Negishi cross-coupling reactions Subject

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. 

In 2012, Organ and co-workers were finally able to confirm the presence of high-order zincates in the alkyl-alkyl Negishi reaction by synthesizing the RZnBrj - zincates and then subjecting them to Negishi reaction conditions. A variety of cross-coupled products were obtained in just 2h and in excellent yield (Scheme 32). 

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