Bipyridyl-substituted thiophenes

Direct Arylation of Thiophenes. For 2-substituted thiophenes, the C5 position is more reactive compared with the C4 position. Mechanistic studies were performed on the C4-selective direct C-H arylation of 2-substituted thiophenes. To study the effect of the counteranion on C4/C5 selectivity, stoichiometric amounts of arylpalladium bipyridyl complexes were reacted with 2-substituted thiophenes in the presence of various additives. Silver triflate showed high C4 selectivity with minimal amounts of biphenyl by-product (10%), whereas AgOAc and Ag2C03 favored the C5 product (eq 75). 

Crayston, J., A. Iraqi, J.J. Morrison, and J.C. Walton. 1997. Synthesis of thiophene substituted ruthenium and rhenium bipyridyl complexes. Synth Met 84 441-442. 

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