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Synlett 2008(19): 3021-3025  
DOI: 10.1055/s-0028-1083631
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Rapid Palladium-Catalyzed C3-Arylation of 2(1H)-Pyrazinones: Effect of Simultaneous Cooling on Microwave-Assisted Reactions on Solid Support

Brajendra K. Singha,b, Virinder S. Parmarb, Erik Van der Eycken*a
a Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), University of Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
Fax: +32(16)327990; e-Mail: erik.vandereycken@chem.kuleuven.be;
b Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi 110 007, India
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Publication History

Received 27 June 2008
Publication Date:
12 November 2008 (online)

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Abstract

An unprecedented microwave-assisted palladium-catalyzed reaction on polymer support with simultaneous cooling has been developed. It has also been illustrated that under simultaneous cooling, certain decomposition and side reactions during the reaction, because of heating, can be minimized.

Key words

2(1H)-pyrazinones - palladium catalysis - solid support - microwave - simultaneous cooling

    References and Notes

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7

See power profile in Supporting Information.

8

All microwave-irradiation experiments were carried out in a dedicated CEM-Discover-Coolmate monomode microwave apparatus (CEM Corporation P.O. Box 200 Matthews, NC 28106), operating at a frequency of 2.45 GHz with continuous irradiation power from 0-300 W. Reaction mixtures were efficiently stirred with a magnetic stirrer. The reactions were carried out in an open 10 mL double-walled glass vial which was cooled to 0-35 ˚C using a microwave transparent cooling liquid. The temperature of the cooling liquid was between 15 ˚C and 18 ˚C. Irradiation and cooling were started simultaneously, starting with the reaction mixture at r.t. The temperature was measured with a fiber-optic probe device inserted into the reaction vessel; a schematic representation of the setup can be found at
http://cemsynthesis.com

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Experimental details and characterization data (¹H NMR, ¹³C NMR, and HRMS) of all new compounds are available in the Supporting Information.