Use of the vinyl group as an efficient protecting group for azole N-atoms: Synthesis of polyfunctionalized imidazoles and thieno[2,3-d]reversible arrow[3,2-d]imidazole

2,4,5-Tribromo-1-vinylimidazole was prepared from 2,4,5-tribromoimidazole and 1,2-dibromoethane and its Br-atoms were replaced regioselectively in the order 2 --> 5 --> 4 via Br --> MgBr and other exchange reactions. Efficient removal of the vinyl groups from die resulting polyfunctionalized imidazoles was achieved with ozone or potassium permanganate. An extension of this methodology has allowed the first synthesis of thieno[2,3-d] reversible arrow [3,2-d]imidazole. (C) 1997 Elsevier Science Ltd.