, 105.3, 70.5, 46.0, 26.3, 13.5. EI-MS: m/z (%) = 166 (0.7) [M+], 149 (1.7) [M+ - OH], 135 (0.7), 125 (91.5), 109 (10.3), 95 (2.1), 43 (100), 39 (20.6). Anal. Calcd for C10H14O2: C, 72.26; H, 8.49. Found: C, 72.28; H, 8.64.