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First selective mono- and double-halogen migrations on 5,5'-dibromo-2,2'-bithiophene

J. Fröhlich and R. Bobrovsky

Institute of Organic Chemistry, Technical University of Vienna, Getreidemarkt 9, A-1060 Vienna, Austria


Halogen-dance (HD) reactions at aromatic systems, in particular applied to various brominated thiophenes and furans, lead to rearranged lithiated species after treatment of the halogenated starting compounds with LDA. They have been studied thoroughly within our group [1-4], as they open promising pathways to highly substituted heterocycles. Until now, no efforts have been made to adopt this approach to 2,2-bithiophene-systems.
In this work we present HD techniques to afford mono- and double-rearranged lithium intermediates which yield - after treatment with various electrophiles - mono- and double-substituted dibromo-2,2'-bithiophenes A,B and C.