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Synlett 2011(2): 273-279  
DOI: 10.1055/s-0030-1259290
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Palladium-Catalyzed Novel Arylations of Cyclic β-Bromo α,β-Unsaturated Aldehydes with Triarylbismuths as Multicoupling Organometallic Nucleo­philes

Maddali L. N. Rao*, Debasis Banerjee, Ritesh J. Dhanorkar
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
Fax: +91(512)2597532; e-Mail: maddali@iitk.ac.in;
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Publication History

Received 13 August 2010
Publication Date:
23 December 2010 (online)

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Abstract

Cross-coupling arylations of cyclic β-bromo α,β -unsaturated aldehydes were carried out with triarylbismuths as atom-­efficient multicoupling organometallic reagents under palladium-catalyzed conditions. These reactions afforded the corresponding arylated alkenes in an efficient manner with good to high yields.

Key words

palladium catalysis - cyclic β-bromo α,β -unsaturated aldehyde - cross-coupling - triarylbismuths - tetrasubstituted alkenes

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Representative Procedure: An oven-dried Schlenk tube under a nitrogen atmosphere was charged with 1-bromo-3,4-dihydronaphthalene-2-carbaldehyde (0.825 mmol, 0.196 g) followed by triphenylbismuth (0.25 mmol, 0.11 g), K3PO4 (0.50 mmol, 0.106 g), PdCl2(PPh3)2 (0.0225 mmol, 0.0158 g) and anhyd DMF (3 mL). The reaction mixture was stirred in an oil bath at 90 ˚C for 1 h. Then the contents were cooled to r.t. and the reaction was quenched with H2O (10 mL) and the mixture was extracted with EtOAc (3 × 15 mL). The combined organic extracts were washed with H2O (2 × 10 mL), brine (10 mL), dried over anhyd MgSO4 and concentrated. The crude product mixture thus obtained was purified by silica gel column chromatography using 1% EtOAc-petroleum ether as eluent to obtain 1-phenyl-3,4-dihydronaphthale-2-carbaldehyde(2a) as a pale yellow solid (0.169 g, 96%). All the products were characterized by ¹H NMR, ¹³C NMR, IR spectroscopic data and HRMS (ESI).

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In all the coupling reactions, 0.3 equiv of bromoaldehydes was employed in excess. However, the product yields were calculated based on the three couplings from triaryl-bismuths. Thus, 0.75 mmol of the cross-coupled product corresponds to 100% yield.