Synthesis 2006(22): 3883-3887  
DOI: 10.1055/s-2006-950305
PAPER
© Georg Thieme Verlag Stuttgart · New York

Regioselective Couplings of Dibromopyrrole Esters

Scott T. Handy*, Yanan Zhang
Department of Chemistry, Binghamton University, Binghamton, NY 13902, USA
Fax: +1(615)8985182; e-Mail: shandy@mtsu.edu;
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Publikationsverlauf

Received 25 May 2006
Publikationsdatum:
12. Oktober 2006 (online)

Abstract

The regioselectivity of the Suzuki couplings of several 4,5- and 3,4-dibromopyrrole-2-carboxylate esters has been studied. In general, regioselectivity can be achieved for initial coupling at the more electron-deficient site (C5 and C3, respectively). At the same time, conversions are often modest (40-60%) and attempts to force the reactions to higher conversions often lead to competitive dicoupling.

1

Current address: Department of Chemistry, Middle Tennessee State University, Murfreesboro, TN 37132, USA.

7

The one remaining isomeric dibromopyrrole ester (3,5-dibromo) has also been prepared. The regioselectivity of the Suzuki couplings of this substrate exhibit an unusual solvent dependency that remains under investigation.

12

Bases tried include the following: Na2CO3, K2CO3, Cs2CO3, K3PO4, and Ba(OH)2. Solvents tried include the following: DMF, EtOH-toluene, acetone, and H2O.