Synlett 2005(3): 523-525  
DOI: 10.1055/s-2005-862355
LETTER
© Georg Thieme Verlag Stuttgart · New York

Efficient Role of Mg-ZnCl2 for Selective Reduction of α,β-Unsaturated ­Carbonyl Compounds in Aqueous Medium

Anil Saikia, Madan Gopal Barthakur, Romesh Chandra Boruah*
Medicinal Chemistry Division, Regional Research Laboratory, Jorhat-785006, India
e-Mail: rc_boruah@yahoo.co.in;
Further Information

Publication History

Received 28 October 2004
Publication Date:
04 February 2005 (online)

Abstract

A facile strategy for the convenient reduction of α,β-unsaturated carbonyl compounds and conjugated alkynes has been ­accomplished by Mg-ZnCl2 system in aqueous medium.

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Illustrative Experimental Procedure of 1,3-Diphenyl-propan-1-one (Entry 1).
To a suspension of 1,3-diphenylprop-2-en-1-one (1.04 g, 5 mmol) in distilled H2O (20 mL) was added magnesium turnings (1.80 g, 7.5 mmol) and ZnCl2 (1.0 g, 7.5 mmol) under stirring. Immediately after addition, an exothermic reaction took place and the magnesium turnings were consumed giving a grey opaque mixture. After stirring for 20 min, the reaction mixture was extracted with CH2Cl2 (3 × 10 mL), and the combined organic extracts were washed with H2O, dried and evaporated to give a residue which was purified by column chromatography over silica gel (EtOAc-hexane = 2:8) to afford 1,3-diphenyl-propan-1-one as an off-white solid, yield 0.19 g (94%), mp 69-70 °C. IR: 1685 cm-1. 1H NMR (CDCl3): δ = 2.90 (2 H, t, J = 6.1 Hz), 3.05 (2 H, t, J = 6.1 Hz), 6.75-7.70 (10 H, m). MS (ESI): m/z = 233 [M+ + 23]. Anal. Calcd for: C, 85.68; H, 6.71. Found: C, 85.21; H, 6.68.