Synthesis of 1-aryl-1H-indazoles via the palladium-catalyzed cyclization of N-aryl-N′-(o-bromobenzyl)hydrazines and [N-aryl-N′-(o-bromobenzyl)-hydrazinato-N′]-triphenylphosphonium bromides

✍ Scribed by Jinhua J Song; Nathan K Yee

• Book ID: 104230346
• Publisher: Elsevier Science
• Year: 2001
• Tongue: French
• Weight: 72 KB
• Volume: 42
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)00273-8

✦ Synopsis

1-Aryl-1H-indazoles were synthesized by the palladium-catalyzed intramolecular amination [Pd(OAc) 2 /dppf/tBuONa (150 mol%)/toluene/90°C] of the corresponding N-aryl-N%-(o-bromobenzyl)hydrazines. It was further demonstrated that cyclization of [N-aryl-N%-(o-bromobenzyl)-hydrazinato-N%]-triphenylphosphonium bromides under the conditions of [Pd(OAc) 2 /dppf/ tBuONa (250 mol%)/dioxane/90°C] also led to the formation of the corresponding 1-aryl-1H-indazoles. These methods were applied to a group of representative substrates to give indazole products in moderate to very good yields.