Synthesis of 2, 5, 6-Trisubstituted Benzimidazoles by Heck and Subsequent 6π-Electrocyclization-Dehydrogenation Reactions of 2, 4, 5-Tribromo-N-methylimidazole …

SMT Toguem, P Langer

Index: Toguem, Serge-Mitherand Tengho; Langer, Peter Synlett, 2010 , # 12 p. 1779 - 1782

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Abstract

Commercially available tribromoimidazole (1) was transformed into tribromo-N-methyl-imidazole (2) by reaction with potassium carbonate and methyl iodide in DMF (Scheme [¹] ). The Heck reaction of 2 with acrylates 3a-g (3.3 equiv) afforded the tri(alkenyl)-N-methyl-imidazoles 4a-g in 73-86% yield (Table [¹] ). [¹³] [¹4] The Heck reaction of 2 with styrene 3h gave product 4h. The best yields were obtained when Pd(OAc) 2 (5 mol%) in the presence of tris(cyclohexyl) ...