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Synlett 2004(7): 1171-1174  
DOI: 10.1055/s-2004-822924
LETTER
© Georg Thieme Verlag Stuttgart · New York

Allylation of Carbonyl Compounds Mediated by Nanometer-Sized Bismuth in Water

Xiaolan Xua, Zhenggen Zhaa, Qian Miao*a,b, Zhiyong Wang*a
a Department of Chemistry, University of Science & Technology of China, Hefei 230026, P. R. China
Fax: +86(551)3603185; e-Mail: zwang3@ustc.edu.cn;
b Current address: Department of Chemistry, Columbia University, New York, NY 10027, USA
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Publication History

Received 19 February 2004
Publication Date:
28 April 2004 (online)

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Abstract

It is found that nanometer-sized bismuth mediates the allylation of carbonyl compounds in water to afford the corresponding homoallylic alcohol in high yields. Nanometer-sized bismuth is much more effective than regular bismuth powder in this reaction.

Key words

allylation - carbonyl compounds - water - aromatic - stereoselectivity

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General procedure for the allylation of aldehydes with allyl bromide mediated by Bi nanotubes in distilled water. To a suspension of bismuth nanotube (0.250 g, 1.2 mmol) and allyl bromide (0.18 mL, 2 mmol) in water was added benzaldehyde (0.11 mL, 1 mmol). The reaction mixture was stirred at r.t. and monitored by TLC. After 2-7 h, the mixture was filtered to remove the white precipitate and the filtrate was extracted with ether (3 × 15 mL). The combined organic layer was washed with water, dried over anhydrous magnesium sulfate and evaporated in vacuo. The residue, in most cases, afforded the corresponding homoallylic alcohols in sufficient purity as judged by TLC and 1H NMR. When necessary, purification was performed by flash column chromatography over silica gel.

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General procedure for the allylation of aldehydes with allyl bromide mediated by regular Bi in distilled water. To a suspension of bismuth powder (0.250 g, 1.2 mmol) and allyl bromide (0.18 mL, 2 mmol) in water was added benzaldehyde (0.11 mL, 1 mmol). The reaction mixture was stirred at r.t. and monitored by TLC. After 24 h, the mixture was filtered to remove the white precipitate and the filtrate was extracted with ether (3 × 15 mL). The combined organic layer was washed with water, dried over anhydrous magnesium sulfate and evaporated in vacuo. The residue was purified by flash column chromatography over silica gel, affording the corresponding homoallylic alcohols.

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General procedure for the allylation of aldehydes with allyl bromide mediated by in situ nano-Bi. To a suspen-sion of Bi(NO3)3 (0.728 g, 1.5 mmol) in water (4 mL) was added CTAB (0.1 mmol) and a solution of KBH4 (0.106 g, 2 mmol) in H2O (2 mL). After the addition was completed, the reaction mixture was stirred continuously for 15 min, then benzaldehyde (0.11 mL, 1 mmol) and allyl bromide (0.18 mL, 2 mmol) were added. Then the reaction mixture was treated as described in ref. 10.

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See Figure [2] :

Figure 2