Kumada coupling thiophenes

In the synthesis of 2-bromobisthiophene (37), mono-arylation was achieved using the Kumada coupling of 2-thienyhnagnesium bromide with 2,5-dibromothiophene in the presence of PdfdppfjCl, although mckel(O)-catalyzed coupling failed [43]. Unlike the conversion of 2,5-dibromothiophene to 37, a related thiophene, 38, was converted to thiophene 39 in high yield in the presence of a nickel catalyst [44]. 

Fig. 6 Synthesis of alkylated thiophenes via Kumada coupling reaction 3.3.1 Kumada Coupling Reaction...

In symmetrically substituted 3,4-dihalothiophenes, several stepwise cross-coupling reactions have been performed <2005T2245>. Thus, 3,4-dibromothiophene undergoes a Negishi coupling with benzylzinc bromide to yield the monobromothiophene 84. This can be subjected to a Kumada cross-coupling to give the unsymmetrically substituted thiophenes 85. 

Polythiophenes by Kumada Cross-Coupling 175 Table 7.1 Summary of reported poly(3-functionalized)thiophenes. 

I 7 The Synthesis of Conjugated Polythiophenes by Kumada Cross-Coupling Table 7.2 Polymerization data for symmetrical and fused thiophenes. 

Branched terthiophene 5.77 was synthesized by Kumada-type cross-coupling of the Grignard reagent of 2-bromo-5-TMS-thiophene and 2,3-dibromothiophene in 79% yield. Higher generation DOTs were... 

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