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DOI: 10.1055/s-2006-950305
Regioselective Couplings of Dibromopyrrole Esters
Publication History
Publication Date:
12 October 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.
Key words
Suzuki cross-coupling - regioselectivity - electronic effects - pyrroles - palladium
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References
Current address: Department of Chemistry, Middle Tennessee State University, Murfreesboro, TN 37132, USA.
7The 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.
12Bases tried include the following: Na2CO3, K2CO3, Cs2CO3, K3PO4, and Ba(OH)2. Solvents tried include the following: DMF, EtOH-toluene, acetone, and H2O.