Halogenation of [2-(trimethylsilyl)ethoxy]methyl (SEM) protected 2,2′-Bi-H-imidazole

2,2′-Bi-1H-imidazole, when protected with the 2-(trimethylsilyl)ethoxy]methyl (SEM) blocking group, on treatment with N-bromosuccinimide or N-chlorosuccinimide yields predominantly the monohalogenated derivatives 4a and 4b. The 2-(trimethylsilyl)ethoxy]methyl group is subsequently removed to yield pure mono-halo-2,2′-bi-H-imidazoles 2 .