Selective Halogenation of Bithiophenes Using 2-Halopyridazin-3(2H)-ones ­under Ambient Conditions

2,2′-Bithiophene and halogenated-2,2′-bithiophenes were halogenated with 2-halo-4,5-dichloropyridazin-3(2H)-one in the presence of zinc halide to give selectively the corresponding dihalo-, trihalo-, and tetrahalo-2,2′-bithiophenes involving the same or different halogens in excellent yields, respectively.