Synthesis 2006(11): 1882-1894  
DOI: 10.1055/s-2006-942367
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart · New York

Pseudo-Cross-Conjugated Mesomeric Betaines and N-Heterocyclic Carbenes of Indazole

Andreas Schmidt*, Ariane Beutler, Tobias Habeck, Thorsten Mordhorst, Bohdan Snovydovych
Clausthal University of Technology, Institute of Organic Chemistry, Leibnizstrasse 6, 38678 Clausthal-Zellerfeld, Germany
Fax: +49(5323)723861; e-Mail: schmidt@ioc.tu-clausthal.de;
Further Information

Publication History

Received 28 March 2006
Publication Date:
05 May 2006 (online)

Abstract

1,2-Dimethylindazolium-3-carboxylates are pseudo-cross-conjugated mesomeric betaines (PCCMB) and derivatives of the indazole alkaloid Nigellicin. They decarboxylate on heating to give intermediary N-heterocyclic carbenes of indazole that can be trapped with iso(thio)cyanates to amidates. Alternatively, 1,2-di­methylindazolium-3-amidates can be prepared starting from the corresponding 1H-indazol-3-carboxylic acid which is converted into its chloride, reacted with anilines and deprotonated on anion exchange resin. The heterocumulene moieties of these amidates, which are new representatives of pseudo-cross-conjugated mesomeric betaines, can be exchanged to 3,5-dichlorophenyl isocyanate via the N-heterocyclic carbene.