Cobalt-Catalyzed Reductive Alkylation of Heteroaryl Bromides: One-Pot Access to Alkylthiophenes, -furans, -selenophenes, and -pyrroles

A practical and convenient Co-catalyzed alkylation method for the facile introduction of various alkyl chains into organic electronically significant heteroaryl compounds, including thiophenes, furans, selenophenes, and pyrroles, is reported. Under well-optimized reaction conditions, a wide range of alkylated heteroaryl compounds have beeen efficiently prepared in moderate to good isolated yields. Notably, 2- or 3-alkylthiophenes, which play a decisive role in polymer chemistry and organic materials, have been synthesized step-economically for the first time by this reductive-coupling methodology using inexpensive cobalt salts as catalysts. This straightforward synthetic procedure avoids the preparation of moisture-unstable organometallic reagents (RMgX or RZnX) required in conventional alkylation protocols. Various alkyl chains have been introduced into organic, electronically important heteroaryl compounds step-economically through Co-catalyzed reductive alkylation reactions. The resulting alkylheteroarenes are indispensable building blocks for polymer chemistry and π-functional organic materials.