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Synlett 2010(13): 1915-1918  
DOI: 10.1055/s-0030-1258504
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

An Efficient Electrochemical Method for the Paired Synthesis of Carbonyl Compounds and Homoallylic Alcohols in a Simple Home-Made Cell

Li Zhang, Zhenggen Zha*, Zhiyong Wang*
Hefei National Laboratory for Physical Science at Microscale, Joint-lab of Green Synthetic Chemistry and Department of Chemistry, University of Science and Technology of China, Hefei 230026, P. R. of China
Fax: +86(551)3603185; e-Mail: zwang3@ustc.edu.cn;
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Publication History

Received 28 January 2010
Publication Date:
16 July 2010 (online)

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Abstract

An efficient electrochemical synthesis of carbonyl compounds and homoallylic alcohols was developed in excellent yields using a simple home-made cell. The catalytic redox behavior of the electrode surface and the reaction mechanism was investigated by cyclic voltammetry (CV).

Key words

electrochemistry - paired synthesis - carbonyl compounds - homoallylic alcohols - home-made cell

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For details see the experimental section in the Supporting Information.

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Representative Procedure for 1-Phenylbut-3-en-1-ol and Benzaldehyde
A divided cell with salt bridge of KNO3 was equipped with a graphite electrode (dia. 3.0 mm) as anode and a graphite electrode (dia. 3.0 mm vs. SCE) as cathode (Figure S1 in Supporting Information). To a solution of KNO3 (5 mL, 0.4 M) in the anodic compartment, benzyl alcohol (5 mmol) was added. In the cathodic compartment, a solution of allyl bromide (7.5 mmol) was added into 0.2 M SnCl2 (5 mL)
and KNO3 (0.4 M). The electrolytes were stirred and electrolyzed at constant potential of 0.6 V until the alcohols were transformed. The produced aldehyde was transferred to cathodic chamber by simple phase separation. Meanwhile, the same benzyl alcohol (5 mmol) was added in anodic chamber. The electrolytes were stirred and electrolyzed at constant potential of 0.6 V for 4-5 h. Meanwhile, the electrolytes were also electrolyzed at a constant current of
20 mA (14 h, 2 F/mol of current was consumed). Considering the period of reaction, we chose the potentiostatic method to carry out this reaction instead of galvanostatic method. Then the allylation product in cathode compartment was extracted with Et2O (3 × 10 mL), washed with H2O and dried over anhyd Na2SO4, respectively. The solvents were removed under reduced pressure, and the residues were purified by flash column chromatography. The produced aldehyde in the anodic compartment was separated by a phase separation and was added to the cathodic compartment for the next cycle.