Synthesis 2006(2): 299-304  
DOI: 10.1055/s-2005-918509
PAPER
© Georg Thieme Verlag Stuttgart · New York

2-Trifluoromethanesulfonyloxyindole-1-carboxylic Acid Ethyl Ester: A Practical Intermediate for the Synthesis of 2-Carbosubstituted Indoles

Elisabetta Rossi*, Giorgio Abbiati, Valentina Canevari, Giuseppe Celentano, Elsa Magri
Istituto di Chimica Organica ‘Alessandro Marchesini’, Facoltà di Farmacia, Università degli Studi di Milano, Via Venezian 21, 20133 Milano, Italy
Fax: +39(02)50314476; e-Mail: elisabetta.rossi@unimi.it;
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Publikationsverlauf

Received 15 July 2005
Publikationsdatum:
21. Dezember 2005 (online)

Abstract

Ready accessible 2-trifluoromethanesulfonyloxyindole-1-carboxylic acid ethyl ester undergoes palladium-catalyzed coupling reactions with different partners giving rise to 2-aryl, heteroaryl, vinyl, allyl, and alkynyl indoles in good to excellent yields.

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We synthesized the trifluoromethanesulfonic acid 1-trifluoromethanesulfonyl-1H-indol-2-yl ester 3 from 1,3-dihydroindol-2-one(5) in 70% yield following the procedure described by Gribble.7 However, 3 is stable only at low temperatures and after reaction with phenylacetylene or with 2-methyl-3-butyn-2-ol under Sonogashira conditions at 60 °C, the corresponding coupled products were isolated in poor yields (31% and 32%, respectively).