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Synlett 2002(12): 2059-2061
DOI: 10.1055/s-2002-35600
LETTER
© Georg Thieme Verlag Stuttgart · New York

A Novel and One Step Procedure for Preparation of α-Bromo-α,β-unsaturated Carbonyl Compounds

G. V. Ramanarayanan, Vidyanand G. Shukla, K. G. Akamanchi*
Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, University of Mumbai, Matunga, Mumbai-400 019, India
Fax: +91(22)4145614; e-Mail: kgap@rediffmail.com;
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Publication History

Received 8 October 2002
Publication Date:
20 November 2002 (online)

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Abstract

A new one step method is developed for the preparation of α-bromo-α,β-unsaturated carbonyl compounds in moderate to good yields from corresponding α,β-unsaturated carbonyl compounds using DMP [1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one] and tetraethylammonium bromide under neutral and mild reaction conditions at room temperature.

Key words

DMP - tetraethylammonium bromide - α-bromo-α,β- unsaturated carbonyl compounds - bromination.

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Typical procedure: 3-Bromo-2H-1-benzopyran-2-one (entry 8): To a suspension of DMP (6.97 g, 16.4 mmol) in dry dichloromethane (30 mL) was added Et4N+Br- (3.45 g, 16.4 mmol) in one portion with stirring and the color of solution turned to orange-yellow. After 10 min of stirring at room temperature coumarin (2.00 g, 13.7 mmol) was added. The reaction was monitored by TLC. At the end of the reaction (24 h) the precipitate formed was filtered, washed with dichloromethane (2 × 20mL). The filtrate was then washed with saturated sodium bisulphite solution, followed by saturated bicarbonate solution and water. The organic layer was dried over anhydrous sodium sulfate and concentrated in vacuo to get a crude product, which was purified by column chromatography to give 3-bromo-2H-1-benzopyran-2-one (2.14 g, 70%) as off-white solid. Mp 108 °C (ref. [24] 110 °C). IR (KBr): 1735, 1606 cm-1. 1H NMR (500 MHz, CDCl3): δ 8.10 (s, 1 H, Ha), 7.57 (t, 1 H, J = 7.6 Hz, Hb), 7.46 (d, 1 H, J = 7.6 Hz, Hc), 7.36 (d, 1 H, J = 8.4 Hz, Hd), 7.32 (t, 1 H, J = 7.6 Hz, He). 13C NMR (CDCl3): δ 157.0 (d, J = 8.4 Hz, C-1), 153.1 (s, C-2), 144.4 (d, J = 167.6 Hz, C-3), 132.0 (dd, J = 161.2 Hz, 8.4 Hz, C-4), 127.1 (d,
J = 162.1 Hz, C-5), 125.0 (dd, J = 164.0 Hz, 6.9 Hz, C-6), 119.2 (s, C-7), 116.7 (dd, J = 164.4 Hz, 6.8 Hz, C-8), 111.7 (s, C-9).