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Synthesis 2001(14): 2124-2128
DOI: 10.1055/s-2001-18054
PAPER
© Georg Thieme Verlag Stuttgart · New York

A New Synthetic Approach to Thiophenes

Mikhail V. Lebedev, Valentine G. Nenajdenko*, Elizabeth S. Balenkova*
Department of Chemistry, Moscow State University, 119899 Moscow, Russia
Fax: +7(095)9328846; e-Mail: Nen@acylium.chem.msu.ru;
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Publication History

Received 27 April 2001
Publication Date:
09 August 2004 (online)

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Abstract

A new simple and efficient way to 3-hydroxy(methoxy)thiophenes is described. The reactions of (ethylsulfanyl)acetyl fluoride/boron trifluoride (1) and 2-(ethylsulfanyl)butanoyl fluoride/boron trifluoride (6) complexes with acetylenes give rise to the 5-membered cyclic sulfonium salts (3a-f). The last ones (3e, 3f) after being refluxed with thiourea in methanol or acetonitrile are converted into 3-methoxythiophenes or 3-(2H)-thiophenones respectively. Several 3-methoxythiophenes unsubstituted in the 2-position were obtained by the reactions of 1 with acetylenes. Reactions of 6 with acetylenes allows the synthesis of 2-ethylsubsituted 3-methoxythiophenes. The method allows the synthesis of a variety of mono-, di-, tri- and tetrasubsituted thiophenes.

Key words

acylation - thiophene - acylsulfonium salt - alkynes - electrophilic addition