Selective Functionalization of 2,2'-Bithiophenes

The selective functionalization of the 2,2'-bithiophene molecule is described. Selective alkyl substitution at the 3,3' positions was achieved by sequential bromination of the 3,3' and 5,5' positions followed by debromination at the 5,5' positions. The resultant 3,3'-dibromo-2,2'-bithiophene was transformed via a Grignard reaction to give a series of 3,3'-dialkyl-2,2'-bithiophenes. Finally, nitration of the active 5,5' positons gave the corresponding 3,3'-dialkyl-5,5'-dinitro-2,2'-bithiophenes