Synlett 2007(1): 0103-0106  
DOI: 10.1055/s-2006-956467
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Tri- and Tetrasubstituted Olefins by Palladium Cross-Coupling Reaction

Carolina M. Nunes, Daniela Steffens, Adriano L. Monteiro*
Group of Molecular Catalysis, Instituto de Química, UFRGS. Av. Bento Gonçalves, 9500 Porto Alegre 91501-970, CP 15003, RS, Brazil
Fax: +55(51)33167304; e-Mail: almonte@iq.ufrgs.br;
Further Information

Publication History

Received 5 September 2006
Publication Date:
20 December 2006 (online)

Abstract

Tri- and tetrasubstituted olefins were obtained in high yields and regioselectivities using stilbene as starting material. First, stilbene was converted into (E)-bromostilbene by a bromination-dehydrobromination sequence. Then, (E)-bromostilbene was coupled with arylboronic acids at room temperature and low loading of Pd catalyst precursor (0.5-0.05 mol%) to afford selectively (E)-1-aryl-1,2-phenylethylenes in high yields (87-98%). Bromination of triphenylethylene afforded directly the bromotriphenylethylene that also underwent coupling reactions with arylboronic acids under mild conditions to afford tetrarylethylene (88-90% yield). Under the same conditions attempted Suzuki cross-coupling reactions of (E)-bromostilbene or 1,1,2-triphenylethene with alkylboronic acids were unsuccessful. However, the alkyl group could be introduced under mild conditions and high yields by using a Pd-catalyzed Negishi coupling protocol.